Hypoxia-inducible factor-targeting therapy augmented the sensitivity to programmed death ligand-1 blockade by enhancing interferon-γ-induced chemokines in tumor cells.

Immune checkpoint inhibitors (ICIs) targeting programmed death ligand-1 (PD-L1) provide clinical benefits for various advanced malignancies. However, the predictive factors that determine sensitivity to ICIs have not been fully elucidated. We focused on tumor-derived CXCL10/11 as a pivotal factor that determines the response to PD-L1 blockade by regulating T cell accumulation and tumor angiogenesis. We previously reported that CXCL10/11 was upregulated by interferon (IFN)-γ in ICI-sensitive tumor cells but not in ICI-resistant cells, including mouse Lewis lung carcinoma (LLC). In the present study, gene silencing of tumor-derived CXCL10/11 induced resistance to PD-L1 blockade in AB1-HA mesothelioma cell-bearing mice. To identify the mechanisms underlying ICI resistance, we performed a microarray analysis to compare the IFN-γ-inducible genes between ICI-sensitive AB1-HA and ICI-resistant LLC in vitro. A pathway analysis based on microarray data indicated that hypoxia-inducible factor (HIF) 1A is the key signal that inhibits CXCL10/11 expression. We revealed that the HIF1A inhibitors echinomycin (EC) and YC-1 upregulated CXCL10/11 genes induced by IFN-γ in tumor cells in vitro. In addition, combination therapy with PD-L1 blockade and EC demonstrated synergistic antitumor effects in LLC-bearing mice. Combination therapy enhanced tumor infiltration of CD8 T cells and suppressed tumor angiogenesis. The present study suggests that HIF1A signaling in tumor cells dominates ICI resistance via the downregulation of tumor-derived CXCL10/11.