Overexpression of the EphA2 tyrosine kinase in prostate cancer

BACKGROUND. Molecules that are highly expressed by human prostate cancers m ay serve as therapeutically relevant targets or tumor markers. Tyrosine kin ases are frequently overexpressed in metastatic tumor cells and this prompt ed us to screen for tyrosine kinases that are overexpressed in prostate can cer cells. METHODS. Expression levels of the EphA2 receptor tyrosine kinase were deter mined by Western blot analysis in canine and human prostate cancer cell lin es and in immortalized and transformed variants of 267B1 prostatic epitheli al cells. EphA2 levels in benign human prostate and prostate cancers were a lso determined in formalin-fixed, paraffin-embedded tissues using immunohis tochemical staining. RESULTS. Metastatic prostate cancer cells overexpressed EphA2 by 10-100 fol d as compared with non-invasive prostatic epithelial cells. EphA2 immunorea ctivity in vivo was also significantly greater in human prostate cancers as compared with benign prostate epithelium. CONCLUSIONS. The EphA2 receptor tyrosine kinase is differentially expressed in human and canine prostate cancer cell lines and overexpressed in human prostate cancers as compared with benign prostate tissues. Metastasis-deriv ed canine prostate carcinoma cell lines overexpress EphA2 and may provide p re-clinical models to further evaluate the role of EphA2 in prostate carcin ogenesis. Further investigations are needed to determine the utility of Eph A2! as a tumor marker and a novel target in human prostate cancer. (C) 1999 Wiley-Liss, Inc.