Lasarte, Juan José

Abstract Glutamine dependence of cancer cells reduces local glutamine availability, which hinders antitumor T-cell functionality and facilitates immune evasion. We thus speculated that glutamine deprivation might be limiting efficacy of chimeric antigen receptor (CAR) T-cell therapies in patients with cancer. We have seen that antigen-specific T cells are unable to proliferate or produce interferon gamma (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 B-cell maturation antigen (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-γ, and heightened cytotoxic activity, even under conditions of low glutamine concentration. Mechanistically, Asct2 overexpression reprogrammed the metabolic fitness of CAR T cells by upregulating the mechanistic target of rapamycin complex 1 gene signature, modifying the solute carrier transporter repertoire, and improving both basal oxygen consumption rate and glycolytic function, thereby enhancing 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, higher-level 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 antitumor CAR T-cell functionality in MM. This approach may also be effective for other cancers that depend on glutamine as a key energy source and metabolic hallmark.

Abstract Purpose: The purpose of this research was to identify promiscuous T-helper cell determinants (THd) from carcinoembryonic antigen (CEA) to be used to prime T-cell help for cancer therapy. CEA was selected because this antigen is expressed in an important variety of carcinomas. Experimental Design: Potential promiscuous THd from CEA were predicted using available computer algorithms. Predicted peptides were synthesized and tested in binding experiments to different HLA-DR molecules. Binder peptides were then used to prime T-cell responses both in vitro and in vivo. Results: Twenty 15-mer peptides from CEA were predicted to bind to different HLA-DR molecules. The promiscuous character of these peptides was demonstrated in binding experiments. Fifteen of 20 peptides tested were able to bind to HLA-DR4, but only CEA (625–639) was shown to be presented after processing of recombinant CEA. CEA (625–639) was also found to be presented by HLA-DR53. Moreover, immunization of HLA-DR4 transgenic mice with CEA (625–639) in conjunction with class I epitope OVA (257–264), induced a CTL response specific of OVA (257–264). Conclusions: CEA (625–639) might be a relevant promiscuous THd peptide for cancer therapy.