Experimentally induced cancer of the colon

Abstract

1–2 Dimethylhydrazine (DMH) injected weekly at a dose of 20 mg/kg body weight induced colon cancer in CF1 mice with an incidence of over 90% by 186 days treatment. An unusual specificity was shown for the production of neoplasms in the distal colon. A tritiated thymidine-labeling index curve, developed over nine treatment periods, demonstrated a marked elevation at 87 days. At this time, in addition to increased numbers of labeled epithelial cells, an expanded proliferative compartment closer to the luminal surface was noted. Focal atypias confined to one or two crypts were seen as early as 38 days. The frequency and size of these lesions within each animal increased with treatment time. Labeled indices of the focal atypias were often two to three times greater than that of the normal surrounding mucosa. A variable response among similarly treated animals indicated that multiple factors, i.e. physiological, genetic, and unknown, play a role in the induction of colon cancer.