Suppression of Implanted MDA-MB 231 Human Breast Cancer Growth in Nude Mice by Dietary Walnut

Abstract

Walnuts contain components that may slow cancer growth including omega 3 fatty acids, phytosterols, polyphenols, carotenoids, and melatonin. A pilot study was performed to determine whether consumption of walnuts could affect growth of MDA-MB 231 human breast cancers implanted into nude mice. Tumor cells were injected into nude mice that were consuming an AIN-76A diet slightly modified to contain 10% corn oil. After the tumors reached 3 to 5 mm diameter, the diet of one group of mice was changed to include ground walnuts, equivalent to 56 g (2 oz) per day in humans. The tumor growth rate from Day 10, when tumor sizes began to diverge, until the end of the study of the group that consumed walnuts (2.9 ± 1.1 mm³/day; mean ± standard error of the mean) was significantly less (P > 0.05, t-test of the growth rates) than that of the group that did not consume walnuts (14.6 ± 1.3 mm ³ /day). The eicosapentaenoic and docosahexaenoic acid fractions of the livers of the group that consumed walnuts were significantly higher than that of the group that did not consume walnuts. Tumor cell proliferation was decreased, but apoptosis was not altered due to walnut consumption. Further work is merited to investigate applications to cancer in humans.

ACKNOWLEDGMENTS

This work was funded by grants from the American Institute for Cancer Research and the California Walnut Commission. Neither group had input on interpretation or reporting of the findings. The authors gratefully acknowledge the technical assistance of H-C Jo, Mike Brown, and Juliana Akinsete. W. E. Hardman was the principle investigator on the grant, designed the experiment, interpreted the results, and prepared this report. G. Ion directed the day-to-day animal care feeding and measurements, directed the biochemical and image analyses assays, and provided input on preparation of this report.

Notes

^a The AIN-76-A was modified to 10% wt/dry wt corn oil or 2.63% corn oil and 18% of calories from walnut. The control (corn oil) and walnut diets were balanced for nutrients, protein, fat, carbohydrates, and calories.