Hypoxia-Targeted Immunotherapy with PD-1 Blockade in Head and Neck Cancer

Simple Summary Intratumoral hypoxia is associated with poor prognosis and therapeutic resistance by modifying the tumor microenvironment in several cancers. MTH1, a member of the Nudix family, maintains the genomic integrity and viability of tumor cells under hypoxic conditions. This study aimed to investigate whether the antitumor activity of immune cells is effective under hypoxia and whether hypoxia-induced MTH1 could be a target for immunotherapy. We found that MTH1 expression is elevated in hypoxic head and neck cancer cell lines and tissues. A novel MTH1 epitope peptide activates CD4+ helper T cells with cytotoxic activity, and is effective even under hypoxic conditions. Combining MTH1-targeted immunotherapy with PD-1 blockade enhances cytotoxicity. These results suggest that MTH1-targeted immunotherapy combined with checkpoint blockade could effectively treat hypoxic tumors by maintaining T-cell activity and increasing cytotoxicity under hypoxic conditions.Abstract Intratumoral hypoxia is associated with tumor progression, aggressiveness, and therapeutic resistance in several cancers. Hypoxia causes cancer cells to experience replication stress, thereby activating DNA damage and repair pathways. MutT homologue-1 (MTH1, also known as NUDT1), a member of the Nudix family, maintains the genomic integrity and viability of tumor cells in the hypoxic tumor microenvironment. Although hypoxia is associated with poor prognosis and can cause therapeutic resistance by regulating the microenvironment, it has not been considered a treatable target in cancer. This study aimed to investigate whether hypoxia-induced MTH1 is a useful target for immunotherapy and whether hypoxic conditions influence the antitumor activity of immune cells. Our results showed that MTH1 expression was elevated under hypoxic conditions in head and neck cancer cell lines. Furthermore, we identified a novel MTH1-targeting epitope peptide that can activate peptide-specific CD4+ helper T cells with cytotoxic activity. The proliferation and cytotoxic activity of T cells were maintained under hypoxic conditions, and PD-1 blockade further augmented the cytotoxicity. These results indicate that MTH1-targeted immunotherapy combined with checkpoint blockade can be an effective strategy for the treatment of hypoxic tumors.