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Restoration of LAT signaling through the expression of a novel Adjunctive LAT-Activating CAR (ALA-CART) enhances the antigen-sensitivity and persistence of CAR T cells

ABSTRACT: Chimeric antigen receptor (CAR) T cell therapy have demonstrated remarkable success in treating B-cell malignancies that are refractory to standard therapies; however, preclinical and clinical studies have demonstrated that CAR T cell efficacy is greatly reduced against antigen-low tumors. This was exemplified in a clinical trial of CD22-directed CAR T cells where post-CAR relapses were driven by a decrease in the surface expression of the CD22 antigen. To address the poor response of CAR T cells to antigen-low tumor cells, we performed global phosphoproteomics using a SILAC/mass spectrometry approach to examine signal transduction events within CAR T cells in response to high- and low-levels of CD22 antigen. Stimulation with low levels of CD22 antigen resulted in decreased activation of several canonical T cell signaling pathways in CAR T cells, suggesting poor utilization of LAT. To overcome this inefficiency of LAT activation, we designed a bicistronic construct consisting of a clinically active 2nd generation CD22-BBz CAR along with a novel Adjunctive LAT Activating CAR incorporating the intracellular signaling domain of LAT (ALA-CART). ALA-CART cells demonstrated enhanced phosphorylation of LAT and restored downstream signaling in response to low levels of CD22. In xenograft models, ALA-CART cells completely eradicated CD22-low leukemia, significantly extending survival of mice in comparison to the clinically-active, standard CD22-BBz CAR T cells. Compared to the standard CD22-BBz CAR T cells, ALA-CART cells exhibited transcriptional differences in the resting state reflecting a less differentiated state, which corresponded to an enrichment of T stem cell memory cells and enhanced in vivo persistence. Thus, through the identification of CAR signaling deficits, we rationally designed the ALA-CART platform which improves the sensitivity and persistence of CAR T cells to target antigen-low cells, overcoming a mechanism of resistance to standard CAR therapies.

ORGANISM(S): Homo sapiens

PROVIDER: GSE236468 | GEO | 2025/02/04

REPOSITORIES: GEO

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Project description:Purpose: To compare cell states between control Her2-BBz and JUN-overexpression Her2-BBz human CAR T cells in a mouse model of osteosarcoma. Methods: 8-week old NSG mice were implanted with 1 million 143B osteosarcoma tumor cells intramuscularly in the right leg. 14 days post tumor implantation, mice were infused intravenously with 10 million human CAR+ T cells via tail vein injection. Before T cell transfer, mice were randomized for tumor size and treated with either control Her2-BBz or JUN-overexpressing Her2-BBz CAR T cells. T cells were 70% CAR+ at infusion for both groups. 14 days post T cell treatment (day 28 post tumor engraftment), 6 mice per group were euthanized, solid tumor tissue was collected, mechanically dissociated, and single cell suspensions were labeled with human-CD45 antibody and viability dye. Live hCD45+ tumor-infiltrating lymphocytes were sorted from each tumor and 6 samples were pooled for each group. ~35,000-40,000 sorted live cells (counted post sort) for each group were delivered to the Stanford Functional Genomics Facility for 3' single-cell RNA-sequencing on the 10X Genomics platform. Results: We found that substantially more JUN-overexpressing Her2-BBz CAR T cells were within the G2/M and S phases of the cell cycle than control Her2-BBz CAR T cells, consistent with increased in vivo proliferation of JUN-Her2-BBz CAR T cells. Furthermore, JUN-Her2-BBz CAR T cells also demonstrated a more activated transcriptional program (as measured by IL2RA and CD38), while many exhaustion-associated genes were downregulated (PDCD1, BTLA, TIGIT, CD200, ENTPD1, NR4A2) compared to control Her2-BBz CAR T cells. Finally, a small cluster of cells characterized by high IL7R expression (IL7R+ KLF2+ CD27+ TCF7+ SELL+) was apparent in JUN-overexpressing but not in control Her2-BBz CAR T cells, consistent with maintenance of a memory-like population capable of self-renewal. Conclusions: This study provides insights into cell states that could explain the improved efficacy of JUN-overexpression Her2-BBz CAR T cells compared to control Her2-BBz CAR T cells in a mouse model of osteosarcoma.

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Restoration of LAT signaling through the expression of a novel Adjunctive LAT-Activating CAR (ALA-CART) enhances the antigen-sensitivity and persistence of CAR T cells

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