Hedyotis diffusa Willd overcomes 5-fluorouracil resistance in human colorectal cancer HCT-8/5-FU cells by downregulating the expression of P-glycoprotein and ATP-binding casette subfamily G member 2

Abstract

Previous studies have demonstrated that Hedyotis diffusa Willd (HDW), a traditional Chinese herbal medicine, exhibits potent anticancer activity in models of colorectal cancer (CRC). Aggressive forms of CRC exhibit resistance to widely used chemotherapeutic drugs, including the antimetabolite, 5‑fluorouracil (5‑FU); however, less is known with regard to the activity of HDW against 5‑FU‑resistant cancer. In the present study, the mechanism of action and the potency of ethanol extracts of HDW (EEHDW) were investigated on a multidrug‑resistant CRC HCT‑8/5‑FU cell line. Using an MTT cell proliferation assay, EEHDW treatment was shown to significantly reduce the cell viability of HCT‑8/5‑FU cells in a dose‑ and time‑dependent manner. Furthermore, EEHDW significantly increased the retention of the ATP‑binding cassette (ABC) transporter substrate, rhodamine‑123, as compared with the untreated controls. To further investigate the molecular mechanisms targeted by EEHDW in the resistant cells, the expression levels of the ABC drug transporter protein, P‑glycoprotein (P‑gp), and ABC subfamily G member 2 (ABCG2), were analyzed using reverse‑transcription polymerase chain reaction and western blot analysis. The mRNA and protein expression levels of P‑gp and ABCG2 were reduced in the HCT‑8/5‑FU cells following EEHDW treatment, indicating that EEHDW inhibits ABCG2‑mediated drug resistance by downregulating the expression of ABCG2 and P‑gp. Therefore, the potential application of EEHDW as a chemotherapeutic adjuvant represents a promising alternative approach to the treatment of drug‑resistant CRC.