Chemoresponsiveness associated with canonical molecular changes in colorectal adenocarcinomas

Background: The canonical molecular changes in colorectal tumorigenesis were assessed for correlation with response to chemotherapy, in order to identify candidate markers. Patients and Methods: In total, 156 patients received adjuvant postoperative fluoropyrimidine-based chemotherapy and 32 patients received oxaliplatin- or irinotecan-based chemotherapy following palliative surgery or for metastatic or recurrent colorectal tumors. Representative molecular changes in tumor tissues, including adenomatous polyposis coli (APC) gene, wingless-type MMTV integration site family (Wnt), mismatch repair (MMR), RAF, transforming growth factor (TGF)-β, bone morphogenetic protein, and p53, had been previously determined, with an additional 42 patients included in this analysis. Results: The disease-free survival period (mean±SEM) was significantly longer after fluoropyrimidine-based adjuvant chemotherapy in tumors with TGF-β2 expression (42±1.4 vs. 21±4.7 months; p=0.005) and D18S46 loss of heterozygosity or microsatellite instability (45.7±1.5 vs. 40.5±1.4 months; p=0.048). In the metastatic settings, the high disease-control rate of oxaliplatin and irinotecan regimens correlated significantly with wild-type APC and intact MMR, respectively, relative to mutant APC and defective MMR (p=0.013, respectively). Interestingly, specific molecular steps of tumorigenensis were closely associated with particular toxicities. Conclusion: A subset of molecular changes occurring during colorectal tumorigenesis showed significant associations with therapeutic responses and toxicities to chemotherapy regimens, suggesting that these changes may be candidate predictors of chemoresponsiveness with further validation.