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ATM inhibition enhances cancer immunotherapy by promoting mtDNA leakage and cGAS/STING activation.

ABSTRACT: Novel approaches are needed to boost the efficacy of immune checkpoint blockade (ICB) therapy. Ataxia telangiectasia mutated (ATM) protein plays a central role in sensing DNA double-stranded breaks (DSBs) and coordinating their repair. Recent data indicated that ATM might be a promising target to enhance ICB therapy. However, the molecular mechanism involved has not been clearly elucidated. Here, we show that ATM inhibition could potentiate ICB therapy by promoting cytoplasmic leakage of mitochondrial DNA (mtDNA) and activation of the cGAS/STING pathway. We show that genetic depletion of ATM in murine cancer cells delayed tumor growth in syngeneic mouse hosts in a T cell-dependent manner. Furthermore, chemical inhibition of ATM potentiated anti-PD-1 therapy of mouse tumors. ATM inhibition potently activated the cGAS/STING pathway and enhanced lymphocyte infiltration into the tumor microenvironment by downregulating mitochondrial transcription factor A (TFAM), which led to mtDNA leakage into the cytoplasm. Moreover, our analysis of data from a large patient cohort indicated that ATM mutations, especially nonsense mutations, predicted for clinical benefits of ICB therapy. Our study therefore provides strong evidence that ATM may serve as both a therapeutic target and a biomarker to enable ICB therapy.

SUBMITTER: Hu M

PROVIDER: S-EPMC7843232 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background: Sterile inflammation contributes to the pathogenesis of cardiac dysfunction caused by various conditions including pressure overload in hypertension. Mitochondrial DNA (mtDNA) released from damaged mitochondria has been implicated in cardiac inflammation. However, the upstream mechanisms governing mtDNA release and how mtDNA activates sterile inflammation in pressure-overloaded hearts remain largely unknown. Here, we investigated the role of inducible NO synthase (iNOS) on pressure overload-induced cytosolic accumulation of mtDNA and whether mtDNA activated inflammation through the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway. Methods: To investigate whether the cGAS-STING cascade was involved in sterile inflammation and cardiac dysfunction upon pressure overload, cardiomyocyte-specific STING depletion mice and mice injected with adeno-associated virus-9 (AAV-9) to suppress the cGAS-STING cascade in the heart were subjected to transverse aortic constriction (TAC). iNOS null mice were used to determine the role of iNOS in cGAS-STING pathway activation in pressure-stressed hearts. Results: iNOS knockout abrogated mtDNA release and alleviated cardiac sterile inflammation resulting in improved cardiac function. Conversely, activating the cGAS-STING pathway blunted the protective effects of iNOS knockout. Moreover, iNOS activated the cGAS-STING pathway in isolated myocytes and this was prevented by depleting cytosolic mtDNA. In addition, disruption of the cGAS-STING pathway suppressed inflammatory cytokine transcription and modulated M1/M2 macrophage polarization, and thus mitigated cardiac remodeling and improved heart function. Finally, increased iNOS expression along with cytosolic mtDNA accumulation and cGAS-STING activation were also seen in human hypertensive hearts. Conclusion: Our findings demonstrate that mtDNA is released into the cytosol and triggers sterile inflammation through the cGAS-STING pathway leading to cardiac dysfunction after pressure overload. iNOS controls mtDNA release and subsequent cGAS activation in pressure-stressed hearts.

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ATM inhibition enhances cancer immunotherapy by promoting mtDNA leakage and cGAS/STING activation.

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