Gene-specific methylation: potential markers for colorectal cancer

IGFBP3 gene promoter methylation analysis and its association with clinicopathological characteristics of colorectal carcinoma

Promoter methylation mediated silencing of tumor suppressor genes plays an important role in the tumorigenesis of colorectal carcinoma (CRC). Tumor suppressor gene, Insulin-like Growth Factor Binding Protein-3 (IGFBP-3) expression is frequently downregulated in CRC due to promoter methylations. The aim of this study was to analyze the methylation status of IGFBP-3 gene promoter in stage II and III of CRC cases; find its association with clinicopathological characteristics of CRC patients and the methylation patterns as a prognostic biomarker. 58 histopathologically confirmed cases of CRC were included in the study. Methylation status of IGFBP-3 gene promoter was determined by using methylation specific PCR (MS-PCR) and bisulfite sequencing. Kaplan-Meier survival curve and univariate cox regression analysis were used for survival analysis; Chi-square test used for association analysis. IGFBP3 promoter methylation was found in 37 (63.8%) out of 58 CRC cases. This promoter methylation status was significantly associated with lymph-node metastasis (P = 0.013) and the survival period. In stage II CRC cases, unmethylated gene promoter status showed better survival than the methylated. Mean overall survival (OS) of methylated and unmethylated group was 22.23 months, and 49.15 months respectively (P = 0.045), HR = 6.432, 95% CI 0.986-41.943. The IGFBP-3 promoter methylations found in 63.8% CRC cases in this study. The methylations was found to be associated with lymph-node metastasis and overall survival of the patients particularly in stage II CRC patients. However, promoter methylation was not associated with other clinocopathological characteristics such as age, gender, tumor location etc.