Abstract 3196: CRTAM defines effector functionality and robust anti-tumor response of cytotoxic CD8+T cells

Abstract The effectiveness of current cancer immunotherapies, such as immune checkpoint blockade (ICB), adoptive T cell therapy (ACT), and chimeric antigen receptor (CAR) T-cell therapy, is limited in solid tumors due to the scarcity of tumor-specific immunogenic targets, impaired tumor antigen processing, and immune cell dysfunction. Cytotoxic CD8+ T lymphocytes (CTLs) are the primary effectors in antitumor immunity, yet their dysfunctional or exhausted states present significant challenges to successful immunotherapy. Recent study of pre-infusion CAR T cells in non-Hodgkin lymphoma (NHL) have identified polyfunctional T cell subsets that exhibit engagement of diverse immune programs, characterized by the production of various cytokines and chemokines (IFN-γ, GMZB, and MIP1a) which corroborated with enhanced patient survival. In our previous clinical study involving ACT in melanoma patients (NCT00665470), we observed engraftment of CD8+ T cell clones without objective antitumor responses (non-responders), while spontaneous complete responses were noted in two patients prior to ACT (responders). A comparative analysis of CD8+ T cell clones derived from responders versus non-responders identified Cytotoxic and Regulatory T cell Molecule (CRTAM) as a differentially expressed gene in activated CD8+ T cell clones from responders. We propose CRTAM as a predictive marker for a potent and durable CD8+ T cell-mediated antitumor response and to explore its potential role in enhancing the antitumor efficacy of ACT and CAR T cell therapy in solid tumors. We have thus far established the role of CRTAM in defining enhanced effector functions of murine cytotoxic CD8+ T cells by examining antigen specific P - Mel CRTAMHi Vs CRTAMLo CD8+ T cell subsets with CRTAMHi T cells showing enhanced cytotoxic profile (perforin/ GMZB), cytokine production (IFN- γ), antitumor cytotoxicity, immunophenotype and gene profile using both in vitro and in vivo models. RNA sequencing analysis reveals that CRTAMHi P-Mel T cells exhibit a unique gene expression profile associated with cytokine activity, signal transduction, cell migration, and cytotoxicity. Furthermore, increased overall survival in patients with solid tumors exhibiting T cell infiltration and increased CRTAM expression was demonstrated by query of publicly available databases, such as The Cancer Genome Atlas (TCGA). Therefore, CRTAM identifies a unique subset of CTL with enhanced effector functions, with deployment of diverse immune programs leading to improved antitumor activity. T cells engineering to knockout and express CRTAM is currently underway to evaluate the feasibility of enhancing antitumor responses in, in vivo murine models of ACT. Engineering CD8+ T cells for CRTAM may generate more effective and durable T cell products for ACT and CAR T cell therapy in solid tumors. Citation Format: Zheng Liu, An Nguyen, Amy Olex, Mikail Bala, Jose Trevino, Bhaumik Patel, Jolene Windle, Xiang-Yang Wang, Syed Ammer Shah. CRTAM defines effector functionality and robust anti-tumor response of cytotoxic CD8+T cells [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 3196.