Department of Biochemistry, Government Medical College, Srinagar, India.
J Biol Regul Homeost Agents. 2013 Apr-Jun;27(2):297-307.
Colorectal cancer (CRC) commonly known as bowel cancer is the third most common cause of cancer-related deaths in the western world and has been reported to show geographical variation in its incidence. Cancer development and progression is a complex process dictated by changes in expression and regulation of various genes which include tumor suppressor genes, DNA repair genes, translation regulatory genes and others. The aim of this case control study was to analyze the promoter hypermethylation at CpG islands of p16 gene in CRC patients among the Kashmiri population and co- relate it with expression pattern of p16. Genomic DNA was isolated from surgically resected tumor and adjacent normal samples and was modified using bisulphite modification kit. Methylation-specific polymerase chain reaction (PCR) was setup for the analysis of the promoter hypermethylation of p16 gene. The epigenetic analysis revealed that unlike other high risk regions, Kashmiri population has a different promoter hypermethylation profile of p16 gene as 66 percent of the cases showed p16 promoter hypermethylation in comparison to 20 percent of the normal cases which also showed promoter hypermethylation of p16 gene. The association of promoter hypermethylation with colorectal cancer was found to be significant (P=0.0006). Occurrence of p16 promoter hypermethylation was found to be unequally distributed in males and females with more frequency in males than in females but the difference was not statistically significant(P =0.7635). Similarly, frequency of p16 promoter hypermethylation was found to be certainly higher in Stage III/IV (83.33 percent) compared to Stage I/II (56.25 percent) but the difference was not statistically significant (P =0.0673). Also, the degree of p16 promoter hypermethylation increased with the increasing severity of the lesion but the difference was not again statistically significant (P =0.6145). Promoter hypermethylation correlated with the decrease in expression of the p16 gene in CRC patients leading to the diseased phenotype. These results suggest that p16 aberrant promoter hypermethylation in Kashmiri population contributes to the process of carcinogenesis in CRC and may be developed into a valuable tool for CRC diagnosis at early stages.
结直肠癌（CRC）通常被称为肠癌，是西方世界癌症相关死亡的第三大常见原因，据报道其发病率存在地域差异。癌症的发生和发展是一个复杂的过程，由各种基因表达和调控的变化决定，这些基因包括肿瘤抑制基因、DNA 修复基因、翻译调控基因等。本病例对照研究旨在分析克什米尔人群 CRC 患者中 p16 基因启动子 CpG 岛的高甲基化，并与 p16 的表达模式相关。从手术切除的肿瘤和相邻正常样本中分离基因组 DNA，并使用亚硫酸氢盐修饰试剂盒进行修饰。建立甲基化特异性聚合酶链反应（PCR）分析 p16 基因启动子的高甲基化。表观遗传学分析显示，与其他高危区域不同，克什米尔人群的 p16 基因启动子高甲基化模式不同，66%的病例显示 p16 启动子高甲基化，而 20%的正常病例也显示 p16 基因启动子高甲基化。启动子高甲基化与结直肠癌的相关性具有统计学意义（P=0.0006）。p16 启动子高甲基化的发生在男性和女性中分布不均，男性的频率高于女性，但差异无统计学意义（P=0.7635）。同样，III/IV 期（83.33%）的 p16 启动子高甲基化频率明显高于 I/II 期（56.25%），但差异无统计学意义（P=0.0673）。此外，p16 启动子高甲基化的程度随着病变严重程度的增加而增加，但差异再次无统计学意义（P=0.6145）。p16 基因启动子高甲基化与 CRC 患者 p16 基因表达降低相关，导致疾病表型。这些结果表明，克什米尔人群中 p16 基因异常启动子高甲基化导致 CRC 中癌发生的过程，可能成为早期 CRC 诊断的有价值工具。
