Once prostate cancer has metastasized, current treatment methods are generally ineffective. Due to the reported anti-tumor properties of specific nutrients, we investigated the effect of a unique formulation (NS) of lysine, proline, arginine, ascorbic acid, and epigallocatechin gallate on human prostate cancer cell lines: PC-3, DU145 (androgen insensitive) and LNCaP (androgen sensitive), by measuring cell proliferation, MMP expression, and invasion potential. Cell lines DU145, PC-3, and LNCaP were treated at near confluence with NS at various concentrations. Cell proliferation was measured by MTT assay after 24 hours, MMP expression was measured by gelatinase zymography in condition media, and invasion activity was measured by Matrigel. The nutrient mixture did not significantly inhibit PC-3 cell proliferation at 50 microg/ml, but showed significant antiproliferative effect at 500 ug/ml. When treated with NS, proliferation of LNCaP cells was inhibited by 80% of control at 100 microg/ml. NS showed dose-dependent inhibition of DU145 cell proliferation with 47% reduction at 1000 microg/ml. NS showed a dose-dependent inhibition of both MMP-2 and MMP-9 expression by PC-3 cells and MMP-9 expression by PMA-treated (200 ng/ml) DU145 cells. Neither MMP-2 nor MMP-9 gelatinolytic activity was detected in LNCaP cell culture. Invasion of DU145 and LNCaP cells through Matrigel was completely inhibited at 500 microg/ml and PC-3 at 1000 microg/ml. Inhibition of MMP expression and invasion suggests the mixture of nutrients studied is a potent, natural anticancer agent for the treatment of prostate cancer.