Inhibitory Effects of Bound Polyphenol from Foxtail Millet Bran on Colitis-Associated Carcinogenesis by the Restoration of Gut Microbiota in a Mice Model

Colorectal cancer (CRC) is a common malignant tumor occurring in the colon. It has been known that the gut microbiota is a complex ecosystem and plays an important role in the pathogenesis of colorectal cancer. Our previous study showed that bound polyphenol of the inner shell (BPIS) from foxtail millet bran exhibited significant antitumor activities in cancer cells and nude mice models. In the present study, the anticancer potential of BPIS is evaluated in the azoxymethane (AOM) and dextran sodium sulfate (DSS)-induced mouse CRC model. Results showed that BPIS could decrease the number and volume of tumors and protect the epithelial architecture from damage. Certain biomarkers associated with CRC formation, such as COX-2, EMR1, PCNA, and caspase-3, were strongly changed by BPIS. Moreover, by 16S rRNA gene sequence analysis, it was found that BPIS could remodel the overall structure of the gut microbiota from tumor-bearing mice toward that of the normal counterparts, including two phyla and eight genera, together with regulations on several genes that are responsible for 17 signaling pathways.

Reversal Effects of Bound Polyphenol from Foxtail Millet Bran on Multidrug Resistance in Human HCT-8/Fu Colorectal Cancer Cell

Foxtail millet is the second-most widely planted species of millet and the most important cereal food in China. Our previous study showed that bound polyphenol of inner shell (BPIS) from foxtail millet bran displayed effective antitumor activities in vitro and in vivo. The present research further implied that BPIS has the ability to reverse the multidrug resistance of colorectal cancer in human HCT-8/Fu cells, the IC₅₀ values of 5-fluorouracil (5-Fu), oxaliplatin (L-OHP), and vincristine (VCR) were decreased form 6593 ± 53.8, 799 ± 48.9, and 247 ± 10.3 μM to 5350 ± 22.3 (3261 ± 56.9), 416 ± 16.6 (252 ± 15.6), and 144 ± 8.30 (83.8 ± 5.60) μM when HCT-8/Fu cells were pretreated with 0.5 (1.0) mg/mL BPIS for 12 h. The 12 phenolic acid compounds of BPIS were identified by ultraperformance liquid chromatography-triple-time of flight/mass spectrometry (UPLC-Triple-TOF/MS) method. Especially, the fraction of molecular weight (MW) < 200 of BPIS reversed the multidrug resistance in HCT-8/Fu cells, and ferulic acid and p-coumaric acid were the main active components, the IC₅₀ values were 1.23 ± 0.195 and 2.68 ± 0.163 mg/mL, respectively. The present data implied that BPIS significantly enhanced the sensitivity of chemotherapeutic drugs through inhibiting cell proliferation, promoting cell apoptosis, and increasing the accumulation of rhodamine-123 (Rh-123) in HCT-8/Fu cells. Real-time polymerase chain reaction (RT-PCR) and Western blot data indicated that BPIS also decreased the expression levels of multidrug resistance protein 1 (MRP1), P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP). Collectively, these results show that BPIS has potential ability to be used as a new drug-resistance reversal agent in colorectal cancer.