Combined blockade of CXCR4 and PD1 enhances intratumoral dendritic cell activation and immune responses against hepatocellular carcinoma

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of unresectable hepatocellular carcinoma (HCC), but their impressive efficacy is seen in a fraction of patients. One key mechanism of immunotherapy resistance is the paucity of dendritic cells (DCs) in liver malignancies. Here, we tested the combined blockade of programmed death receptor 1 (PD1) and CXCR4, a receptor for CXCL12, a pleiotropic factor that mediates immunosuppression in tumors. Using orthotopic grafted and autochthonous HCC models with underlying liver damage, we evaluated treatment feasibility and efficacy. To establish an orthotopic HCC mouse model with liver damage, RIL-175 cells were implanted in male C57Bl/6 mice, after five weeks of CCl4 treatment (20% (vol/vol) in olive oil, 150-µl gavage, three times per week). When the largest tumors reached ~5mm in diameter (after 12-16 weeks), mice were randomly assigned to a treatment group. Tumor growth was monitored by high-frequency ultrasound imaging. Tumors were collected from mice treated with control IgG, anti-PD1 antibody alone, anti-CXCR4 antibody alone, and anti-PD1 antibody in combination with anti-CXCR4 antibody. Total RNA was extracted from the freshly isolated tumor tissues using Qiagen kits. The RNA quality examination and sequencing library construction were conducted at the Molecular Biology Core Facilities of the Dana Farber Cancer Institute (Boston, USA).