p16基因启动子区甲基化在人嗜铬细胞瘤和副神经节瘤中的变化

目的 检测嗜铬细胞瘤(PHEO)和副神经节瘤(PGL)中p16基因突变和启动子区DNA甲基化改变,分析其与患者临床特征之间的关系.方法收集34例(PHEO 20例、PGL14例)组织标本及患者临床资料,通过甲基化特异性PCR(MSP)测定p16基因启动子区甲基化状态,DNA测序检测基因序列以及RT-PCR方法测定其mRNA表达.结果 (1)34例肿瘤组织中未发现p16基因纯合缺失及点突变;(2)35.3%(12/34)的患者存在p16基因高甲基化,p16基因甲基化阳性标本中,PHEO和PGL分别占25%和75%,两者差异有统计学意义(P=0.005);p16基因甲基化在恶性、单发肿瘤、发病年龄早的亚组中有增高趋势(P＞0.05);(3)甲基化与非甲基化肿瘤组织之间p16 mRNA表达无统计学差异;不同特点的肿瘤中其mRNA表达亦无统计学差异,但恶性肿瘤p16 mRNA表达与良性肿瘤相比有下降的趋势(0.83±0.65对1.12±0.81,P=0.278).结论人PHEO和PGL中,p16基因纯合缺失和突变并不常见,但p16基因启动子区甲基化是其失活的主要形式.

Methylation of p16 gene promoter in human pheochromocytomas and paragangliomas

Objective To elucidate gene mutation and promoter methylation changes of p16 gene in pheochromocytomas (PHEO) and paragangliomas (PGL) and to assess its relation with tumor clinical characters. Methods A total of 34 tumors (20 PHEO, 14 PG L, 15 benign, 19 malignant) were collected.Direct sequencing of p16 gene after PCR was performed to analyze genetic alterations. Hypermethylation of p16 gene promoter CpG island was analyzed by methylation specific PCR(MSP). In addition, mRNA expression was detected by RT-PCR. Results Homozygous deletion and gene mutation were not observed in 34 PHEO and PGL. Aberrant methylation of p16 gene promoter CpG island was found in 35.3% (12 of 34 tumors, 3 PHEO, 9 PGL). The p16 promoter hypermethylation in PGL was significantly higher than PHEO (P=0. 005). The higher p16 promoter hypermethylation was associated with malignant behavior, tumor number, and younger age at presentation, but no statistical significance, due to the limited number of cases. The p16 mRNA expression in malignant cases was lower than in benign tumors(0.83±0.65 vs 1.12±0.81 ,P=0.278). Conclusion p16 gene homozygous deletion and mutation were not frequent in PHEO and PGL. The promoter hypermethylation is mainly attributed to inactivation of the p16 gene.