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  • C12Q2600/00—Oligonucleotides characterized by their use
  • C12Q2600/158—Expression markers

Definitions

• the present invention provides a biomarker that is predictive for the clinical benefit of EGFR inhibitor treatment in cancer patients.
• EGF epidermal growth factor receptor
• TGF- ⁇ transforming growth factor- ⁇
• TGF- ⁇ transforming growth factor- ⁇
• tumour cell proliferation in vitro. It has been postulated that stimulation of tumour cells via the EGFR may be important for both tumour growth and tumour survival in vivo.
• TarcevaTM an inhibitor of the EGFR tyrosine kinase
• Clinical phase I and II trials in patients with advanced disease have demonstrated that TarcevaTM has promising clinical activity in a range of epithelial tumours. Indeed, TarcevaTM has been shown to be capable of inducing durable partial remissions in previously treated patients with head and neck cancer, and NSCLC (Non small cell lung cancer) of a similar order to established second line chemotherapy, but with the added benefit of a better safety profile than chemo therapy and improved convenience (tablet instead of intravenous [i.v.] administration).
• a recently completed, randomised, double-blind, placebo-controlled trial (BR.21) has shown that single agent TarcevaTM significantly prolongs and improves the survival of NSCLC patients for whom standard therapy for advanced disease has failed.
• TarcevaTM (erlotinib) is a small chemical molecule; it is an orally active, potent, selective inhibitor of the EGFR tyrosine kinase (EGFR-TKI).
• Lung cancer is the major cause of cancer-related death in North America and Europe. In the United States, the number of deaths secondary to lung cancer exceeds the combined total deaths from the second (colon), third (breast), and fourth (prostate) leading causes of cancer deaths combined. About 75% to 80% of all lung cancers are NSCLC, with approximately 40% of patients presenting with locally advanced and/or unresectable disease. This group typically includes those with bulky stage IHA and MB disease, excluding malignant pleural effusions.
• the crude incidence of lung cancer in the European Union is 52.5, the death rate 48.7 cases/ 100000/year. Among men the rates are 79.3 and 78.3, among women 21.6 and 20.5, respectively. NSCLC accounts for 80% of all lung cancer cases. About 90% of lung cancer mortality among men, and 80% among women, is attributable to smoking.
• the present invention provides an in vitro method of predicting the clinical benefit of a cancer patient in response to treatment with an EGFR inhibitor comprising the steps: determining an expression level of a STCH gene in a tumour sample of a patient and comparing the expression level of the STCH gene to a value representative of an expression level of the STCH gene in tumours of a population of patients deriving no clinical benefit from the treatment, wherein a lower expression level of the STCH gene in the tumour sample of the patient is indicative for a patient who will derive clinical benefit from the treatment.
• STCH means stress 70 protein chaperone.
• Seq. Id. No. 1 shows the nucleotide sequence of human STCH.
• a value representative of an expression level of the STCH gene in tumours of a population of patients deriving no clinical benefit from the treatment refers to an estimate of a mean expression level of the marker gene in tumours of a population of patients who do not derive a clinical benefit from the treatment.
• Clinical benefit was defined as either having an objective response or disease stabilization for >12 weeks.
• the STCH gene shows between 1.1 and 1.8 or more fold lower expression level in the tumour sample of the patient compared to a value representative of the population of patients deriving no clinical benefit from the treatment.
• the expression level of the marker gene is determined by microarray technology or other technologies that assess RNA expression levels like quantitative RT-PCR, or by any method looking at the expression level of the respective protein, eg immunohistochemistry (IHC).
• IHC immunohistochemistry
• the construction and use of gene chips are well known in the art. see, U. S. Pat Nos. 5,202,231; 5,445,934; 5,525,464; 5,695,940; 5,744,305; 5,795, 716 and 1 5,800,992. See also, Johnston, M. Curr. Biol. 8:R171-174 (1998); Iyer VR et al., Science 283:83-87 (1999).
• the gene expression level can be determined by other methods that are known to a person skilled in the art such as e.g. northern blots, RT- PCR, real time quantitative PCR, primer extension, RNase protection, RNA expression profiling.
• the marker gene of the present invention can be combined with other biomarkers to biomarker sets.
• Biomarker sets can be built from any combination of predictive biomarkers to make predictions about the effect of EGFR inhibitor treatment in cancer patients.
• the biomarkers and biomarkers sets described herein can be used, for example, to predict how patients with cancer will respond to therapeutic intervention with an EGFR inhibitor.
• gene as used herein comprises variants of the gene.
• variant relates to nucleic acid sequences which are substantially similar to the nucleic acid sequences given by the GenBank accession number.
• substantially similar is well understood by a person skilled in the art.
• a gene variant may be an allele which shows nucleotide exchanges compared to the nucleic acid sequence of the most prevalent allele in the human population.
• a substantially similar nucleic acid sequence has a sequence similarity to the most prevalent allele of at least 80%, preferably at least 85%, more preferably at least 90%, most preferably at least 95%.
• variants is also meant to relate to splice variants.
• the EGFR inhibitor can be selected from the group consisting of gefitinib, erlotinib, PKI-166, EKB-569, GW2016, CI-1033 and an anti-erbB antibody such as trastuzumab and cetuximab.
• the EGFR inhibitor is erlotinib.
• the cancer is NSCLC.
• Techniques for the detection and quantification of gene expression of the genes described by this invention include, but are not limited to northern blots, RT-PCR, real time quantitative PCR, primer extension, RNase protection, RNA expression profiling and related techniques. These techniques are well known to those of skill in the art see e.g. Sambrook J et al., Molecular Cloning: A Laboratory Manual, Third Edition (Cold Spring Harbor Press, Cold Spring Harbor, 2000).
• IHC immunohistochemistry
• test cells show a biomarker expression profile which corresponds to that of a patient who responded to cancer treatment, it is highly likely or predicted that the individual's cancer or tumour will respond favorably to treatment with the EGFR inhibitor.
• test cells show a biomarker expression pattern corresponding to that of a patient who did not respond to cancer treatment, it is highly likely or predicted that the individual's cancer or tumour will not respond to treatment with the EGFR inhibitor.
• the biomarker of the present invention i.e. the gene listed in table 3, is a first step towards an individualized therapy for patients with cancer, in particular patients with refractory NSCLC.
• This individualized therapy will allow treating physicians to select the most appropriate agent out of the existing drugs for cancer therapy, in particular NSCLC.
• the benefit of individualized therapy for each future patient are: response rates / number of benefiting patients will increase and the risk of adverse side effects due to ineffective treatment will be reduced.
• the present invention provides a therapeutic method of treating a cancer patient identified by the in vitro method of the present invention.
• Said therapeutic method comprises administering an EGFR inhibitor to the patient who has been selected for treatment based on the predictive expression pattern of the gene of table 3.
• a preferred EGFR inhibitor is erlotinib and a preferred cancer to be treated is NSCLC.
• Figure 1 shows the study design
• FIG. 1 shows the scheme of sample processing
• Figure 3a shows STCH expression levels versus clinical outcome for Genechip® profiling
• Figure 3b shows STCH expression levels versus clinical outcome for qRT-PCR
• Figure 3c shows the correlation between Genechip® and qRT-PCR measurements for STCH.
• tumour sample was collected at the same time and stored in paraffin (formalin fixed paraffin embedded, FFPE). This sample was analysed for alterations in the EGFR signaling pathway. The ability to perform tumour biopsies via bronchoscopy was a prerequisite for this study. Bronchoscopy is a standard procedure to confirm the diagnosis of lung cancer. Although generally safe, there is a remaining risk of complications, e.g. bleeding.
• This study was a first step towards an individualized therapy for patients with refractory NSCLC. This individualized therapy will allow treating physicians to select the most appropriate agent out of the existing drugs for this indication.
• TarcevaTM was given orally once per day at a dose of 150 mg until disease progression, intolerable toxicities or death.
• the selection of this dose was based on pharmacokinetic parameters, as well as the safety and tolerability profile of this dose observed in Phase I, II and III trials in heavily pre-treated patients with advanced cancer.
• Drug levels seen in the plasma of patients with cancer receiving the 150 mg/day dose were consistently above the average plasma concentration of 500 ng / ml targeted for clinical efficacy.
• BR.21 showed a survival benefit with this dose.
• the secondary objectives were to assess alterations in the EGFR signaling pathways with respect to benefit from treatment.
• Tumour tissue and blood samples were obtained for molecular analyses to evaluate the effects of TarcevaTM and to identify subgroups of patients benefiting from therapy. Predictive Marker Assessments
• Biopsies of the tumour were taken within 2 weeks before start of treatment. Two different samples were collected:
• the first sample was always frozen immediately in liquid N2
• the second sample was fixed in formalin and embedded in paraffin Snap frozen tissue had the highest priority in this study.
• Figure 2 shows a scheme of the sample processing.
• the snap frozen samples were used for laser capture microdissection (LCM) of tumour cells to extract tumour RNA and RNA from tumour surrounding tissue.
• the RNA was analysed on Affymetrix microarray chips (HG-U 133A) to establish the patients' tumour gene expression profile. Quality Control of Affymetrix chips was used to select those samples of adequate quality for statistical comparison.
• the DNA mutation status of the genes encoding EGFR and other molecules involved in the EGFR signaling pathway were analysed by DNA sequencing. Gene amplification of EGFR and related genes were be studied by FISH. Protein expression analyses included immunohistochemical [IHC] analyses of EGFR and other proteins within the EGFR signalling pathway. Response Assessments
• the RECIST Uni-dimensional Tumour Measurement
• RECIST Uni-dimensional Tumour Measurement
• These criteria can be found under the following link: http://www.eortc.be/recist/ Note that:To be assigned a status of CR or PR, changes in tumour measurements must be confirmed by repeated assessments at least 4 weeks apart at any time during the treatment period. In the case of SD, follow-up measurements must have met the SD criteria at least once after study entry at a minimum interval of 6 weeks.
• RNases are RNA degrading enzymes and are found everywhere and so all procedures where RNA will be used must be strictly controlled to minimize RNA degradation. Most mRNA species themselves have rather short half-lives and so are considered quite unstable.
• RNA concentration and quality profile can be assessed using an instrument from Agilent (Agilent Technologies, Inc., Palo Alto, CA) called a 2100 Bioanalyzer®.
• the instrument software generates an RNA Integrity Number (RIN), a quantitation estimate (Schroeder, A., et al., The RIN: an RNA integrity number for assigning integrity values to RNA measurements. BMC MoI Biol, 2006. 7: p. 3), and calculates ribosomal ratios of the total RNA sample.
• the RIN is determined from the entire electrophoretic trace of the RNA sample, and so includes the presence or absence of degradation products.
• the RNA quality was analysed by a 2100 Bioanalyzer®.
• Target labeling was carried out according to the Two-Cycle Target Labeling Amplification Protocol from Affymetrix (Affymetrix, Santa Clara, California), as per the manufacturer's instructions.
• the method is based on the standard Eberwine linear amplification procedure but uses two cycles of this procedure to generate sufficient labeled cRNA for hybridization to a microarray.
• Total RNA input used in the labeling reaction was IOng for those samples where more than IOng RNA was available; if less than this amount was available or if there was no quantity data available (due to very low RNA concentration), half of the total sample was used in the reaction. Yields from the labeling reactions ranged from 20-180 ⁇ g cRNA.
• a normalization step was introduced at the level of hybridization where 15 ⁇ g cRNA was used for every sample.
• RNA Human Reference RNA (Stratagene, Carlsbad, CA, USA) was used as a control sample in the workflow with each batch of samples. IOng of this RNA was used as input alongside the test samples to verify that the labeling and hybridization reagents were working as expected. Microarray hybridizations
• Affymetrix HG-U 133 A microarrays contain over 22,000 probe sets targeting approximately 18,400 transcripts and variants which represent about 14,500 well- characterized genes.
• Hybridization for all samples was carried out according to Affymetrix instructions (Affymetrix Inc., Expression Analysis Technical Manual, 2004). Briefly, for each sample, 15 ⁇ g of biotin-labeled cRNA were fragmented in the presence of divalent cations and heat and hybridized overnight to Affymetrix HG-U 133 A full genome oligonucleotide arrays. The following day arrays were stained with streptavidin-phycoerythrin (Molecular Probes; Eugene, OR) according to the manufacturer's instructions. Arrays were then scanned using a GeneChip Scanner 3000 (Affymetrix), and signal intensities were automatically calculated by GeneChip Operating Software (GCOS) Version 1.4 (Affymetrix). Statistical Analysis Analysis of the AffymetrixTM data consisted of five main steps. Step 1 was quality control. The goal was to identify and exclude from analysis array data with a sub-standard quality profile.
• GCOS GeneChip Operating Software
• Step 2 was pre-processing and normalization. The goal was to create a normalized and scaled "analysis data set", amenable to inter-chip comparison. It comprised background noise estimation and subtraction, probe summarization and scaling.
• Step 3 was exploration and description. The goal was to identify potential bias and sources of variability. It consisted of applying multivariate and univariate descriptive analysis techniques to identify influential covariates.
• Step 4 was modeling and testing. The goal was to identify a list of candidate markers based on statistical evaluation of the difference in mean expression level between "clinical benefit” and "no clinical benefit” patients. It consisted in fitting an adequate statistical model to each probe-set and deriving a measure of statistical significance.
• Step 5 was a robustness analysis. The goal was to generate a qualified list of candidate markers that do not heavily depend on the pre-processing methods and statistical assumptions. It consisted in reiterating the analysis with different methodological approaches and intersecting the list of candidates.
• This step also included visual inspection of virtual chip images for detecting localized hybridization problems, and comparison of each chip to a virtual median chip for detecting any unusual departure from median behaviour. Inter-chip correlation analysis was also performed to detect outlier samples. In addition, ancillary measures of RNA quality obtained from analysis of RNA samples with the Agilent BioanalyzerTM 2100 were taken into consideration.
• Step 2 Data pre-processing and normalization
• the rma algorithm (Irizarry, R.A., et al., Summaries of Affymetrix GeneChip probe level data. Nucl. Acids Res., 2003. 31(4): p. el5) was used for pre-processing and normalization.
• the mas5 algorithm (AFFYMETRIX, GeneChip® Expression: Data Analysis
• Probe-sets called “absent” or “marginal” in all samples were removed from further analysis; 5930 probe-sets were removed from analysis based on this criterion.
• the analysis data set therefore consisted of a matrix with 16353 (out of 22283) probe-sets measured in 102 patients.
• Descriptive exploratory analysis was performed to identify potential bias and major sources of variability.
• a set of covariates with a potential impact on gene expression profiles was screened. It comprised both technical and clinical variables.
• Technical covariates included: date of RNA processing (later referred to as batch), RIN (as a measure of RNA quality/integrity), Operator and Center of sample collection.
• Clinical covariates included: Histology type, smoking status, tumour grade, performance score (Oken, M.M., et al., Toxicity and response criteria of the Eastern Cooperative Oncology Group. Am J Clin Oncol, 1982. 5(6): p. 649-55), demographic data, responder status and clinical benefit status.
• the analysis tools included univariate ANOVA and principal component analysis. For each of these covariates, univariate ANOVA was applied independently to each probe-set.
• the normalized data set after batch effect correction served as the analysis data set in subsequent analyses.
• Step 4 Data modeling and testing.
• Table 2 Description of the variables included in the linear model.
• the aim of the statistical test was to reject the hypothesis that the mean expression levels in patients with clinical benefit and patients without clinical benefit are equal, taking into account the other adjustment covariates listed in table 2.
• the null hypothesis of equality was tested against a two sided alternative. The corresponding p- values are reported in table 3.
• linear modeling is a versatile, well-characterized and robust approach that allows for adjustment of confounding variables when estimating the effect of the variable of interest.
• sample size of 102 and the normalization and scaling of the data set, the normal distribution assumption was reasonable and justified.
• the goal of the robustness analysis was to reduce the risk that the results of the analysis might be artifactual and a result of the pre-processing steps or assumptions underlying the statistical analysis.
• the following three aspects were considered: a) inclusion or exclusion of a few extra chips at the quality control step; b) pre-processing and normalization algorithm; c) statistical assumptions and testing approach.
• the list of candidate markers was defined as the subset of genes consistently declared as significant with different analysis settings.
• the different applied analysis options were the following: a) An additional subset of 8 chips was identified based on more stringent quality control criteria. A "reduced data set" was defined by excluding these 8 chips.
• MAS5 was identified as an alternative to rma for pre-processing and normalization. MAS5 uses different methods for background estimation, probe summarization and normalization.
• Table 3 Gene marker for Clinical Benefit based on the robustness analysis after application of the composite Criterion.
• Column 1 is the Affymetrix identifier of the probe-set.
• Column 2 is the GenBank accession number of the corresponding gene sequence.
• Column 3 is the corresponding official gene name.
• Column 4 is the corresponding adjusted mean fold change in expression level between clinical and no clinical benefit patient, as estimated from the linear model.
• Column 5 is the p-value for the test of difference in expression level between clinical benefit and no clinical benefit patients as derived from the linear model.
• Column 6 is the 95% confidence interval for the adjusted mean fold change in expression level.
• qRT-PCR cDNA was synthesized using SuperscriptTM III First-strand Synthesis SuperMix for qRT-PCR (Invitrogen, CA, USA) according to the manufacturer's instructions but without inclusion of an RNase H digest. Quantitative PCR was performed using TaqMan ® Gene Expression Assays on an ABI
• the used primers and probes crossed exon boundaries or were within the Affymetrix Genechip ® probe sequence of interest.
• Two house-keeping genes were included as endogenous controls: beta-2-microglobulin (B2M; Assay Hs99999907_ml) and hypoxanthinephosphoribosyl transferase (HPRT; Assay Hs99999909_ml).
• Figure 3a shows expression levels versus clinical outcome for Genechip ® profiling and Figure 3b shows expression levels to qRT-PCR.
• STCH stress 70 protein chaperone
• the protein encoded by this gene is a member of the heat shock protein 70 family and is found associated with microsomes. Members of this protein family play a role in the processing of cytosolic and secretory proteins, as well as in the removal of denatured or incorrectly-folded proteins.
• the encoded protein contains an ATPase domain and has been shown to associate with a ubiquitin-like protein.

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