Effect of SLC1A5 overexpression on T cell metabolism and function

Glutamine-dependence of cancer cells reduces local glutamine availability, which hinders anti-tumor T-cell functionality and facilitates immune evasion. We thus speculated that glutamine deprivation might be limiting efficacy of CAR T-cell therapies in cancer patients. We have seen that antigen-specific T cells are unable to proliferate or produce IFN-γ in response to antigen stimulation when glutamine concentration is limited. Using multiple myeloma (MM) as a glutamine-dependent disease model, we found that murine CAR-T cells selectively targeting BCMA in MM cells were sensitive to glutamine deprivation. However, CAR-T cells engineered to increase glutamine uptake by expression of the glutamine transporter Asct2 exhibited enhanced proliferation and responsiveness to antigen stimulation, increased production of IFN-, and heightened cytotoxic activity, even under conditions of low glutamine concentration. Mechanistically, Asct2 overexpression reprogrammed CAR-T cell metabolic fitness, improving basal oxygen consumption rate and glycolytic function that enhanced CAR-T cell persistence in vivo. Accordingly, expression of Asct2 increased the efficacy of BCMA CAR-T cells in syngeneic and genetically-engineered mouse models of MM, which prolonged mouse survival. In patients, reduced expression of Asct2 by MM cells predicted poor outcome to combined immunotherapy and BCMA-CAR T-cell therapy. Our results indicate that reprogramming glutamine metabolism may enhance anti-tumor CAR T-cell functionality in multiple myeloma. This approach may also be effective for other cancers that depend on glutamine as a key energy source and metabolic hallmark.