Effects of dietary menhaden oil and retinyl acetate on the growth of DU 145 human prostatic adenocarcinoma cells transplanted into athymic nude mice

Abstract

The effects of feeding menhaden oil (MO), rich in ω-3 fatty acids, or supplemental vitamin A [as retinyl acetate (RA)], on the growth of DU 145 human prostate cancer cells were studied in athymic nude mice. The mice were fed AIN-76A diets containing either 23% corn oil (CO), a mixture of 17% MO and 6% CO, or 23% CO plus RA. After irradiation sterilization, the RA-supplemented diet was found to contain ∼15 times the amount of vitamin A present in the control diet. There were 24 mice in each dietary group. Three weeks after commencement of feeding the experimental diets, 1×10⁶ or 5×10⁶ DU 145 cells were inoculated into subgroups of 12 animals, and the appearance and growth of solid tumors followed over a 6-week period. There was no significant difference in tumor latency between mice fed MO plus CO, and those fed CO alone, regardless of the inoculum size. However, the appearance of palpable tumors was more rapid in mice inoculated with 5×10⁶ cells and fed the RA-supplemented CO diet (91% after 17 days) compared with mice receiving the same tumor cell load but fed the unsup-plemented CO diet (55% after 17 days). Growth of the solid tumors was retarded significantly in mice inoculated with 1×10⁶ cells and fed the MO-containing diet compared with the CO controls; this effect was not evident in animals who received 5 ∼ 10⁶ cells. RA supplementation caused accelerated tumor growth, which, again, only achieved statistical significance in thegroup inoculated with 1 ∼ 10⁶ cells.