Abstract 4860: Pseudohypoxia induced by iron chelator activates tumor immune response in lung cancer

Abstract Hypoxia-inducible factor (HIF) plays a critical role in cellular to adaptation low oxygen levels and has been extensively studied as a biomarker of hypoxia. In cancer cells, HIF upregulation is believed to facilitate survival under hypoxic conditions, contributing to poor prognosis. However, recent studies have demonstrated that HIF signaling is crucial for immune cell function. Oxygen or iron depletion elevates HIF expression by inhibiting HIF-prolyl hydroxylase (HIF-PH) and preventing HIF degradation. Pseudohypoxia, characterized by normoxic HIF upregulation, is facilitated by iron chelators. In this study, we investigated whether pseudohypoxia induced by an iron chelator suppresses tumor growth by activating tumor immune responses, and elucidated the underlying mechanisms. Iron chelators, including Super-polyphenol 10 (SP10) and deferoxamine (DFO), were utilized to induce iron deficiency and pseudohypoxic condition. These compounds reduced the viability of human NSCLC cell lines (A549 and PC-3) but had no significant effect on murine NSCLC cell lines (LLC). Furthermore, SP10 and DFO did not impair the viability of murine CD8+ T cells isolated from normal spleen, while upregulating HIF-1α expression in these cells. Pseudohypoxia by iron chelators stimulated the secretion of IL-2, a cytokine with immunostimulatory properties, from lymphocytes (CD3+ T cells) and NSCLC cell lines (A549, PC-3, and LLC). In contrast, although hypoxic conditions promoted IL-6, a pro-inflammatory cytokine, pseudohypoxia did not induce IL-6 secretion in these cells. Oral administration of SP10 suppressed tumor growth in C57BL/6 mice with implanted tumors, a phenomenon absent in immunodeficient RAG1-deficient C57BL/6 mice. Western blot analysis revealed SP10-induced upregulation of HIF-1α expression within tumors. Immunohistochemistry and flow cytometry demonstrated that SP10 treatment enhanced IL-2 expression in both tumor and spleen tissues. Moreover, SP10 synergistically amplified the efficacy of PD-1 antibody therapy in lung cancer by increasing the infiltration of tumor-infiltrating lymphocytes (TILs). Iron chelation-induced pseudohypoxia directly upregulated HIF-1α, enhanced T cell functionality, and stimulated IL-2 secretion from CD4+, CD8+ T cells, and cancer cells, thereby enhancing the immune response and augmenting the therapeutic efficacy of PD-1 blockade in lung cancer. Citation Format: Toshiaki Ohara, Yusuke Hamada, Yuehua Chen, Manato Terada, Hotaka Kawai, Masayoshi Fujisawa, Kazuhiro Noma, Hiroshi Tazawa, Toshiyoshi Fujiwara, Akihiro Matsukawa. Pseudohypoxia induced by iron chelator activates tumor immune response in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4860.