Relationship of Src activity and prior oxaliplatin on outcomes after hepatectomy for metastatic colorectal cancer.

Abstract

3561 Background: The nonreceptor tyrosine kinase Src regulates pathways critical to tumor proliferation, chemoresistance, and epithelial-to-mesenchymal transition. In vitro, Src is activated after acute oxaliplatin exposure and in acquired oxaliplatin resistance, but not after 5-FU alone. Activation of Src and its substrate FAK in metastatic colorectal cancer treated with oxaliplatin has not been studied in human specimens. Methods: Samples from 170 hepatic resections from two cohorts of patients with metastatic colorectal cancer were examined by IHC for expression of activated Src (pSrc) and FAK (total and pFAK). In the first cohort (n=50), tissue was collected at consecutive hepatic resections before and after oxaliplatin. Patients in the second cohort (n=120) were compared based on whether or not oxaliplatin was administered after resection. IHC was graded semi-quantitatively, 0 to 4 based on intensity (first cohort), and by automated image analysis (second cohort). Results: In the first cohort, pFAK expression increased after oxaliplatin exposure (mean IHC score 2.04 vs. 1.18, p<0.01). In the second cohort, Src activation was correlated with pFAK expression (p<0.01). Patients pretreated with oxaliplatin demonstrated increased expression of activated FAK (p=0.02) compared to 5-FU alone or irinotecan regimens. There was a weak association between total Src expression and the number of oxaliplatin cycles (p=0.06). Among patients in the second cohort, five-year relapse-free survival was inversely related to levels of pFAK (21.1%, 16.5%, and 7.4% for low, medium, and high levels of pFAK, respectively; p=0.02) and of pSrc (19.6%, 13.6%, and 8.2% for low, medium, and high levels of pSrc, respectively; p= 0.01). Conclusions: Patients treated with neoadjuvant oxaliplatin demonstrated increased Src signaling in liver metastases, a finding associated with worse relapse-free survival. These results are consistent with prior in vitro studies correlating oxaliplatin exposure with Src pathway activation and support the idea that inhibition of Src, when used in combination with platinum chemotherapy, warrants further investigation in patients with metastatic colorectal cancer.