Lü Qing-jie, Zhao Xiao-dong, Song Ji-ye, Li Xiao-han, Ma Ying, Meng Hui, Jiang Wei-guo
Department of Pathology, The Second Clinical College, China Medical University, Shenyang 110004, China.
Zhonghua Bing Li Xue Za Zhi. 2005 May;34(5):266-9.
To investigate the mechanisms of PTEN gene inactivation starting from DNA, mRNA and protein levels in ovarian cancers.
Tumor tissue samples were obtained from 48 patients with epithelial ovarian cancers. Using four polymorphic markers (D10s541, D10s583, D10s1687 and D10s2491) within and flanking the PTEN gene located in chromosome 10q 23.3, polymerase chain reaction (PCR) and loss of heterozygosity (LOH) were introduced to examine LOH of PTEN gene; PCR-single strand conformation polymorphism (PCR-SSCP) was introduced to examine mutations of the fifth, sixth, seventh, and eighth exons of PTEN. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry (SP method) were applied to detect PTEN mRNA and PTEN protein expressions, respectively.
LOH of PTEN gene was observed in 19 of 48 (39.6%) ovarian cancers. PTEN mutations were found only in 2 (4.2%) of the cases. Absence of PTEN mRNA expression was 18.8% (9 of 48). Immunostaining of 48 cancer samples revealed that 13 (27.1%) were PTEN immunostain negative. Of these 13 samples, only 2 (15.4%) had structural, biallelic inactivation by intragenic PTEN mutations and loss of the remaining wild-type allele; 7 (53.8%) showed evidence of LOH, 5 of these 7 samples showed deletion of PTEN mRNA expression, another 2 samples showed positive expression of PTEN mRNA; 4 (30.8%) tumors had neither PTEN gene mutation nor LOH but exhibited no PTEN protein expression, 2 of these 4 cases showed deletion of PTEN mRNA expression, another 2 showed positive expression of PTEN mRNA. For the cases of PTEN protein absent staining, the rate of LOH was 69.2% (9 of 13), higher than 28.6% (10 of 35) for the positive staining (P < 0.05).
PTEN gene inactivation may contribute to epithelial ovarian carcinogenesis. There may be several mechanisms of PTEN gene inactivation in ovarian cancers. Protein expression deletions may be a significant mechanism.
从DNA、mRNA和蛋白质水平研究卵巢癌中PTEN基因失活的机制。
收集48例上皮性卵巢癌患者的肿瘤组织样本。利用位于10q 23.3染色体上PTEN基因内部及侧翼的4个多态性标记（D10s541、D10s583、D10s1687和D10s2491），采用聚合酶链反应（PCR）和杂合性缺失（LOH）检测PTEN基因的LOH情况；采用PCR-单链构象多态性（PCR-SSCP）检测PTEN基因第5、6、7和8外显子的突变情况。分别应用逆转录-聚合酶链反应（RT-PCR）和免疫组织化学（SP法）检测PTEN mRNA和PTEN蛋白的表达。
48例卵巢癌中19例（39.6%）检测到PTEN基因的LOH。仅2例（4.2%）发现PTEN突变。48例中PTEN mRNA表达缺失的占18.8%（9例）。48例癌组织样本免疫染色显示，13例（27.1%）PTEN免疫染色阴性。在这13例样本中，仅2例（15.4%）因基因内PTEN突变和剩余野生型等位基因缺失而发生结构上的双等位基因失活；7例（53.8%）存在LOH证据，其中5例样本PTEN mRNA表达缺失，另外2例样本PTEN mRNA表达阳性；4例（30.8%）肿瘤既无PTEN基因突变也无LOH，但PTEN蛋白无表达，其中2例PTEN mRNA表达缺失，另外2例PTEN mRNA表达阳性。PTEN蛋白染色阴性的病例中，LOH发生率为69.2%（13例中的9例），高于阳性染色病例的28.6%（35例中的10例）（P<0.05）。
PTEN基因失活可能参与上皮性卵巢癌的发生。卵巢癌中PTEN基因失活可能存在多种机制。蛋白表达缺失可能是一种重要机制。
