The Initiation and Growth of Tumors. Introduction. I. Effects of Underfeeding.

Abstract

The tumor process, in the main, consists of initiation and growth. In these studies initiation implies the conversion of normal tissue to malignant tissue without consideration of intermediary phases, of which little is known. Since, for practical purposes, initiation and growth are readily differentiated, they have been studied separately. Great importance has been attached to the dissimilarity between normal and tumor tissue, such as rate of growth and tissue respiration (Warburg). The fact remains, however, that there is, in general, no striking difference in chemical composition, enzyme content, and metabolism between the normal and the tumor cell; both follow certain fundamental laws of growth. Much attention has been given to the experimental retardation and acceleration of tumor growth, in the expectation that such studies would bring to light the factors concerned in the initiation and propagation of neoplasms. At first transplantable tumors were used; but of late, particularly since cancerigenic chemicals have become readily available, the induced tumor has been widely used for such investigations. Much of the earlier work can be criticized because of the paucity of animals used in the experiments, and the inadequacies and indefiniteness of the diets. In fact, some authors report that their animals on experimental diets died within a few weeks.