Androgen receptor enhances the efficacy of sorafenib against hepatocellular carcinoma through enriched EpCAM stemness

Background/Aim: The role of androgen receptor (AR) in hepatocellular carcinoma (HCC) development is controversial. Therefore, the translational value of targeting AR in HCC is unknown. Sorafenib, a multiple kinase inhibitor, is the standard therapy for patients with unresectable HCC. This study investigated sorafenib effect on AR in experimental models of HCC. Material and Methods: AR cDNA was introduced into HCC cells and in vitro cell growth and in vivo tumor growth were measured. Sphere cells, as well as epithelial cell adhesion molecule-positive (EpCAM+) and CD133+ cells were isolated from HCC cells with/without AR expression to observe in vitro/in vivo effects. Liver specific AR knockout in mouse models of spontaneous HCC (carcinogen-induced and hepatitis B virus-related HCC) was also implemented to examine gene expression. HCC cells/tumors were treated with sorafenib in order to determine effects on tumor growth and related gene expression. Result: AR cDNA increased transactivation function, increased colony/sphere-forming activities, and enhanced tumorigenicity in HCC cells compared to their parental cells. Expression of the stemness marker EpCAM was also dramatically increased. In carcinogen-and HBV-induced HCC models, EpCAM+ cells were significantly reduced in AR-knockout mice compared to wild-type HCCs. In addition, AR reduced sorafenib-related signals, e.g. extracellular-regulated kinase, AKT serine/threonine kinase 1, and p38 mitogen-activated protein kinase, compared to that in parental cells. Regarding sorafenib cytotoxicity, AR-expressing cells were vulnerable to treatment. Moreover, the half maximalinhibitory concentration (IC50) was drastically lowered in AR⁺/EpCAM⁺ compared to AR^-/EpCAM^- sphere cells. Strikingly, the IC50. in AR⁺/CD133+ vs. AR^-/CD133+ cells were similar. Moreover, sorafenib robustly suppressed tumor growth in implanted AR⁺/EpCAM⁺ cells but not AR^-/EpCAM^- ones. Finally, bioinformatics analyses revealed EpCAM to be a prognostic biomarker in Asian and non-alcohol-consuming patients with HCC, suggesting suitability of a sorafenib regimen for such patients. Conclusion: AR⁺/EpCAM⁺ may be a marker of responsiveness to sorafenib for patients with HCC. Prospective surveys associating AR/EpCAM expression with therapy outcomes are essential.