Red rice bran polyphenols suppress invasive properties of HepG2 cells, possibly through Wnt/β-catenin-mediated EMT reversal

Background Hepatocellular carcinoma (HCC) is the most invasive liver cancer, with high incidence rates and resistance to chemotherapy. Polyphenols from red rice bran extract (RRBE) exert diverse anti-cancer effects on certain cancers. This study, for the first time, examined the suppressive effects of RRBE on proliferation, migration, and invasion in HepG2 cells with a preliminary investigation into how its inhibitory effects are linked to reversing the EMT process via the Wnt/β-catenin pathway. Methods The anti-proliferative and cytotoxic effects of RRBE on HepG2 were determined by the resazurin cell viability assay. Its effects on the cell cycle distribution and the apoptosis induction in HepG2 cells were assessed by flow cytometry. Its ability to impede migration was tested using the scratch assay and the transwell migration assay. An initial study was conducted to explore the link between its inhibitory effect and the reversal of EMT via the Wnt/β-catenin signaling pathway using Western blot analysis. Polyphenols and flavonoids were quantified using the Folin-Ciocalteu assay and the aluminum chloride colorimetric assay, respectively. Results RRBE exhibited specific anti-proliferative and cytotoxic effects against HepG2 liver cancer cells compared to normal BNL CL2 liver cells in a dose- and time-dependent manner. RRBE caused a halt in the progression of HepG2 cells at the G2/M phase, resulting in subsequent apoptosis with variations in DNA content. The non-toxic doses of RRBE fully blocked the invasive migration of HepG2 cells after 24 h of its exposure as opposed to the untreated cells. Moreover, E-cadherin protein levels in HepG2 cells dose-dependently increased after 48 h of RRBE exposure, while the levels of β-catenin, vimentin, and MMP-9 proteins dose-dependently decreased compared to their respective untreated cells. The results indicated that RRBE-treated HepG2 cells showed a transition to epithelial characteristics along with diminished malignant features. Preliminary findings from the analysis of these proteins suggest that the inhibitory effects of RRBE may be connected to reversing EMT by regulating the Wnt/β-catenin signaling pathway. The phytochemical analysis revealed that RRBE contained high levels of polyphenols and flavonoids. Conclusions Red rice bran polyphenols demonstrated anti-proliferative, anti-migratory, and anti-invasive effects, which are possibly through Wnt/β-catenin-driven EMT reversal.