Abstract 42: Tunneling CARs: Gene modifications to enhance CAR-T infiltration into solid tumors

Abstract

Abstract Background: CAR-T therapy has been largely ineffective in solid tumors because the dense, rigid, extracellular matrices (ECMs) and basement membranes (BMs) that encapsulate these tumors exclude T cells. Tumor-specific ECMs and BMs, made of type I and type IV collagen respectively, are heavily cross-linked and characterized by small pores. T cell infiltration into tumors relies upon the enzymatic degradation of these matrix fibers, and adhesion molecule-mediated movement. Gene expression analysis of tumor infiltrating leukocytes from patient samples showed that MMP-7, an enzyme that degrades type IV collagen, and osteopontin (OPN), a molecule that interacts with adhesion molecules to mediate movement, were highly upregulated in infiltrating cells compared to those that were tumor adjacent, suggesting they may be important in navigating tumor-specific environments. We hypothesized that overexpressing MMP-7 and/or OPN in CAR-T cells will enhance their infiltration into solid tumors. Methods: We overexpressed MMP-7 and OPN in second-generation CAR-Ts (GD2-28Z and HER2-28Z) and evaluated their infiltration in vitro using Halo invasion assays. T cell movement out of type IV collagen and into tumor droplets, composed of tumor targets polymerized in type I collagen, was visualized over time to characterize T cell movement through the tumor-specific BM and ECM, respectively. The expansion, phenotype, and cytotoxicity of OPN and MMP-7-modified GD2-28Z CAR-Ts was compared to unmodified GD2 CAR-Ts by counting, flow cytometry and chromium release, respectively. We then used a xenograft model of neuroblastoma to determine if increases in GD2 CAR-T infiltration led to reduced tumor burden. Results: In vitro, MMP-7 overexpression increased GD2-28Z (2.05-fold, p<0.0001) and HER2-28Z (3.16-fold, p<0.0001) CAR-T infiltration, and OPN overexpression increased GD2-28Z (1.20-fold, p=0.0496) and HER2-28Z (1.49-fold, p=0.002) CAR-T infiltration. In vivo, 52 days after CAR-T infusions, mice treated with OPN-modified GD2-28Z CAR-Ts had reduced tumor burden (0.206 cm, ±0.21) compared to GD2-28Z CAR-Ts (0.903 cm, ±0.33, p=0.0449). Conclusions: The overexpression of MMP-7 or OPN in second-generation CAR-Ts enhances CAR-T infiltration in vitro, and the expression of these genes does not impair CAR-T expansion, phenotype or cytotoxicity. The overexpression of OPN in GD2-28Z CAR-T enhances tumor clearance in a xenograft model of neuroblastoma, and may increase overall survival. Citation Format: Stacey N. Van Pelt, Bilal Omer, Lindsay Talbot, Cliona Rooney, Rohan Fernandes, Candise Tat, Mark White. Tunneling CARs: Gene modifications to enhance CAR-T infiltration into solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 42.