Lee Minjin, Sup Han Woon, Kyoung Kim Ok, Hee Sung Sun, Sun Cho Min, Lee Shi Nae, Koo Heasoo
Department of Pathology, College of Medicine, Hallym University, Seoul, Korea.
Pathol Res Pract. 2006;202(6):415-24. doi: 10.1016/j.prp.2005.11.011. Epub 2006 May 3.
The INK4a/ARF locus (9p21) encodes two unique and unrelated cell cycle regulators, p16INK4a and p14ARF. This study was performed to evaluate the methylation status of p16INK4a and p14ARF genes, as well as its association with p16 and p53 expression, microsatellite instability (MI) status, and various clinicopathologic parameters in sporadic colorectal cancer. Sixty-five cases of primary colorectal adenocarcinoma with a series of clinicopathological parameters were obtained. We performed methylation-specific PCR of p16INK4a and p14ARF genes in colorectal cancer paraffin blocks with its paired normal samples, as well as immunohistochemical stainings for p16 and p53, and MI analysis. Aberrant methylations of p16INK4a and p14ARF gene were present in 21 (32.3%) and 33 (50.8%) out of 65 cases, respectively. p16INK4a aberrant methylation was correlated with p16 negativity (P=0.021) and p53 overexpression (P=0.007). p16INK4a aberrant methylation was more frequently present in poorly differentiated adenocarcinomas (P=0.002). Aberrant methylation of p14ARF gene occurred more frequently in patients under 50 years of age and in left-sided colon cancers, and was not statistically significant. Compared with the group with simultaneous absence of methylation in both promoters, the group showing concomitant alterations in both p16INK4a and p14ARF genes (n=10) more frequently presented lymph node metastasis (P=0.020) and higher tumor grade (P=0.014). There was no correlation between p16INK4a and p14ARF gene hypermethylation or MI status. This study suggests that simultaneous hypermethylation of both p16INK4a and p14ARF genes is greater prognostic value in sporadic human colorectal cancer.
INK4a/ARF基因座（9p21）编码两种独特且不相关的细胞周期调节因子，即p16INK4a和p14ARF。本研究旨在评估p16INK4a和p14ARF基因的甲基化状态，及其与散发性结直肠癌中p16和p53表达、微卫星不稳定性（MI）状态以及各种临床病理参数的相关性。获取了65例具有一系列临床病理参数的原发性结直肠腺癌病例。我们对结直肠癌石蜡块及其配对的正常样本进行了p16INK4a和p14ARF基因的甲基化特异性PCR，以及p16和p53的免疫组织化学染色和MI分析。65例病例中，分别有21例（32.3%）和33例（50.8%）存在p16INK4a和p14ARF基因的异常甲基化。p16INK4a异常甲基化与p16阴性（P = 0.021）和p53过表达（P = 0.007）相关。p16INK4a异常甲基化在低分化腺癌中更常见（P = 0.002）。p14ARF基因的异常甲基化在50岁以下患者和左侧结肠癌中更频繁发生，但差异无统计学意义。与两个启动子均无甲基化的组相比，p16INK4a和p14ARF基因同时发生改变的组（n = 10）更频繁出现淋巴结转移（P = 0.020）和更高的肿瘤分级（P = 0.014）。p16INK4a和p14ARF基因高甲基化与MI状态之间无相关性。本研究表明，p16INK4a和p14ARF基因同时高甲基化在散发性人类结直肠癌中具有更大的预后价值。
