Relationship between TYMS and ERCC1 mRNA Expression and In Vitro Chemosensitivity in Colorectal Cancer

Aim: The aim of this study was to determine whether the relative mRNA expressions of the thymidylate synthase (TYMS) and the excision repair cross-complementing 1 (ERCC1) genes are associated with in vitro chemosensitivity to 5-fluorouracil (5-FU) and oxaliplatin in colorectal cancer, respectively. Patients and Methods: This study included 67 patients with pathologic TNM stage II, III, and IV. TYMS and ERCC1 mRNA expression was determined using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The chemosensitivity was examined using an ATP-based chemotherapy response assay. A high response was defined as a response producing >= 40% reduction in ATP. Results: The mean level of TYMS mRNA expression in the groups with low and high response to 5-FU was 2.35x10(-3) +/- 2.16x10(-3) 2(-(Delta Ct)) and 4.54x10(-3) +/- 2.46x10(-3) 2(-(Delta Ct)), respectively. The mean level of ERCC1 mRNA expression in the groups with low and high response to oxaliplatin was 13.92x10(-3) +/- 9.90x10(-3) 2(-(Delta Ct)) and 23.59x10(-3) +/- 5.88x10(-3) 2(-(Delta Ct)), respectively. Groups with high response to 5-FU and oxaliplatin had significantly higher expression of TYMS and ERCC1 mRNA, respectively (p<0.01 and p=0.01, respectively). Conclusion: High expression of TYMS and ERCC1 mRNA was associated with better in vitro chemosensitivity to 5-FU and oxaliplatin, respectively, in patients with colorectal cancer.