EXTRINSIC FACTORS THAT INFLUENCE CARCINOGENESIS

Abstract

"The extrinsic factors that alter the action of carcinogenic agents include various chemical and physical agents such as fats, oils, ''irritating'' substances, trauma and radiant energy all of which have a pronounced influence on tumor formation when applied directly to the tissues undergoing carcinogenic changes. Other factors are active when administered at a distance from the tissues undergoing neoplastic conversion. These include alterations in the diet involving calories, fats, proteins and amino acids, vitamins, and modifications in the balance of certain hormones. It should be stressed that altering the carcinogenic process does not necessarily imply a similar effect on the growth of tumors. The investigations cited illustrate the extreme caution necessary in the interpretation of results observed. Factors that influence tumor growth might be obscured when overwhelming doses of carcinogen are employed, and any treatment that interferes with the dietary intake or with the general health of the animal may lead to false conclusions. The ultimate aim of expts. of this nature is a better understanding of the mechanism of neoplastic development. Minor successes have been attained in this direction, and the suggestion has been made that carcinogenesis progresses not as a single process but rather in 2 or more distinct stages: a, the pre-neoplastic stage or the latent period of carcinogenesis, and b, the neoplastic stage. Various agents have been shown to act on one or the other period. In general, however, the expts. raise more questions than they answer. Thus, the nature of the effect due to fat, to croton resin, to calories, or to the factors involved following injury, as well as the various effects of dietary constituents all must await further experimentation.".