Proteomics-based identification of secreted protein dihydrodiol dehydrogenase 2 as a potential biomarker for predicting cisplatin efficacy in advanced NSCLC patients

Background and purpose: Cisplatin is the major agent in the standard first-line chemotherapy for NSCLC. However, only a small portion of patients achieve a tumor response to cisplatin-based chemotherapy and eventually develop acquired resistance. The aim of this study was to identify potential biomarkers that could predict the efficacy of cisplatin. Methods: Human lung adenocarcinoma cell line A549 was exposed to cisplatin for development of a resistant cell line, A549/DDP, and cisplatin-sensitivity was tested through the MTT assay. The global protein profiles from A549 and A549/DDP were compared using a proteomic approach. Western blot, real-time PCR and immunohistochemistry validated the expression of DDH2 in cell lines and tumor xenografts. Serum levels of DDH2 were measured by ELISA in 105 NSCLC patients treated with cisplatin-based chemotherapy. Result: The resistance of A549/DDP to cisplatin was 8.07-fold higher than that of A549 cells. Proteomic approach identified eight differentially (>5-fold) expressed proteins. Among them, secreted protein DDH2 was further investigated and it was found overexpressed through the method of Western blot, real-time PCR in cell lines, consistent with immunohistochemistry validation in xenograft. Clinical research showed that baseline serum DDH2 level in the patients with a progression disease was significantly higher than the patients of response or stable disease (9.036 vs. 3.529 and 3.982 ng/mL, P < 0.001) and serum DDH2 levels were significantly increased after cisplatin-based doublet chemotherapy (5.515 vs. 12.935 vs. 18.406 ng/mL P < 0.001, respectively). Conclusion: DDH2 expression might be a potential predictor and monitor of cisplatin efficacy in advanced NSCLC patients.