ABSTRACT
Epithelial ovarian cancer is one of the increasingly incident malignancies that is notorious because of its evasiveness for early diagnosis and high mortality rates. Epithelial ovarian cancers are highly dependent on pathologic vasculature and Vascular Endothelial Growth Factor is known to be one of the most efficient angiogenic factors. Polymorphisms of the VEGF gene, in this study, were assessed for association with the malignancy and other clinico-pathological factors. 300 case samples and 320 age and mensus status matched controls were inculcated into the study. rs699947, rs833061, rs1570360, rs2010963, rs1413711 and rs3025039 were the six single nucleotide polymorphisms that were scrutinized. Genotyping was carried out by polymerase chain reaction and restriction fragment length polymorphism. rs 3025039 showed immense promise as a marker for disease aggression and recurrence and a factor for poor prognosis. rs699947 showed least association with the disease and clinico-pathologic factors studied. rs833061, rs 1570360 showed significant association with some clinico-pathological factors such as bilateral affliction of ovaries and post operative CA-125 levels. rs2010963 associated with presence of ascites in higher volumes. The SNPs under consideration showed no formidable linkage in our study samples. A haplotype analysis (excluding rs699947 and rs1413711) revealed 5 frontrunners being present in >85% of the population with TGGC and CGCC associating significantly as protective and risk factors respectively. These haplotypes showed a dose dependent additive effect of their seeming functionality. This study is unique and a first of its kind carried out in the Indian population of South-east Asia.
Subject(s)
Neoplasms, Glandular and Epithelial/genetics , Ovarian Neoplasms/genetics , Polymorphism, Single Nucleotide , Vascular Endothelial Growth Factor A/genetics , Adult , CA-125 Antigen/metabolism , Carcinoma, Ovarian Epithelial , Chi-Square Distribution , Disease Progression , Female , Gene Frequency , Genotype , Haplotypes , Humans , India , Linkage Disequilibrium , Logistic Models , Middle Aged , Neoplasms, Glandular and Epithelial/pathology , Neoplasms, Glandular and Epithelial/surgery , Ovarian Neoplasms/pathology , Ovarian Neoplasms/surgery , Polymerase Chain ReactionABSTRACT
Silencing of tumor suppressor and tumor-related genes by promoter hypermethylation is one of the major events in ovarian carcinogenesis. In this study, we analyzed aberrant promoter methylation of p16 and RAR-ß genes in 134 epithelial ovarian carcinomas (EOCs), 23 low malignant potential (LMP) tumors, 26 benign cystadenomas, and 15 normal ovarian tissues. Methylation was investigated by methylation-specific PCR (MSP), and the results were confirmed by bisulfite DNA sequencing. Relative gene expression of p16 and RAR-ß was done using quantitative reverse transcriptase PCR (qRT-PCR) on 51 EOC cases, 9 LMP tumors, and 7 benign cystadenomas with 5 normal ovarian tissues. Aberrant methylation for p16 and RAR-ß was present in 43 % (58/134) and 31 % (41/134) in carcinoma cases, 22 % (05/23) and 52 % (12/23) in LMP tumors, and 42 % (11/26) and 69 % (18/26) in benign cystadenomas. No methylation was observed in any of the normal ovarian tissues. The mRNA expression level of p16 and RAR-ß was significantly downregulated in EOC and LMP tumors than the corresponding normal tissues whereas the expression level was normal in benign cystadenomas for p16 and slightly reduced for RAR-ß. A significant correlation of p16 promoter methylation was observed with reduced gene expression in EOC. For RAR-ß, no significant correlation was observed between promoter methylation and gene expression. Our results suggest that epigenetic alterations of p16 and RAR-ß have an important role in ovarian carcinogenesis and that mechanism along with methylation plays a significant role in downregulation of RAR-ß gene in ovarian cancer.
