Tumor growth reduction is regulated at the gene level in Walker 256 tumor-bearing rats supplemented with fish oil rich in EPA and DHA

We investigated the effect of fish oil (FO) supplementation on tumor growth, cyclooxygenase 2 (COX-2), peroxisome proliferator-activated receptor gamma (PPAR gamma), and RelA gene and protein expression in Walker 256 tumor-bearing rats. Male Wistar rats (70 days old) were fed with regular chow (group W) or chow supplemented with 1 g/kg body weight FO daily (group WFO) until they reached 100 days of age. Both groups were then inoculated with a suspension of Walker 256 ascitic tumor cells (3 x 10(7) cells/mL). After 14 days the rats were killed, total RNA was isolated from the tumor tissue, and relative mRNA expression was measured using the 2(-Delta Delta CT) method. FO significantly decreased tumor growth (W = 13.18 +/- 1.58 vs WFO = 5.40 +/- 0.88 g, P<0.05). FO supplementation also resulted in a significant decrease in COX-2 (W = 100.1 +/- 1.62 vs WFO = 59.39 +/- 5.53, P<0.001) and PPAR gamma (W = 100.4 +/- 1.04 vs WFO = 88.22 +/- 1.46, P<0.05) protein expression. Relative mRNA expression was W = 1.06 +/- 0.022 vs WFO = 0.31 +/- 0.04 (P<0.001) for COX-2, W = 1.08 +/- 0.02 vs WFO = 0.52 +/- 0.08 (P<0.001) for PPAR gamma, and W = 1.04 +/- 0.02 vs WFO = 0.82 +/- 0.04 (P<0.05) for RelA. FO reduced tumor growth by attenuating inflammatory gene expression associated with carcinogenesis.