p16 gene methylation in colorectal cancer patients with long-term follow-up.

ABSTRACT

INTRODUCTION: p16 gene plays an important role in the cell cycle regulation and is considered an important tumor suppressor gene. Several mechanisms of gene inactivation have been described; in this study we have focused on p16 gene promoter methylation. In colorectal cancer p16 gene methylation is a frequent event. METHODS: 326 patients with sporadic colorectal cancer were included. DNA was extracted from tumor tissue samples obtained during the surgical procedure. Promoter methylation was analyzed using bisulfite modification and was detected by quantitative methylation-specific PCR. Frequency of p16 methylation was analyzed and compared with other clinicopathological variables. RESULTS: p16 gene methylation was detected in 24.8% of patients. Methylation was associated with differentiation grade and with tumor location methylation was frequent in poorly differentiated tumors and had low frequency in distal colon. The p16 promoter methylation discriminated a subgroup of patients with better prognosis in poorly differentiated tumors. CONCLUSIONS: p16 methylation was a frequent event in our population and was able to induce differences in the overall survival of patients with poorly differentiated tumors.