Dietary fish oil inhibits human breast carcinoma growth: A function of increased lipid peroxidation

Abstract

Female athymic nude mice were implanted subcutaneously with human breast carcinoma MDA‐MB231. Seven to ten days later, the mice were divided into groups and fed a purified diet containing the following types of fat (% of diet):(i) 20% corn oil (CO); (ii) 15% CO:5% fish (menhaden) oil (FO); (iii) 10% CO:10% FO; (iv) 5% CO:15% FO; (v) 1% CO:19% FO; and (vi) 1% CO:19% FO plus antioxidants (α‐tocopherol acetate, 2000 IU/kg diet and tertiary butyl‐hydroquinone, 2% of the total fat). The linoleic acid levels (% of diet) of the groups were 12.0, 9.1, 6.2, 3.3, 0.9 and 0.9%, respectively. After 6–8 wk, the carcinomas were assessed for tumor volume (cm 3) and assayed for thiobarbituric acid reactive substances (TBARS). Human breast carcinoma growth was suppressed in mice consuming FO diets without antioxidants as compared to mice fed CO; the greater the amount of dietary FO fed, the greater the carcinoma growth suppression (P<0.05). The addition of antioxidants to the FO diet significantly (P<0.05) reversed the FO‐induced carcinoma growth suppression. Concentrations of TBARS in the human breast carcinomas were increased in all the FO (without antioxidants) fed mice, compared to mice fed CO; the level of increase in TBARS was directly related to the increase in the level of FO fed (P<0.05). The addition of antioxidants to the FO diet significantly (P<0.05) reduced the concentration of TBARS in the breast carcinomas. Thus, these results provide evidence that dietary FO can significantly suppress growth of human breast carcinoma MDA‐MB231, even in the presence of substantial amounts of linoleic acid (3.3–9.1%). The inhibitory effect of FO on growth of these carcinomas was associated with an increased concentration of TBARS in the tumor tissue. In conclusion, dietary FO induced suppression of human breast carcinoma growth is a function, at least in part, of an accumulation of lipid peroxidation products in the tumor tissues.