Chromosomal control of chemical carcinogenesis

Malignant cell transformation and its reversion, in cells transformed after treatment with the chemical carcinogen dimethylnitrosamine, are controlled by the balance between chromosomes that determine the expression (E) of malignancy and those that determine its suppression (S). Malignancy is due to a change in chromosome balance so as to produce an excess of E over S. The chromosome groups that contain these two types of chromosomes have been identified as the same groups that determine the expression and suppression of malignancy in cells transformed by polyoma virus. The balance between these two types of chromosomes also controls the resistance of cells to treatment with 5‐bromodeoxyuridine and visible light. The data suggest that viral and non‐viral carcinogens induce malignancy by inducing chromosome re‐arrangements that result in a change in the balance between E and S.