Omega-3 fatty acids inhibiting the growth of a transplantable rat mammary adenocarcinoma.

BN/Bi inbred female rats fed diets containing different amounts of polyunsaturated fatty acids, either of the omega-3 or omega-6 type, each received an implant of a syngeneic mammary adenocarcinoma. When the diameter of the tumors reached 20 mm, they were surgically removed; 2 weeks thereafter the animals were sacrificed and lung metastases were counted. Cellular immune response was determined before tumor inoculation; certain prostaglandin values in plasma and platelet aggregation were measured before and after tumor inoculation.

Conversion of diets at tumor induction shows the pattern of tumor growth and metastasis of the first given diet.

In a previous study, significant differences in the growth rate of a transplantable mammary adenocarcinoma were observed between rats receiving a diet rich in saturated fatty acids (lard, diet A), and rats on a diet in which the saturated fat was partly replaced by polyunsaturated fatty acid of the omega-3 type (Menhaden oil, diet B). In the present investigation, it was our aim to study tumor growth in rats on diet A and B, as well as in rats that had, at tumor inoculation, a change of diets, from diet A to diet B. Tumor growth of rats receiving diet A throughout the whole experiment was the same as in those rats that had a conversion of diets.

Diets rich in fish oil cannot control tumor cell metastasis.

Rats fed diets containing different amounts of polyunsaturated fatty acids either of the n-3 or n-6 type, received cultured, syngeneic mammary tumor (BN472) cells intravenously. Animals were sacrificed 2 weeks after tumor inoculation, and the number of pulmonary tumor foci was counted. No significant differences in the number of metastatic foci were observed between the dietary groups.