IL-15 improves the effectiveness of GPC3 CAR T cells in fighting solid tumors

IL-15 increases the growth and survival of GPC3 CAR T cells, improving their ability to attack and fight solid tumors

In a recent study published in NatureResearchers 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 shrink tumors in people with solid cancers fight.

Their conclusions suggest that IL-15 made GPC3 CAR T cells more effective overall at fighting cancer.

background

CAR T cells have demonstrated a complete response rate of over 80% in certain blood cancers. CAR T-cell therapy promises to improve the survival of patients with solid tumors. However, conventional chemotherapy and radiation therapies have limited ability to treat bulky or metastatic cancers and have significant side effects.

The effectiveness of CAR T cells in solid tumors is often affected by the tumor microenvironment (TME). The TME may contain inhibitory signals that block immune responses and lack cytokines such as 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 with a second-generation CAR targeting GPC3 in liver tumors. Two studies focused on pediatric patients and two on adults. The aim of the studies was to evaluate the safety, tolerability and recommended dose for the treatment of recurrent liver tumors.

Retroviral vectors carrying the GPC3-CAR and IL-15 genes were created using a cell line and modified to prevent certain protein translations. T cells from patients were stimulated and transduced with the CAR genes. The cells were expanded, tested and cryopreserved.

Flow cytometry was used to assess the immune properties of CAR-T cells and check their persistence and function after infusion. In cytotoxicity tests, T cells were mixed 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 the production of cytokines (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.

Serum cytokine levels were measured using a bead-based assay. Patients were given a drug to control CAR-T cell activity at specific doses. Single-cell ribonucleic acid sequencing (scRNA-seq) was then used to analyze the behavior of CAR-T cells at the molecular level, contributing to the understanding of their function and persistence.

Insights

IL-15 significantly improved the antitumor efficacy of CAR-T cell therapies compared to conventional CAR-T cells, as demonstrated in this study. The researchers developed 15.CAR-T cells were engineered to co-express IL-15, a cytokine that improves T cell survival and function. These modified T cells demonstrated superior expansion, function and tumor targeting, which is related to the ability of IL-15 to increase oxidative phosphorylation and promote a memory T cell phenotype, thereby improving long-term persistence in the TME becomes.

The study found that IL-15 enhances oxidative metabolism in 15.CAR-T cells and increases their cytotoxic activity and differentiation into effector cells. This resulted in increased polyfunctionality, which is essential for effective tumor destruction.

Gene expression analysis identified key markers, including Jun Proto-Oncogenes (JUN) and Interferon Regulatory Factor 7 (IRF7), which are associated with regulating the immune response and improving tumor infiltration through improved T cell function. These signaling pathways, particularly interferon type I (T1IFN) signaling and oxidative phosphorylation, were upregulated in the 15.CAR-T cells, further increasing their tumor-killing ability.

Safety was carefully monitored and no signs of IL-15-induced malignant transformation were detected in the engineered T cells. However, cytokine release syndrome (CRS) occurred more frequently in patients receiving 15.CAR-T cells, although it was manageable with immunomodulation therapies. Notably, the 15.CAR group had a higher incidence of CRS, highlighting the need for close monitoring.

An important observation in the study was the antigen-dependent expansion of 15.CAR-T cells. The absence of GPC3-CAR expression in certain T cells suggested that their expansion was due to interactions with tumor antigens, which may contribute to sustained antitumor responses and improved T cell persistence.

To mitigate CRS, safety mechanisms such as inducible caspase 9 (iC9) were used in three patients to successfully eliminate toxicities and ensure patient safety. Gene expression analysis revealed that 15.CAR-T cells had greater cytolytic activity and tumor response than conventional CAR-T cells, with a shift toward effector memory subsets such as Cluster of Differentiation 8 (CD8) and Homing Best Oriented T cell transcription factor (HOBIT). ). In addition, responders showed better proliferation of 15.CAR-T cells compared to non-responders, further highlighting the role of IL-15 in increasing CAR-T cell effectiveness.

Conclusions

Overall, the study highlights the potential of IL-15-modified CAR T cells to improve treatment outcomes in solid tumors by improving T cell function, expansion and tumor targeting while maintaining a manageable safety profile.