Association between serotonin transporter promoter gene polymorphism and clinicopathological factors and effect of the polymorphism on the prognosis of colorectal cancer patients

Abstract

To examine the association between the genotype (LL, LS and SS) of serotonin transporter promoter gene polymorphism(5-HTTLPR) and clinicopathological factors, and to investigate the effect of 5-HTTLPR on the prognosis of colorectal cancer patients. Data of peripheral blood samples of 161 colorectal cancer patients at the Second Affiliated Hospital of Guangzhou Medical University from October 2009 to January 2014 were collected retrospectively. The genotyping of 5-HTTLPR was determined by PCR and agarose gel electrophoresis. Coincidence Chi-square test was used to examine the 5-HTTLPR genotype with Hardy-Weinberg law. Chi-square test and Cox multifactor model were used to analyze the association of 5-HTTLPR genotype with clinicopathology and prognosis. All the patients were informed and agreed to participate in the study. This study was approved by the Hospital Ethics Committee (2015056). Of 161 colorectal cancer patients, 89 were male and 72 were female; the median age was 64 (25-85) years; 86 (53.5%) cases were colon cancer and 75 (46.5%) were rectal cancer. Genotype was LL in 12 cases, LS in 59 cases and SS in 90 cases, which complied with the law of Hardy-Weinberg genetic balance (χ²=0.288, P=0.592). Univariate analysis showed that 5-HTTLPR gene polymorphism was only associated with lymph node metastasis [lymph node metastasis rate: LL and LS genotype 21.1% (15/71);SS genotype 40.0% (36/90), χ²= 6.532, P=0.011]. The 3-year and 5-year overall survival rates of whole patients were 71% and 63% respectively. Multivariate analysis revealed that the SS genotype was an independent risk factor affecting the overall survival of colorectal cancer patients(HR=1.933, 95%CI:1.090-3.428, P=0.024). Among genotypes of 5-HTTLPR gene, colorectal cancer patients with SS genotype have higher risk of lymph node metastasis and poorer prognosis.