Effect of dietary restriction on induced hamster cheek pouch carcinogenesis

Abstract

Effects of dietary restriction on DMBA (9,10-dimethyl-1,2-benzanthracene)-induced carcinogenesis in the hamster cheek pouch were investigated with particular reference to changes in epithelial thickness, mitotic activity and dysplasia. Eighty-four hamsters on either an unrestricted or a 75 per cent diet were painted with DMBA or with liquid paraffin only. Animals were killed 2 weeks before the start of painting and at 6, 12 and 18 weeks afterwards, vinblastine being injected before killing. Blocked mitoses were counted and epithelial thickness measured in a section from the pouch wall. In paraffin-painted animals, dietary restriction produced a rapid reduction in epithelial thickness and mitotic index which persisted to 18 weeks. Hyperplasia induced by DMBA applications obscured these diet-induced changes although at 12 weeks a significant reduction in mitotic index was present in the restricted group. At 12 weeks, there were fewer tumours in the restricted than in the unrestricted group but this difference disappeared by 18 weeks. The largest tumours were located consistently in the unrestricted group. Epithelial dysplasia occupied about 10 per cent of pouch mucosa in both groups. It was concluded that dietary restriction reduces epithelial thickness and mitotic activity but that these effects are overwhelmed by the action of DMBA. The delay in tumour formation caused by dietary restriction accords with other quoted studies.