The ability of nicotinamide to inhibit the growth of a C3H mouse mammary carcinoma.

Experimental studies have suggested that nicotinamide and its analogs may inhibit the growth of murine tumours. We have now investigated this using a C3H mouse mammary carcinoma implanted into the right rear foot of female CDF1 mice. From days 1 to 30 after implantation mice were intraperitoneally (i.p.) injected with either 100, 200, 500 or 1,000 mg/kg nicotinamide. The tumour volume (+/- 1 S.E.) after 30 days in saline-treated mice had reached 1540 mm3 (+/- 260). No change in tumour growth was seen at that time with daily doses of up to 500 mg/kg nicotinamide, but at 1,000 mg/kg tumour volume was reduced to 904 mm3 (+/- 233). However, this large dose of nicotinamide was also toxic to the mice with some 16% of animals dying during the 30-day treatment period. A similar growth inhibition was seen with daily i.p. injections of 5 mg/kg fumagillin (tumour volume at 30 days = 821 +/- 191 mm3), a known inhibitor of angiogenesis, but whether this mechanism also explains the nicotinamide effect is not clear.