Antiangiogenic Treatment Facilitates the Abscopal Effect of Radiation Therapy Combined With Anti-PD-1 in Hepatocellular Carcinoma.

Abstract

Purpose: Metastasis is one of the most important factors contributing to poor prognosis in hepatocellular carcinoma. Radiation therapy (RT), along with its induced abscopal effect, is a promising treatment for metastatic patients. However, the incidence of abscopal effect in clinical practice is rare, even when RT is combined with immune checkpoint inhibitors (ICIs). In this study, we aim to investigate the role of antiangiogenic treatment on the abscopal effect induced by RT + ICIs.

Methods and materials: Bilateral subcutaneous and orthotopic Hepa1-6 and Hep53.4 models were established and treated with different combination treatments. We evaluated changes in the immune microenvironment and vascular normalization by flow cytometry, T cell receptor sequencing, chemotactic gene array, enzyme linked immunosorbent assays, and immunofluorescence.

Results: Our studies showed that antiangiogenic treatment with RT + ICIs increased the antitumor response of the unirradiated lesions. Mechanistically, the blockade of vascular endothelial receptor 2 (anti-VEGFR2) increased the activation and maturation of dendritic cells and promoted the production of CD8⁺ T cells in irradiated tumors. These CD8⁺ T cells were attracted by anti-VEGFR2-induced CCL5 secretion from M1 macrophages in unirradiated tumors. Besides that, anti-VEGFR2 enhanced the function of CD8⁺ T cells by reducing myeloid-derived suppressor cells and regulatory T cells.

Conclusions: This study demonstrated that the combination of antiangiogenic treatment with RT and ICIs enhanced the abscopal effects. The application of triple therapy and its induced abscopal effect may offer a novel therapeutic approach for hepatocellular carcinoma, particularly for cases with multiple metastatic lesions.