WO2013082660A1 - Prediction method - Google Patents

Abstract

The invention relates to a method for predicting responsiveness of a cancer in a subject to treatment with an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor, a method for identifying a subject with a cancer unsuitable for treatment with an Mcl-1 inhibitor and optionally a Bcl-2 or Bc1-xL inhibitor, and a method for treating a cancer in a subject, comprising administering to the subject an Mc1-l inhibitor and optionally a Bcl-2 or Bc1-xL inhibitor. Each method comprises detecting Bak expression in a sample of the cancer. The invention also relates to a method of identifying a compound which inhibits Mcl-1 and a kinase by determining the effect of the compound on either CDK7 or CDK9 and either PI3K or FLT3 kinase activity.

Description

PREDICTION METHOD

FIELD

The invention relates to methods for predicting responsiveness of a cancer in a subject to treatment with an Mcl-1 inhibitor.

BACKGROUND

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Phosphoinositol 3-kinases (PI3Ks) are potent regulators of cell survival through their ability to phosphorylate phosphoinositols in the inner leaflet of the plasma membrane that, in turn, provide docking sites for the recruitment of pleckstrin homology domain proteins such as Akt. Class I PI3Ks are heterodimeric enzymes comprising an adapter protein bound to one of four 1 10kDa catalytic subunits (ρ1 10α, ρ1 10β, ρ1 10δ and ρ110γ). Constitutive activation of PI3K is commonly associated with cellular transformation and deregulated cell survival making the development of signal transduction therapies for the blockade of specific p1 10 isoforms an attractive clinical prospect. For example, the p1 10a isoform of PI3K is activated in diverse tumours and some p1 10a isoform- selective kinase inhibitors have shown anti-cancer activity in animal models. In addition to PI3K, Bcl-2 and closely related pro-survival family members Bcl-x_L, Bcl-w, Mcl-1 and A1 are also central regulators of cell survival in diverse cell types. Over-expression of individual members of the Bcl-2 pro-survival family is commonly observed in human cancer, and their oncogenic potential has been clearly demonstrated for both solid tumours and leukemias. High expression of Bcl-2 family members has also been shown to protect transformed cells from apoptosis induced by chemotherapy and gamma irradiation and is associated with poor clinical outcomes. For example, Myeloid cell leukemia 1 (Mcl-1 ) over-expression has been observed in a variety of solid and hematopoietic malignancies and elevated Mcl-1 has been shown to antagonize cell death induced by a number of drugs that are either in the clinic or in clinical development.

In order to streamline healthcare and correctly target therapy, i.e. deliver personalised medicine, there is a need to predict and differentiate which subjects will respond to specific therapies and which subjects will not respond to those therapies.

SUMMARY

A first aspect provides a method for predicting responsiveness of a cancer in a subject to treatment with an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor, the method comprising detecting Bak expression in a sample of the cancer and comparing the Bak expression level to a reference Bak expression level, wherein a reduced Bak expression level compared to the reference Bak expression level in or absence of Bak expression from the cancer predicts a negative response to treatment with the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor.

A second aspect provides a method for identifying a subject with a cancer unsuitable for treatment with an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor, the method comprising detecting Bak expression in a sample of the cancer and comparing the Bak expression level to a reference Bak expression level, and identifying as unsuitable for Mcl-1 inhibitor treatment and optionally Bcl-2 or Bcl-x_L inhibitor treatment the subject in whom the Bak expression level is reduced compared to the reference Bak expression level or is absent from the cancer.

A third aspect provides a method for treating a cancer in a subject, the method comprising detecting Bak expression in a sample of the cancer, and administering to the subject in whom Bak expression is detected in the cancer an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor.

An alternative form of the third aspect relates to an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor for use in a method for treating a cancer in a subject, the method comprising detecting of Bak expression in a sample of the cancer, and administering to the subject in whom Bak expression is detected in the cancer the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor.

Another alternative form of the third aspect relates to use of an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor in the manufacture of a medicament for treating a cancer in a subject, wherein the medicament is administered to the subject in whom Bak expression is detected in the cancer.

The method of the third aspect may further comprise determining Bak protein function when Bak expression is detected, and continuing administering to the subject in whom Bak protein is detected and functional in the cancer the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor, and discontinuing administering to the subject in whom Bak protein is non-functional in the cancer the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor.

The methods of the first or second aspects may be carried out in vitro.

Although it is known that cancer cells survive and resist treatment by de-regulating intracellular cell survival pathways, such as by over-expressing pro-survival proteins, a complete picture of which pro-survival proteins may be over-expressed is not yet known. Nor is it known what inter-individual variability exists between cancers in subjects. Knowledge of such inter-individual variation is important for personalised medicine, both in providing effective treatment to the subject as early as possible and minimising healthcare costs by avoiding treating non-responsive patients with expensive anti-cancer therapies. The present inventors have surprisingly identified that certain subjects will not respond to inhibitors of the Mcl-1 pathway, because the cancers in these subjects lack expression of pro-apoptotic Bak, or lack functional pro-apoptotic Bak protein. Accordingly, by identifying such patients, Mcl-1 inhibitors and optionally Bcl-x_L inhibitors may be effectively directed only to those patients in whom the cancer will respond to treatment.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 graphs the expression of Mcl-1 in AML and the suppressive effect of PIK-75 on RNA polymerase 2 (RNAP2) C-terminal domain (CTD) phosphorylation and Mcl-1 expression which correlates with apoptosis in human AML cells as demonstrated in the Example. (A) Western blot expression analysis of Mcl-1 in AML cell lines. (B) Western blot expression analysis of Mcl-1 and phosphorylated RNAP2 in primary AML samples. (C) AML cell lines were plated in increasing concentrations of PIK-75 and the IC50s for cell death were determined using propidium iodide viability assay at 24h. Immunoblotting for Mcl-1 and phosphorylated RNAP2 were as described in the Examples. (D) FDM cells were treated for 6h, 8h or 24h with 50μΜ LY294002, 1 μΜ Flavopiridol or 1 μΜ PIK-75 following which cell lysates were immunoblotted for Mcl-1 , Bcl-xL or HSP70.

Figure 2 graphs the pro-apoptotic activity of PIK-75, which is distinct from other inhibitors targeting the PI3K signalling pathway. MV4;1 1 cells were cultured for 24h in the presence of: (A) TGX221 , IC871 1 14, AS252424 or PIK-75; (B) BEZ235, PI-103, LY294002, Wortmannin or PIK-75; and (C) Ara C, Etopside, CEP701 , RAD001 or PIK-75, and cell survival determined by flow cytometric enumeration of Pl-negative cells. (D) siRNA-mediated knockdown of either Mcl-1 or Cdk-9 combined with PI3K inhibition using either GDC-0941 or A66 induces cell death in primary human AML blasts.

Figure 3 graphs PIK-75 targeting of Mcl-1 , which induces Bak-dependent apoptosis. (A) FDM lines generated from the indicated wild type and knockout mice were cultured for 24h in the presence of PIK-75 and cell survival measured by flow cytometric enumeration of Pl-negative cells. Cell lysates from (B) newly diagnosed and (C) chemotherapy relapsed and refractory primary AML samples were immunoblotted with the indicated antibodies. (D) Bak low AML is resistant to methods targeting Mcl-1. Primary human AML cells from a patient with high Bak expression (AML 7 in Fig 3B; open bars) or low Bak expression (AML3 in Fig 3B; filled bars) were transfected using Lipofectamine RNAiMAX (Invitrogen) and 50nM BLOCK-iT fluorescent oligo (Invitrogen) together with 50-1 OOnM of either ON-TARGET plus control siRNA, Mcl-1 siRNA or Cdk9 siRNA (Dharmacon) in the presence of 10ng/ml IL-3 and FCS. Where indicated, 1 μΜ GDC-0941 was added. Cell survival was analysed at 48h by propidium iodide staining and flow cytometry. (E) Primary human AML cells were plated at 5x10⁵/ml in RPMI supplemented with 10ng/ml IL-3 and FCS and incubated in the indicated concentrations of PIK-75 for 24h following which cell survival was quantified by propidium iodide staining and flow cytometry showing that Bak deficient AML is resistant to Mcl-1 targeting by PIK-75.

Figure 4A shows the binding affinity of PIK-75 toward CDK9, CDK7, FLT3-ITD and CDK2. The binding affinity of PIK-75 to purified recombinant Cdk9, Cdk7, Cdk2 or FLT3-ITD was measured in a competition assay (Ambit Biosciences, CA) as described in Fabian ef a/. (2005) Nat. Biotechnol. 23, 329-336. Briefly, affinity of the specific kinases for PIK-75 was measured by combining DNA-tagged kinase, immobilized ATP and PIK-75. The ability of PIK-75 to compete with the immobilized ATP was measured via quantitative PCR of the DNA tag.

Figure 4B shows expresssion changes of genes involved in the regulation of apoptosis by LY294002, Flavopiridol and PIK-75. MV4; 1 1 cells were treated with either DMSO, Flavopiridol or PIK-75 for 2 hours following which total RNA was extracted (Trizol™; Invitrogen), purified and cDNA made (Sensiscript™; Qiagen). Gene expression was analysed by multiple ligation probe analysis as described (MRC Holland). The resulting signals obtained following treatment were expressed as the percent change relative to DMSO normalised control such that negative histograms indicate drug inhibition of gene expression. Figure 5A depicts a Western blot of LY294002, Flavopiridol or PIK-75 treatment of MV411 cells for 8 hours at the indicated concentrations for expression of phosphorylated RNAP2 (p RNA pol II CTD), Mcl-1 , phosphoBad, Bad, Bak, pGSK3b, GSK3a/b, and Tubulin.

Figure 5B depicts a Western blot of LY294002, Flavopiridol, PIK-75 or BKM120 treated murine Bax/Bak double knock-out cells at the indicated concentrations and time for expression of Mcl-1 and Bcl-2.

Figure 6 depicts the amino acid sequence of human Bak (SEQ ID NO: 1 ; gi|4502363|ref|NP_001179.11 bcl-2 homologous antagonist/killer [Homo sapiens]). DETAILED DESCRIPTION

The inventors have demonstrated that certain cancers do not express Bcl-2 homologous antagonist/killer (Bak) protein, or do not express functional Bak protein. Subjects in whom such cancers exist are unlikely to respond to treatment with direct or indirect inhibitors of Mcl-1 expression, function or stability. Consequently, by identifying those subjects with cancers likely to respond negatively to therapy and those subjects with cancers likely to respond positively to therapy, the present invention enables faster and more effective treatment of subjects with cancers that express functioning Bak.

In addition, the inventors have shown that apoptosis is enhanced when cancer cells are dually targeted with an Mcl-1 inhibitor and a tyrosine kinase (e.g. PI3K) inhibitor. Moreover, the inventors have demonstrated that a known PI3K inhibitor, PIK-75, in fact dually targets these separate pathways. Accordingly, the inventors provide a method of identifying compounds with enhanced drugability, but with a similar mode of action as PIK-75.

The prior art discloses: 1 ) a method of measuring Bak gene transcription (amongst other genes) in cancer samples using an RNA FISH method to determine potential sensitivity to therapeutic drugs; 2) a method for measuring the functional activation of Bak using reagents (e.g. antibodies) in patient cancer samples following drug treatment to determine the effectiveness of that treatment; 3) methods or reagents that mediate Bax and Bak-dependent apoptosis; 4) use of a kinase inhibitor (such as a FLT3 inhibitor) combined with a treatment that activates Bak to sensitise cancer cells for apoptosis; and 5) a method for screening patient tumour samples by PCR to identify mRNA expression profiles of Bcl-2 family members to allow identification of patients that respond to specific therapies. Thus, the prior art may disclose examination of Bak mRNA or protein expression and/or Bak activation for the use of identifying and/or guiding a wide array of therapeutic treatments/approaches (e.g. chemotherapy, radiotherapy, BH3 mimetics (similar to ABT-737) other small molecule or antibody entities) that require the presence of both Bax and Bak. However, the prior art does not disclose or suggest the present invention that relates to the analysis of Bak expression levels in cancer samples for the use of determining sensitivity to drugs/agents that kill cancer cells via a Bak-mediated, but not a Bax-mediated, apoptosis (e.g. direct or indirect inhibitors of Mcl-1 alone or in addition to direct or indirect inhibitors of Bcl-2 or Bcl-X_L).

As used herein, the terms "cancer" and "cancerous" refer to or describe the physiological condition typically characterized by unregulated cell growth, which may result in invasion and destruction of adjacent tissues, and may metastasize in which cancer cells spread to other locations in the body via the lymphatic system or through the bloodstream. A cancer may be a solid tumour or a hematopoietic neoplasm. Examples of cancer include but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, melanoma and leukemia or lymphoid malignancies. More particular examples of such cancers include adrenocortical carcinoma, adenocarcinoma of the lung, AIDS-related cancers and lymphomas, anal cancer, astrocytoma, B-cell lymphomas (including low grade/follicular non- Hodgkin's lymphoma (NHL), small lymphocytic NHL, intermediate grade/follicular NHL, intermediate grade diffuse NHL, high grade immunoblastic NHL, high grade lymphoblastic NHL, high grade small non-cleaved cell NHL, bulky disease NHL, mantle cell lymphoma, AIDS-related lymphoma and Waldenstrom's Macroglobulinemia), bladder cancer, breast cancer (including male breast cancer), bronchial cancer, cancer of the intrahepatic bile duct, carcinoid tumours, cervical cancer, chronic lymphocytic leukemia, chronic myeloblasts leukemia, chronic myelogenous leukemia, chronic myeloproliferative disorders, clear cell sarcoma, colon cancer, colorectal cancer, cutaneous T-cell lymphoma, endometrial cancer, ependymoma, esophageal cancer, Ewing's sarcomas, gall bladder cancer, gastric or stomach cancer (including gastrointestinal cancer, germ cell tumours, gestational trophoblastic tumours, glioma or brain cancers (including glioblastoma), hairy cell leukemia, head and neck cancers, hepatocellular carcinoma, hypopharyngeal cancer, islet cell carcinoma, intraoccular melanoma, Kaposi's sarcoma, kidney cancer, laryngeal cancer, acute lymphoblastic leukemia, acute myeloid leukemia (AML), hairy cell leukemia, lip and oral cavity cancer, liver cancer, lung cancer (including non-small cell and small-cell lung cancers), cutaneous T-cell lymphoma, Hodgkin's lymphoma, non-Hodgkin's lymphoma, malignant fibrous histiocytoma, malignant mesothelioma, medulloblastoma, Merkel cell carcinoma, malignant mesothelioma, squamous neck cancer with occult primary, multiple endocrine neoplasia syndrome, multiple myeloma, mycosis fungoides, myelodysplastic syndromes, acute myeloid leukemia, myeloproliferative disorders, nasal cavity and paranasal sinus cancer, nasopharyngeal cancer, neuroblastoma, oropharyngeal cancer, osteosarcoma, ovarian cancer, ovarian epithelial cancer, ovarian germ cell tumour, pancreatic cancer, islet cell pancreatic cancer, parathyroid cancer, penile cancer, peritoneal cancer, pheochromocytoma, pituitary tumour, plasma cell neoplasms, pleuropulmonaryblastoma, post-transplant lymphoproliferative disorder, primary central nervous system lymphoma, primary liver cancer, primitive neuroectodermal tumours, prostate cancer, rectal cancer, renal cell (kidney) cancer, transitional cell cancer of the renal pelvis and ureter cancer, retinoblastoma, rhabdomyosarcoma, salivary gland cancer, soft tissue sarcoma, Sezary syndrome, skin cancer, skin melanoma, Merkel cell skin carcinoma, small intestine cancer, squamous cell cancer, squamous carcinoma of the lung, testicular cancer, thymoma, thymic carcinoma, thyroid cancer, gestational trophoblastic tumour, carcinoma of unknown primary site, urethral cancer, uterine cancer, uterine sarcoma, vaginal cancer, vulvar cancer, Wilms' tumour, as well as abnormal vascular proliferation associated with phakomatoses, edema (such as that associated with brain tumours), and Meigs' syndrome.

In one embodiment, the cancer may be breast cancer, myeloma or glioblastoma.

In one embodiment, the hematopoietic neoplasm may be a leukemia. The leukemia may be acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), acute myelogenousleukemia (AML) or chronic myelogenousleukemia (C L). In one embodiment, the cancer is AML.

As used herein, "subject" means any organism susceptible to developing a cancer.

Preferably, the subject is a mammal. The mammal may be a human, or may be a domestic, zoo, or companion animal. While it is particularly contemplated that the methods of the invention are suitable for humans, they are also applicable to veterinary treatment, including treatment of companion animals such as dogs and cats, and domestic animals such as horses, cattle and sheep, or zoo animals such as felids, canids, bovids, and ungulates and for use on laboratory animals including rats, mice, monkeys and apes.

"Treating" or "treatment" refers to both therapeutic treatment and prophylactic or preventative measures, wherein the aim is to prevent, ameliorate or slow down (lessen) a cancer.

"Preventing", "prevention", "preventative" or "prophylactic" refers to keeping from occurring, or to hinder, defend from, or protect from the occurrence of a condition, disease, disorder, or phenotype, including an abnormality or symptom. A subject in need of prevention may be prone to develop the condition.

The term "ameliorate" or "amelioration" refers to a decrease, reduction or elimination of a condition, disease, disorder, or phenotype, including an abnormality or symptom. A subject in need of treatment may already have the condition, or may be prone to have the condition or may be in whom the condition is to be prevented.

As used herein, "negative response to treatment" refers to a cancer lacking Bak gene or protein expression, or in which Bak protein activity is insufficient to induce apoptosis.

A subject with a cancer that is "unsuitable for treatment" with an Mcl-1 inhibitor is a subject in whom the cancer lacks Bak gene or protein expression, or in which Bak protein activity is insufficient to induce apoptosis.

As used herein, "treating a cancer" refers to inhibiting the growth and proliferation of neoplastic cells, and/or causing the death of neoplastic cells. Preferably, the treatment involves the administration of an effective amount of the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor.

An "effective amount" of the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor refers to an amount of the inhibitor(s) that is sufficient to inhibit, halt or eradicate the cancer being treated when the compound is administered alone or in conjunction with another agent. The treatment may involve the co-administration of more than one therapeutic compound. Co-administration may be simultaneous or sequential.

As used herein, "administer", "administering" and "administration" refer to contacting a subject with a compound. Administering may be achieved by any means by which the inhibitor maybe delivered to the site to be treated. Suitable types of administration include both systemic and localized forms of administration, such as intravenously, intraperitoneally, intranasally, transdermal^, topically, via implantation, subcutaneously, parentally, intramuscularly, orally and via adsorption.

As used herein, "medicament" refers to a medicine or therapeutic agent in a specified formulation. As used herein, "inhibitor", "inhibits" and "inhibition" refer to hindering, restraining or preventing a specified activity, for example the activity of a target protein.

An inhibitor may be a small molecule, a drug, a peptide, a protein or polypeptide including an antibody or antigen binding fragment thereof, or a nucleic acid such as short inhibitory nucleic acid (siNA, e.g. siRNA), short hairpin nucleic acid (shNA, e.g. shRNA), micro nucleic acid (miNA, e.g. miRNA), nucleic acid interference (NAi, e.g. RNAi), or an antisense nucleic acid. An nucleic acid inhibitor may be RNA or DNA.

An inhibitor, for example an Mcl-1 inhibitor, may inhibit its target protein. An inhibitor may inhibit transcription of the gene or DNA encoding the target protein. An inhibitor may inhibit translation of the RNA encoding the target protein into the target protein per se. An inhibitor may reduce the stability of the target protein. An inhibitor may inhibit another entity that in turn inhibits the target protein. I n other words, an inhibitor may act directly or indirectly on the target protein, e.g. Mcl-1 , i.e. the inhibitor may be a direct inhibitor or an indirect inhibitor. Accordingly, an Mcl-1 inhibitor may inhibit Mcl-1 protein. Alternatively or additionally, an Mcl-1 inhibitor may inhibit Mcl-1 transcription or translation.

It follows that an "Mcl-1 inhibitor" is an agent that hinders, restrains or prevents Mcl-1 from performing its biological activity. In the context of the present invention, the relevant biological activity of Mcl-1 is binding and keeping in check Bak protein. In one embodiment, an "Mcl-1 " inhibitor is SNS- 032, flavopiridol, cryptosphaerolide, TW-37 (CAS No. 877877-35-5), GX015-070 (CAS No. 803712- 17-6), lapatinib (CAS No. 231277-92-2), roscovitine (CAS No. 186692-46-6), CR8 (CAS No. 294646- 77-8), or EU-517.

An "Mcl-1 inhibitor" may be a "cyclin-dependent kinase inhibitor" or "Cdk inhibitor", which is an agent that hinders, restrains or prevents a Cdk from performing its biological activity. An "Mcl-1 inhibitor" may inhibit RNAP2. In the context of the present invention, a Cdk inhibitor may be an inhibitor of Cdk7 or Cdk9, and the "Cdk inhibitor" may be SNS-032 or flavopiridol that inhibits RNA polymerase II (RNAP2) activity and Mcl-1 gene transcription. Other relevant Cdk inhibitors include UCN-01 (CAS No. CAS Number: 1 12953-1 1 -4), E-7070 (CAS No.165668-41 -7), AZD 5438 (CAS No. 602306-29-6), ZK 304709, PHA 690509 (CAS No. 492445-28-0), PD 0332991 (CAS No. 571 190-30- 2), AG 024321 , RGB 286199, JNJ 7706621 (CAS No. 443797-96-4).

While not wishing to be bound to any particular theory, the inventors propose that inhibition of Cdk7 or Cdk9 inhibits phosphorylation, and hence activation, of RNAP2, thereby inhibiting transcription of the gene encoding Mcl-1. Accordingly, the biological activity of Mcl-1 is thereby inhibited.

Likewise, a "Bcl-2 or Bcl-x_L inhibitor" is an agent that hinders, restrains or prevents Bcl-2 or Bcl-x_L from performing its biological activity, relevantly, in combination with Mcl-1 , binding and keeping in check Bak protein. In one embodiment, a "Bcl-2 or Bcl-x_L inhibitor" is EU-517, gossypol (CAS No. 303-45-7), obatoclax, chelerythrine (e.g. CAS No. 34316-15-9), Z36, or 2,3-DCPE hydrochloride (CAS No. 418788-90-6). In one embodiment, a "Bcl-2 or Bcl-x_L inhibitor" is ABT199, ABT-737 or ABT-263. In one embodiment, a "Bcl-2 or Bcl-x_L inhibitor" comprises Bcl-2 or Bcl-x_L antisense or RNA interference technology. In one embodiment, a "Bcl-2 or Bcl-x_L inhibitor" is a BAD BH3-like mimetic.

A "kinase inhibitor" is an agent that hinders, restrains or prevents a kinase from performing its biological activity. For the purpose of the present invention, a "kinase inhibitor" may be a tyrosine kinase inhibitor, a serine/ threonine kinase inhibitor, a lipid kinase inhibitor, or a PI3K inhibitor.

As used herein, "PI3K inhibitor" includes any compound capable of inhibiting PI3K/ AKTV mTOR signalling. Examples of such compounds include A66 (C₁₇H₂₃N₅0₂S_2; CAS No. 1 166227-08- 2); AS 252424 (5-[1 -[5-(4-Fluoro-2-hydroxy-phenyl)-furan-2-yl]-meth-(Z)-ylidene]-thiazolidine-2,4- dione); AS-605240 (5-(6-Quinoxalinylmethylene)-2,4-thiazolidine-2,4-dione; C₁₂H₇N₃0₂S; CAS No. 648450-29-7); AZD6482 (C22H24N4O4; CAS No. 1173900-33-8); BAG956 (2-methyl-2-[4-(2-methyl-8- pyridin-3-ylethynyl-imidazo[4,5-c]quinolin-1 -yl)-phenyl]-propionitrile); BBD130 (2-Methyl-2-[4-(3- methyl-2-oxo-8-pyridin-3ylethynyl-2,3-dihydro-imidazo[4,5-c]quinolin-1 -yl)-phenyl]-propionitrile); BEZ235 (2-Methyl-2-[4-(3-methyl-2-oxo-8-quinolin-3-yl-2,3-dihydro-imidazo[4,5-c]quinolin-1 -yl)- phenyl]-propionitrile; C₃oH₂3N₅0; CAS No. 915019-65-7); BKM-120 (C₁₈H2i F₃N₆0₂; CAS No. 1202777-78-3); CAL101 (C₂₂H₁₈FN₇0; CAS No. 870281 -82-6); D-87503 (C₁₇H₁₆N₅OS; CAS No. 800394-83-6); D-106669 (C₁₇H₁₈N₆0; CAS No. 938444-93-0); Deguelin ((7aS, 13aS)-9, 10-Dimethoxy- 3,3-dimethyl-13, 13a-dihydro-3H,7aH-pyrano[2,3-c;6,5-f']dichromen-7-one); demethoxyviridin; GDC- 0941 (2-(1 H-lndazol-4-yl)-6-(4-methanesulfonyl-piperazin-1 ylmethyl)-4-morpholin-4-yl-thieno[3,2- d]pyrimidine bismesylate; C₂₃H₂₇N₇0₃S₂; CAS No. 957054-30-7); GSK1059615 (GSK615; 5-[[4-(4- Pyridinyl)-6-quinolinyl]methylene]-2,4-thiazolidenedione; C^Hn NaOzS; CAS No. 958852-01 -1 ); GSK2126458 (GSK212; C₂₅H₁₇F₂N₅0₃S; CAS No. 1086062-66-9); IC871 14 (C₂₂H₁₉N₇0; CAS No. 371242-69-2); KU-55933 (2-Morpholin-4-yl-6-thianthren-1 -yl-pyran-4-one); LY294002 (2-(4- Morpholinyl)-8-phenyl-4H-1 -benzopyran-4-one; C₁₉H₁₇N0₃; CAS No. 154447-36-6); 3-Methyladenine (3-Methyl-3H-purin-6-amine; C₆H₇N₆; CAS No. 5142-23-4); MK-2206 (8-(4-(1 - aminocyclobutyl)phenyl)-9-phenyl-8,9-dihydro-[1 ,2,4]triazolo[3,4-fJ[1 ,6]naphthyhdin-3(2H)- one);myricetin (3,5,7-trihydroxy-2-(3,4,5-trihydroxyphenyl)-4H-1 -benzopyran-4-one; C₁₅H₁₀O₈; CAS No. 529-44-2); NU 7026 (2-(4-Morpholinyl)-4H-naphthol[1 ,2-£>]pyran-4-one; C₁₇H₁₅N0₃; CAS No. 154447-35-5); NU 7441 (8-Dibenzothiophen-4-yl-2-morpholin-4-yl-chromen-4-one); OSU-03012 (2- Amino-N-[4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1 H-pyrazol-1 -yl]phenyl]-acetamide; C₂6H₁₉F₃N₄0; CAS No. 742112-33-0); Perifosine (1 , 1 -dimethylpiperidinium-4-yl octadecyl phosphate); P1103 (3-[4- (4-Morpholinylpyhdo[3',2':4,5]furo[3,2-d]pyrimidin-2-yl]phenol hydrochloride; C₁₉H₁₆N₄0₃; CAS No. 371935-74-9); PI828 (2-(4-Morpholinyl)-8-(4-aminopheny)l-4H-1 -benzopyran-4-one; C₁₉H₁₈N₂0₃; CAS No. 942289-87-4); PIK-293 (C₂₂H₁₉N₇0; CAS No. 900185-01 -5); PIK-294 (C₂₈H₂₃N₇0₂; CAS No. 900185-02-6); PIK75 (N'-[(1 E)-(6-bromoimidazo[1 ,2-a]pyridin-3-yl)methylene]-N,2-dimethyl-5- nitrobenzenesulfonohydrazide hydrochloride; CAS No. 372196-67-3); PIK90 (N-(7,8-Dimethoxy-2,3- dihydro-imidazo[1 ,2-c]quinazolin-5-yl)-nicotinamide; C₁₈H₁₇N₅0₃; CAS No. 677338-12-4); PI K93 (C₁₄H₁₆CIN₃0₄S₂; CAS No. 593960-1 1 -3); PKI-587 (C₃₂H₄iN₉0₄; CAS No. 1 197160-78-3); PP-121 (1 - Cyclopentyl-3-(1 /-/-pyrrolo[2,3-£>]pyridin-5-yl)-1 /-/-pyrazolo[3,4-c/]pyrimidin-4-amine; C₁₇H₁₇N₇; CAS No. 1092788-83-4); PX-866 ([(3aR,6£,9S,9aR, 10R, 11 aS)-6-[[bis(prop-2-enyl)amino]methylidene]-5- hydroxy-9-(methoxymethyl)-9a, 1 1 a-dimethyl-1 ,4,7-trioxo-2,3,3a,9, 10, 1 1-hexahydroindeno[4,5- h]isochromen-10-yl] acetate; C₂₉H₃₅N0₈; CAS No. 502632-66-8); quercetin (sophoretin; C₁₅H₁₀O₇; CAS No. 1 17-39-5); SF1 126 ((3S)-4-[[(1 S)-1 -carboxy-2-hydroxyethyl]amino]-3-[[2-[[(2S)-5- (diaminomethylideneamino)-2-[[4-oxo-4-[[4-(4-oxo-8-phenylchr^

yl]methoxy]butanoyl]amino]pentanoyl] amino]acetyl] amino]-4-oxobutanoic acid acetate; C₄₁ H₅₂N₈0₁₆); tandutinib (1 -piperazinecarboxamide, 4-[6-methoxy-7-[3-(1 -piperidinyl)propoxy]-4- quinazolinyl]-N-[4-(1 -methylethoxy)phenyl]-); tetrodotoxin citrate; TG100-1 15 (C₁₈H₁₄N₆0₂; CAS No. 677297-51 -7); TGX-1 15 (8-(2-Methylphenoxy)-2-(4-morphonilyl)-4(1 H)-quinolinone; C₂oH₂₀N₂O₃; CAS No. 351071 -62-0); TGX-221 (7-Methyl-2-(4-morpholinyl)-9-[1 -(phenylamino)ethyl]-4H-pyrido-[1 ,2- a]pyrimidin-4-one; C21 H24N4O2; CAS No. 663619-89-4); thioperamide maleate; WHI-P 154 (2-Bromo- 4-[(6,7-dimethoxy-4-quinazolinyl) amino]phenol; C₁₆H₁₄BrN₃0₃; CAS No. 21 1555-04-3); wortmannin; XL147 (C₂₁ H₁₆N₆0₂S₂; CAS No. 956958-53-5); XL765 (C₃iH₂₉N₅0₆S; CAS No. 1 123889-87-1 ); ZSTK474 (C₁₉H₂₁ F₂N₇0_2; CAS No. 4751 10-96-4). In particular embodiments, PI K-75 or YM-024may be used to inhibit the p1 10a isoform of PI3K, TGX-221 , IC871 14 and AS252424 may be used to inhibit the ρ1 10β- , p1 105- and ρ110γ isoforms of PI3K, respectively, LY294002 and Wortmannin may be used as pan-specific PI3K inhibitors, and BEZ235 and PI-103 may be used as dual PI3K/mTOR inhibitors.

The kinase inhibitor, PIK3 inhibitor or FLT3 inhibitor may be a PIK-75 analogue. As used herein, an "analogue" is a small molecule that is chemically structurally related to PIK-75 and possesses similar biological activity to PIK-75, i.e. at least binds to and inhibits Cdk7 or Cdk9 and PI3K or at least binds to and inhibits Cdk7 or Cdk9 and FLT3.

In another embodiment, the kinase inhibitor or PIK3 inhibitor may be a PIK-75 mimetic. As used herein, a "mimetic" is an agent, e.g. a small molecule, that possesses similar biological activity to PIK-75, i.e. at least binds to and inhibits Cdk7 or Cdk9 and PI3K.

An "analogue" is also a "mimetic", but a "mimetic" is not necessarily an "analogue".

An "FLT3 inhibitor" may be tyrphostin AG 1296, CEP-701 (Lestaurtinib), 5'-

Fluoroindirubinoxime (CAS No. 861214-33-7), SU5416 (CAS No. 204005-46-9), SU1 1248 (CAS No. 341031 -54-7), PKC412 (CAS No. 120685-1 1 -2), MLN518 (CAS No. 387867-13-2), NVP-AST487, Fl- 700, Flt3 Inhibitor IV (CAS No. 819058-89-4), AC220 (CAS No. 950769-58-1 ), TKI258 (Dovitinib; CAS No. 405169-16-6), Ponatinib or Sorafenib (CAS No. 284461 -73-0).

As used herein, detecting Bak expression "in the cancer" may entail obtaining a sample of the cancer, cancer cells or cancerous tissue and then determining the level of Bak expression or function in the sample. Bak expression may be gene expression (e.g. RNA transcription) or protein expression (e.g. protein translation).

A "sample" may be obtained from the cancer by methods known in the art. Such methods include phlebotomy, fine needle aspiration, core needle biopsy, vacuum assisted biopsy, large core biopsy, open surgical biopsy, shave biopsy, punch biopsy and elliptical biopsy. In the case of a leukemia, the sample may comprise blood, bone marrow aspirate, bone marrow trephine, cytology, tissue biopsy and Bak expression is detected in leukemic cells.

The step of "detecting" absence or presence of Bak protein in the cancer may be conducted by any method known to the person skilled in the art for detecting proteins including, but not limited to, for example immunoassays such as, for example ELISA, enzyme immunoassay (EIA), Western blot, slot blot, dot blot, or immunoprecipitation followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, (SDS-PAGE), chromatography and the like. Dendrimer-enhanced radial partition immunoassays and immunofluorescence assays, for example, are known in the art and are commercially available.

One exemplary agent for detecting Bak protein is an antibody, or antigen binding fragment thereof, capable of specifically binding to Bak protein. The antibody may detectably labelled, either directly or indirectly.

Anti-Bak antibodies are commercially available from suppliers such as Abeam and include rabbit monoclonal [Y164] (ab32371 ), mouse monoclonal [AT8B4] (ab104124), and rabbit polyclonal (ab69404 and ab62486) antibodies.

Immunoassays for Bak protein may comprise incubating a sample with a detectably labelled antibody, or antibody fragment, capable of specifically binding Bak protein, and detecting the bound antibody by any of a number of techniques known in the art. As discussed in more detail below, the term "labelled" may refer to direct labelling of the antibody via, e.g., coupling (i.e., physically linking) a detectable substance to the antibody, and may also refer to indirect labelling of the antibody by reactivity with another reagent that is directly labelled. An example of indirect labelling includes detection of a primary antibody using a fluorescently labelled secondary antibody.

The sample maybe brought in contact with and immobilised on a solid support or carrier, or other solid support, which is capable of immobilising soluble proteins. The support may then be washed with suitable buffers followed by treatment with the detectably labelled antibody. The solid support may then be washed with the buffer a second time to remove unbound antibody. The amount of bound label on solid support may then be detected by conventional methods.

By "solid support or carrier" is intended any support capable of binding an antigen or an antibody. Well-known supports or carriers include nitrocellulose, glass, polystyrene, polypropylene, polyethylene, dextran, nylon, amylases, natural and modified celluloses, polyacrylamides and magnetite. The nature of the solid support or carrier may be either soluble to some extent or insoluble. The solid support may have virtually any possible structural configuration so long as the coupled molecule is capable of binding to an antigen or antibody. Thus, the support configuration may be spherical, as in a bead, or cylindrical, as in the inside surface of a test tube, or the external surface of a rod. Alternatively, the surface may be flat such as a sheet, test strip, etc. Those skilled in the art will know many other suitable carriers for binding antibody or antigen, or will be able to ascertain the same by use of routine experimentation.

One of the ways in which an antibody specific for Bak protein may be detectably labelled is by linking the antibody to an enzyme for use in an enzyme immunoassay. The enzyme bound to the antibody will react with an appropriate substrate, preferably a chromogenic substrate, in such a manner as to produce a chemical moiety which may be detected, for example, by spectrophotometric, fluorimetric or by visual means. Enzymes that may be used to detectably label the antibody include, but are not limited to, malate dehydrogenase, staphylococcal nuclease, delta-5-steroid isomerase, yeast alcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, triose phosphate isomerase, horseradish peroxidase, alkaline phosphatase, asparaginase, glucose oxidase, beta-galactosidase, ribonuclease, urease, catalase, glucose-6-phosphate dehydrogenase, glucoamylase and acetylcholinesterase. The detection and measurement may be accomplished by colorimetric methods which employ a chromogenic substrate for the enzyme. Detection and measurement may also be accomplished by visual comparison of the extent of enzymatic reaction of a substrate in comparison with similarly prepared standards.

Detection and measurement may also be accomplished using any of a variety of other immunoassays. For example, by radioactively labelling the antibody or functional antibody fragment, it is possible to detect Bak protein through the use of a radioimmunoassay (RIA). The radioactive isotope (e.g., ¹²⁶1 , ¹³¹1, ³⁵S, ³²P or ³H) may be detected by such means as the use of a gamma counter or a scintillation counter or by autoradiography.

It is also possible to label the antibody with a fluorescent or luminescent compound. When the fluorescently labelled antibody is exposed to light of the appropriate wavelength, its presence may then be detected due to fluorescence. Among the most commonly used fluorescent labelling compounds are fluorescein isothiocyanate, rhodamine, phycoerythrin, phycocyanin, allophycocyanin, o-phthaldehyde and fluorescamine.

The antibody may also be detectably labelled using fluorescence emitting metals such as ¹⁵²Eu, or others of the lanthanide series. These metals may be attached to the antibody using such metal chelating groups as diethylenetriaminepentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA).

Fluorescence energy transfer compounds may also be employed.

The antibody also may be detectably labelled by coupling it to a chemiluminescent compound. The presence of the chemiluminescent-tagged antibody is then determined by detecting the presence of luminescence that arises during the course of a chemical reaction. Examples of particularly useful chemiluminescent labelling compounds are luminol, isoluminol, theromaticacridinium ester, imidazole, acridinium salt and oxalate ester. Likewise, a bioluminescent compound may be used to label the antibody. Bioluminescence is a type of chemiluminescence found in biological systems in, which a catalytic protein increases the efficiency of the chemiluminescent reaction. The presence of a bioluminescent protein is determined by detecting the presence of luminescence. Important bioluminescent compounds for purposes of labelling are luciferin, luciferase and aequorin.

In another embodiment, specific binding molecules other than antibodies, such as aptamers, may be used to bind Bak protein.

Other means for detecting Bak protein include chromatography or electrophoresis with dye- based detection, or proteomics approaches employing spectrometry such as mass spectrometry. Spectrometry may be used to measure dye-based assays, including visible dyes, and fluorescent or luminescent agents.

A protein chip assay may be used to measure Bak protein.

Bak protein may also be detected, measured or assayed using of one or more of the following methods. For example, methods may include nuclear magnetic resonance (NMR) spectroscopy, a mass spectrometry method, such as electrospray ionization mass spectrometry (ESI- MS), ESI-MS/MS, ESI-MS/( S)n (n is an integer greater than zero), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS), desorption/ionization on silicon (DIOS), secondary ion mass spectrometry (SIMS)3 quadrupole time-of-flight (Q-TOF), atmospheric pressure chemical ionization mass spectrometry (APCI- S), APCI-MS/MS, APCI-( S), atmospheric pressure photoionization mass spectrometry (APPI-MS), APPI-MS/MS, and APPI-(MS). Other mass spectrometry methods may include quadrupole, Fourier transform mass spectrometry (FTMS) and ion trap. Other suitable methods may include chemical extraction partitioning, column chromatography, ion exchange chromatography, hydrophobic (reverse phase) liquid chromatography, isoelectric focusing, one-dimensional polyacrylamide gel electrophoresis (PAGE), two-dimensional polyacrylamide gel electrophoresis (2D-P AGE) or other chromatography, such as thin-layer, gas or liquid chromatography, or any combination thereof.

In one embodiment, LDI-TOF-MS allows the generation of large amounts of information in a relatively short period of time. A biological sample is applied to one of several varieties of a support that binds Bak protein in the sample. Samples are applied directly to these surfaces in volumes as small as 0.5 μΙ_, with or without prior purification or fractionation. The sample may be concentrated or diluted prior to application onto the support surface. Laser desorption/ionization is then used to generate mass spectra of the sample in as little as three hours.

A bead assay may be used to measure Bak protein.

As used herein, Bak protein "function" refers to the ability of Bak protein to induce apoptosis when released by cl-1 and/or Bcl-x_L. Bak protein may be absent from the cancer such that Bak activity is also absent. Otherwise, Bak protein may be present in the cancer, but may be expressed at a level insufficient to induce apoptosis when released by Mcl-1 and/or Bcl-x_L. Alternatively, Bak protein may comprise an amino acid change, e.g. substitution, deletion or insertion, that renders the expressed Bak protein insufficient to induce apoptosis when released by Mcl-1 and/or Bcl-x_L.

Accordingly, as used herein, "non-functional Bak protein" includes Bak protein possessing reduced or no apoptotic induction activity and Bak protein expressed at levels insufficient to induce apoptosis when released by Mcl-1 and/or Bcl-x_L.

As used herein, "expression" or "expressed" refers to transcription producing RNA from

DNA and may also refer to translation producing protein or polypeptide from RNA. The person skilled in the art will understand that the definition of "expression" or "expressed" will be dictated by context. Accordingly, a method of the invention may comprise detecting Bak RNA expression and/or Bak protein expression.

If Bak protein is detected in the cancer and is sufficient to induce apoptosis when released by Mcl-1 and/or Bcl-x_L, Bak protein is considered to be "present and functional".

The BH3 region of Bak appears to be necessary for inducing apoptosis. An amino acid change in the BH3 region may alter the conformation of the BH3 region and its ability to induce apoptosis. One amino acid change in the BH3 region that renders Bak protein non-functional is L78A of SEQ ID NO: 1. As known to one skilled in the art, apoptosis in response to Mcl-1 inhibition or Mcl-1 and Bcl-x_L inhibition and subsequent Bak protein release may be assayed by performing a caspase assay, a TUNEL or DNA fragmentation assay, a cell permeability assay, an annexin V assay, a protein cleavage assay, or a mitochondrial or ATP/ADP assay.

The caspases are a group of aspartic acid-specific cysteine proteases which are activated during apoptosis. These unique proteases, which are synthesized as zymogens, are involved in the initiation and execution of apoptosis once activated by proteolytic cleavage. Caspase assays are based on the measurement of zymogen processing to an active enzyme and proteolytic activity.

TUNEL and DNA Fragmentation Assays are based on the cleavage of DNA into 180- 200 b.p. increments during the execution phase of apoptosis.

Annexin V is a highly conserved 35 kDa protein that forms the voltage-dependent Ca²⁺ channels in phospholipid bilayers. This calcium-dependent protein binds to phosphatidylserine normally situated on the inner surface of the cytoplasmic membrane. During apoptosis, phosphatidylserine is translocated to the outer surface, thus enabling it to be detected indirectly by annexin V staining.

Methods for measuring the expression level of a nucleic acid, i.e. transcription of the gene encoding Bak protein, include both direct and indirect methods, such as quantitative real time polymerase chain reaction (Q-RT-PCR), array and Northern blot.

Measuring the expression level of the gene encoding Bak protein may occur after a cancer has been diagnosed and prior to initiation of a standard of care cancer therapy (e.g., surgery, chemotherapy, or radiotherapy). I n some embodiments, measuring the expression level of the gene encoding Bak protein occurs after a cancer has become resistant to a standard of care therapy. These embodiments are not mutually exclusive.

In certain embodiments, therapeutic agents of the invention may be used alone. Alternatively, the agents may be used in combination with other conventional anti-cancer therapeutic approaches directed to treatment or prevention of proliferative disorders (e.g., tumour). For example, such methods may be used in prophylactic cancer prevention, prevention of cancer recurrence and metastases after surgery, and as an adjuvant of other conventional cancer therapy. The present invention recognizes that the effectiveness of conventional cancer therapies (e.g., chemotherapy, radiation therapy, phototherapy, immunotherapy, and surgery) may be enhanced through the use of a subject therapeutic agent.

To assess the expression level of the gene encoding Bak protein, the level of the gene encoding Bak protein in the cancer may be subjected to one or more of various comparisons. It may be compared to: (a) the corresponding expression level in a non-cancerous tissue from the organ in which the cancer originated in the same or a different subject; (b) the corresponding expression level in a collection of comparable cancer samples; (c) the corresponding expression level in a collection of non-cancerous samples; or (d) the corresponding expression level in an arbitrary standard. Any of these comparative expression levels may be the "reference Bak expression level". Optionally, "comparing" may include statistical distribution information for the multiple measurements, such as standard deviation. In some embodiments, the Bak expression level in a cancer is compared to a predetermined "cut-off' reference Bak expression level that has been determined from observations to represent a measure of Bak expression that is predictive of efficacy of treatment with an cl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor. Determination of a suitable cut-off is made using, e.g., statistical analysis of Bak expression level data collected from multiple non-cancerous and/or cancerous samples. If a "cut-off' value is employed, the cut-off concentration may be determined statistically to have optimal discriminating value for subjects who would respond positively to treatment with an Mcl- 1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor (e.g., to have maximum sensitivity and specificity). It will be appreciated that statistical analysis of a dataset will permit clinicians to make informed decisions based on concentrations other than the optimal discriminating concentration (e.g., above or below the optimal discriminating concentration).

Considerations regarding a positive response to treatment of a cancer with an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor based on measurement of Bak expression levels, versus the probability of success of alternative therapies based on any available clinical data, may guide the selection of an appropriate cut-off concentration of the Bak expression level for making a treatment decision.

In one embodiment, the expression level in the cancer of the gene encoding Bak protein compared to the reference Bak expression level is less than 50%. Alternatively, the expression level in the cancer of the gene encoding Bak protein compared to the reference Bak expression level is less than 100, 99, 98, 97, 96, 95, 94, 93, 92, 91 , 90, 89, 88, 87, 86, 85, 84, 83, 82, 81 , 80, 79, 78, 77, 76, 75, 74, 73, 72, 71 , 70, 69, 68, 67, 66, 65, 64, 63, 62, 61 , 60, 59, 58, 57, 56, 55, 54, 53, 52, 51 , 49, 48, 47, 46, 45, 44, 43, 42, 41 , 40, 39, 38, 37, 36, 35, 34, 33, 32, 31 , 30, 29, 28, 27, 26, 25, 24, 23, 22, 21 , 20, 19, 18, 17, 16, 15, 14, 13, 12, 1 1 , 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 %.

Also disclosed is a method of identifying a compound that inhibits Mcl-1 and a kinase, the method comprising contacting Cdk7 or Cdk9 with the compound and determining binding and inhibition of Cdk7 or Cdk9 kinase activity, and contacting PI3K or FLT3 with the compound and determining binding and inhibition of PI3K or FLT3 kinase activity, wherein binding to and inhibition of Cdk7 or Cdk9 and PI3K or FLT3 identifies a compound that inhibits Mcl-1 and a kinase, wherein the identified compound is suitable for treating a cancer in which Bak is expressed.

Also disclosed is a kit comprising Cdk7 or Cdk9 and a kinase. The kit may comprise the isolated Cdk7 or Cdk9 protein and/or the kinase protein, may comprise cells expressing Cdk7 or Cdk9 and/or the kinase, or may comprise Cdk7 or Cdk9 and/or the kinase in conjunction with another moiety such as a solid support. As used herein, "means to express" includes a nucleic acid molecule, such as a vector or plasmid, encoding Cdk7 or Cdk9 and/or the kinase, and a cell transformed or transfected with a nucleic acid molecule encoding Cdk7 or Cdk9 and/or the kinase from which Cdk7 or Cdk9 proteins and/or the kinase protein is expressed. The kit may be used in the above method of identifying. The kinase may be PI3K or FLT3.

In one embodiment, the kit comprises Cdk7 or Cdk9, or means to express Cdk7 or Cdk9, and a kinase, or means to express a kinase, when used according to the above method of identifying. The kinase may be PI3K or FLT3. A compound identified by the above method of identifying may be used in a method for treating a cancer in a subject according to the third aspect.

With respect to the above method of identifying, the person skilled in the art will know how to determine binding of a compound to Cdk7 or Cdk9 and PI3K or FLT3. However, for clarity, as used herein, "determining binding" refers to the detection and identification of intermolecular interaction between the compound and Cdk7, Cdk9, PI3K and/or FLT3 as receptors for the compound. "Determining binding" may be achieved using a competition assay, an example of which is disclosed herein. Other methods for "determining binding" include surface plasmon resonance, dual polarisation interferometry, and Microscale Thermophoresis (MST).

The method of identifying may be carried out in vitro.

The invention also provides a kit comprising a reagent when used for detecting absence or presence of Bak protein in the cancer according to the method of the first or second aspect, and/or a reagent when used for determining Bak protein function according to the method of the first or second aspect. The reagent of such a kit may comprise a Western blot, flow cytometry, immunohistochemistry or an ELISA reagent (e.g. antibody),an array reagent, a sequencing reagent, a PCR reagent, a Q-RT-PCR reagent (e.g. polymerase, oligonucleotide), a restriction enzyme, or a Northern blot reagent necessary to carry out the described methods.

A kit may include instructions for carrying out a method of the invention.

Also disclosed is a kit comprising an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor when used according to the method of the third aspect.

Also disclosed is a medicament comprising an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl- xL inhibitor when used according to the method of the third aspect.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It must also be noted that, as used in the subject specification, the singular forms "a", "an" and "the" include plural aspects unless the context clearly dictates otherwise.

It will be apparent to the person skilled in the art that while the invention has been described in some detail for the purposes of clarity and understanding, various modifications and alterations to the embodiments and methods described herein may be made without departing from the scope of the inventive concept disclosed in this specification. EXAMPLES

Reagents

Rapamycin, LY294002 (CAS No. 1 54447-36-6), PI-103 (CAS No. 371935-74-9), TGX-221 (CAS No. 663619-89-4), AS252424 (CAS No. 900515-16-4) and zVAD-fmk (CAS No. 187389-52-2) were from Calbiochem; PIK-75 (CAS No. 372196-67-3) was from Symansis (New Zealand) and Axon Medchem (The Netherlands); RAD001 (Everolimus; CAS No. 159351 -69-6), BEZ235 (CAS No. 915019-65-7) and SNS-032 (BMS-387032;CAS No. 345627-80-7) were from Selleck Chemicals (Houston, TX); Akt Inhibitor 1 (1 L-6-Hydroxymethyl-chiro-inositol-2-[(R)-2-0-methyl-3-0- octadecylcarbonate]) was from MBL (Woburn, MA); AG1296 (Tyrphostin AG 1296;CAS No. 146535- 1 1-7) and flavopiridol (CAS No. 146426-40-6) were from Sigma-Aldrich; CEP-701 (Lestaurtinib; CAS No. 1 1 1358-88-4) was from Cephalon (Frazer, PA); YM-024 and IC871 14 (CAS No. 371242-69-2) were gifted from Australian Centre for Blood Diseases, VIC. Ara-C (Cytarabine; CAS No. 147-94-4) and Etoposide (CAS No. 33419-42-0) were from Pharmacia and Upjohn. Antibodies against phospho- Akt (Ser473), phospho-RNAP2 CTD (Ser2/5), RNAP2, ERK, Cdk9, phospho-Cdk9 (Thr186) and Bcl-2 were from Cell Signalling Technology. Anti-Mcl-1 was from Santa Cruz and Rockland. Anti-Bcl-x_L (clone 44) was from BD Pharmingen. Anti-CD34, -CD38, -CD123 were obtained from BD Biosciences. Anti-Bak, anti-PARP were from Cell Signalling Technology. Anti-B220, anti-CD3e, anti- CD1 1 b, anti-Ly6G, anti-Ly6A/E, anti-Ter1 19, anti-CD41 were from BD Biosciences. Goat anti-mouse and goat anti-rabbit IgG HRP were from Thermo Scientific. HSP70 antibody was gifted by Drs Welch and Anderson. Anti-bak, anti-Bax, anti-Bcl-xL and anti-Bcl-2 antibodies were gifted by Prof. David Huang from WEHI.

Cell lines and culture

MV4;1 1 cells were cultured in RPMI supplemented with 10% fetal calf serum (FCS; JRH Laboratories). IL-3 factor dependent myeloid (FDM) cells from wild type and knockout mice were generated and cultured as previously described (Ekert ei a/. (2004) J. Cell Biol. 165, 835-842). U937 cells were maintained in IMDM and 10% FCS. HEK293T cells were transfected using lipofectamine 2000 (Invitrogen) in 0.5% FCS and DMEM for 4h.

Primary AML samples

Apheresis product, BM or peripheral blood samples were obtained from patients diagnosed with AML. AML patient samples were collected after informed consent according to institutional guidelines and studies were approved by the Alfred Hospital Human Research Ethics Committees. Mononuclear cells (MNC) were isolated by Ficoll-Hypaque density-gradient centrifugation and resuspended in PBS containing 0.1 % human albumin (CSL) (Powell ei a/. (2009) Blood 1 14, 4859- 4870). Morphological analysis revealed >70% AML blasts after Ficoll-Hypaque density-gradient centrifugation. FACS purification of primary human CD34+CD38-CD123+ LSPCs was performed as previously described (Powell ei a/. (2009) Blood 1 14, 4859-4870).

Cell Survival and Colony Assays

Cell survival was determined by either trypan blue exclusion, annexin V-FITC or annexin V- Alexa 568 (Roche) negativity, propidium iodide exclusion (5pg/ml, Sigma-Aldrich) or flow cytometer counting of viable cells in reference to Flow Count Fluorospheres (BD Biosciences) as described previously (Guthridge ef a/. (2000) Mol. Cell 6, 99-108; Guthridge ei a/. (2004) Blood 103, 820-827; Powell et al. (2009) Blood 1 14, 4859-4870). Enumeration was by a FACSCalibur (Becton Dickinson).

Generation of ceil iysates

Cells were harvested by centrifugation at 4°C, 1200rpm for 5 minutes. The supernatant was discarded, and the pellets were washed once with 4°C PBS (1 mL). The cells were pelleted by centrifugation at 4°C, 6000g for 5 minutes. The supernatant were discarded, and the cells resuspended in NP40 lysis buffer (10mM Tris-HCI, pH 7.4, 137mM NaCI, 10% glycerol, 1 % NP-40) supplemented with PMSF (1 x), a protease inhibitor (complete, Mini, EDTA-free, Roche, Cat No. 1 1 836 170 001 , 1x) and a phosphatase inhibitor (PhosSTOP, Roche, Cat. No. 04 906 845 001 , 1 x) at a ratio of 5 million cells: 100μΙ_ lysis buffer. Lysis was allowed to proceed for 10 minutes on ice. Unlysed material and debris were removed by centrifugation at 4°C, 13000rpm for 10 minutes using a benchtop centrifuge. 2μΙ_ of lysate was used for protein quantification, and the remaining lysate was mixed with 4X sample loading buffer (bromophenol-based 4x loading dye, or Li-Cor 928-40004 4x sample loading dye for Odyssey with 10% v/v beta-mercaptoethanol), heated to 100°C for 5 minutes, and then stored at -20°C.

Protein quantification assays

Protein quantification was performed in triplicate using Bio-Rad DC protein assay. 2μΙ_ of lysate is diluted 1 : 10 with milliQ water (2μΙ_ lysate:^L milliQ water), and 5μΙ_ of the lysate mixture was mixed with 25μΙ_ of solution AS (made up of 1 mL solution A, Cat No 500-01 13 and 20μΙ_ solution S Cat No 500-01 15) and 200μΙ_ of solution B (Cat No. 500-1 -01 14). The mixture was incubated in the dark for 15 minutes, and then analyzed by absorbance spectrometry at 595nm. The absorbance was compared to that of a standard curve generated by using known concentrations of bovine serum albumin.

SDS-PAGE immunoblotting

25-100μg of protein lysate was used for Western Blotting (depending on protein of interest).

Lysates were resolved on 8-12% polyacrylamide gels at 100V in SDS running buffer (25mM Tris base, 191.8mM glycine, 0.1 % SDS). The resolved proteins were transferred onto nitrocellulse (Amersham Hybond-ECL, GE Healthcare) or PVDF membranes (Immobilon, Cat No IPVH00010, Millipore) in transfer buffer (25mM Tris base, 191 .8mM Glycine, 10% v/v methanol). After blocking for 1 hour in 5% skim milk/BSA TBS-T (150mM NaCI, 10mM Tris base, 0.1 % Tween 20) or or Odyssey blocking buffer (Prod No 927-40000), the membranes were then incubated overnight with the antibody against the protein of interest (final antibody concentration of ^g/mL) diluted in 5% skim milk/BSA TBS-T/Odyssey blocking buffer. The membranes were washed 3 times in TBS-T or PBS, then incubated with indicated HRP-conjugated secondary antibody (DAKO) diluted in 5% skim milk/BSA in TBS-T/Odyssey blocking buffer for 1 hour. The membranes were washed 3 times in TBS- T/PBS, and the proteins detected by enhanced luminescence (SuperSignal West Pico chemiluminescent substrate, Thermo Scientific, Prod No. 34078) onto film (Agfa Curix Ortho HT-G Medical X-ray film) or fluorescence (Odyssey (Li-Cor) imaging system). Tab!e. Antibodies used

siRNA

Primary human AML cells were transfected using Lipofectamine RNA iMAX (Invitrogen) and 50nM BLOCK-iT fluorescent oligo (I nvitrogen) together with 50-1 OOnM of either ON-TARGET plus control siRNA, Mcl-1 siRNA or Cdk9 siRNA (Dharmacon).

Kinase Binding Assays

Affinity of PIK-75 for specific purified kinases was measured using a competition assay (Ambit Biosciences, CA). The assay was performed essentially as described (Fabian ei al. (2005) Nat. Biotechnol. 23, 329-336) by combining DNA-tagged kinase, immobilized ATP and PIK-75. The ability of PI K-75 to compete with the immobilized ATP was measured via quantitative PCR of the DNA tag.

PIK-75, PI3K p110a isoform-selective inhibitor, potently inhibits survival of AML cells

To demonstrate the relevance of targeting Mcl-1 in AML, the inventors have shown that Mcl- 1 is expressed in a number of AML cell lines including HEL, K562, Mv4;1 1 , OCI-AML3, U937 and HL60 cells (Figure 1 A). The inventors also show that Mcl-1 is expressed in primary AML samples and that this correlates with expression of phosphorylated C-terminal domain (CTD) of RNA polymerase 2 (RNAP2) (Figure 1 B). It has been shown previously that PI3K-regulated survival programs are constitutively active in AML. Therefore, the inventors compared the ability of PI3K p1 10 isoform- selective inhibitors to induce cell death in the MV4; 1 1 AML cell line, which expresses a gain-of- function mutant form of the FLT3 tyrosine kinase receptor in which there is an internal tandem duplication (FLT3-ITD). The imidazolidine derivative PIK-75, which has previously been shown to inhibit the p1 10a isoform of PI3K, demonstrated potent killing of AML cell lines (Figure 1 C) correlating with its ability to suppress RNAP2 CTD phosphorylation and Mcl-1 expression (Figure 1 C). Similar to flavopiridol which is a CDK7/9 inhibitor, PIK-75 but not the PI3K inhibitor LY294002 was able to inhibit Mcl-1 expression in factor dependent myeloid cells (FDM) (Figure 1 D). Compared to PIK-75, selective inhibitors of ρ1 10β- (TGX-221 ), ρ1 10δ- (IC871 14) and ρ110γ (AS252424) were less effective at inducing apoptosis (Figure 2Aa). Similar results were observed in the KG1 cell lines (data not shown). HL-60 cells were moderately resistant (not shown). The pro-apoptotic activity of PIK-75 is distinct from other inhibitors targeting the PI3K signalling pathway.

To determine if the activity of PIK-75 was specifically related to its ability to target the PI3K p110a isoform, additional pan-specific PI3K inhibitors (LY294002 and Wortmannin), dual PI3K/mTOR inhibitors (BEZ235) and a p1 10a-selective inhibitor (PI-103) were examined for their ability to induce cell death in the MV4;1 1 cell line (Figure 2B). Remarkably, the activity of PI K-75 was substantially greater than that seen with all other PI3K inhibitors (Figure 2B). Blockade of PI3K downstream targets such as Akt or mTOR in primary AML cells also failed to recapitulate the cell killing activity observed for PIK-75 (Figure 2C). Thus, while PIK-75 was originally identified as a PI3K p110a inhibitor, the present results demonstrated that its ability to induce apoptosis was clearly distinct from all other inhibitors of the PI3K pathway tested (Figure 2B), indicating that its mechanism of action was unlikely to be due to the inhibition of p1 10a alone. To recapitulate the activity of PIK-75 in targeting both Cdk9 or Mcl-1 together with Pi3K, siRNA-mediated knockdown of either Mcl-1 or Cdk-9 was combined with PI3K inhibition using either GDC-0941 or A66. This demonstrated significantly enhanced cell death in primary human AML blasts with the combined action of either targeting Cdk9 or Mcl-1 with PI3K inhibition (Figure 2D).

PIK-75 targets Mcl-1 to induce apoptosis in a Bak dependent manner.

Therefore, the inventors sought to further understand the mechanism by which PI K-75 induced apoptosis in AML cells and whether additional targets may be involved. The inventors first examined the ability of PI K-75 to promote cell death using factor-dependent myeloid (FDM) lines derived from mice in which specific pro-apoptotic members of the Bcl-2 family had been knocked out. While no significant differences in PIK-75 sensitivity were observed between wild type (wt) FDM cells and FDM knockout cells derived from either Bid'^', Bad ^~Bim ^/~ or Noxa^''^' Puma^''^' mice, FDM cells from BaW^1' mice were completely resistant to PI K-75, as were cells from Bax'^~ Bak'^~ double knockout mice (Figure 3A). FDM cells from Bax '^~ mice, however, were as sensitive to PIK-75 as wt FDM cells (Figure 3A). These findings indicated an important role for Bak in PIK-75-mediated apoptosis and potentially other Mcl-1 targeted drugs.

Given that PI K-75 induced apoptosis in a Bak-dependent manner (Figure 3A), the inventors considered the possibility that Bak protein levels might be reduced in some PIK-75-resistant primary AML samples. Examination of newly diagnosed AML cases showed that Bak was reduced/absent in several cases (Figure 3B) with proportionally more cases with complete Bak deficiency in patients with chemotherapy relapsed/refractory AML (Figure 3C). Thus, at least in some AMLs, reduced Bak expression may provide a mechanism by which leukemic cells can evade PIK-75-induced apoptosis. To verify the functional relevance of Bak deficiency in the mechanism of action of Mcl-1 targeted therapies, siRNA directed at Mcl-1 or Cdk9 in primary AML blasts alone and in combination with the PI3K inhibitor GDC0941 was performed (Figure 3D). The combination was effective in AML blasts expressing Bak (AML 7 from Fig 3B), but not in blasts with Bak deficiency (AML3 from Fig 3B). The requirement of Bak to enable Mcl-1 dependent killing of primary AML cells was also demonstrated by the reduced sensitivity of Bak low cells to PIK-75 induced apoptosis (Figure 3E). The pro-apoptotic activity of Bak is known to be held in check by Mcl-1 and Bcl-x_L raising the possibility that PIK-75 might target the pro-survival function of Mcl-1 and/or Bcl-x_L leading to Bak- dependent apoptosis. Therefore, the inventors examined whether PIK-75 affected the expression levels of Mcl-1 or Bcl-x_L. As expected, both PIK-75 and LY294002 blocked Akt phosphorylation in MV4; 1 1 cells (data not shown). However, PIK-75 treatment but not LY294002 resulted in a dramatic down-regulation of Mcl-1 protein levels while no significant reduction of Bcl-x_L or Bcl-2 was observed (Figure 1 C,D, 5B). Flavopiridol, which has been shown by others to reduce Mcl-1 expression, was also able to down-regulate Mcl-1 levels in a similar manner to PIK-75 (Figure 1 D). Furthermore, while two independent FLT3 tyrosine kinase inhibitors (AG1296 and CEP701 ) were able to down-regulate Akt phosphorylation, they only had modest effects on Mcl-1 levels (data not shown). These results demonstrate that in addition to its ability to inhibit PI3K signalling, PIK-75 possessed the unique ability to down-regulate Mcl-1 protein in a PI3K- and FLT3-independent manner.

Dual targeting of PI3K and Cdk9 by PIK-75 induces apoptosis in AML cells.

Cdk9 is a key regulator of Mcl-1 gene transcription through its ability to phosphorylate RNAP2, so the inventors considered the possibility that, in addition to its ability to inhibit PI3K p1 10a, PIK-75 may also directly inhibit Cdk9 kinase activity. In vitro kinase assays demonstrated high affinity binding of PIK-75 to the ATP binding pocket of Cdk9 (K_d=4-4.2nM), Cdk7 (K_d=1 .9-2.5nM) and FLT3- ITD (K_d=0.79-2nM), whereas the affinity for the related Cdk2 was over 100-fold lower (K_d=520- 550nM) (Figure 4a). The binding of PI K-75 to Cdk9 was in a similar range to that previously reported for PI3K p1 10a (IC50=5.8 nM). Thus, while PI3K p1 10a and Cdk9 belong to diverse ancestral branches of the kinome tree and are only 25% identical within their catalytic domains, PIK-75 is able to inhibit both kinases with IC50s in the low nanomolar range.

Consistent with the ability of PIK-75 to inhibit Cdk9 kinase activity, the phosphorylation of RNAP2 CTD on Ser2 and Ser5 was also suppressed (Figure 5, p RNA pol II CTD). Importantly, PIK- 75-mediated inhibition of RNAP2 CTD phosphorylation as well as Mcl-1 gene expression (Figure 4b) and protein down-regulation was similar to that mediated by Flavopiridol while there was no impact on Bcl-xL or Bcl-2 protein (Figure 5B). Furthermore, because LY294002 had no effect on the phosphorylation of RNAP2 CTD (Figure 5), the results indicate that the ability of PIK-75 to inhibit Cdk9 activity was not an indirect consequence of PI3K inhibition. Consistent with these observations in MV4; 1 1 cells, treatment of primary human AML cells with PIK-75 also down-regulated both RNAP2 CTD phosphorylation and Mcl-1 protein levels but had no significant impact on Bcl-2 levels (Figure 5B). Thus, these findings identify Cdk9 as a biologically important PIK-75 target and that inhibition of Cdk9 results in the blockade of de novo Mcl-1 gene transcription leading to the rapid down-regulation of Mcl-1 protein within the cell.

Discussion

Constitutive PI3K signalling and over-expression of Bcl-2 pro-survival proteins are two pivotal mechanisms by which malignant cells acquire the ability to over-ride apoptosis programs. In particular, PI3K and the Mcl-1 pro-survival protein are both deregulated with high frequency in cancer and therapeutics capable of simultaneously targeting both proteins may have clinical potential. The inventors now show that PIK-75, originally identified as a PI3K p1 10a inhibitor, potently and selectively induced apoptosis in AML cell lines and primary AML (Figures 1 C, 2 and 3E).

The ability of PIK-75 to target AML cells was not solely due to blockade of PI3K p1 10a, as both pan-specific PI3K inhibitors (LY294002, Wortmannin) and p1 10a-selective inhibitors (PI-103,) were significantly less effective at inducing apoptosis (Figure 2). In addition to its ability to inhibit p110a, PIK-75 was also able to reduce Mcl-1 protein levels while the levels of both Bcl-xL and Bcl-2 were unaffected (Figures 3 and 5). The highly plastic genetic and epigenetic landscape within transformed cells allows multiple independent signalling pathways to be recruited and corrupted not only during the tumorigenic process, but also in response to cytotoxic and targeted therapies. A clinical consequence of this plasticity is that blockade of a single oncogenic pathway while leaving others unperturbed may allow the survival of a reservoir of cells from which drug resistance and relapse can occur. Although Mcl-1 targeting alone may be sufficient to kill AML cell lines, the inventors show here that in primary AML blasts, a combination of Mcl-1 targeting (either directly or indirectly via Cdk9 targeting) may be necessary for optimal killing. Furthermore, Mcl-1 targeted therapies require the presence of pro-apoptotic Bak for effective cell death actions.

The relative balance between the expression of pro-survival and pro-death Bcl-2 family members sets an intrinsic threshold that controls the cell survival: death axis. Drugs that are capable of targeting members of the Bcl-2 pro-survival family are also under investigation. For example, ABT- 737 has been shown to inhibit the prosurvival activity of Bcl-2, Bcl-x_L and Bcl-w. However, it is becoming increasingly clear that a variety of malignancies including chronic and acute leukemias are resistant to ABT-737, in part due to Mcl-1 overexpression. Furthermore, Mcl-1 overexpression in a number of solid and hemopoietic malignancies is an independent prognostic indicator of poor patient outcomes. Thus, Mcl-1 represents an important therapeutic target and small molecule inhibitors that block upstream regulators of Mcl-1 expression (as opposed to targeting Mcl-1 directly with small molecule inhibitors such as BH3 mimetics) have the advantage of being able to rapidly deplete cellular pools of Mcl-1 protein due to its very short half-life. Thus, even transient blockade of Cdk9 results in almost complete loss of Mcl-1 and the rapid onset of apoptosis.

Mcl-1 heterodimerizes with, and inactivates, the pro-apoptotic activity of Bak. Thus, agents able to target Mcl-1 will sensitize cells to Bak-mediated apoptosis. Consistent with this, the inventors have shown that PIK-75 down-regulates Mcl-1 expression and induces apoptosis in a Bak-dependent manner (Figure 3). Clearly, one mechanism by which AML cells evade apoptosis induced by PIK-75 is through a loss of Bak expression. Note that the inventors have identified a subset of AML samples with reduced sensitivity to PIK-75 that also demonstrated decreased Bak expression (Figure 3).

Because Bcl-2 does not heterodimerize with Bak, transformed cells over-expressing Bcl-2 would not be resistant to drugs inducing Bak-dependent apoptosis such as PI K-75. In fact, PIK-75 was found to be a potent inducer of apoptosis even in those AML samples where Bcl-2 was overexpressed (data not shown). Thus, drugs, therapeutics or approaches that target the prosurvival activity or expression Mcl-1 can be effective in cancer samples that express active Bak. Furthermore, drugs, therapeutics or approaches that target the prosurvival activity or expression of Mcl-1 can be effective even in those transformed cells where other members of the Bcl-2 pro-survival family, such as Bcl-2, are over-expressed. The method of identifying disclosed herein can be used to identify compounds with similar activities to PIK-75 that will be useful in treatment of such cancers.

The present findings identify a new approach that enables targeting of AML cells and possibly other cancer cell types through the dual blockade of two independent biochemical pathways (PI3K and Cdk9 signalling) that converge to promote cell survival. Since both PI3K and Cdk inhibitors are already in trials, these findings provide an immediate clinical rationale for combining these inhibitors in the treatment of AML. Furthermore, the discovery of PIK-75 as a first-in-class dual PI3K p110a and Cdk9 inhibitor will pave the way for the identification of other dual kinase inhibitors for clinical development in AML. Significantly, the inventors have also shown that PIK-75 has potent cell killing activity against a spectrum of cancer cell lines derived from breast cancer, myeloma and glioblastoma (data not shown). Thus, the results indicate that the clinical application of dual PI3K/Cdk9 inhibitors represents an effective approach for treating diverse malignancies beyond AML and that detecting Bak expression is an important biomarker of activity with such drugs or drug combinations.

Claims

1. A method for predicting responsiveness of a cancer in a subject to treatment with an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor, the method comprising detecting Bak expression in a sample of the cancer and comparing the Bak expression level to a reference Bak expression level, wherein a reduced Bak expression level compared to the reference Bak expression level in or absence of Bak expression from the cancer predicts a negative response to treatment with the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor.

2. A method for identifying a subject with a cancer unsuitable for treatment with an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor, the method comprising detecting Bak expression in a sample of the cancer and comparing the Bak expression level to a reference Bak expression level, and identifying as unsuitable for Mcl-1 inhibitor treatment and optionally Bcl-2 or Bcl-x_L inhibitor treatment the subject in whom the Bak expression level is reduced compared to the reference Bak expression level or is absent from the cancer.

3. The method of claim 1 or claim 2, further comprising determining Bak protein function when Bak expression is detected, wherein non-functional Bak protein in the cancer predicts a negative response to treatment with the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor, or identifies the subject as unsuitable for treatment with the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor.

4. The method of claim 3, wherein determining Bak protein function comprises identifying an amino acid change in the Bak protein.

5. The method of claim 4, wherein the amino acid change is in the Bcl-2 homology 3 (BH3) region.

6. The method of claim 5, wherein the amino acid change is L78A of SEQ ID NO: 1.

7. The method of any one of claims 1 to 6, wherein reduced Bak expression level is defined by a Bak expression level in the cancer of less that 50% of the reference Bak expression level.

8. The method of claim 3, wherein non-functional Bak protein is defined by a Bak protein expression level of less that 50% of the reference Bak expression level.

9. A method for treating a cancer in a subject, the method comprising detecting Bak expression in a sample of the cancer, and administering to the subject in whom Bak expression is detected in the cancer an Mcl-1 inhibitor and optionally a Bcl-2 or Bcl-xL inhibitor.

10. The method of claim 9, further comprising determining Bak protein function when Bak expression is detected, and continuing administering to the subject in whom Bak protein is functional in the cancer the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor, and discontinuing administering to the subject in whom Bak protein is non-functional in the cancer the Mcl-1 inhibitor and optionally the Bcl-2 or Bcl-xL inhibitor.

11 . The method of any one of claims 1 to 10, wherein the Mcl-1 inhibitor inhibits RNA polymerase 2 (RNAP2).

12. The method of claim 1 1 , wherein the Mcl-1 inhibitor is a cyclin-dependent kinase inhibitor, optionally a Cdk7 or Cdk9 inhibitor.

13. The method of claim 12, wherein the Cdk7 or Cdk9 inhibitor is flavopiridol or SNS-032 (CAS No. 345627-80-7).

14. The method of any one of claims 1 to 13, wherein the Bcl-x_L inhibitor is a BAD BH3-like mimetic.

15. The method of claim 14, wherein the Bcl-x_L inhibitor is ABT-737 (CAS Number 852808-

04-9).

16. The method of any one of claims 1 to 15, further comprising administering a kinase inhibitor.

17. The method of claim 16, wherein the kinase inhibitor is a phosphoinositol 3 kinase (PI3K) inhibitor, a FMS-like tyrosine kinase receptor-3 (FLT3) inhibitor, a tyrosine kinase inhibitor or a serine/ threonine kinase inhibitor.

18. The method of claim 17, wherein the Mcl-1 inhibitor and the PI3K inhibitor comprises one compound, optionally PIK-75 or a PIK-75 analogue or mimetic.

19. A method of identifying a compound that inhibits Mcl-1 and a kinase, the method comprising contacting Cdk7 or Cdk9 with the compound and determining binding and inhibition of Cdk7 or Cdk9 kinase activity, and contacting PI3K or FLT3 with the compound and determining binding and inhibition of PI3K or FLT3 kinase activity, wherein binding to and inhibition of Cdk7 or Cdk9 and PI3K or FLT3 identifies a compound that inhibits Mcl-1 and a kinase, wherein the identified compound is suitable for treating a cancer in a subject in whom Bak expression is detected in the cancer.

20. The method of any one of claims 1 to 19, wherein the subject is human.