Glycoprotein non- metastatic melanoma protein B as a predictive prognostic factor in clear- cell renal cell carcinoma following radical nephrectomy

Current cancer therapies are largely reliant upon drugs and radiation that kill dividing cells or inhibit cell division in the primary tumor after radical surgery, whereas metastatic tumors should be more commonly the focus of targeted molecular therapies. Glycoprotein non-metastatic melanoma protein B (Gpnmb) is expressed in various types of cancer, and promotes the migration, invasion and metastasis of tumor cells. Thus, it was hypothesized that a unique clear-cell renal carcinoma (ccRCC) subclone expressing a high level of Gpnmb may metastasize more easily and thus be associated with poor prognosis. In the present study, the expression of Gpnmb was analyzed in primary and metastatic ccRCC samples, and the expression levels of Gpnmb were significantly higher in metastatic ccRCCs than in matched primary samples (P=0.036). Receiver operating characteristic (ROC) curve analysis was then performed to determine a cutoff score for Gpnmb expression in another 43 primary ccRCCs. For validation, the ROC-derived cutoff score was subjected to an analysis of the association between Gpnmb expression and patient outcome/clinical characteristics. Kaplan-Meier analysis demonstrated that elevated Gpnmb expression predicted a poorer overall survival (OS) in 43 cases of primary ccRCC. In addition, multivariate analyses revealed that Gpnmb expression served as an independent risk factor for ccRCC. Thus, the overexpression of Gpnmb identified patients at high risk and Gpnmb is a potential therapeutic molecular target for this type of tumor.