IL-15 enhances the growth and survival of GPC3 CAR T cells, improving their ability to target and fight solid tumors
Study: Interleukin-15-armoured GPC3 CAR T cells for patients with solid cancers. Image Credit: Maryna Olyak/Shutterstock.com
In a recent study published in Nature, researchers tested whether adding Interleukin-15 (IL-15) to Glypican-3 Chimeric Antigen Receptor T (GPC3 CAR T) cells could improve the cells' ability to expand, survive, and fight tumors in people with solid cancers.
Their conclusions indicate that, overall, IL-15 made the GPC3 CAR T cells more effective in fighting cancer.
Background
CAR T cells have shown over 80% complete response rates in certain blood cancers. CAR T cell therapy holds promise for improving survival in patients with solid tumors. However, conventional chemo- and radiotherapies are limited in their ability to treat bulky or metastatic cancers and have significant side effects.
The effectiveness of CAR T cells in solid tumors is often hindered by the tumor microenvironment (TME). The TME may contain inhibitory signals blocking immune responses and lacking cytokines like IL-15, which are essential for optimal T cell function and survival.
About the study
Four clinical trials were conducted to evaluate T-cell therapy using a second-generation CAR targeting GPC3 in liver tumors. Two trials focused on pediatric patients and two on adults. The trials aimed to assess safety, tolerability, and recommended dose for treating relapsed liver tumors.
Retroviral vectors carrying the GPC3 CAR and IL-15 genes were produced using a cell line and modified to prevent certain protein translations. T cells from patients were stimulated and transduced with the CAR genes. Cells were expanded, tested, and cryopreserved.
Flow cytometry was used to assess the immune characteristics of the CAR T cells and to check their persistence and function after infusion. Cytotoxicity assays involved mixing T cells with tumor cells to measure how effectively the CAR T cells killed the tumor cells.
After activation with tumor cells, the T cells were tested for cytokine production (immune signaling molecules) to assess their functionality. The persistence of CAR T cells in the body was measured by tracking their genetic material using quantitative polymerase chain reaction (PCR) methods.
Cytokine levels in the serum were measured using a bead-based assay. A drug used to control CAR T cell activity was administered in specific doses to patients. Single-cell ribonucleic acid sequencing (scRNA-seq) was then used to analyze the behavior of CAR T cells at a molecular level, helping to understand their function and persistence.
Findings
IL-15 significantly improved the antitumor efficacy of CAR T cell therapies compared to traditional CAR T cells, as shown in this study. The researchers developed 15.CAR T cells are engineered to co-express IL-15, a cytokine that enhances T cell survival and function. These modified T cells exhibited superior expansion, function, and tumor targeting, linked to IL-15's ability to boost oxidative phosphorylation and promote a memory T cell phenotype, thereby enhancing long-term persistence in the TME.
The study found that IL-15 reinforced oxidative metabolism in 15.CAR T cells, enhancing their cytotoxic activity and differentiation into effector cells. This led to increased polyfunctionality, which is essential for effective tumor destruction.
Gene expression analysis identified key markers, including Jun Proto-Oncogene (JUN) and Interferon Regulatory Factor 7 (IRF7), associated with regulating immune response and improving tumor infiltration through enhanced T cell functioning. These pathways, particularly Type I Interferon (T1IFN) signaling and oxidative phosphorylation, were upregulated in the 15.CAR T cells, further enhancing their tumor-killing ability.
Safety was carefully monitored, revealing no signs of IL-15-induced malignant transformation in the engineered T cells. However, cytokine release syndrome (CRS) was more frequent in patients receiving 15.CAR T cells, though manageable with immunomodulation therapies. Notably, the 15.CAR group exhibited a higher CRS incidence, emphasizing the need for close monitoring.
A key observation in the study was the antigen-dependent expansion of 15.CAR T cells. The absence of GPC3 CAR expression in certain T cells indicated that their expansion relied on interactions with tumor antigens, which may contribute to sustained antitumor responses and enhanced T cell persistence.
To mitigate CRS, safety mechanisms such as inducible caspase 9 (iC9) were used in three patients, successfully resolving toxicities and ensuring patient safety. Gene expression analysis revealed that 15.CAR T cells exhibited greater cytolytic activity and a stronger tumor response than conventional CAR T cells, with a shift toward effector memory subsets like Cluster of Differentiation 8 (CD8) and Homing Best Oriented T cell Transcription Factor (HOBIT). Additionally, responders showed a better expansion of 15.CAR T cells compared to non-responders, further demonstrating IL-15's role in enhancing CAR T cell efficacy.
Conclusions
Overall, the study highlights the potential of IL-15-modified CAR T cells to improve treatment outcomes in solid tumors by enhancing T cell function, expansion, and tumor targeting while maintaining a manageable safety profile.
Journal reference:
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Interleukin-15-armoured GPC3 CAR T cells for patients with solid cancers. Steffin, D., Ghatwai, N., Montalbano, A., Rathi, P., Courtney, A.N., Arnett, A.B., Fleurence, J., Sweidan, R., Wang, T., Zhang, H., Masand, P., Maris, J.M., Martinez, D., Pogoriler, J., Varadarajan, N., Thakkar, S.G., Lyon, D., Lapteva, N., Zhuyong, M., Patel, K., Lopez-Terrada, D., Ramos, C.A., Lulla, P., Armaghany, T., Grilley, B.J., Gottschalk, S., Dotti, G., Metelitsa, L.S., Heslop, H.E., Brenner, M.K., Sumazin, P., Heczey, A. Nature (2024). doi: 10.1038/s41586-024-08261-8 https://www.nature.com/articles/s41586-024-08261-8
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