The Dependence of the Genesis of Induced Skin Tumors on the Caloric Intake during Different Stages of Carcinogenesis*

VOLUME 4 NOVEMBER, 1944 NUMBER 11 The Dependence of the Genesis of Induced Skin Tumors on the Caloric Intake during Different Stages of Carcinogenesis* Albert Tannenbaum, M.D. (From the Department o/ Cancer Research, Michael Reese Hospital, Chicago I6, I1l.) (Received for publication June 28, 1944) In earlier investigations (11, 12) it has been shown that calorie-restricted diets inhibit the formation of tumors in mice. This effect has been demonstrated for the spontaneous breast tumor, induced skin tumor, induced sarcoma, and primary lung tumor. In those investigations the restricted diet was fed throughout the entire experiment. The experiments with spontaneous breast tumors were carried out on dba female mice, in which tumors normally begin to appear when the mice are 9 to 10 months old; in one of the experiments the restricted diet was instituted when the mice were, on the average, 9 months of age, i. e., when tumors begin to appear, yet there was a pronounced inhibition of tumor formation. This suggested that the inhibitory effect on tumor formation may be dependent chiefly on caloric restriction during the period in which tumors appear, rather than in the previous period of carcinogenic preparation (12). Tumors may arise long after exposure to the carcinogenic stimulus has ceased. Skin cancer of tar workers and bladder carcinomas of dye workers have often occurred many years after the persons exposed have given up employment in these industries. Results of experimental carcinogenesis are in agreement with these clinical observations. Such a separation of a carcinogenic stimulus find its result in terms of a tumor was shown as early as 1922 by Leitch (7), in experiments in which he tarred mice for a limited period. The production of skin tumors by means of a limited application of carcinogenic hydrocarbon offers an excellent technic for separating arbitrarily the carcinogenic process into two stages. By terminating the * Presented at the Boston Meeting of the American Association for Cancer Research, April 1, 1942. paintings with the carcinogen just before tumors are expected, one may regard the period of carcinogenesis as being divided into: I. The period of carcinogenic application; followed by II. The period in which tumors appear. This paper