Inhibitory effect of vitamin A on carcinogenesis.

In two experiments, f3-carotene applied to mice initiated with 7,12-dimethylbenz[a]anthracene (DMBA), concomitantly with croton resin and croton oil, increased tumor incidence by 58 and 29%. In the same experiments, retinyl acetate reduced tumor incidence by 76 and 29%. Retinol in one experiment reduced the number of papillomas by 75%. f3-lonone, squalene, and isoprene had little or no effect on the incidence of tumors. In the mice treated with DMBA and phenol, retinol also reduced the number of tumors. The polyene antibiotic, filipin, dramatically reduced the number of animals with croton oil-induced tumors and also the total number of tumors. After the lysosomal labilizers, filipin and vitamin A, were applied for 3 weeks to DMBA-initiated mice, only a few tumors developed after use of croton oil. The lysosomal stabilizers, chloroquine and hydrocortisone, increased the number of the tumors. In the same experiments, acid phosphatase and aryl sulfatase activities were decreased by chloroquine and hydrocortisone and increased by filipin and vitamin A.J Nat Cancer Inst 47: 667-673,1971.