HRAS and prostate cancer: To overexpress ERBB2 and RAS oncogenes in prostate cancer cell lines, we transfected prostate cancer cells with pBabe-Puromycin- (PBP-) based retroviruses overexpressing an activated form of ERBB2 (PBP-ERBB2) or a mutated form of H-RAS (PBP-RAS).