Aberrant p16INK4a methylation is a frequent event in colorectal cancers: prognostic value and relation to mRNA expression and immunoreactivity
Aberrant p16INK4a methylation is a frequent event in colorectal cancers: prognostic value and relation to mRNA expression and immunoreactivity
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DOI：
10.1007/s00432-009-0688-z
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发表时间：
2010-02-01
影响因子：
3.6
通讯作者：
Yao, Takashi
中科院分区：
文献类型：
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作者：
Mitomi, Hiroyuki;Fukui, Naoshi;Yao, Takashi
P16(INK4a)启动子异常甲基化在结直肠癌中很常见，但其临床病理意义仍存在争议。因此，本研究旨在分析p16(INK4a)甲基化及其与临床病理特征、mRNA水平和免疫反应性的关系。采用甲基化特异的实时荧光定量聚合酶链式反应检测30例正常粘膜和212例结直肠癌标本中p16(INK4a)的甲基化，并通过免疫组化染色检测福尔马林固定的石蜡包埋标本中p16(INK4a)的表达。此外，采用逆转录-聚合酶链式反应分析了61例新鲜DNA与p16(INK4a)基因表达的关系。正常组织中p16(INK4a)甲基化指数介于0至2%之间(平均0.23%；中位数0.02%)，而肿瘤标本中p16(INK4a)甲基化指数介于0至100%之间(平均25.7%；中位数7.1%)，差异有统计学意义(P<；0.001)。在151例石蜡包埋的结直肠癌组织标本中，51例(34%)、54例(36%)和46例(30%)的p16(INK4a)异常甲基化被归类为低、中和高度甲基化。P16(INK4a)高甲基化与肿瘤大小显著相关(P=0.025)。与低甲基化组相比，高甲基化患者的复发频率更高，癌症相关生存期(风险比，3.379；P<；0.001)和无复发生存期(多因素分析，HR，3.962；P<；0.001)缩短。P16(INK4a)甲基化与免疫反应性呈显著负相关(P=0.017)。P16(INK4a)基因甲基化导致转录沉默，是一组预后较差的癌组织。
Aberrant p16(INK4a) promoter methylation is common in colorectal cancer (CRC), but its clinicopathological significance remains controversial. The present study was therefore conducted to analyze p16(INK4a) methylation and its relationship to clinicopathological features, mRNA levels and immunoreactivity in a series of lesions.p16(INK4a) methylation was assessed for normal mucosa (n = 30) and CRC samples (n = 212) by methylation-specific real-time quantitative PCR, and p16(INK4a) expression by immunostaining in formalin-fixed paraffin-embedded specimens. In addition, fresh DNA (n = 61) was analyzed for relationships to p16(INK4a) mRNA by reverse-transcription PCR.The p16(INK4a) methylation index of normal mucosa samples ranged from 0 to 2% (mean, 0.23%; median, 0.02%), while the values for tumor samples varied widely from 0 to 100% (mean, 25.7%; median, 7.1%), the difference being statistically significant (P < 0.001). Of 151 paraffin-embedded CRC tissue samples, 51 (34%), 54 (36%), and 46 (30%) were classified as low, intermediate, and high for aberrant methylation of p16(INK4a). High p16(INK4a) methylation was significantly associated with large tumor size (P = 0.025). Patients with higher methylation further showed more frequent recurrence as compared with the low-methylation group, and shortened cancer-related survival (Hazard ratio [HR], 3.379; P < 0.001) and recurrence-free survival (HR, 3.962; P < 0.001 on multivariate analysis). A significant inverse relationship was apparent between the p16(INK4a) methylation and immunoreactivity (P = 0.017). A similar tendency was also observed for the methylation status and the mRNA level (P = 0.195).We conclude that p16(INK4a) methylation results in transcriptional silencing and defines a group of CRCs with a poor prognosis.