Abstract T cell-based immunotherapy, including immune checkpoint blockade (ICB), has dramatically changed the paradigm of cancer treatment. However, many cancer patients do not achieve durable responses to immunotherapy, and resistance to these treatments remains a major clinical challenge. We previously showed that immune pressure imposed by immunotherapy selects for immune-resistant tumors that acquire both tumor cell-intrinsic and tumor cell-extrinsic refractoriness through NANOG-driven transcriptional upregulation of HDAC1. In this study, we identify CRY1 as a pivotal NANOG-dependent effector that integrates these refractory traits. In NANOGhigh tumor cells, CRY1 stabilizes Cyclin A and MCL1, thereby promoting cancer stem cell-like properties and resistance to cytotoxic T lymphocyte (CTL)-mediated killing, a process that depends on HDAC1-mediated epigenetic silencing of APC3 and TRIM17. In parallel, CRY1 suppresses CXCL10 expression via HDAC1-dependent transcriptional repression, leading to reduced recruitment of CD8+ T cells into the tumor microenvironment (TME). Importantly, pharmacological inhibition of CRY1 synergizes with anti-PD-1 antibody treatment and adoptive CTL transfer to reduce tumor growth by converting immune-resistant tumors into an immune-sensitive state. Thus, our findings implicate CRY1 as a central molecular target for controlling NANOGhigh tumors and provide a rationale for combining CRY1 inhibitors with T cell-based immunotherapy to reverse the complex refractoriness of tumors. Citation Format: Tae Woo Kim, Oh Se Jin. Cry1 inhibition reverses resistance to T cell-based immunotherapy by promoting anti-tumor immunity abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3791.
Kim et al. (2026) studied this question.