WO2018222432A1 - A predictive biomarker for let-7 microrna-based therapeutics for the treatment of human cancer - Google Patents

Abstract

The disclosure provides methods for suppressing BRAF-driven tumorigenesis by administering one or more lethal-7 miRNA-based therapeutics to a patient in need thereof. The disclosure also provides methods for treating cancer that has an active BRAF oncogene by administering one or more lethal-7 miRNA-based therapeutics to a patient in need thereof. The disclosure further provides methods for predicting favorable treatment responses to lethal-7 microRNA-based therapeutics by administering one or more lethal-7 miRNA-based therapeutics to a patient in need thereof; and monitoring active BRAF signaling for predicting favorable treatment responses in the patient.

Description

A PREDICTIVE BIOMARKER FOR LET-7 MICRORNA-BASED THERAPEUTICS FOR

THE TREATMENT OF HUMAN CANCER CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority benefit under 35 U.S.C § 119 to U.S. Provisional Patent Application Serial No. 62/511,993, titled "A NOVEL PREDICTIVE BIOMARKER FOR LET-7 MICRORNA-BASED ANTICANCER THERAPIES," filed on May 27, 2017, the disclosure of which is hereby incorporated by reference in its entirety for all purposes.

FIELD OF THE INVENTION

[0002] The present disclosure generally relates to biomarkers and more particularly, to a predictive biomarker for lethal-7 (let-7) microRNA-based therapeutics for the treatment of human cancer.

BACKGROUND OF THE INVENTION

[0003] MicroRNAs (miRNAs) suppress gene expression subsequent to transcription, can have broad reaching effects, and have emerged as important regulators of various aspects of tumorigenesis. Some miRNAs promote tumorigenesis, while others have been found to suppress the process.

[0004] Members of the let-7 family of miRNAs share very high sequence similarity and therefore, are believed to possess similar biological activities. The let-7 family of miRNAs were initially identified as tumor suppressors and subsequently, have been explored as potential therapeutics for the treatment of human cancer. For example, let-7 miRNAs have binding sites in the three-prime untranslated region (3'-UTR) of RAS and MYC oncogenes, and can specifically suppress the expression of these two oncogenes. This suppression has been shown to cause regression of tumorigenesis driven by RAS or MYC. Therefore, let-7 miRNAs have been proposed to be potential therapeutics for the treatment of human cancer driven by these two oncogenes.

SUMMARY OF THE INVENTION

[0005] The let-7 family of miRNAs has been intensively studied as both a tumor suppressor and therapeutic for the treatment of human cancer. Tumorigenesis driven by either of RAS or MYC is sensitive to suppression by let-7 miRNAs, because of the presence of let-7 binding sites in the 3'-UTR of these oncogenes. Tumors with driver oncogenes that are not let-7 targets, however, are not suspected to be suppressed by let-7 miRNAs. It was surprisingly discovered that tumorigenesis by BRAF^V600B was particularly susceptible to suppression by let-7, despite expression of the oncogene was not affected by let-7. Similar suppression was observed with fibroblasts and epithelial cell lines transformed by BRAF^V600E, mouse lung cancer initiated by a transgene of BRAF^V600E and human cancer cell lines that harbor BRAF^V600E. The cytokine IL-6 is a recognized facilitator of tumorigenesis and a known target for repression by let-7 miRNAs. Accordingly, the increased expression of let-7 miRNAs reduced the expression of IL-6 and disabling IL-6 with a neutralizing antibody mimicked overexpression of let-7 and impaired BRAF^v600E-driven tumorigenesis.

[0006] These findings indicate that BRAF-driven tumorigenesis is sensitive to suppression by let-7, this suppression is mediated at least partially through down-regulation of IL-6, let-7 could be useful to treat tumors that harbor BRAF^V600E, and BRAF^V600E might serve as a biomarker for predication of sensitivity to let-7 microRNA-based therapeutics. By contrast with these findings with BRAF^V600E, it also found that tumorigenesis driven by an active RAS allele lacking let-7 binding sites was enhanced by overexpression of let-7. The enhancement raises a safety concern issue regarding to the treatment of RAS tumors with let-7 miRNAs, strongly suggesting that such treatment should be approached with caution and sequencing of 3'-UTR of RAS must be conducted to exclude patients with an RAS allele resistant to let-7 miRNAs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present disclosure, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict exemplary embodiments of the disclosure. These drawings are provided to facilitate the reader's understanding of the disclosure and should not be considered limiting of the breadth, scope, size, or applicability of the disclosure. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale.

[0008] Figure 1 illustrates a variety of oncogenes that can elicit tumorigenesis when overexpressed in iMREC cells;

[0009] Figure 2 illustrates the effect of let-7 miRNAs on the histology of iMREC cells;

[0010] Figures 3A, 3B, and 3C illustrate the overexpression of let- 7b miRNAs delaying tumorigenesis;

[0011] Figures 4A, 4B, and 4C illustrate the overexpression of let-7 miRNAs enhancing tumorigenesis;

[0012] Figure 5 illustrates that Let-7 is ectopically expressed at comparable levels among cell lines that express a variety of oncogenes;

[0013] Figures 6A and 6B illustrate lung tumorigenesis driven by BRAF^V600E but not MYC is impeded by let-7 miRNAs;

[0014] Figures 7A and 7B illustrate let-7 miRNAs impedes tumorigenesis of human cancer cells that harbor BRAF^V600E mutations; and [0015] Figures 8A, 8B, and 8C illustrate that disabling IL6 delays tumorigenesis by

_BRAFV600E

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0016] The following description is presented to enable a person of ordinary skill in the art to make and use embodiments described herein. Descriptions of specific devices, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the disclosure. The word "exemplary" is used herein to mean "serving as an example illustration." Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Thus, the present disclosure is not intended to be limited to the examples described herein and shown but is to be accorded the scope consistent with the claims.

[0017] As used herein, reference to any biological daig includes any fragment, modification or variant of the biologic, including any pegylated form, glycosylated form, lipidated form, cyclized form or conjugated form of the biologic or such fragment, modification or variant or prodrug of any of the foregoing. As used herein, reference to any small molecule drug includes any salt, acid, base, hydrate, solvate, ester, isomer, or polymorph thereof or metabolite or prodrug of any of the foregoing.

[0018] It should be understood that the specific order or hierarchy of steps in the process disclosed herein is an example of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged while remaining within the scope of the present disclosure. Any accompanying method claims present elements of the various steps in a sample order and are not meant to be limited to the specific order or hierarchy presented. Abbreviations used herein have their conventional meaning within the chemical and biological arts.

[0019] As used herein, the terms "treating" or "treatment" in reference to a particular disease includes prevention of the disease.

[0020] In therapeutic and/or diagnostic applications, the disclosed miRNA-based therapeutics can be formulated for a variety of modes of administration, including systemic and topical or localized administration. Techniques and formulations generally may be found in Remington: The Science and Practice of Pharmacy (20^th ed.) Lippincott, Williams & Wilkins (2000).

[0021] The disclosed miRNA-based therapeutics are effective over a wide dosage range. For example, in the treatment of adult humans, dosages from 0.01 to 1000 mg, from 0.5 to 100 mg, from 1 to 50 mg per day, and from 5 to 40 mg per day are examples of dosages that may be used. Other dosages include 10 to 30 mg per day. The exact dosage will depend upon the route of administration, the form in which the compound is administered, the subject to be treated, the body weight of the subject to be treated, and the preference and experience of the attending physician,

[0022] Accordingly, the let-7 family of miRNAs have been demonstrated to possess tumor- suppressor activities. This family of miRNAs have an abundant presence in many human cancers, indicating that they might also have an oncogenic activity. Consistent with this hypothesis, it has been found that let-7 miRNAs can suppress expression of a variety of genes that function to restrict tumorigenesis. Thus, it is likely that let-7 miRNAs might elicit opposite roles in tumorigenesis in a molecular context-dependent manner. This complexity implies that clinical application of let-7 microRNA-based therapeutics requires a full understanding of the potential interaction between oncogenic signaling pathways and let-7 miKNAs.

[0023] A panel of isogenic model tumor cell lines were used to test their sensitivity to let-7 miRNAs in immunocompromised mice. Tumorigenesis promoted by an active RAS that lacks the let-7 binding site was enhanced, rather than suppressed by let-7. Let-7 also moderately enhanced tumorigenesis by AKT.

[0024] By contrast, tumorigenesis by a variety of other oncogenic elements including MYC, ID1, Bcl-2, and Survivin was not affected by let-7. Tumorigenesis driven by BRAF^V600E was found to be particularly sensitive to let-7. Similar suppression of BRAF^V600E-driven tumorigenesis was observed by let-7 in a variety of other cell lines from mouse and human cancer. This suppression could be partially attributed to suppression of cytokine IL-6, a recognized facilitator of tumorigenesis and a known target for repression by let-7 miRNAs.

[0025] These findings strongly support that let-7 miRNAs are useful for the treatment of BRAF-driven tumors, and active mutations of BRAF could be used as a biomarker to recruit patients for the anticancer treatment.

[0026] By contrast, treatment of tumors harboring RAS mutations has a previously unknown complication and requires sequencing of 3'-UTR of RAS to exclude patients whose let-7 binding sites are missing.

[0027] Results and Discussion

[0028] Generation of Isogenic Model Tumor Cell Lines from Mouse Renal Epithelial Cells

[0029] To identify oncogenic signaling pathways that might render cancer cells particularly sensitive to let-7-based therapy, immortalized moiise renal epithelial cells (iMREC) were generated. These cells did not form tumors within two months after being transplanted into immunocompromised mice. The iMREC were then infected with a variety of active oncogenes including H-RAS^V12D, MYC, MyrAKT, ID1, Bcl-2 and BRAF^V600B, and the infected cells were subjected to testing of tumor formation in mice.

[0030] As shown in Figure 1, a variety of oncogenes elicit tumorigenesis when overexpressed in iMREC cells. iMREC cell lines were infected with either control retrovirus (pMig) or retrovirus expressing a variety of oncogenes including MYC, H-RAS^V12G, BRAF^V600E, MyrAKT, Bcl-2 and ID1, and then implanted subcutaneously into athymic mice (one million cells per mouse and five mice in each group). Tumor volumes were measured at the indicated times and the average of tumor volumes are presented. As shown in this figure, iMREC cells infected with pMIG failed to form tumors within the time frame examined in this study.

[0031] As shown in Figure 2, cells transduced with any one of the above oncogenes rapidly formed adenocarcinomas that became detectable within 20 days after implantation with 100% penetrance and reached a volume of 300-1000 mm³ by day 40 (see, Figure 1). The effect of let- 7 miRNAs on histology of iMREC tumors iMREC cells that overexpress BRAF^V600E (a and b), MyrAKT (c and d) or H-RAS^V12D (e and r) were infected with either empty pMSCV virus (a, c and e) or let-7b virus (b, d and f), and then implanted into athymic mice to allow tumor formation. Histological analysis of size-matched tumors was performed with hematoxylin and eosin staining after fixation with PFA. This panel of the isogenic experimental system were then used to examine how distinct oncogenic signaling influence treatment responses to therapies that exploits let-7 miRNAs.

[0032] Let-7 miRNAs Elicit Distinct Responses in Model Tumor Cells that Express Different Oncogenes [0033] As shown in Figure 3, tumorigenesis by a variety of oncogenic elements including MYC, Bcl-2, Survivin and ID1 was not affected by let-7. That is, the over expression of let-7b miRNAs delays tumorigenesis driven by BRAF but not AKT or MYC.

[0034] As shown in Figure 3 A, iMREC cells were infected with either control retrovirus (pMSCV) or retrovirus expressing MYC and let-7b miRNAs either individually or in combination and then implanted subcutaneously into athymic mice (one million cells per mouse and ten mice in each group). Tumor volumes were measured at the indicated times. Error bars represent one standard deviation.

[0035] As shown in Figure 3B, iMREC cells were infected with either control retrovirus (pMSCV) or retrovirus expressing MyrAKT and let-7b miRNAs either individually or in combination and then implanted subcutaneously into athymic mice (one million cells per mouse and ten mice in each group). Tumor volumes were measured at the indicated times. Error bars represent one standard deviation.

[0036] As shown in Figure 3C, iMREC cells were infected with either control retrovirus (pMSCV) or retrovirus expressing BRAF^V600E and let-7b miRNAs either individually or in combination and then implanted subcutaneously into athymic mice (one million cells per mouse and ten mice in each group). Tumor volumes were measured at the indicated times. Error bars represent one standard deviation.

[0037] Surprisingly, tumorigenesis promoted by an active RAS that lacks the let-7 binding site was enhanced, rather than suppressed by let-7.

[0038] As shown in Figure 4, three different members of let-7 miRNAs, let-7b, let-7 c and let-7e exerted similar enhancement. As shown in this figure, overexpression of let-7 miRNAs enhances tumorigenesis by H-RAS^V12D, iMREC cells were infected with either control retrovirus (pMSCV) or retrovirus expressing H-RAS^V12D and a member of let-7 family of miRNAs either individually or in combination and then implanted subcutaneously into athymic mice (one million cells per mouse and ten mice in each group). Tumor volumes were measured at the indicated times. Error bars represent one standard deviation, (see, Figure 4A, let- 7b; Figure 4B, let-7c; and Figure 4C, let-7e).

[0039] In addition, let-7b moderately enhanced tumorigenesis driven by MyrAKT (see, Figure 3). These findings are in sharp contrast with the well demonstrated suppressor activity of let-7 miRNAs against tumorigenesis driven by an active RAS that has an intact 3'-UTR. This contrast raises caution regarding let-7 microRNA-based therapies against cancer,

[0040] The effect of ectopic expression of let-7 miRNAs on tumorigenesis driven by BRAF^V600E was then assessed. Overexpression of either let-7a or let-7b extended the length of tumor latency approximately three-fold compared with an empty pMSCV vector (see, Figure 3).

[0041] As a control, the effects of over- expressing mir-348 were examined, which has no sequence similarity with let-7 miRNAs. It was found that overexpression of mir-348 failed to delay tumorigenesis driven by BRAF.

[0042] As shown in Figure 5, the distinct responses to let-7 were not due to different levels of let-7 expression, since Tagman assays detected similar high levels of mature let-7 among various cell lines after retroviral induction of the microRNA. BRAF-driving tumorigenesis of

Rati A cells was also impeded by let-7a, suggesting that suppression of BRAF -driven tumorigenesis by let-7 is conserved between fibroblasts and epithelial cells.

[0043] Let-7 miRNAs Suppresses Both Mouse and Human Cancer Driven by Active BRAF

Signaling [0044] Tumors initiated by BRAF^V600E in vivo were tested to see if they could be suppressed by let-7. Overexpression of BRAF^V600E in mice has been shown to elicit adenocarcinomas in lung. The tumor cells from the mouse model can grow in vitro and develop tumors in recipient mice with 100% penetrance. This property allows for infecting of the BRAF lung tumor cells with let-7-expressing viruses in vitro and subsequently, testing the effect of let-7 on tumorigenesis upon transplantation of the infected cells into nude mice.

[0045] As shown in Figure 6, lung tumorigenesis driven by BRAF^V600E but not MYC is impeded by let-7 miRNAs. As shown in this figure, the overexpression of let~7b dramatically delayed tumorigenesis of lung tumor cells MM-BRAF, whereas infection of the cells with an empty vector or miR-348, an unrelated microRNA had no appreciable effect. Let-7a mimicked let-7b in suppression of tumorigenesis of MM-BRAF cells.

[0046] As shown in Figure 6A₅ overexpression of let-7b delays tumorigenesis driven by BRAF^V600E. Mouse adenocarcinomas elicited by BRAF^V600E (MM-BRAF) were infected for 24 hours with either control pMSCV retrovirus or pMSCV retrovirus that expresses either let~7b or mir-348. The infected cells were implanted subcutaneously into athymic mice to monitor growth rate of tumors (five mice in each group).

[0047] As shown in Figure 6B, overexpression of let-7b had no effect on tumorigenesis driven by MYC. Mouse adenocarcinomas elicited by MYC (TH-MYC) were infected for 24 hours with either control pMSCV retrovirus or pMSCV retrovirus that expresses either let- 7b or mir-348. The infected cells were implanted subcutaneously into athymic mice to monitor growth rate of tumors (five mice in each group).

[0048] By contrast, mouse lung cancer cells (TH-MYC) initiated by a transgene of MYC that lacks let-7 binding sites was immune to suppression by let- 7b. This contrast provides further evidence that tumorigenesis driven by BRAF^V600E but not MYC is selectively sensitive to let-7- based anticancer therapies.

[0049] The BRAF^V600E mutation is frequently found in human primary cancer and cancer cell lines. For example, human colon cancer ceil line HCT-29 and breast cancer cell line MDA-MD- 231 are known to harbor the BRAF^V600E mutation.

[0050] As shown in Figure 7, it was found that tumorigenesis of these cells in athymic mice was significantly suppressed by introduction of let-7b. As shown in this figure, Let-7 miRNAs impedes tumorigenesis of human cancer cells that harbor BRAF^V600E mutations. Human cancer cell line MDA-MB231 (A) or HCT29 (B) was infected for 24 hours with either control pMSCV retrovirus or pMSCV retrovirus that expresses either let-7b or mir-348. The infected ceils were implanted subcutaneously into athymic mice to monitor growth rate of tumors (Ten mice in each group). Tumors were dissected 40 days post-implantation and weighted. Error bars represent one standard deviation. By contrast, miR-348 had no detectable effect on tumorigenesis of both cell lines.

[0051] Suppression of IL6 contributes to the negative effect of let-7 miRNAs on tumorigenesis driven by BRAF^V600E.

[0052] Next, it was sought to ascertain the mechanism by which let-7 miRNAs impede tumorigenesis by BRAF. One possibility was that the miRNAs might impair the expression of BRAF directly, as they are laiown to do with oncogenes such as RAS, MYC and HMGA2. The sequence of BRAF RNA, however, contains no binding sites for let-7 miRNAs as analyzed with the miRNA database, miRDB, and expression of BRAF was not affected by ectopic overexpression of let-7b, as judged by Western blotting.

[0053] As shown in Figure 8, disabling IL6 delays tumorigenesis by BRAF^V600E. [0054] In Figure 8 A, ectopic expression of let-7b suppresses IL6 but not BRAF. iMREC cells overexpressing BRAF^V600 via pMIG retroviral vector were infected with control pMSCV retrovirus or pMSCV retrovirus that expresses let-7b and then extracted for Western blotting analysis of IL-6, BRAF and Actin in one gel.

[0055] In Figure 8B, disabling IL-6 restricts BRAF^v600E-driven tumorigenesis. iMREC celts were infected with virus expressing BRAF^V600E and then implanted subcutaneously into athymic mice (one million cells per mouse). Cohorts of ten recipient mice were mock-treated or treated once every two days with either a control IgG or an anti-IL6 antibody, beginning immediately after the implantation (100 μg antibody each intraperitoneal injection). The volume of tumors was measured at the indicated time points. Error bars, here and in panel C, represent one standard deviation. Anti-IL6 IgG vs Control IgG, *p < 0.005.

[0056] In Figure 8C, disabling IL-6 fails to restrict MYC-driven tumorigenesis. iMREC cells were infected with virus expressing MYC and then implanted subcutaneously into athymic mice (one million cells per mouse). Cohorts of ten recipient mice were mock-treated or treated once every two days with either a control IgG or an anti-IL-6 antibody, beginning immediately after the implantation (100 μg antibody each intraperitoneal injection). Anti-IL6 IgG vs Control IgG, *p > 0.1.

[0057] By contrast, a well-established let-7 target IL-6 was downregulated (see, Figure 8A). IL-6 is known to augment tumorigenesis driven by HRAS, which signals in part through BRAF. Thus, IL6 might also facilitate tumorigenesis driven by BRAF^V600E. To test this possibility, a neutralizing antibody was used to disable IL-6 systemically. The neutralizing antibody elicited a 2.5-fold inhibition of tumorigenesis of iMREC cells transduced with BRAF^V600E in comparison with an isotype-matched control antibody (see, Figure 8B). By contrast, the IL-6 antibody had no effect on tumorigenesis driven by MYC (see, Figure 8C). Based on this, it can be concluded that repression of IL-6 by let-7 miRNAs contributes to the negative effect of the miRNAs on tumorigenesis driven by BRAF^V600E. Depletion of IL-6 might serve as a surrogate for monitoring therapeutic doses of let-7 therapeutics.

[0058] In summary, the tumor suppressor function of let-7 miRNAs has been attributed to their ability to silence expression of oncogenes that drive tumorigenesis. However, it was found that let-7 miRNAs impede tumorigenesis driven by BRAF^V600E without affecting expression of the oncogene. Instead, it appeared possible that the demonstrable suppression of IL-6 expression by let-7 miRNA might contribute to the impedance of tumorigenesis. This possibility was confirmed by showing that disablement of IL-6 with a neutralizing antibody mimicked overexpression of let-7 miRNAs in delaying tumorigenesis driven by BRAF^V600E. IL-6 may not be the only target whose down-regulation contributes to the tumor suppressor activity of let-7 miRNAs, however, because overexpression of let-7 miRNA was more potent than disablement of IL-6 in impeding BRAF^v600E-driven tumorigenesis. Other possibilities include inhibition of self-renewal of cancer-initiating cells by down-regulating the let-7 miRNA target LIN28, a stem cell factor, a compromise of glucose metabolism by the let-7 -mediated repression of some components in the insulin-PI3K-mTOR pathway, and prevention of mTORCl activation by suppressing multiple components in the amino acid sensing pathway. In any event, it appears possible that let-7 miRNAs suppress BRAF^V600E~driven tumorigenesis through both IL-6- dependent and IL-6-independent mechanisms. These analyses were generally restricted to the a, b, c and e forms of let-7. Since the all forms of let-7 typically act in a similar manner, it is reasonable to presume that the other forms may also be capable of the actions demonstrated in this study. [0059] Examples

[0060] Materials and Methods

[0061] Cell Lines, media, DNA constructs and chemicals

[0062] Renal epithelial cells were isolated from mice and were trans fected with a combination of a dominant negative p53 and the adenoviral oncoprotein El A, Cells that formed foci were cloned and pooled for propagation and termed as iMREC for transformation experiments. MM-BRAF, TH-MYC, MREC, Rati A, HCT-29, MDA-MB-231 and retroviral packaging cell line BOSC-23 were maintained at 37 °C in DMEM medium supplemented with 10% fetal bovine serum (vol/vol) (HyClone) and 2 mM glutamine. pMig-BRAF^V600E , pMig- MYC, pMig-Survivin, pMig-MyrAKT, pMig-HRAS^vl2D, pMig-Bcl-2, pMig-IDl, pMSCV-let- 7a, pMSCV-let-7b, pMSCV-let-7c, pMSCV~let-7e and pMSCV-Mir348 were generated through standard PCR and sub cloning procedure.

[0063] Retroviral infection

[0064] BOSC-23 packaging cells were cultured in 35 mm dishes and cotransfected with pCL-Eco/lOAl envelop protein plasmid (0.5 μg) (Clontech) and a retroviral vector (2 μg) with lipofectinamine 2000 (mvitrogen) according to the manufacture's instruction. Sixteen hours after transfection, the medium was changed, and collection of virus- containing medium began on day 2 and was repeated once on day 3. The medium was sterilized by filtering through a 0.45-μπι low protein affinity Millex^®HV filter (Millipore) and then either used immediately or stored at -20°C. For retroviral infection, the retro virus-containing medium was supplemented with polybrene (0,4 μ^τηΐ, Sigma) and then added to cells of interest in 6 -well plates. The plates were centrifuged at room temperature for 1 h at 600 x g, The conditioned medium was then discarded, and fresh DMEM medium was added to the cells. [0065] Western blot analysis of cell extracts

[0066 j Immunoblotting was performed as described [6], A rabbit polyclonal antibodies were used for IL-6, BRAF and tubulin. Horseradish peroxidase-conjugated anti-rabbit immunoglobulins were from Santa Cruz Biotechnology. Western blots were developed with the Super Signal West Femto or Pico ECL detection kit (Thermo Scientific), For each sample, fifty micrograms of proteins were loaded in each lane.

[0067] MicroRNA by Taqman assays and Northern blot

[0068] For Taqman assays of let-7, cells in exponential growth were collected, the isolated total RNAs were analyzed by quantitative PCR for mature let-7a and mature let-7b with primers from Applied Biosystems. For quantification of mature let-7a (Assay ID, 002478, Applied Biosystems) and let-7b (Assay ID, 002619, Applied Biosystems), target-specific stem-loop reverse transcription primers were used to extend the 3 ' end of mature let-7 miRNAs before amplification. Relative gene expression was normalized to a mouse U6 snRNA (Assay ID, 001973, Applied Biosystems).

[0069] Tumorigenicity assays

[0070] Experimental mice were housed and treated according to the protocol approved by the Institutional Animal Care and Use Committee of MB ICR. Assays for tumorigenicity were performed by injecting 1 -5 million cells in phosphate buffered saline (PBS) subcutaneously into the right flanks of BALB/c athymic mice. A cohort of five to ten mice was used for each group. Tumor diameter was monitored with a digital caliper and the volume calculated using the formula: V (mm3) = A x B x B/2, where A and B represent the largest and smallest diameters of the tumor respectively.

[0071] Tumor tissue processing and histology [0072] Tumors were dissected away from mice and then either frozen in liquid nitrogen or fixed in 4% paraformaldehyde at room temperature overnight. Processing of tissues and staining of tissue sections with hematoxylin & eosin were performed by using standard methods.

[0073] Statistical analysis

[0074] Statistical analyses were performed with the GraphPad Prism software. Statistical significance of the differences was evaluated with Student's unpaired two-tailed t test. P values less than 0.05 were considered statistically significant.

[0075] While the inventive features have been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those in the art that the foregoing and other changes may be made therein without departing from the sprit and the scope of the disclosure. Likewise, the various diagrams may depict an example architectural or other configuration for the disclosure, which is done to aid in understanding the features and functionality that can be included in the disclosure. The disclosure is not restricted to the illustrated example architectures or configurations but can be implemented using a variety of alternative architectures and configurations. Additionally, although the disclosure is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described. They instead can be applied alone or in some combination, to one or more of the other embodiments of the disclosure, whether or not such embodiments are described, and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments.

Claims

What is claimed is:

1. A method of suppressing BRAF-driven tumorigenesis, comprising:

administering one or more lethal-7 miRNA-based therapeutics to a patient in need thereof.

2. The method of claim 1, wherein administering the one or more lethal-7 miRNA-based therapeutics suppresses cytokine IL-6 in the patient.

3. The method of claim 1, wherein the BRAF-driven tumorigenesis includes BRAF ^V600E- driven tumorigenesis.

4. The method of claim 1, wherein the one or more lethal-7 miRNA-based therapeutics include one or more lethal-7 miRNA-based therapeutics, one or more lethal-7b miRNA-based therapeutics, one or more lethal-7c miRNA-based therapeutics, or one or more lethal-7e miRNAs-based therapeutics.

5. A method of treating cancer that has an active BRAF oncogene, comprising:

administering one or more lethal-7 miRNA-based therapeutics to a patient in need thereof.

6. The method of claim 5, wherein administering the one or more lethal-7 miRNA-based therapeutics suppresses cytokine IL-6 in the patient.

7. The method of claim 5, wherein the BRAF-driven tumorigenesis includes BRAF driven tumorigenesis.

8. The method of claim 5, wherein the one or more lethal-7 miRNA-based therapeutics include one or more lethal-7 miRNA-based therapeutics, one or more lethal~7b miRNA-based therapeutics, one or more lethal-7c miRNA-based therapeutics, or one or more lethal-7e miRNA- based therapeutics.

9. A method of predicting favorable treatment responses to lethal-7 microRNA-based therapeutics, comprising

administering one or more lethal-7 miRNA-based therapeutics to a patient in need thereof; and

monitoring active BRAF signaling for predicting favorable treatment responses in the patient.

10. The method of claim 9, wherein administering the one or more lethal-7 miRNA-based therapeutics suppresses cytokine IL-6 in the patient.

11. The method of claim 9, wherein the BRAF-driven tumorigenesis includes BRAF ^V600E- driven tumorigenesis.

12. The method of claim 9, wherein the one or more lethal-7 miRNA-based therapeutics include one or more lethal-7 miRNA-based therapeutics, one or more lethal-7b miRNA-based therapeutics, one or more lethal-7c miRNA-based therapeutics, or one or more lethal-7e miRNAs-based therapeutics.