Objective methods for diagnosing a predisposition to developing prostate cancer (PRC) are described herein. In one embodiment, the diagnostic method involves the determining a expression level of EphA4. The present invention further provides methods of screening for therapeutic agents useful in the treatment of PRC, methods of treating PRC. The invention also features a method for inhibiting growth of a cancer cell by contacting the cell with a composition of a siRNA of EPHA4. Methods of treating cancer are also within the invention. The invention also features products, including nucleic acid sequences and vectors as well as to compositions comprising them, useful in the provided methods. The invention also provides a method for inhibiting of tumor cell, for example pancreatic cancer cell, particularly pancreatic ductal adenocarcinoma (PDACa).