KRAS is mutated in about 40% of colorectal cancers; it is the only validated predictive marker used in patients with metastatic CRC 1. It is also a negative prognosticator in NSCLC. BRAF missense V600E mutations are present in approximately 10–15% of colorectal cancers, are more common in right-sided colon tumors and are prognostic of decreased tumor response and overall survival 2. ERCC1 is a critical enzyme in nucleotide excision repair and is associated with disease response, progression free and overall survival in patients with NSCLC, colorectal, and gastric cancer treated with platinum-based chemotherapy 3. Resistance to EGFR-directed antibodies in KRAS-wildtype metastatic colorectal cancer patients may be related to interactions with the concurrent cytotoxic chemotherapy used (e.g. oxaliplatin, fluoropyrimidine) 4,5. In NSCLC patients, KRAS mutations predict lack of benefit from platinum-based chemotherapy and worse outcomes in those treated with a combination of platinum agents and EGFR-TKIs 6. The EGFR targeted tyrosine kinase inhibitor, erlotinib, in combination with gemcitabine improves survival in patients with metastatic pancreatic cancer 7. The role of EGFR antibodies combined with platinum chemotherapy is under investigation. Understanding the interactions between the EGFR and ERCC1 molecular pathways will help individualize cancer therapy and identify targets for drug development. BACKGROUND Formalin fixed paraffin embedded tumor specimens from 1,514 patients (573 colorectal; 91 pancreatic; 850 lung) were microdissected; DNA and RNA were extracted. Specifically designed primers and probes were used to detect 7 different base substitutions in codons 12 and 13 of KRAS (GLy12Ala; GLy12Asp; Gly12Arg; Gly12Cys; Gly12Ser; Gly12Val; Gly13Asp) and the V600E BRAF mutation. ERCC1 mRNA expression levels were measured by quantitative RT-PCR in a CLIA approved laboratory. Differences in mRNA ERCC1 levels by mutation status were tested using Wilcoxon two-sample tests. METHODS RESULTS Mutant KRAS tumors had significantly lower ERCC1 mRNA levels relative to wildtype KRAS tumors in both colorectal (0.89 vs. 1.06; p<0.001) and pancreatic (1.20 vs. 1.80; p=0.006) cancer patients. While mutant KRAS lung tumors showed decreased ERCC1 expression (1.25 vs. 1.39), the trend did not meet significance (p=0.069). Within the colorectal subset, mutant BRAF cancers trended towards less ERCC1 expression than tumors harboring both wildtype KRAS/BRAF genes (0.96 vs. 1.06; p=0.25). CONCLUSIONS & DISCUSSION This is one of the first reports linking KRAS mutation status with ERCC1 gene expression in colon, pancreatic and lung adenocarcinoma. KRAS mutation status may predict sensitivity to platinum based therapy in colon and pancreatic cancer. Colorectal tumors with either the BRAF or KRAS mutation have decreased ERCC1 expression, relative to those that carry both wildtype genes. CRC patients whose tumors have both wildtype BRAF and KRAS genes may have a decreased response to oxaliplatin based regimens. The uniform downregulation of ERCC1 amongst mutant KRAS and BRAF cancers suggests that ERCC1 expression may be driven by MAPK activation. Concomitant use of MEK inhibitors may therefore improve the efficacy of oxaliplatin based chemotherapy in patients with mutant KRAS or BRAF tumors. Prospective biomarker driven studies should explore these hypotheses, guide clinical decision making and improve patient outcomes. KRAS/BRAF Mutation Status Median ERCC1 Expression (Range) KRAS Mutant/ BRAF Wildtype KRAS Wildtype/ BRAF Wildtype KRAS Wildtype/ BRAF Mutant Colorectal Cancer 0.89 ( ) N = ( ) N = ( ) P < 0.001P = 0.25 Pancreatic Cancer 1.20 ( ) N = ( ) N = 11 P = Lung Cancer 1.25 ( ) N = ( ) N = 614 P = Table 1: ERCC1 mRNA Expression by KRAS/BRAF Mutation Status in Colorectal, Pancreatic, Lung Cancer OBJECTIVE We tested whether ERCC1 mRNA expression correlates with KRAS and BRAF mutation status in patients with colorectal, pancreatic, and lung adenocarcinoma. Figure 2: ERCC1 mRNA Expression by KRAS Mutation Status in Pancreatic Cancer Figure 1: ERCC1 mRNA Expression by KRAS Mutation Status in Colorectal Cancer REFERENCES 1.Neumann, J., et al., Frequency and type of KRAS mutations in routine diagnostic analysis of metastatic colorectal cancer. Pathol Res Pract, (12): p De Roock, W., et al., Effects of KRAS, BRAF, NRAS, and PIK3CA mutations on the efficacy of cetuximab plus chemotherapy in chemotherapy-refractory metastatic colorectal cancer: a retrospective consortium analysis. Lancet Oncol, (8): p Shirota, Y., et al., ERCC1 and thymidylate synthase mRNA levels predict survival for colorectal cancer patients receiving combination oxaliplatin and fluorouracil chemotherapy. J Clin Oncol, (23): p Tveit, K.M., et al., Phase III trial of cetuximab with continuous or intermittent fluorouracil, leucovorin, and oxaliplatin (Nordic FLOX) versus FLOX alone in first-line treatment of metastatic colorectal cancer: the NORDIC-VII study. J Clin Oncol, (15): p Maughan, T.S., et al., Addition of cetuximab to oxaliplatin-based first-line combination chemotherapy for treatment of advanced colorectal cancer: results of the randomised phase 3 MRC COIN trial. Lancet, (9783): p Eberhard, D.A., et al., Mutations in the epidermal growth factor receptor and in KRAS are predictive and prognostic indicators in patients with non-small-cell lung cancer treated with chemotherapy alone and in combination with erlotinib. J Clin Oncol, 2005 Sep 1;23(25): Moore, M.J., et al., Erlotinib plus gemcitabine compared with gemcitabine alone in patients with advanced pancreatic cancer: a phase III trial of the National Cancer Institute of Canada Clinical Trials Group. J Clin Oncol, 2007 May 20;25(15): Epub 2007 Apr 23. Abstract ID: Diana L. Hanna 1, Martin K. H. Maus 2,3, Craig Stephens 3, Peter Philipp Grimminger 2, Stephanie H. Astrow 3, Dongyun Yang 1, Fotios Loupakis 1, Jack Hsiang 1, Gary Zeger 4, Afsaneh Barzi 1, Heinz-Josef Lenz 1 Correlation of ERCC1 mRNA expression with KRAS mutation status in colorectal, pancreatic, and lung adenocarcinoma 1 USC Norris Comprehensive Cancer Center, Los Angeles, CA; 2 Department of General, Visceral, and Tumor Surgery, University of Cologne, Cologne, Germany; 3 Response Genetics, Inc., Los Angeles, CA; 4 Keck School of Medicine, Department of Pathology, University of Southern California, Los Angeles, CA Adapted from: Nature Reviews Cancer 4, (September 2004) Figure 3: Oncogenic Activation of KRAS, BRAF, MAPK Pathways