biostudies-literatureKar ADST | Science and Engineering Research BoardNCI NIH HHSDBT/Wellcome Trust India AllianceWellcome Truste2315989121https://www.ebi.ac.uk/biostudies/studies/S-EPMC10945783biostudies-literatureUnknown121(11)PD1 blockade therapy, harnessing the cytotoxic potential of CD8⁺ T cells, has yielded clinical success in treating malignancies. However, its efficacy is often limited due to the progressive differentiation of intratumoral CD8⁺ T cells into a hypofunctional state known as terminal exhaustion. Despite identifying CD8⁺ T cell subsets associated with immunotherapy resistance, the molecular pathway triggering the resistance remains elusive. Given the clear association of CD38 with CD8⁺ T cell subsets resistant to anti-PD1 therapy, we investigated its role in inducing resistance. Phenotypic and functional characterization, along with single-cell RNA sequencing analysis of both in vitro chronically stimulated and intratumoral CD8⁺ T cells, revealed that CD38-expressing CD8⁺ T cells are terminally exhausted. Exploring the molecular mechanism, we found that CD38 expression was crucial in promoting terminal differentiation of CD8⁺ T cells by suppressing TCF1 expression, thereby rendering them unresponsive to anti-PD1 therapy. Genetic ablation of CD38 in tumor-reactive CD8⁺ T cells restored TCF1 levels and improved the responsiveness to anti-PD1 therapy in mice. Mechanistically, CD38 expression on exhausted CD8⁺ T cells elevated intracellular Ca²⁺ levels through RyR2 calcium channel activation. This, in turn, promoted chronic AKT activation, leading to TCF1 loss. Knockdown of RyR2 or inhibition of AKT in CD8⁺ T cells maintained TCF1 levels, induced a sustained anti-tumor response, and enhanced responsiveness to anti-PD1 therapy. Thus, targeting CD38 represents a potential strategy to improve the efficacy of anti-PD1 treatment in cancer.Proceedings of the National Academy of Sciences of the United States of AmericaCD38-RyR2 axis-mediated signaling impedes CD8⁺ T cell response to anti-PD1 therapy in cancer.PMC10945783CRG/2019/001334R01 CA236379R01 CA250458R41 CA239952IA/I/19/1/504277R42 CA239952Ganesan SKGautam ABasak DChowdhury SMukhopadhyay APaul SBhoumik AMehrotra SKar AGhosh PChakraborty PSarkar IBarman SChatterjee SfalseCD38-RyR2 axis-mediated signaling impedes CD8⁺ T cell response to anti-PD1 therapy in cancer.PD1 blockade therapy, harnessing the cytotoxic potential of CD8⁺ T cells, has yielded clinical success in treating malignancies. However, its efficacy is often limited due to the progressive differentiation of intratumoral CD8⁺ T cells into a hypofunctional state known as terminal exhaustion. Despite identifying CD8⁺ T cell subsets associated with immunotherapy resistance, the molecular pathway triggering the resistance remains elusive. Given the clear association of CD38 with CD8⁺ T cell subsets resistant to anti-PD1 therapy, we investigated its role in inducing resistance. Phenotypic and functional characterization, along with single-cell RNA sequencing analysis of both in vitro chronically stimulated and intratumoral CD8⁺ T cells, revealed that CD38-expressing CD8⁺ T cells are terminally exhausted. Exploring the molecular mechanism, we found that CD38 expression was crucial in promoting terminal differentiation of CD8⁺ T cells by suppressing TCF1 expression, thereby rendering them unresponsive to anti-PD1 therapy. Genetic ablation of CD38 in tumor-reactive CD8⁺ T cells restored TCF1 levels and improved the responsiveness to anti-PD1 therapy in mice. Mechanistically, CD38 expression on exhausted CD8⁺ T cells elevated intracellular Ca²⁺ levels through RyR2 calcium channel activation. This, in turn, promoted chronic AKT activation, leading to TCF1 loss. Knockdown of RyR2 or inhibition of AKT in CD8⁺ T cells maintained TCF1 levels, induced a sustained anti-tumor response, and enhanced responsiveness to anti-PD1 therapy. Thus, targeting CD38 represents a potential strategy to improve the efficacy of anti-PD1 treatment in cancer.2024-01-01T00:00:00Z2024 Mar2025-04-26T12:02:16.116Z2025-02-19T03:09:39.29ZS-EPMC109457833845194810.1073/pnas.2315989121