ABSTRACT
<p><b>OBJECTIVE</b>To investigate the expression of two major alternative transcripts of RASSF1 gene (RASSF1A and RASSF1C) in human primary ovarian cancers and their biological implication as a new tumor suppressor gene.</p><p><b>METHODS</b>Reverse transcription-polymerase chain reaction (RT-PCR) and laser capture microdissection (LCM) were used to determine mRNA expression of the two major alternative transcripts of RASSF1 gene (RASSF1A and RASSF1C) in 3 ovarian cancer cell lines and 80 cases of primary ovarian cancers.</p><p><b>RESULTS</b>RASSF1A mRNA was undetectable in SK-OV-3 cell line. Expression of RASSF1A and RASSF1C in 80 primary ovarian cancers were 40.0% (32/80) and 91.3% (73/80) respectively. RASSF1A mRNA expression was detectable more frequently in stage I and II (71.4%, 10/14; 75.0%, 9/12) than in stage III and IV ovarian cancers (26.7%, 12/45; 14.1%, 1/9) (P < 0.05). The expression level was also higher in well and moderately differentiated tumor groups (58.6%, 17/29; 50.0%, 10/20) than in poorly differentiated tumor group (16.1%, 5/31) (P < 0.05).</p><p><b>CONCLUSION</b>There is a preferential loss of RASSF1A expression in human ovarian cancers and its expression is correlated with the tumor stage and the degree of histological differentiation which, as a tumor suppressor gene, might play an important role in the tumorigenesis of human primary ovarian cancer.</p>
Subject(s)
Female , Humans , Carcinoma, Endometrioid , Metabolism , Pathology , Cell Line, Tumor , Cystadenocarcinoma, Mucinous , Metabolism , Pathology , Cystadenocarcinoma, Serous , Metabolism , Pathology , Gene Expression Regulation, Neoplastic , Genes, Tumor Suppressor , Neoplasm Staging , Ovarian Neoplasms , Metabolism , Pathology , Prognosis , RNA, Messenger , Genetics , Reverse Transcriptase Polymerase Chain Reaction , Tumor Suppressor Proteins , GeneticsABSTRACT
<p><b>OBJECTIVE</b>To investigate hypermethylation of promoter region of RASSF1A and its relationship with ovarian malignant epithelial tumors.</p><p><b>METHODS</b>Methylation-specific PCR (MSP) was used to determine the hypermethylation of promoter region of ras association domain family 1 (RASSF1A) gene in 80 cases of ovarian malignant epithelial tumors.</p><p><b>RESULTS</b>No methylation of promoter region of RASSF1A gene was found in all 80 normal control tissues (0). Of 80 ovarian malignant epithelial tumors 42 were hypermethylated in promoter region of RASSF1A gene (52.5%). There was no statistically significant difference in the frequency of hypermethylation of RASSF1A gene among serious adenocarcinomas, mucinous adenocarcinomas and endometrioid adenocarcinomas (54.2%, 52.4% and 45.5%, respectively; P > 0.05). Hypermethylation of RASSF1A gene happened more often in tumors in stage III and IV (66.7% and 77.8%) than that in stage I and II (21.4% and 16.7%; P < 0.05). It was less frequently observed in well and moderately differentiated tumors (34.5% and 35.0%) than in poorly differentiated tumors (80.6%; P < 0.05).</p><p><b>CONCLUSION</b>High frequency of methylation of RASSF1A promoter exists in ovarian malignant epithelial tumors as a tumor suppressor gene, its suppressor activity may be abrogated by an epigenetic mechanism. Hypermethylation of RASSF1A promoter in patients with epithelial malignant ovarian tumors is related to clinical stage and histopathological grade. It indicates poor prognosis.</p>