Growth inhibition of human prostate tumor cells by an agonist of gonadotrophin-releasing hormone

The effect of [D-Leu 6 ,des-Gly-NH 2 10 , Proethylamide 9 ]-GnRH, leuprolide, was determined for the human primary prostate tumor cell line ALVA-31 by in vitro mitogenic assays. Prostate tumor cell proliferation was inhibited up to 50% by leuprolide. Inhibition was not observed in parallel cultures treated with other low molecular weight bioactive peptides. The incorporation and metabolic reduction of testosterone was not affected by concentrations of leuprolide that were inhibitory in the mitogenic assay. Specific high-affinity binding of 125 I-labeled leuprolide was also demonstrated on intact tumor cells with an estimated effective median dose (ED 50 ) of