Targeting CXCR6 Disrupts β-Catenin Signaling and Enhances Sorafenib Response in Hepatocellular Carcinoma

<b>Background/Objectives</b>: Hepatocellular carcinoma (HCC) therapies are limited by poor response, rapid resistance, and recurrence of aggressive disease. Sorafenib, a multi-tyrosine kinase inhibitor, can trigger β-catenin stabilization and activation, contributing to resistance. Overexpression of the chemokine receptor CXCR6 and its ligand CXCL16 and hyperactivation are implicated in HCC progression and β-catenin stabilization. We hypothesized that SBI-457, a small-molecule CXCR6 antagonist we developed, could disrupt CXCR6/β-catenin crosstalk and enhance sorafenib sensitivity. <b>Methods</b>: We tested SBI-457 alone and in combination with sorafenib in SK-Hep-1 xenograft models and a panel of human HCC cell lines. Tumor burden, β-catenin activation, and CXCR6 expression were assessed by tumor volume measurements, immunohistochemistry, Western blotting, and immunofluorescence. Soluble CXCL16 levels were quantified by ELISA, and cell death responses were evaluated using MTT assays. <b>Results</b>: In vivo, SBI-457 combined with sorafenib reduced normalized tumor volume by 55% compared to vehicle controls, modestly exceeding monotherapy effects, and attenuated sorafenib-induced β-catenin upregulation. In vitro, SBI-457 blocked nuclear accumulation of β-catenin and reversed sorafenib-induced increases in β-catenin levels. Enhanced cell death was observed in specific "responder" HCC cell lines (Hep-3B, SNU-398, JHH-5), which correlated with high intracellular β-catenin, secretion of soluble CXCL16, and expression of a high molecular weight form of CXCR6. In contrast, "non-responder" cell lines with conventional CXCR6 expression and low CXCL16 secretion showed no enhanced cell death response. <b>Conclusions</b>: CXCR6 antagonism with SBI-457 can modulate β-catenin activation and may help overcome sorafenib resistance in selected HCC models. These findings support further development of CXCR6 antagonists as single agents or combination therapies to improve treatment outcomes in HCC.