Injection of siRNA-loaded biodegradable nanoparticles into xenografts of AR-positive LNCaP cells and AR-negative PC3 cells downregulated RXFP1 and resulted in a significant reduction in tumor proliferation and metastasis, implicating RXFP1 as an important growth and survival factor in prostate cancer (20). The gene discussed is RXFP1; the disease is prostate cancer.