Efflux inhibition by H2S confers sensitivity to doxorubicin-induced cell death in liver cancer cells

Abstract Aims Hydrogen sulfide (H 2 S), an important gasotransmitter, is involved in a variety of cellular functions and pathophysiologic processes. Drug resistance due to alterations in drug trafficking and metabolism severely limits the effectiveness of cancer therapy. This study examined the role of H 2 S in drug resistance in liver cancer cells. Materials and methods Human primary hepatocellular carcinoma cell line (HepG2) and doxorubicin (Dox)-resistant cells were used in this study. Cell survival was analyzed by MTT, Annexin V-FITC/propidium iodide staining and clonogenic assay. Western blotting was used for analysis of protein expression, and immunoprecipitation was used to determine interactions of LXR/RXR. Key findings The expression of H 2 S-generating enzyme cystathionine gamma-lyase (CSE) was inhibited by doxorubicin treatment in HepG2 cells, and H 2 S sensitized Dox-inhibited cell survival and colony formation. In addition, H 2 S promoted cellular retention of Dox by suppressing the expressions of ABCA1 and ABCG8. H 2 S significantly blocked Dox-induced heterodimer formation between LXRα and RXRβ and attenuated the binding of LXRα/RXRβ to the promoters of ABCA1 and ABCG8 genes. RXRβ but not LXRα was S -sulfhydrated by H 2 S, and blockage of RXRβ S -sulfhydration abolished the inhibitory role of H 2 S on LXRα/RXRβ heterodimer formation. CSE expression was reduced in Dox-resistant cells in comparison with their parental cells, while H 2 S could reverse drug resistance in Dox-resistant cells. Significance Our study provides a novel solution for reversing drug resistance in cancer cells by targeting H 2 S signalling.