Abstract A115: Mitochondrial analysis and epithelial ovarian carcinoma

Abstract

Abstract Survival rates of ovarian cancer patients are low, largely due to late diagnosis. Early detection plays a major role towards improving outcomes in ovarian cancer, however few candidate biomarkers have shown efficacy for the detection of preclinical disease. Human mitochondrial gene mutations have increasingly been associated with various cancers. The mitochondrial genome is highly susceptible to oxidative damage and may accumulate damage over a long period of time. Consequently, variations in (mtDNA) may potentially play a role as a modifying risk factor in the development of age-related diseases such as ovarian cancer. The goal of this study is to examine correlations between mitochondrial gene alterations and three subtypes of ovarian tumor progression. Mitochondrial DNA fragments were obtained from 120 epithelial ovarian cancer tissue samples (40 serous; 40 endometrioid and 40 mucinous ovarian tumors respectively). The entire mitochondrial genome was PCR amplified using 9 overlapping primers sets and analyzed using both high resolution restriction digest and PCR-based sequencing techniques. Additionally, the levels of carbonyl proteins in cytosolic fraction of tissues were assessed by standard colorimetric technique, using 2-4-dinitrophenylhydrazine (DNPH) to derivatize protein, and measure the absorbance of the DNP-hydrazones at 370 nm. In this study we revealed the presence thirty-nine polymorphisms of which 28 were unreported. The observed mutations with notably frequencies (41-93%) among these samples were at np C7028T, C7256T, G7520A, T8548G, T8588C, A8860G, C9488G, C9500T, T9540C, C9857T, and T9951C. Furthermore, six unreported point mutations with frequencies of 14-41 % were observed at np G7520A, T8548G, C9488G, C9500T, C9857 and T9951C. A combined mutation of G7520A and C7256T was frequent at 45% in endometrioid stage III only. Interestingly, variants C7020T (56%) and at np A8860G (92%) were evenly distributed in all three studied ovarian tumor subtype and stages. Variants T9540C and C7520T showed significant higher frequency in African American samples compare to Caucasian samples and these may be used for further investigation for cancer disparity study. A number of the observed sequence variants were germ-lines with variants found in these mitochondrial genes/regions; D-Loop, 12S rRNA-tRNAphe, tRNAval, COX I, tRNAser, tRNAasp, COX II, tRNAlys, ATPase 6, ATPase 8, COX III, ND2, and ND3 genes among the three subtypes of ovarian cancer. Our results showed the elevation of the ratio of protein carbonyl/total protein in all three types of serous polyp as compare to their surrounding tissue. The level of the ratio of protein carbonyls/total protein decreased as a result of serous ovarian tumor progression. Our study suggests that certain mitochondrial DNA sequence variants and protein carbonyl (CO) groups, oxidative stress may play a potential role in etiological differences that may exist between the pathogenicity of subtypes and stages of benign and invasive epithelial ovarian tumors. Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):A115.