Mining the malignant ascites proteome for pancreatic cancer biomarkers

Pancreatic cancer (PC) is one of the most lethal malignancies and disease-specific biomarkers are desperately needed for better diagnosis, prognosis, monitoring treatment efficacy and for accelerating the development of novel targeted therapeutics. Being an advanced stage manifestation and a proximal fluid in contact with cancer tissues, the ascitic fluid presents itself as a promising rich source of biomarkers. Herein, we present a comprehensive proteomic analysis of pancreatic ascitic fluid. To fractionate the complex ascites proteome, we adopted a multi-dimensional chromatographic approach that included size-exclusion, ion-exchange and lectin-affinity chromatographic techniques. Our detailed proteomic analysis with high-resolution Orbitrap(®) mass spectrometer resulted in the identification of 816 proteins. We followed rigorous filtering criteria that consisted of PC-specific information obtained from three publicly available databases (Oncomine, Protein Atlas and Unigene) to segregate 20 putative biomarker candidates for future validation. Since these proteins are of membranous and extra-cellular origin, most are glycosylated, and many of them are over-expressed in cancer tissues, the probability of these proteins entering the peripheral blood circulation is high. Their validation as serological PC biomarkers in the future is highly warranted.