CXCR4 inhibition in tumor microenvironment facilitates anti‐programmed death receptor‐1 immunotherapy in sorafenib‐treated hepatocellular carcinoma in mice

Abstract

Sorafenib—a broad tyrosine kinase inhibitor—is the only approved systemic therapy for advanced hepatocellular carcinoma (HCC), but provides limited survival benefits. Recently, immunotherapy has emerged as a promising treatment strategy, but its role remains unclear in HCCs, which are associated with decreased cytotoxic CD8+ T-lymphocyte infiltration in both murine and human tumors. Moreover, we have shown in mouse models that after sorafenib treatment, intratumoral hypoxia is increased and may fuel evasive resistance. Using orthotopic HCC models, we now show that increased hypoxia after sorafenib treatment promotes immunosuppression, characterized by increased intratumoral expression of the immune checkpoint inhibitor programmed death-ligand 1 (PD-L1) and accumulation of T-regulatory cells and M2-type macrophages. We also show that the recruitment of the immunosuppressive cells is mediated in part by hypoxia-induced upregulation of stromal cell-derived 1 alpha (SDF1α). Inhibition of the SDF1α receptor (C-X-C receptor type 4 or CXCR4) using AMD3100 prevented the polarization toward an immunosuppressive microenvironment after sorafenib treatment, inhibited tumor growth, reduced lung metastasis, and improved survival. However, combination of AMD3100 and sorafenib did not significantly change cytotoxic CD8+ T-lymphocyte infiltration into HCC tumors and did not modify their activation status. In separate experiments, antibody blockade of the PD-L1 receptor PD-1 showed anti-tumor effects in treatment-naïve tumors in orthotopic (grafted and genetically engineered) models of HCC. However, anti-PD-1 antibody treatment had additional anti-tumor activity only when combined with sorafenib and AMD3100, and not when combined with sorafenib alone. Conclusion Anti-PD-1 treatment can boost anti-tumor immune responses in HCC models. When used in combination with sorafenib, this immunotherapy approach shows efficacy only with concomitant targeting of the hypoxic and immunosuppressive microenvironment with agents such as CXCR4 inhibitors.

Molecular Pathways: Targeting the CXCR4–CXCL12 Axis—Untapped Potential in the Tumor Microenvironment

“…Others have suggested that modulation of the CXCR4-CXCL12 axis could revert the tolerogenic polarization of the microenvironment rich of immunosuppressive cells such as regulatory T cells (Treg), M2, and N2 neutrophils (40)(41)(42). Recent data show that blocking the interaction of T cells expressing CXCR4 with cells in the microenvironment secreting CXCL12 may modulate immunotherapy with anti-CTLA-4 or anti-PD-1 (41,42).…”

“…Recent data show that blocking the interaction of T cells expressing CXCR4 with cells in the microenvironment secreting CXCL12 may modulate immunotherapy with anti-CTLA-4 or anti-PD-1 (41,42). Although inhibition checkpoints have been shown to induce immune-mediated tumor shrinkage, major responses have been reported in only a subset of patients following PD-1 blockade (43).…”

Rationally combining anti-VEGF therapy with checkpoint inhibitors in hepatocellular carcinoma

“…In this model, we also showed that immune checkpoint molecule, PD-L1 expression in the tumor was increased after sorafenib treatment and potentially mediated immune evasion. Indeed, triple combination therapy with sorafenib, AMD3100 and anti-PD-1 antibody enhanced the infiltration of activated CTL inside the tumor and significantly delayed tumor growth and metastasis [96]. Thus, sorafenib (and potentially other antiangiogenic agents) may be effective in combination with immune checkpoint inhibition in HCC in the face of increased hypoxia with appropriate inhibition of immunosuppression.…”

Development of a radiofrequency ablation platform in a clinically relevant murine model of hepatocellular cancer

“…We are hopeful that the combination of RFA and blockade of immune checkpoints may overcome the limitations of either monotherapy and generate a more powerful therapeutic strategy in HCC. 31 The successful RFA platform established in the present study provides our team with a unique opportunity to test this hypothesis.…”