Ranitidine and cimetidine differ in their in vitro and in vivo effects on human colonic cancer growth

Histamine has recently been shown to be a growth factor for some gastric and colorectal cancer cells. Previous studies have shown that cimetidine blocks in vitro and in vivo histamine-stimulated growth and cAMP release from the human colonic cancer cell line, C170. In this study, ranitidine, another H-2 receptor antagonist, did not affect either basal or histamine-stimulated in vitro proliferation of C170, and Failed to prevent cAMP release in vitro. Ranitidine did not inhibit in vivo growth of C170 at a dose of 1, 10, 25, 50 or 100 mg kg(-1), in contrast to 50 mg kg(-1) day(-1) cimetidine, which produced 39.3% inhibition of tumour volume (P < 0.01) after 23 days' treatment. Ranitidine did not inhibit in vivo histamine-stimulated growth of C170 cells. LIM2412, another colonic cancer cell line, was significantly stimulated by both cimetidine and ranitidine in vivo. Ranitidine had no effect on in vitro cell proliferation.