(P03-022-23) Leaf Extract From High-Polyphenol Sorghum Varietal Affects Selenoprotein Expression and Activity in Human Colon Cancer Cells

Objectives: Sorghum bicolor is a cereal grain, and high-polyphenol varietals are currently investigated by the USDA. Polyphenols are secondary plant metabolites, and thus part of normal human diet. Many polyphenols have been implicated in regulation of colon cancer through modulating the cellular antioxidant defense systems. These systems include the thioredoxin reductases (TXNRD) and glutathione peroxidases (GPX), which are Selenoproteins. These Selenoproteins are involved in both cancer prevention and promotion. Additionally, the 15kDA Selenoprotein, SelenoF, has a redox motif, and therefore is thought to also be involved in the regulation of cellular homeostasis. The goal of our study is to assess the impact of high-polyphenol sorghum varietals on the expression and activity of these Selenoproteins in colon cancer cells.

Methods: Human (HCT116, HT29) colon cancer cells were incubated for 24-48h with ethanol extracts generated from Sorghum bran or leaves. RNA and proteins were extracted. mRNA expression of Selenoproteins was quantitated using qPCR; protein lysates were used for Western blotting and catalytic activity assays. qPCR and activity data were analyzed with ANOVA.

Results: Compared to solvent control, the Sorghum leaf extracts nearly doubled TXNRD1 mRNA expression (p < 0.01), and significantly increased TXNRD activity (p < 0.05) in both cell lines. In contrast, expression of GPX1&2 was lowered in the HCT116 cell line (p < 0.05). Additionally, GPX activity was also significantly lowered. Although no statistical significance was detected, bran and leaf extracts seemed to decrease SelenoF mRNA expression.

Conclusions: High-polyphenol varietals of Sorghum affect Selenoprotein expression and activity. Further investigations will help elucidate the effects of these new sorghum varietals on Selenoproteins important in prevention and promotion of colon cancer.

Funding Sources: Financial support was provided by Towson University and the USDA ARS Kansas.