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Observations on Carcinogenesis by 4-Dimethylaminoazobenzene^*

( Lilly Research Laboratories, Indianapolis, Ind.)

1. Folic acid at the levels of 0.02 mg and 1.9 mg/kg of diet had no effect on tumor formation or cirrhosis of the liver induced by DAB.

2. No unequivocal evidence was obtained that strain differences in rats influence susceptibility to DAB.

3. Tumors developed at the same rate with diets containing 5, 10, and 20 per cent of cottonseed oil.

4. Tumors developed more slowly with a diet containing 5 per cent of corn oil than with diets containing 10 and 20 per cent of corn oil.

5. Tumors developed more slowly with a diet containing 20 per cent of olive oil than with diets containing 5 and 10 per cent of olive oil.

6. On comparing results with the same concentrations of oils, tumor development was found to be slowest with diets containing 5 per cent of corn oil and 20 per cent of olive oil, but was essentially the same for the other concentrations and kinds of oil.

7. There was no difference in tumor development with diets low in riboflavin and containing 10 per cent and 30 per cent of casein, but it was greatly retarded with a 10 per cent casein diet high in riboflavin.

8. It appears that liver contains one or more factors other than riboflavin, pyridoxine, and biotin that influenced tumor development.

9. Thiosalicylic acid at the level of 1 per cent in the diet gave protection against tumor development but had no effect upon cirrhosis.

10. Thiouracil at the level of 0.05 per cent in the diet gave protection against tumor development and against cirrhosis of the liver. It is thought that this result was not due entirely to lowered intake of the carcinogen.

^* Most of this material was presented at the 1948 and 1949 meetings of the American Association for Cancer Research.

Received 12/ 5/51.