Proteomic Analysis of Ovarian Cancer Cells Reveals Dynamic Processes of Protein Secretion and Shedding of Extra-Cellular Domains

Abstract

BackgroundElucidation of the repertoire of secreted and cell surface proteins of tumor cells is relevant to molecular diagnostics, tumor imaging and targeted therapies. We have characterized the cell surface proteome and the proteins released into the extra-cellular milieu of three ovarian cancer cell lines, CaOV3, OVCAR3 and ES2 and of ovarian tumor cells enriched from ascites fluid.Methodology and FindingsTo differentiate proteins released into the media from protein constituents of media utilized for culture, cells were grown in the presence of [13C]-labeled lysine. A biotinylation-based approach was used to capture cell surface associated proteins. Our general experimental strategy consisted of fractionation of proteins from individual compartments followed by proteolytic digestion and LC-MS/MS analysis. In total, some 6,400 proteins were identified with high confidence across all specimens and fractions.Conclusions and SignificanceProtein profiles of the cell lines had substantial similarity to the profiles of human ovarian cancer cells from ascites fluid and included protein markers known to be associated with ovarian cancer. Proteomic analysis indicated extensive shedding from extra-cellular domains of proteins expressed on the cell surface, and remarkably high secretion rates for some proteins (nanograms per million cells per hour). Cell surface and secreted proteins identified by in-depth proteomic profiling of ovarian cancer cells may provide new targets for diagnosis and therapy.

Comparative secretome of ovarian serous carcinoma: Gelsolin in the spotlight

“…Despite the relatively small number of tissue and ascites specimens studied, the majority of proteins identified in the present study as being significantly differentially secreted from malignant and CTRL cell samples had been detected in previous studies (8)(9)(10)(11)(12)(13)(14)(15)(16), confirming their potent and important role. To the best of our knowledge, proteins including HSP-10 and DKK3, had not previously been identified by a proteomic approach, but had been suggested as potent markers using alternate approaches (19,30); however the present study was unable to confirm their utility as biomarkers of serous ovarian cancer by the immunological method.…”

“…Although in vitro culture conditions may not fully reflect the in vivo conditions, identification of ovarian proteins differentially secreted by malignant cells may be a first step towards the elucidation of ovarian cancer markers in blood samples. In this context, secretome analysis of ovarian cancer cell lines has contributed to the establishment of a list of potent biomarkers (11,15,16). However, the pathological relevance of the cell line secretome is debatable.…”

“…Certain previous studies have analyzed the proteomic profiles of ovarian tumor tissues, cell lines, urine, ascites fluid and blood samples (8)(9)(10)(11)(12)(13)(14). Analysis of the ovarian cancer cell line secretome has also provided information on potential markers (11,15).…”

“…Analysis of the ovarian cancer cell line secretome has also provided information on potential markers (11,15). However, these studies were based on cancer cell line comparison analyses, and the in vivo physiological and pathological relevance was questionable.…”

Mining the Ovarian Cancer Ascites Proteome for Potential Ovarian Cancer Biomarkers

“…Also recently Faç a et al (32) characterized the cell surface proteome and the proteins released into the extracellular milieu of three ovarian cancer cell lines and identified over 6000 proteins as candidate biomarkers and therapeutic targets.…”