(P03-047-23) High Polyphenol Sorghum Modulates Expression of Carcinogen-Metabolizing Phase I Enzymes in Colon Cancer Cells

Objectives: The aromatic hydrocarbon Benzo[a]pyrene (BaP) is a ubiquitous carcinogen associated with increased cancer risk. Exposure to BaP occurs through anthropogenic and natural sources. It is metabolically activated by Phase I enzymes, mainly cytochrome P450 (CYP) isoforms, that modify BaP into more hydrophilic metabolites. This facilitates their export but also their potential to bind to DNA. However, Phase II enzymes potentially inactivate BaP-metabolites. Many plant polyphenols are known for their cancer preventive properties. Leaf and bran extracts from three varietals of Sorghum bicolor were provided by the USDA. Here, we compare the effect of high and low-polyphenol sorghum varietals on the expression of Phase I & II enzymes in human colon cancer cells. We hypothesize that high polyphenol sorghum extracts will decrease expression of Phase I and increase expression of Phase II enzymes in BaP-treated cells.

Methods: Caco2, human colorectal cancer cells, were incubated with 2.5 µM BaP, 1 µl/mL sorghum extract, or both for 6 hours. RNA and protein were isolated. mRNA expression of Phase I/II enzymes was quantified using qPCR. Cytosolic protein expression was assessed with Western blotting relative to β-ACTIN.

Results: Compared to untreated cells, BaP increased CYP1A1 and CYP1B1 mRNA expression 5-fold and 3-fold, respectively. Meanwhile, BaP had no effect on the mRNA expression of Epoxide Hydrolase. The addition of high-polyphenol Sorghum extracts significantly decreased the BaP-induced mRNA expression of CYP1A1 and CYP1B1. Our results also suggest decreased protein expression of CYP1A1 and CYP1B1. Interestingly, the mRNA expression of select Phase II enzymes was unaffected. We continue to analyze mRNA and protein expression and activity of Phase I & II enzymes.

Conclusions: BaP increased select Phase I enzyme expression as expected. Co-treatment with high-polyphenol sorghum extracts decreased Phase I mRNA expression. Inhibition of Phase I and induction of Phase II enzymes may shift the balance toward BaP detoxification and suppress the ability of the BaP-metabolite to bind to DNA. Consequently, reducing the risk of mutagenesis and subsequent tumor formation.

Funding Sources: This study is supported by Towson University’s Fisher College of Science and Mathematics, the Bridges to the Doctorate program, and USDA ARS Kansas.