Influence of lipid diets on the number of metastases and ganglioside content of H59 variant tumors

Dietary fatty acids modulate chronic colitis, colitis-associated colon neoplasia and COX-2 expression in IL-10 knockout mice

OBJECTIVE

The effects of different dietary oils on the development of colitis-associated colon cancer have not been studied. The present study examined the effect of different dietary oils on the severity of chronic colitis, development of colitis-associated premalignant changes, and colonic expression of cyclooxygenase-2 (COX-2) in interleukin-10 knockout (IL-10-/-) mice.

METHODS

IL-10-/- mice were fed chow supplemented with corn oil (CO; control, n=28), olive oil (OO; n=29), or fish oil (FO; n=35) for 12 wk and their colons were studied for colitis score, premalignant changes, and COX-2 expression.

RESULTS

The average colitis score was higher in the FO than in the CO group. Similarly, the incidence of severe colitis (score>or=3) was significantly higher in the FO than in the CO and OO groups (50% versus 7.7% and 3.7%, respectively, P<0.05). Dysplasia was more frequent in the FO and less frequent in the OO than in the CO group (47% and 4% versus 15%, respectively, P<0.05). Conversely, aberrant crypt foci and crypt index were significantly higher in the FO than in the CO group. Colitis score, aberrant crypt foci, and crypt index did not differ between the OO and CO groups. COX-2 immunostaining was significantly lower in the OO than in CO group (P<0.05) but not different between the FO and CO groups.

CONCLUSIONS

In IL-10-/- mice, fish oil exacerbates chronic colitis and colitis-associated premalignant changes. Conversely, olive oil inhibits COX-2 immunostaining and decreases the risk of neoplasia associated with chronic colitis.

Systemic treatment with n-6 polyunsaturated fatty acids attenuates EL4 thymoma growth and metastasis through enhancing specific and non-specific anti-tumor cytolytic activities and production of TH1 cytokines

Recently, there has been a great interest in the effects of different types of n-6 polyunsaturated acids (n-6 PUFAs) upon the immune system and cancer development. However, the effects of n-6 PUFAs are still controversial and as yet undefined. The present study aimed to investigate the anti-tumor effects of n-6 PUFAs against EL4 thymoma and the associated immune mechanisms. To this, sesame oil, a vegetable oil enriched with n-6 PUFAs, or free linoleic acid (LA) were administered intraperitoneally into C57BL/6 mice before and after challenge with EL4 lymphoma cells. Treatment with either sesame oil or LA attenuated the growth and metastasis of EL4 lymphoma. The anti-tumor effect of LA was superior to that of sesame oil, and associated with an increase in the survival rate of the tumor-bearing mice. In addition, both sesame oil and LA showed dose-dependent anti-lymphoma growth in vitro. Treatment with LA generated significant increases in the anti-lymphoma cytolytic and cytostatic activities of T cells and macrophages, respectively, and enhanced production of IL-2 and IFN-gamma while decreased production of IL-4, IL-6 and IL-10. In summation, the results suggest that n-6 PUFAs, represented by LA, can attenuate EL4 lymphoma growth and metastasis through enhancing the specific and non-specific anti-tumor cytolytic activities and production of TH1 cytokines. These findings might be of great importance for a proper design of systemic nourishment with PUFAs emulsions for cancer patients.

n-3 polyunsaturated fatty acids and cancer

n-3 Polyunsaturated fatty acids are promising molecules in cancer prevention and the potentiation of cancer treatment. Recent studies have highlighted the importance of their interactions with other food components. Their effects on tumor growth depend upon background levels of n-6 polyunsaturated fatty acids and antioxidants, and this could account for previously inconsistent results in experimental carcinogenesis. Recognition of the role of lipoperoxidation in the anti-tumor effects of polyunsaturated fatty acids, which is apparent in a variety of in-vitro or in-vivo systems, has been a major advance in the field. Consequently, n-3 polyunsaturated fatty acids appear to be excellent substrates for lipid peroxidation in situations where an oxidative stress is involved, such as in the action of several cytotoxic agents in the treatment of cancer.