“It … that 6-mercaptopurine acts as … for Lactobacillus casei?V2 The free purines adenine, guanine, xanthine, and hypoxanthine blocked the inhibitory activity of 6-mercaptopurine for this organism in a …-mercaptopurine has also been demonstrated to have an inhibitory effect on the growth of experimental tumors and human neoplash?-?”