It was previously shown that cFos up-regulation mediated the HXR9-induced apoptosis in melanoma B16F10 cells, and here we show that a similar mechanism exists in the prostate cancer-derived cell lines DU145, PC3 and LNCaP, as siRNA knock-down of cFos can partially rescue each of these cell lines from HXR9 –induced cell death. The gene discussed is FOS; the disease is Familial prostate cancer.