Potent Cytotoxic Tumor-Infiltrating Lymphocytes Can Be Generated From Immune-Excluded Chondrosarcomas Using Regulatable Membrane-Bound IL15

Reporting in Cancer Immunology Research, researchers have demonstrated that potent cytotoxic tumor-infiltrating lymphocytes (TILs) can be generated from immune-excluded chondrosarcomas using regulatable membrane-bound IL15 (cytoTIL15). The authors, from Northwestern University in collaboration with Obsidian Therapeutics, demonstrate cytoTIL15 cells as potentially able to overcome poor lymphocyte infiltration, dense collagenous matrix, and low frequencies of tumor-reactive T cells. These findings may support development of an IL2-free TIL therapy strategy for chondrosarcoma and other immune-excluded cancers.

TIL therapy has shown clinical activity in “hot” tumors such as melanoma, cervical cancer, and renal cancer, but its feasibility in sarcomas remains uncertain. Since these tumors often have low tumor mutational burden and an immunosuppressive tumor microenvironment, chondrosarcoma is particularly challenging to treat due to chemotherapy resistance, the absence of FDA-approved systemic therapies, and a collagenous matrix with sparse immune infiltration. To test whether engineered TILs could be generated from this setting, the authors profiled primary tumors from 24 patients with chondrosarcoma using IHC (n=24), NanoString nCounter gene expression (n=11), TCR sequencing (n=5), and GeoMx spatial transcriptomics (n=4). They then expanded TILs from sarcoma tumors, including three chondrosarcomas, using 4-1BB agonism in pre-REP, followed by rapid expansion with IL21/4-1BBL feeder cells and regulatable membrane-bound IL15.

Spatial profiling confirmed an immune-excluded phenotype, with CD3⁺ T cells, CD68⁺ macrophages, and immune-checkpoint genes enriched mainly in peritumor regions rather than within tumor, while IHC showed significantly higher peritumoral immune-cell infiltration for multiple markers. MAGEC1 expression correlated strongly with intratumoral CD8⁺ T-cell infiltration, suggesting potential immunogenic targets. TILs were successfully expanded from all three chondrosarcoma donors, with cytoTIL15 cells showing acetazolamide-regulated IL15 expression, favorable memory features, polyfunctionality, and oligoclonal repertoires, including dominant Vβ usage of 68% in donor 1 and 76% in donor 3. Functionally, cytoTIL15 cells showed greater cytotoxicity than nonengineered TILs in 2D and 3D autologous tumor models. In spheroids, cytoTIL15 cells infiltrated deeper and expressed granzyme B more effectively, while IL15 lowered TCR signaling thresholds and increased ERK phosphorylation. Thus, IL15-engineered TILs may make adoptive cell therapy feasible for chondrosarcoma and other immune-excluded tumors.

Reference:

Ao Z, Al-Marayaty R, Aksoy BA, et al. Potent Cytotoxic Tumor-Infiltrating Lymphocytes Can Be Generated from Immune-Excluded Chondrosarcomas Using Regulatable Membrane-Bound IL15. Cancer Immunol Res. 2026;14(6):944-957. http:doi.org/10.1158/2326-6066.CIR-25-1016