Abstract 566: PSGL1 KO CAR-T cell can overcome CAR-T cell hurdles: Persistence, exhaustion and off target tissue destruction
Authors: Mavuluri Jayadev , Alli Rajsekhar , Jones Lindsay 
Published: June 2022

Abstract
Chimeric antigen receptor T cell therapy is reported as a fifth pillar of cancer therapy. CAR-T therapy has success against DLBCL’s. Although it is an effective cancer treatment, CAR-T cells still faces challenges like persistence, exhaustion and its leaky entry into the organs causes off-target tissue destruction. Genetic modifications and the use of ectopic stimulants have showed promising way to increase the persistence and decreases the exhaustion. However, most of these modifications either increase persistence or decrease the exhaustion but does not limit its leaky migration to tissues. P-selectin glycoprotein ligand 1 (PSGL-1) is a mucin-like selectin counterreceptor on T-cells that binds to P-selectin, E-selectin, and L-selectin on endothelial cells.In our study, we observed CRISPR-Cas9 knockout of P-Selectin Glycoprotein Ligand-1(PSGL-1)in human Pan-T cells showed increased persistence by enhancing the anti-apoptotic pathway and further reduces the exhaustion by reduced expression of PD-1, TIM3 and LAG3. Interestingly, knocking out PSGL-1 in CD19-CAR-T cells impaired its ability to migrate into tissues. Moreover, CD19-CAR-T cells didn’t lose their cytotoxicity upon Knock out of PSGL-1. Hence PSGL-1 can be used as a potential target in the reprogramming of CAR T-cells and successful CAR T-cell therapy might be achieved with a smaller number of infusions to the patients. Our preclinical study in B6 mouse model, pre-B-ALL disease model clearly shows PSGL-1 KO CD19-CAR-T cells, effectively clears the tumors, persist for longer time by maintain the central memory phenotype and having lower exhaustion profile. KEGG and GSEA pathway enrichment analysis from RNAseq of PSGL-1 KO CD19 CAR-T cells shows PSGL-1 KO CD19-CAR-T cells has central memory phenotype and lower exhaustion profile, further confirmed by immunophenotyping these PSGL1-KO CD19-CAR-T cells. IHC study clearly shows migration of CD19-CAR-T cells into different organs significantly reduced, which limits or reduce the cytokine storm, neurotoxicity and tissue destruction. Recent literature shows VISTA (V-domain Ig suppressor of T cell activation) as a ligand for the PSGL-1, and most of the solid tumors express VISTA and its high level of expression related poor immunotherapeutic outcome and lower survival percentage. From our study, it is evident that PSGL-1 KO CAR-T cells can overcome the limitations of CAR-T cells hurdles like maintaining the memory phenotype, exhaustion and leakiness into different organs, more overPSGL-1 KO CAR-T cells can over comes VISTA dependent CAR-T cell functional inhibition. In summary, our study is clear evident that PSGL-1 KO CAR-T cells can be used as universal CAR-T system to target all kind tumors not limiting to hematological cancers.
Citation Format: Jayadev Mavuluri, Rajsekhar Alli, Lindsay Jones. PSGL1 KO CAR-T cell can overcome CAR-T cell hurdles: Persistence, exhaustion and off target tissue destruction [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 566.