Location: Produce Safety and Microbiology ResearchTitle: Antitumor effects of dietary black and brown rice brans in tumor-bearing mice: relationship to composition Author
|Sun Phil, Choi|
|Sung Phil, Kim|
|Seok Hyun, Nam|
Submitted to: Molecular Nutrition and Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2012
Publication Date: 12/23/2012
Citation: Sun Phil, C., Sung Phil, K., Seok Hyun, N., Friedman, M. 2012. Antitumor effects of dietary black and brown rice brans in tumor-bearing mice: relationship to composition. Molecular Nutrition and Food Research. 57(3):390-400. doi: 10.1002/mnfr.201200515. Interpretive Summary: Pigmented rice brans from whole grain are rich sources of a large number of bioactive compounds. The results of the present and previous studies suggest that dietary black rice bran and to a lesser extent brown rice bran might contribute to the prevention and therapy of human cancers and possibly other diseases. The results of our studies on beneficial effects of pigmented brans have elicited widespread interest including communication from rice farmers in Northern California. They were particularly interested in recently published ARS research on the benefits of black rice bran. Representatives from the growers association met with ARS researchers at the Western Regional Research Center to further discuss and exchange ideas about the possibility of growing black rice in California as a value-added crop. The growers agreed that this is worthwhile objective that has the potential to benefit the health of consumers and the US farm economy.
Technical Abstract: Scope: We investigated the effects of oral feeding of a mouse diet supplemented with 10% (w/w) pigmented black bran from the rice variety Oryza sativa cv. LK1-3-6-12-1-1 and 10% (w/w) nonpigmented brown bran from the commercial rice Oryza sativa cv. Chuchung as an internal control on the growth of transplanted tumors in mice. Methods and results: Mice fed standard diets with added rice brans for 2 weeks with the control diet were intracutaneously inoculated with CT-26 mouse colon cancer cells and fed the same diet for 2 additional weeks. Compared to the control diet, tumor mass was 35% lower in the black rice bran-fed group and 19% lower in the brown rice bran group. Tumor growth inhibition was associated with the following biomarkers: increases in cytolytic activity of splenic natural killer (NK) cells; partial restoration of nitric oxide (NO) production and phagocytosis in peritoneal macrophages; increases in released pro-inflammatory cytokines including tumor necrosis factor-a (TNF-a), interleukin-1ß (IL-1ß), and IL-6 from macrophages; increases in infiltration of leukocyte, probably neutrophils, into the tumor; and reduction in the number of blood vessels inside the tumor (anti-angiogenesis). Pro-angiogenic biomarkers including vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2), and 5-lipoxygenase (5-LOX) were also significantly reduced in mRNA and protein expression. Enzyme-linked-immunosorbent assays (ELISA) of tumor cells confirmed reduced expression of COX-2 and 5-LOX up to 23%. Reduced COX-2 and 5-LOX expression downregulated VEGF and inhibited neoangiogenesis inside the tumors. Conclusions: Induction of NK activity, activation of macrophages, increase in leukocyte infiltration, and inhibition of angiogenesis seem to contribute to the inhibitory mechanism of tumor regression by black rice bran. Dietary black rice bran has the potential to protect against cancer in humans.