CuET overcomes regorafenib resistance by inhibiting epithelial-mesenchymal transition through suppression of the ERK pathway in hepatocellular carcinoma.

Background And Purpose: Regorafenib was approved by the US Food and Drug Administration (FDA) for hepatocellular carcinoma (HCC) patients showing progress on sorafenib treatment. However, there is an inevitably high rate of drug resistance associated with regorafenib, which reduces its effectiveness in clinical treatment. Thus, there is an urgent need to find a potential way to solve the problem of regorafenib resistance. The metabolite of disulfiram complexed with copper, the Diethyldithiocarbamate-copper complex (CuET), has been found to be an effective anticancer drug candidate. In the present study, we aimed to evaluate the effect of CuET on regorafenib resistance in HCC and uncover the associated mechanism.

Experimental Approach: Regorafenib-resistant HCC strains were constructed by applying an increasing concentration gradient. This study employed a comprehensive range of methodologies, including the cell counting kit-8 (CCK-8) assay, colony formation assay, cell cycle analysis, wound healing assay, Transwell assay, tumor xenograft model, and immunohistochemical analysis. These methods were utilized to investigate the antitumor activity of CuET, assess the combined effect of regorafenib and CuET, and elucidate the molecular mechanism underlying CuET-mediated regorafenib resistance.

Key Results: The inhibitory effect of regorafenib on cell survival, proliferation and migration was decreased in regorafenib-resistant MHCC-97H (MHCC-97H/REGO) cells compared with parental cells. CuET demonstrated significant inhibitory effects on cell survival, proliferation, and migration of various HCC cell lines. CuET restored the sensitivity of MHCC-97H/REGO HCC cells to regorafenib in vitro and in vivo. Mechanistically, CuET reverses regorafenib resistance in HCC by suppressing epithelial-mesenchymal transition (EMT) through inhibition of the ERK signaling pathway.

Conclusion And Implications: Taken together, the results of this study demonstrated that CuET inhibited the activation of the ERK signaling pathway, leading to the suppression of the epithelial-mesenchymal transition (EMT) and subsequently reversing regorafenib resistance in HCC both in vivo and in vitro. This study provides a new idea and potential strategy to improve the treatment of regorafenib-resistant HCC.