Functional polymorphisms of circadian positive feedback regulation genes and clinical outcome of Chinese patients with resected colorectal cancer

BACKGROUND: Previous studies have demonstrated that circadian genes play a role in the development and progression of many cancers. This study aims to assess the effects of single nucleotide polymorphisms (SNPs) in circadian genes on recurrence and survival of colorectal cancer (CRC) patients. METHODS: Nine functional SNPs in 3 genes (CLOCK, NPAS2, and BMAL1) on the circadian positive feedback loop were selected and genotyped using the Sequenom iPLEX genotyping system in a cohort of 411 resected Chinese CRC patients. Multivariate Cox proportional hazards model and Kaplan-Meier curve were used for the prognosis analysis. RESULTS: The authors identified 2 SNPs in the CLOCK gene to be significantly associated with CRC overall survival. SNP rs3749474 exhibited a significant association with survival of CRC patients in the additive model (hazard ratio [HR], 0.55; 95% confidence interval [CI], 0.37-0.81; P = .003). In addition, patients carrying the heterozygous variant of rs1801260 had significantly increased overall survival compared with those carrying homozygous wild-type genotype (HR, 0.31; 95% CI, 0.11-0.88; P = .03). Findings from functional assay provided further biological support for these significant associations. Stratified analysis found no modifying effect of chemotherapy on the prognostic significance of both SNPs. Moreover, we observed cumulative effects of these 2 SNPs on CRC overall survival (P for trend = .01). Compared with patients carrying no unfavorable genotypes, those carrying 2 unfavorable genotypes had a 2.92-fold increased risk of death (P = .03). CONCLUSIONS: The results suggest for the first time that CLOCK gene polymorphisms may serve as an independent prognostic marker for CRC patients. Cancer 2012;. © 2011 American Cancer Society.