Fujita M, Enomoto T, Haba T, Nakashima R, Sasaki M, Yoshino K, Wada H, Buzard G S, Matsuzaki N, Wakasa K, Murata Y
Department of Obstetrics and Gynecology, Osaka University Medical School, Suita, Japan.
Int J Cancer. 1997 Apr 22;74(2):148-55. doi: 10.1002/(sici)1097-0215(19970422)74:2<148::aid-ijc2>3.0.co;2-z.
We have examined the roles of 2 putative tumor-suppressor genes, the p16 and p15 inhibitor-of-cyclin-dependent-kinase genes, in the most commonly occurring epithelial tumors of the human ovary. Expression of p16 mRNA, examined by RT-PCR, was significantly reduced in 15 of the 48 tumors. Aberrant expression of p16 protein, detected by immunohistochemistry, occurred in 22 of 60 tumors, more frequently in low-grade tumors, and had significant correlation with low p16 mRNA expression. Hypermethylation of a site within the 5'-CpG island of the p16 gene was significantly associated with loss of p16 mRNA and protein expression. Homozygous gene deletion, evaluated by differential PCR analysis, was found in 2 tumors for the p16 gene and in 1 tumor for the p15 gene among 70 ovarian tumors examined. PCR-SSCP analysis detected point mutations in p16 in 4 tumors and in p15 in 1 tumor. One was a 38-bp deletion, from codons 48 to 60, in a mucinous tumor of low malignant potential; another was a non-sense mutation in codon 60 in a mucinous adenocarcinoma. The remaining 2 mutations were mis-sense mutations, one in codon 58 and the other in codon 60, in 2 endometrioid adenocarcinomas. We conclude that inactivation of p16, by loss of p16 mRNA and protein expression as a consequence of hypermethylation of the 5'-CpG island, rather than by gene deletion or point mutation, may play an important role in the genesis of human ovarian epithelial tumors.
我们研究了2个假定的肿瘤抑制基因，即p16和p15细胞周期蛋白依赖性激酶抑制基因，在人类卵巢最常见的上皮性肿瘤中的作用。通过逆转录聚合酶链反应（RT-PCR）检测，48个肿瘤中有15个肿瘤的p16 mRNA表达显著降低。通过免疫组织化学检测，60个肿瘤中有22个肿瘤出现p16蛋白异常表达，在低级别肿瘤中更常见，且与p16 mRNA低表达显著相关。p16基因5'-CpG岛内一个位点的高甲基化与p16 mRNA和蛋白表达缺失显著相关。在70个检测的卵巢肿瘤中，通过差异聚合酶链反应分析评估，发现2个肿瘤存在p16基因纯合子缺失，1个肿瘤存在p15基因纯合子缺失。聚合酶链反应-单链构象多态性（PCR-SSCP）分析在4个肿瘤中检测到p16点突变，在1个肿瘤中检测到p15点突变。1个是低恶性潜能黏液性肿瘤中第48至60密码子的38 bp缺失；另一个是黏液性腺癌中第60密码子的无义突变。其余2个突变是错义突变，分别在2个子宫内膜样腺癌中，一个在第58密码子，另一个在第60密码子。我们得出结论，p16的失活，即由于5'-CpG岛高甲基化导致p16 mRNA和蛋白表达缺失，而非基因缺失或点突变，可能在人类卵巢上皮性肿瘤的发生中起重要作用。
