p73基因在卵巢上皮性肿瘤中的表达及甲基化研究

目的 探讨卵巢上皮性肿瘤中p73蛋白的表达和基因启动子的甲基化情况,并观察其与临床病理学特征的关系.方法 制备包括68例卵巢癌、37例卵巢交界性肿瘤和21例卵巢良性肿瘤的组织芯片,用免疫组织化学EnVision法检测上述组织中p73蛋白表达情况,用亚硫酸氧盐修饰后测序法检测13例新鲜卵巢癌组织及5例新鲜卵巢交界性肿瘤组织的p73基因启动子甲基化情况.结果 92.6％ (63/68)的卵巢癌表达p73,p73蛋白总体表达率均值为32％(p73表达率指p73阳性细胞数所占的百分比),其中浆液性癌( 26/26)的表达率均值为40％,高于其他组织类型的癌(P=0.006).按照卵巢癌发病模式区分,Ⅱ型卵巢癌p73表达率均值(40％)高于Ⅰ型卵巢癌(24％),P=0.010.卵巢癌中p73的表达与临床分期及组织学分级无相关性(均P＞0.05).卵巢交界性肿瘤组(30/37)和良性肿瘤组(12/21)p73的总体表达率均值分别为16％和15％,该两组肿瘤中浆液性肿瘤表达率均值均高于黏液性肿瘤(P-0.003,P=0.026).卵巢癌组的p73阳性表达率均值明显高于交界性肿瘤组和良性肿瘤组(均P ＜0.05),交界性肿瘤组与良性肿瘤组比较差异无统计学意义(P＞0.05).浆液性肿瘤( 49/53)中,卵巢癌组(26/26) p73阳性表达率均值明显高于交界性肿瘤组(12/14)和良性肿瘤组(11/13;P =0.024和P=0.002),而卵巢交界性肿瘤组和良性肿瘤组比较差异无统计学意义(P=0.428).黏液性肿瘤(15/27)中,卵巢癌组(6/7)p73阳性表达率均值高于良性肿瘤组( 1/8;p=0.032),而卵巢癌组与卵巢交界性肿瘤组(8/12)、交界性肿瘤组与良性肿瘤组比较,差异均无统计学意义(P=0.234和P=0.201).p73启动子的甲基化结果显示,13例卵巢癌有8例发生甲基化,但每例样本甲基化频率有所不同,总体甲基化频率均值为8.0％.5例交界性肿瘤有2例发生甲基化,总体甲基化频率均值为9.0％,两组比较差异无统计学意义(P＞0.05).卵巢癌组p73甲基化额率与组织类型、发病模式、组织学分级及临床分期均无相关性(均P＞0.05).结论 卵巢上皮性肿瘤多数表达p73,卵巢癌p73的表达率均值明显高于交界性肿瘤和良性肿瘤,浆液性肿瘤高于其他组织类型;p73蛋白表达率与p73基因甲基化程度不存在简单线性相关关系.

Expression and promotor methylation of p73 gene in ovarian epithelial tumors

Objective To investigate the expression and promoter methylation status of p73 gene in ovarian epithelial tumors and their clinicopathological correlations.Methods Tissue microarrays ( TMA )consisting of 68 ovarian cancers,37 ovarian borderline tumors and 21 ovarian benign tumors were constructed.p73 expression was detected by immunohistochemistry (EnVision method).Fresh-frozen tissue samples from 13 cases of ovarian carcinomas and 5 cases of borderline tumors were evaluated for the presence of p73 promoter methylation using bisulfite sequencing.Results Overall,92.6％ (63/68) ovarian carcinomas expressed p73,with a mean value of 32％ (percentage of p73 positive cells in the tumor).The mean value of p73 expression rate (40％) in serous carcinoma ( 26/26 ) was higher than those of other cancer types (P =0.006),The mean value of p73 expression rate (40％) in type Ⅱ ovarian carcinoma was significantly higher than that in type Ⅰ ovarian carcinoma (24％,P =0.010).The expression of p73 was not associated with FIGO stage and histological grade ( both P ＞ 0.05 ).The mean values of p73 expression in ovarian borderline tumor (30/37) and benign tumor ( 12/21 ) were 16％ and 15％,respectively.Of the two groups,the mean value of p73 expression rate in serous type was higher than that in mucous type (P =0.003,P=0.026).Ovarian carcinomas had a higher level of p73 expression than borderline tumors and benign tumors ( both P ＜ 0.05 ),while that between ovarian borderline tumors and benign tumors had no statistical difference ( P ＞ 0.05 ).Among serous tumors (49/53),the mean value of p73 expression in the carcinoma group (26/26) was significantly higher than those in the borderline tumor group (12/14) and benign tumor group ( 11/13 ; P =0.024 and P =0.002,respectively),while that between borderline tumor group and benign tumor group had no statistical difference (P =0.428).Among mucous tumors ( 15/27 ),the mean value of p73 expression in carcinoma group (6/7) was higher than that in benign tumor group ( 1/8 ; P =0.032).No statistical difference of p73 expression was seen between the carcinoma group and ovarian borderline tumor group ( 8/12 ) and between the borderline tumor group and benign tumor group (P =0.234,P =0.201,respectively).p73 promotor methylation was found in 8 of 13 cases of carcinomas but at different methylation levels with a mean value of 8.0％.Two of 5 ovarian borderline tumors showed detectable p73 promotor methylation with a mean value of 9.0％.Compared with the borderline tumors,ovarian carcinomas showed a similar p73 methylation level (P ＞ 0.05).The p73 methylation level in ovarian carcinomas was not associated with histological type,pathogenetic type,histological grade and FIGO stage ( all P ＞ 0.05 ).Conclusions Most of ovarian epithelial tumors express p73 protein with mean values higher in ovarian carcinomas than those in the borderline and benign tumors.Ovarian serous carcinomas have the highest expression level of p73. A simple linear correlation does not exist between the promoter methylation and protein expression of p73.