In Vitro: PRMT5:MEP50 PPI (0-10 μM; 72 h) inhibits the growth of prostate cancer cells. PRMT5:MEP50 PPI (250-1000 nM; 72 h) decreases the expression of global arginine 3 residue of histone H4 (H4R3me2s) level in prostate cancer cells. PRMT5:MEP50 PPI (500 nM; 72 h) de-represseses the PRMT5: MEP50-regulated IVL gene of prostate cancer cells. PRMT5:MEP50 PPI treatment inhibits multiple PRMT5-regulated pathways critical to the survival and proliferation of lung and prostate cancer cells.