Abstract C125: Chitinase 3-like-1 as an immunosuppressive modulator in chordoma: Implications for T-cell function and viability

Abstract Background Chordoma is a rare and aggressive cancer with limited therapeutic options. Chitinase 3-like-1 (Chi3l1) is a secreted glycoprotein known to be overexpressed in various solid tumors and is associated with chemoresistance and poor prognosis. Chi3l1 contributes to an immunosuppressive tumor microenvironment (TME) by modulating key immune checkpoint regulators PD-1 and PD-L1 in melanoma and glioma. Preliminary data indicate that Chi3l1 is overexpressed in human chordoma cells, suggesting its role in promoting chordoma development and progression, while the exact molecular mechanism remains elusive. We hypothesized that Chi3l1 modulates immune-chordoma interactions by regulating T-cell proliferation and cytotoxicity. Methods To investigate immune crosstalk in chordoma, we co-cultured peripheral blood mononuclear cells (PBMCs) and CD8+ T-cells—both isolated from chordoma patients—with autologous chordoma cells and the commercially available JHC-7 primary chordoma cell line. Supernatants of co-culture media were collected at defined time points to assess inflammatory factor secretion and cell viability. Cell viability of both immune cells and chordoma cells were measured using CellTiter-Glo viability assays complemented by MTT proliferation assays. T-cell-mediated inflammatory responses were evaluated using Griess assay. Additionally, Chi3l1 production by T-cells isolated from healthy individuals and glioblastoma (GBM) patients were quantified via ELISA. Results Co-culture of patient-derived immune cells with chordoma cells was feasible and consistently showed increased viability in both cell types, suggesting active crosstalk. However, T-cell-mediated inflammatory responses were minimal, indicating that immune cells were not mounting an effective response to chordoma cells—supporting the presence of an immunosuppressive mechanism, potentially involving Chi3l1. PBMCs were less viable when co-cultured with patient-derived chordoma cells compared to JHC-7 cells which express lower levels of Chi3l1. Substantial elevation in Chi3l1 expression was also confirmed in T-cell supernatants from GBM patients, while expression remained low in healthy donors. Conclusions These findings support Chi3l1 as a key mediator of immune suppression in chordoma. The presence of a Chi3l1 facilitated immune tolerance mechanism interferes with immune mediated cytotoxicity, explaining the observed increase in chordoma cell viability and suppression of inflammation. Reduction in PBMC viability when co-cultured with patient-derived chordoma cells, which express higher levels of Chi3l1, further support the role of Chi3l1 in immune evasion. Moreover, elevated Chi3l1 expression in GBM patient T-cells compared to healthy controls underscores its role in promoting tumor-associated immune suppression in brain malignancies. Ongoing experiments focus on quantifying Chi3l1 in CD8+ T-cell supernatants from chordoma patients and investigating the effects of recombinant Chi3l1 and Chi3l1-inhibiting antibodies on T-cell viability to better elucidate its immunomodulatory mechanisms. Citation Format: Tianyi Wang, Beatrice Campilan, Christian Godinez, Madison Michles, Sydney Harris, Jolie Barnard, Ziya Gokaslan, Patricia Sullivan, Margot Martinez-Moreno. Chitinase 3-like-1 as an immunosuppressive modulator in chordoma: Implications for T-cell function and viability [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr C125.