Proteomics of the ascitic fluid for the differentiation of advanced ovarian cancer.

Abstract

e15510 Background: Ovarian cancers are classified as primary, if it arises in the ovary and secondary or metastatic, if the origin is from other parts of the body. The clinical manifestations of these cancers in the advanced stage are very similar making it difficult to distinguish clinically, hiostopathologically and radiologicaly. The therapeutics and management of the primary and secondary malignancies are completely different. While, the advanced primary malignancies are treated by cytoreduction followed by chemotherapy, the metastatic tumors are treated mainly with palliative chemotherapy. The prognosis is better for primary than secondary ovarian cancer making their diagnosis very crucial for patient care. Methods: 1D and 2D-gel based proteomic approaches were used to study the differentially expressed proteins in the ascitic fluid of patients (10 primary and 4 secondary) with advanced ovarian cancer. The relative ratios of the protein expression were estimated by densitometric analysis. The bands/spots with more than three fold difference were subjected to in-gel trypsin digestion and identified by mass spectrometric analysis. The differential expression of one of the proteins was further validated by western blot experiments and ELISA. Results: Programmed Cell Death 1-Ligand 2 and apolipoprotein A1 were seen to be up regulated in the advanced primary ovarian cancer while apolipoprotein A4, and chain L, humanized version of the anti-human fas antibody Hfe7a were seen to be up regulated in the metastatic variant. Validation for the expression of apolipoprotein A1 shows that a 61.8ng/ml cut off is ideal to differentiate the primary and secondary advanced ovarian cancers. The assay has 100% sensitivity, 75% specificity, positive predictive value of 90.9%, negative predictive value of 100%, accuracy of 92.85% and a pre-test odds positive of 2.5. Conclusions: Proteomics of ascitic fluid is useful for the differentiation of advanced ovarian cancers. There are proteins which are differentially expressed in the ascitic fluid of patients with primary and secondary ovarian cancer. Apolipoprotein A1 is a potential biomarker that can be used to differentiate the closely mimicking clinical scenarios of advanced ovarian cancer.