Experimental cancer prophylaxis.

In A-Jax mice, the appearance of MCA-induced sarcomas in delayed by Vitamin A application. Continuous uptake of drinking water containing 0.05% of a retinol palmitate emulsion leads to a significant inhibition. Administration of ethylnitrosourea (ENU) to pregnant Swiss mice on the 17th day of gravidity results in the formation of lymphoblastoid leukemias from the beginning of the 12th week after birth, 90% of the animals dying within 25 weeks. In this case, continuous addition of 0.1% retinol palmitate emulsion to drinking water leads to a dramatic reduction of the tumor risk to about 50%. By additional administration of proteolytic enzymes of animal and plant origin this risk can be further reduced. The lung adenomas developing to 100% in the animals are not influenced by this treatment. Vitamin A, added to drinking water, exerts a strong inhibitory effect on transplacentally induced leukemia.