The Complement Receptors C3aR and C5aR Are a New Class of Immune Checkpoint Receptor in Cancer Immunotherapy.

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Cancer immunotherapy has made remarkable clinical advances in recent years. Antibodies targeting the immune checkpoint receptors PD-1 and CTLA-4 and adoptive cell therapy (ACT) based on ex vivo expanded peripheral CTLs, tumor infiltrating lymphocytes (TILs), gene-engineered TCR- and chimeric antigen receptor (CAR)-T cells have all shown durable clinical efficacies in multiple types of cancers. However, these immunotherapeutic approaches only benefit a small fraction of cancer patients as various immune resistance mechanisms and limitations make their effective use a challenge in the majority of cancer patients. For example, adaptive resistance to therapeutic PD-1 blockade is associated with an upregulation of some additional immune checkpoint receptors. The efficacy of transferred tumor-specific T cells under the current clinical ACT protocol is often limited by their inefficient engraftment, poor persistence, and weak capability to attack tumor cells. Recent studies demonstrate that the complement receptor C3aR and C5aR function as a new class of immune checkpoint receptors. Complement signaling through C3aR and C5aR expressed on effector T lymphocytes prevent the production of the cytokine interleukin-10 (IL-10). Removing C3aR/C5aR-mediated transcriptional suppression of IL-10 expression results in endogenous IL-10 production by antitumor effector T cells, which drives T cell expansion and enhances T cell-mediated antitumor immunity. Importantly, preclinical, and clinical data suggest that a signaling axis consisting of complement/C3aR/C5aR/IL-10 critically regulates T cell mediated antitumor immunity and manipulation of the pathway ex vivo and in vivo is an effective strategy for cancer immunotherapy. Furthermore, a combination of treatment strategies targeting the complement/C3aR/C5aR/IL-10 pathway with other treatment modalities may improve cancer therapeutic efficacy.





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Wang, Yu, Hui Zhang and You-Wen He (2019). The Complement Receptors C3aR and C5aR Are a New Class of Immune Checkpoint Receptor in Cancer Immunotherapy. Frontiers in Immunology, 10. p. 1574. 10.3389/fimmu.2019.01574 Retrieved from

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You-Wen He

Professor of Integrative Immunobiology

We study T cell biology in health and disease. Our current study is divided into two parts. Part I is to investigate T lymphocyte-mediated anti-caner immunity. We have found that host complement inhibits the cytokine IL-10 production in CD8+ tumor infiltrating lymphocytes through complement receptors C3aR and C5aR. Complement-deficient animals are resistant to tumor development in a T cell- and IL-10-dependent manner. CD8+ tumor infiltrating T cells express IL-10 when complement signaling is disabled. We found that tumor infiltrating lymphocytes from human cancers expanded with IL-2 plus IL-10 are potent tumor killers. Complement-mediated inhibition on antitumor immunity is independent of the PD-1/PD-L1 immune checkpoint pathway. Our findings suggest that complement receptors C3aR and C5aR expressed on CD8+ tumor infiltrating lymphocytes represent a novel class of immune checkpoints that needs to be targeted for tumor immunotherapy. Our current effort is to enhance cancer immunotherapy through several strategies. First, we investigate a combined blockade of complement signaling and anti-PD-1 to enhance the antitumor efficacy; second, we are studying the antitumor efficacy of a targeted delivery of IL-10 to antitumor CD8+ T cells by using anti-PD1-IL-10 or anti-CTLA-4-IL-10 fusion proteins; third, we are studying the tumor killing efficacy of addition of IL-10 in the expansion protocol of tumor infiltrating lymphocytes for adaptive cellular therapy.

Part II is to investigate the intracellular process termed autophagy in T lymphocyte function. Autophagy is a highly conserved self-digestion pathway that plays essential roles in maintaining the homeostasis of organelles, degrading long-lived proteins and recycling amino acids under starvation conditions. We have found that autophagy related molecules are expressed in T lymphocytes and autophagy occurs inside T lymphocytes. We have generated autophagy-deficient T lymphocytes in multiple genetic models and investigated the roles of autophagy in T lymphocytes. We found that autophagy plays a critical role in T lymphocyte function. Our current effort is to elucidate the molecular pathways by which TCR signal induces autophagy and the impact of autophagy on intracellular organelle homeostasis in dividing T cells.   




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