Blockade of the AHR restricts a Treg-macrophage suppressive axis induced by L-Kynurenine

Manganese is critical for antitumor immune responses via cGAS-STING and improves the efficacy of clinical immunotherapy






Authors: Mengze Lv, Meixia Chen, Rui Zhang, Wen Zhang, Chenguang Wang, Yan Zhang, Xiaoming Wei, Yukun Guan, Jiejie Liu, Kaichao Feng, Miao Jing, Xurui Wang, Yun-Cai Liu, Qian Mei, Weidong Han & Zhengfan Jiang



CD8+ T cell-mediated cancer clearance is often suppressed by the interaction between inhibitory molecules like PD-1 and PD-L1, an interaction acts like brakes to prevent T cell overreaction under normal conditions but is exploited by tumor cells to escape the immune surveillance. Immune checkpoint inhibitors have revolutionized cancer therapeutics by removing such brakes. Unfortunately, only a minority of cancer patients respond to immunotherapies presumably due to inadequate immunity. Antitumor immunity depends on the activation of the cGAS-STING pathway, as STING-deficient mice fail to stimulate tumor-infiltrating dendritic cells (DCs) to activate CD8+ T cells. STING agonists also enhance natural killer (NK) cells to mediate the clearance of CD8+T cell-resistant tumors. Therefore STING agonists have been intensively sought after. We previously discovered that manganese (Mn) is indispensable for the host defense against cytosolic dsDNA by activating cGAS-STING. Here we report that Mn is also essential in innate immune sensing of tumors and enhances adaptive immune responses against tumors. Mn-insufficient mice had significantly enhanced tumor growth and metastasis, with greatly reduced tumor-infiltrating CD8+ T cells. Mechanically, Mn2+ promoted DC and macrophage maturation and tumor-specific antigen presentation, augmented CD8+ T cell differentiation, activation and NK cell activation, and increased memory CD8+ T cells. Combining Mn2+ with immune checkpoint inhibition synergistically boosted antitumor efficacies and reduced the anti-PD-1 antibody dosage required in mice. Importantly, a completed phase 1 clinical trial with the combined regimen of Mn2+ and anti-PD-1 antibody showed promising efficacy, exhibiting type I IFN induction, manageable safety and revived responses to immunotherapy in most patients with advanced metastatic solid tumors. We propose that this combination strategy warrants further clinical translation.


Reference: Lv, M., Chen, M., Zhang, R. et al. Manganese is critical for antitumor immune responses via cGAS-STING and improves the efficacy of clinical immunotherapy. Cell Res (2020).


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The authors used Bio X Cell’s anti-mouse PD-1 (CD279) (Clone 29F.1A12) and rat IgG2a isotype control (Clone 2A3) in this research study.