Effect of Low Environmental Temperature, Dinitrophenol, or Sodium Fluoride on the Formation of Tumors in Mice*

It has been demonstrated consistently that chronic caloric restriction inhibits the formation of various spontaneous and induced tumors of the mouse (1, 2). The mechanism of this effect is unknown. However some insight might derive if it were known whether the decreased caloric intake, the accompanying restriction in body weight, or the decreased total metabolism, was most directly related to the inhibition of tumor development. The present investigation was undertaken to acquire information relevant to this question by examining the effects on tumor formation of ex perimental procedures which would result in re tarded body growth, despite unchanged or aug mented caloric intake. Two of the procedures were the feeding of dinitrophenol and housing of the mice at low environmental temperature. The third procedure was the feeding of sodium fluoride, inas much as under suitable conditions it effects a sig nificant retardation in body weight without a parallel change in food consumption. In these experiments four types of tumors were utilized—spontaneous mammary carcinoma, in duced sarcoma, induced skin tumor, and primary lung adenoma. Only the spontaneous mammary carcinoma was investigated with all three experi mental procedures; the results have been reported previously (3).