Summary
Skin carcinogenesis by a single application of 9,10-dimethyl-1,2-benzanthracene or methylcholanthrene followed by repeated applications of croton oil has been compared with carcinogenesis by repeated applications of either of the hydrocarbons alone.
The croton oil method yields only a small number of malignant tumors and gives rise to a very high regression rate.
The tumors induced have been classified as either (a) regressions, (b) stationary papillomas, (c) vigorously growing papillomas, or (d) malignancies.
From a consideration of the results obtained it is suggested that the process of initiation should be considered as a graded one, inducing graded changes in growth-potentiality in the latent tumor cells.
A preliminary report of this work was given at the meeting of the American Association for Cancer Research, Inc., Atlantic City, 1950.
Part of this investigation (at the Northwestern University Medical School) was aided by a research grant from the National Cancer Institute of the National Institutes of Health, Public Health Service.
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