Identification and validation of differential plasma proteins levels in epithelial ovarian cancer

Diagnosis of Ovarian cancer (OC) has been a challenge, the purpose, therefore is to identify plasma proteins differentially expressed in epithelial ovarian cancer patients. Human plasma samples from patients with OC (n = 138), benign tumors (n = 20) and controls (n = 238) were used. Tandem Mass Tag (TMT) based quantitative analysis by high resolution mass spectrometry, was followed by validation using Quantibody array and ELISA techniques. 507 plasma proteins showed differential protein levels in OC plasma samples. 21 proteins were validated using Quantibody array. Further, nine proteins (CA125, CFD, CST3, ICAM1, IGFBP2, IGFBP3, SPP1, TSP1 and VEGFA) which showed significant differences in protein levels in Quantibody array analysis were validated using ELISA. In ELISA, the levels of CA125, IGFBP2, ICAM1 and SPP1 were significantly increased and levels of Adipsin and TSP1 were decreased in tumors compared to controls and benign group. Epithelial ovarian cancer diagnosis model combining five markers (CA125, IGFBP2, SPP1, TSP1 and ADI) showed 90.24% sensitivity and 94.87% specificity. In conclusion a panel of 5 plasma proteins has been found to be useful in distinguishing plasma samples from epithelial ovarian cancers from patients with benign tumors and healthy normal subjects. This has the potential as a diagnostic assay for epithelial ovarian cancer. SIGNIFICANCE: The significance of this case-control study is based on the large and well defined ovarian cancer patient population (epithelial ovarian cancers including serous and mucinous subtypes), age matched controls and benign ovarian tumors. This study incorporates a discovery phase involving quantitative proteomic analysis of immune-depleted plasma followed by two levels of validation studies involving a selected list of proteins using antibody arrays and ELISA. The validations were performed on an independent set of samples comprising of epithelial ovarian cancer subtypes, controls and benign tumors. The multiple marker combination comprising of Adipsin, CA125, IGFBP2, SPP1 and TSP1 identified in the study by ELISA could enable rapid translation to a larger screening study.