Modifying factors in pancreatic carcinogenesis in the hamster model. IV. Effects of dietary protein.

The possible effects of dietary protein on pancreatic cancer induced in outbred Syrian golden hamsters by N-nitrosobis(2-oxopropyl)amine (BOP) were studied. Three levels of casein as protein at low [LP = 9 g/385 kilocalories (kcal)], medium (MP = 18 g/385 kcal), or high levels (HP = 36 g/385 kcal) were fed in two sequences to 4 groups of hamsters. The effects of protein level on the initiation phase of BOP carcinogenesis were examined in hamsters fed LP or HP from 3 through 7 weeks of age, followed by MP for the remainder of their lives. The role of protein level on the promotional (developmental) phase of carcinogenesis was evaluated in hamsters fed (from 3 through 7 wk of age) MP, followed by LP or HP for the rest of their lives. One-half of the hamsters from each of the 4 groups received a single sc BOP injection (10 mg/kg body wt) at 8 weeks of age. Changes in diet from one type to the other occurred 2 days after BOP treatment. An MP diet fed before and after BOP served as the experimental control diet. The results demonstrated that the LP diet inhibited the developmental phase of carcinogenesis only in females, whereas the MP and HP diets did not affect initiation or promotion of cancer in either sex. The inhibitory effect of the LP diet in pancreatic carcinogenicity only in females calls for further studies.