The role of somatic mitochondrial DNA (mtDNA) mutations in leukemogenesis remains poorly characterized. To determine the impact of somatic mtDNA mutations on this process, we assessed the leukemogenic potential of hematopoietic progenitor cells (HPCs) from mtDNA mutator mice (Polg D257A) with or without NMyc overexpression. We observed a higher incidence of spontaneous leukemogenesis in recipients transplanted with heterozygous Polg HPCs and a lower incidence of NMyc-driven leukemia in those with homozygous Polg HPCs compared to controls. Although mtDNA mutations in heterozygous and homozygous HPCs caused similar baseline impairments in mitochondrial function, only heterozygous HPCs responded to and supported altered metabolic demands associated with NMyc overexpression. Homozygous HPCs showed altered glucose utilization with pyruvate dehydrogenase inhibition due to increased phosphorylation, exacerbated by NMyc overexpression. The impaired growth of NMyc-expressing homozygous HPCs was partially rescued by inhibiting pyruvate dehydrogenase kinase, highlighting a relationship between mtDNA mutation burden and metabolic plasticity in leukemogenesis.

ABSTRACT The role of somatic mitochondrial DNA (mtDNA) mutations in leukemogenesis remains poorly characterized. To determine the impact of somatic mtDNA mutations on the process, we assessed the leukemogenic potential of hematopoietic progenitor cells (HPCs) from mtDNA mutator mice (Polg D257A) with or without NMyc overexpression. We observed a higher incidence of spontaneous leukemogenesis in recipients transplanted with heterozygous Polg HPCs and a lower incidence of NMyc-driven leukemia in those with homozygous Polg HPCs compared to controls. Although mtDNA mutations in heterozygous and homozygous HPCs caused similar baseline impairments in mitochondrial function, only heterozygous HPCs responded to and supported altered metabolic demands associated with NMyc overexpression. Homozygous HPCs showed altered glucose utilization with pyruvate dehydrogenase inhibition due to increased phosphorylation, exacerbated by NMyc overexpression. The impaired growth of NMyc-expressing homozygous HPCs was partially rescued by inhibiting pyruvate dehydrogenase kinase, highlighting a relationship between mtDNA mutation burden and metabolic plasticity in leukemogenesis. TEASER Somatic mtDNA mutations as drivers of metabolic change in the development of leukemia.

Tumor-associated macrophages (TAMs) shape tumor immunity and therapeutic efficacy. However, it is poorly understood whether and how post-translational modifications (PTMs) intrinsically affect the phenotype and function of TAMs. Here, we reveal that peptidylarginine deiminase 4 (PAD4) exhibits the highest expression among common PTM enzymes in TAMs and negatively correlates with the clinical response to immune checkpoint blockade. Genetic and pharmacological inhibition of PAD4 in macrophages prevents tumor progression in tumor-bearing mouse models, accompanied by an increase in macrophage major histocompatibility complex (MHC) class II expression and T cell effector function. Mechanistically, PAD4 citrullinates STAT1 at arginine 121, thereby promoting the interaction between STAT1 and protein inhibitor of activated STAT1 (PIAS1), and the loss of PAD4 abolishes this interaction, ablating the inhibitory role of PIAS1 in the expression of MHC class II machinery in macrophages and enhancing T cell activation. Thus, the PAD4-STAT1-PIAS1 axis is an immune restriction mechanism in macrophages and may serve as a cancer immunotherapy target.
Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.

Lipid-formulated RNA vaccines have been widely used for disease prevention and treatment, yet their mechanism of action and individual components contributing to such actions remain to be delineated. Here, we show that a therapeutic cancer vaccine composed of a protamine/mRNA core and a lipid shell is highly potent in promoting cytotoxic CD8+ T cell responses and mediating anti-tumor immunity. Mechanistically, both the mRNA core and lipid shell are needed to fully stimulate the expression of type I interferons and inflammatory cytokines in dendritic cells. Stimulation of interferon-β expression is exclusively dependent on STING, and antitumor activity from the mRNA vaccine is significantly compromised in mice with a defective Sting gene. Thus, the mRNA vaccine elicits STING-dependent antitumor immunity.
© 2022 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.

Background: Immune checkpoint inhibitors (ICIs), such as programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1), have been widely applied in clinical and scientific research. Despite their effective antitumor effects in clinical tumor therapy, most tumors are still resistant to ICIs and long-term benefits are lacking. In addition, tumor patients complicated with interstitial lung disease limit the application of ICI therapy. Therefore, for these cases, there is an urgent need to develop new methods to relieve lung complications and enhance the efficacy of ICI therapy. Nintedanib, a potent triple angiokinase inhibitor approved for the treatment of progressive fibrotic interstitial lung disease. However, its immunotherapy synergy properties and mechanism are still pending further exploration. Methods: To explore the therapeutic potential of nintedanib and αPD-L1 combination therapy, MC38, LLC, and 4T1 tumor models were used to investigate antitumor and antimetastatic activities in vivo. An idiopathic pulmonary fibrosis-tumor bearing model was used to evaluate the effect of the synergy therapy on tumor model complicated with lung disease. Moreover, RNA-seq, immunohistochemistry, and flow cytometry were utilized to analyze the effect of combination treatment on the tumor microenvironment. The bioactivity following different treatments was determined by western blotting, CCK-8, and flow cytometry. Results: In this study, nintedanib and αPD-L1 synergy therapy exhibited significant antitumor, antimetastatic and anti-pulmonary fibrosis effects. Both in vitro and in vivo experiments revealed that these effects included promoting vessel normalization, increasing infiltration and activation of immune cells in tumors, enhancing the response of interferon-gamma, and activating the MHC class I-mediated antigen presentation process. Moreover, our results showed an increased expression of PD-L1 and promoted phosphorylation of STAT3 after nintedanib (1 µM) treatment. Conclusion: The combination of nintedanib and αPD-L1 increased ICI therapy responses, relieved lung complications and further activated the tumor immune microenvironment; thus, exhibiting a notable antitumor effect. Accordingly, the nintedanib synergy strategy is expected to be a promising candidate therapy for tumor patients complicated with interstitial lung disease in clinical practice.
© The author(s).