Wang Cuiju, Horiuchi Akiko, Imai Tsutomu, Ohira Satoshi, Itoh Kazuko, Nikaido Toshio, Katsuyama Yoshihiko, Konishi Ikuo
Department of Obstetrics and Gynaecology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
J Pathol. 2004 Feb;202(2):215-23. doi: 10.1002/path.1507.
BRCA1 is a putative tumour suppressor gene responsible for a hereditary ovarian cancer syndrome. To clarify the possible involvement of BRCA1 in the development of sporadic ovarian neoplasms, this study analysed the immunohistochemical expression of BRCA1 protein in normal ovarian surface epithelium and 119 epithelial ovarian tumours (19 benign, 24 borderline, and 76 malignant tumours). Loss of heterozygosity (LOH) of BRCA1 was examined using three microsatellite markers to analyse the relationship between BRCA1 expression and alterations of the BRCA1 gene. Methylation of the BRCA1 promoter was also analysed by methylation-specific PCR. In ovarian carcinomas showing heterogeneous expression of BRCA1 protein in the same tumour, LOH and methylation status were analysed using microdissection techniques. Finally, the relationship of BRCA1 expression or its genetic alteration to clinicopathological parameters and patient survival was analysed. Ovarian surface epithelial cells expressed BRCA1 protein. Decreased expression of BRCA1 was found in 16% of benign tumours, 38% of borderline tumours, and 72% of carcinomas. LOH of BRCA1 was demonstrated in no benign tumours, 15% of borderline tumours, and 66% of carcinomas. Methylation of BRCA1 was not detected in benign or borderline tumours, but was present in 31% of carcinomas. Reduced expression of BRCA1 correlated with the presence of gene methylation. The frequency of BRCA1 methylation and LOH was higher in serous carcinomas than in other types. In one of the three serous carcinomas that showed heterogeneous expression of BRCA1, BRCA1-positive borderline-like tumour cells were LOH-positive and methylation-negative, whereas adjacent BRCA1-negative carcinoma cells were LOH-positive and methylation-positive. The prognosis of carcinoma patients did not correlate with BRCA1 expression or genetic status. These findings suggest that reduced expression of BRCA1 protein along with genetic and epigenetic changes of the BRCA1 gene play an important role in the development of sporadic ovarian carcinomas, particularly those of serous histology.
BRCA1是一种假定的肿瘤抑制基因，与遗传性卵巢癌综合征相关。为阐明BRCA1在散发性卵巢肿瘤发生过程中可能的作用，本研究分析了BRCA1蛋白在正常卵巢表面上皮及119例上皮性卵巢肿瘤（19例良性、24例交界性和76例恶性肿瘤）中的免疫组化表达。使用三个微卫星标记检测BRCA1的杂合性缺失（LOH），以分析BRCA1表达与BRCA1基因改变之间的关系。还通过甲基化特异性PCR分析BRCA1启动子的甲基化情况。对于同一肿瘤中BRCA1蛋白呈异质性表达的卵巢癌，采用显微切割技术分析其LOH和甲基化状态。最后，分析BRCA1表达或其基因改变与临床病理参数及患者生存的关系。卵巢表面上皮细胞表达BRCA1蛋白。在16%的良性肿瘤、38%的交界性肿瘤和72%的癌中发现BRCA1表达降低。在良性肿瘤中未检测到BRCA1的LOH，在15%的交界性肿瘤和66%的癌中检测到BRCA1的LOH。在良性或交界性肿瘤中未检测到BRCA1的甲基化，但在31%的癌中存在BRCA1的甲基化。BRCA1表达降低与基因甲基化的存在相关。浆液性癌中BRCA1甲基化和LOH的频率高于其他类型。在三例BRCA1呈异质性表达的浆液性癌中，其中一例BRCA1阳性的交界样肿瘤细胞LOH阳性且甲基化阴性，而相邻的BRCA1阴性癌细胞LOH阳性且甲基化阳性。癌患者的预后与BRCA1表达或基因状态无关。这些发现表明，BRCA1蛋白表达降低以及BRCA1基因的遗传和表观遗传改变在散发性卵巢癌，尤其是浆液性组织学类型的卵巢癌发生过程中起重要作用。
