Abstract 5271: Pseudohypoxia by HIF-PHD inhibitors activates tumor immune response for MSS colorectal cancer

Abstract

Abstract Purpose: Microsatellite-stable (MSS) colorectal cancer is resistant for immune therapy, necessitating the exploration of novel modalities for its conquest. Recent revelations have revealed the genetic upregulation of HIF-1α as a potential activator of CD8+ T-cells, enhancing an anti-tumor effect. Pseudohypoxia, characterized by normoxic upregulation of Hypoxia-Inducible Factor (HIF-1α), is known to be induced by iron chelators, including HIF-PHD inhibitors. In this study, we aimed to examine whether pseudohypoxia by HIF-PHD inhibitor can enhance immune response and elucidate the underlying mechanism. Method: Colon 26, SW480 and HT29 were used as murine and human MSS colorectal cancer model. Human and murine CD8+ T-cells were represented by Jurkat cells and isolated splenic CD8+ T-cells, respectively. HIF-PHD inhibitors Roxadustat and Vadadustat were used in the study, and a subcutaneous Colon 26 tumor model was established in BALB/c WT and nude mice. Hypoxic culture conditions were maintained for 48 hours at 2% O2. Results: Roxadustat and Vadadustat did not suppress the proliferation of cancer cells under conditions marked by HIF-1α upregulation. Roxadustat and Vadadustat suppress the colon 26 subcutaneous tumor growth in WT mice, the effect was cancelled in the nude mice. The treatment regimen was associated with an augmentation in the total number and effector-like subtypes of CD8+ T-cells (Tex) infiltrating the tumor. Combination therapy involving Roxadustat and PD-1 antibody synergistically inhibited tumor growth and was accompanied by an increase in PD-1lo, Ly108-, TIM-3+ CD8+ T-cells within the tumor microenvironment. Immunohistochemistry revealed that Interleukin-2 (IL-2) expression of murine spleen was stronger in Roxadustat than control group. Interestingly, HIF-PHD inhibitors induced the secretion of IL-2 from isolated CD3+ T-cells of murine spleens in ELISA, a phenomenon uniquely observed under pseudo-hypoxic conditions created by HIF-PH inhibitors, rather than actual hypoxia. This result indicates that pseudo-hypoxia may induce more robust hypoxic response than real hypoxia. Conclusion: The induction of pseudohypoxia by HIF-PHD inhibitors activates the tumor immune response for MSS colorectal cancer via induction of splenic IL-2. Citation Format: Toshiaki Ohara, Yuehua Chen, Yusuke Hamada, Seitaro Nishimura, Hotaka Kawai, Kazuhiro Noma, Hiroshi Tazawa, Toshiyoshi Fujiwara, Akihiro Matsukawa. Pseudohypoxia by HIF-PHD inhibitors activates tumor immune response for MSS colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5271.