(P03-055-23) The Role of Sorghum Bicolor on Antioxidant Signaling in Colorectal Cancer

Objectives: Sorghum bicolor is a cereal grain, and varietals containing high polyphenol concentrations have been implicated in modulating cancer signaling pathways. The objective of our research is to investigate the effects of high and low polyphenol sorghum varietals on the NRF2-regulated antioxidant pathway. This antioxidant pathway regulates the expression of antioxidant enzymes responsible for neutralizing reactive oxygen species that contribute to colorectal cancer (CRC) development.

Methods: Extracts from Sorghum leaves or milled bran were generated with 70% ethanol. Human CRC HCT116 and HT29 cells were treated with extracts (1 µl/ml medium) from bran and leaves of high- and low-polyphenol Sorghum varietals for 24 hours. RNA and protein were isolated. mRNA expression was measured using qPCR and analyzed with a One-way ANOVA using GraphPad Prism. Protein expression was quantified using western blotting.

Results: Leaf and bran extracts from high-polyphenol varietals significantly increased mRNA expression of KEAP1 in HCT116 cells. Compared to low polyphenol bran extracts, mRNA expression of glutathione peroxidase 1 (GPX1) was significantly decreased by high-polyphenol bran and leaf extracts in HT29 and HCT116 cells. There were no significant differences observed in mRNA expression of NRF2, NQO1, or GPX2. Additionally, there were no differences in the protein expression of cytosolic NRF2.

Conclusions: Increased KEAP1 expression may reduce NRF2 nuclear translocation, thereby decreasing GPX1 expression and lowering antioxidant protection in CRC cells. Although mRNA and protein expression of NRF2 remained unchanged, we will investigate whether NRF2 has translocated to the nucleus, where it may actively regulate the expression of antioxidant genes. We are currently measuring protein expression and catalytic activity of NRF2- regulated genes. We hope to elucidate the mechanism of how high-polyphenol Sorghum varietals may contribute to the prevention of colorectal cancer.

Funding Sources: USDA ARS Kansas and Towson University