Immune modulator CD70 as a potential cisplatin resistance predictive marker in ovarian cancer

Abstract Objective We have used mass-spectrometry (MS) based proteomics platform to identify cell surface proteins over-expressed on a cisplatin resistant derivative of an ovarian cancer cell line A2780. Methods Membrane associated glycoproteins from A2780 and its cisplatin resistant derivative cell line, A2780cis, were processed for liquid chromatography (LC)-MS based analysis. The expression of proteins found at elevated levels in A2780cis cell line was confirmed using flow cytometry and Taqman analysis. The expression of these proteins was further evaluated in unrelated ovarian cancer cell lines using MS analysis and flow cytometry. Immunohistochemical (IHC) analysis was performed using ovarian tumor tissues to evaluate the protein density on the cell surface. Monoclonal antibodies were used in an alamar blue proliferation assay to examine the cytotoxic effects on cell proliferation in resistant cell lines. Results Six proteins were identified by LC-MS as being over-expressed on cell surface of A2780cis cell line. Mass spectrometry and flow cytometry confirmed the over-expression of CD49f, CD70 and Her-2/neu in other cisplatin resistant ovarian cancer cell lines. Immunohistochemical analysis revealed that only CD70 was expressed at moderate levels in ovarian tumors. When cisplatin resistant ovarian cell lines A2780cis and SKOV-3 were treated with antibody against CD70, there was a significant decrease in cell proliferation. Conclusion Using a MS based proteomics approach we have shown that expression of CD70 is associated with cisplatin resistance in ovarian cancer cell lines. Follow-up examination of these tumor cell line findings in clinical tumor specimens with available pathology staging and cisplatin treatment history is warranted.