Neoplastic growth of carcinogen-treated mammary transplants as influenced by fat intake of donor and host.

Female Wistar-Furth rats were fed either a high-fat (HF) or a low fat (LF) diet from weaning. The HF and LF diets contained 20% and 0.5% corn oil, respectively. Mammary gland explants from 50-day-old rats of both dietary groups were exposed to dimethylbenz[a]anthracene in organ culture before grafting to HF- or LF-hosts. A total of 4 groups were involved: LF leads to LF, HF leads to LF, LF leads to HF, and HF leads to HF, where the designations before and after the arrow describe the dietary treatment of the donor and host, respectively. Final tumor incidences were as follows: 28%, 20%, 72% and 76%, presented in the order of the above 4 groups. Tumors also appeared earlier in the HF-hosts. Results of this experiment indicate that regardless of the nutritional status of the donor, it was the fat intake of the host that governed the subsequent neoplastic growth of transformed cells, suggesting that the action of fat is primarily exerted at the promotional stage of carcinogenesis.