Metformin synergizes with PD-1 blockade to promote normalization of tumor vessels via CD8T cells and IFNγ.

Tumor blood vessels are highly leaky in structure and have poor blood perfusion, which hampers infiltration and function of CD8T cells within tumor. Normalizing tumor vessels is thus thought to be important in promoting the flux of immune T cells and enhancing ant-tumor immunity. However, how tumor vasculature is normalized is poorly understood. Metformin (Met) combined with ant-PD-1 therapy is known to stimulate proliferation of and to produce large amounts of IFNγ from tumor-infiltrating CD8T lymphocytes (CD8TILs). We found that the combination therapy promotes the pericyte coverage of tumor vascular endothelial cells (ECs) to improve blood perfusion and that it suppresses the hyperpermeability through the increase of VE-cadherin. Peripheral node addressin(PNAd) and vascular cell adhesion molecule (VCAM)-1, both implicated to promote tumor infiltration of CD8T cells, were also increased. Importantly, tumor vessel normalization, characterized as the reduced 70-kDa dextran leakage and the enhancement of VE-cadherin and VCAM-1, were canceled by anti-CD8 Ab or anti-IFNγ Ab injection to mice. The increased CD8TILs were also abrogated by anti-IFNγ Ab injection. In vascular ECs, flow cytometry analysis revealed that pSTAT1 expression was found to be associated with VE-cadherin expression. Moreover, in vitro treatment with Met and IFNγ enhanced VE-cadherin and VCAM-1 on human umbilical vein endothelial cells (HUVECs). The Kaplan-Meier method revealed a correlation of VE-cadherin or VCAM-1 levels with overall survival in patients treated with immune checkpoint inhibitors. These data indicate that IFNγ-mediated cross talk of CD8TILs with tumor vessels is important for creating a better tumor microenvironment and maintaining sustained antitumor immunity.

Nutrient Condition in the Microenvironment Determines Essential Metabolisms of CD8+ T Cells for Enhanced IFNγ Production by Metformin.

Metformin (Met), a first-line drug for type 2 diabetes, lowers blood glucose levels by suppressing gluconeogenesis in the liver, presumably through the liver kinase B1-dependent activation of AMP-activated protein kinase (AMPK) after inhibiting respiratory chain complex I. Met is also implicated as a drug to be repurposed for cancers; its mechanism is believed identical to that of gluconeogenesis inhibition. However, AMPK activation requires high Met concentrations at more than 1 mM, which are unachievable in vivo. The immune-mediated antitumor response might be the case in a low dose Met. Thus, we proposed activating or expanding tumor-infiltrating CD8+ T cells (CD8TILs) in a mouse model by orally administering Met in free drinking water. Here we showed that Met, at around 10 µM and a physiologically relevant concentration, enhanced production of IFNγ,TNFα and expression of CD25 of CD8+ T cells upon TCR stimulation. Under a glucose-rich condition, glycolysis was exclusively involved in enhancing IFNγ production. Under a low-glucose condition, fatty acid oxidation or autophagy-dependent glutaminolysis, or both, was also involved. Moreover, phosphoenolpyruvate carboxykinase 1 (PCK1), converting oxaloacetate to phosphoenolpyruvate, became essential. Importantly, the enhanced IFNγ production was blocked by a mitochondrial ROS scavenger and not by an inhibitor of AMPK. In addition, IFNγ production by CD8TILs relied on pyruvate translocation to the mitochondria and PCK1. Our results revealed a direct effect of Met on IFNγ production of CD8+ T cells that was dependent on differential metabolic pathways and determined by nutrient conditions in the microenvironment.

Effectiveness comparisons of Chinese patent medicine on insomnia: A protocol for systematic review and Bayesian network meta-analysis.

BACKGROUND: In recent years, the incidence of insomnia is increasing. However, the existing therapy methods for cannot fundamentally treat the disease. Meanwhile, Chinese patent medicine (CPM) plays an active role in the treatment of insomnia. However, there is no comparison and ranking of the efficacy of every CPM. Therefore, our study will use network meta-analysis to compare the efficacy of different CPM on insomnia, in order to provide evidence-based medical evidence for clinical treatment. METHODS: We will search CNKI, Wanfang, VIP, CBM, Pubmed, Cochrane Library, Embase for the randomized controlled trials of CPM in the treatment of insomnia (up to December 31, 2020). We will use RevMan5.3, Stata15.1 and ADDIS software for statistical analysis. We will draw the surface under cumulative ranking area to predict the order of efficacy. RESULTS: We aim to rank the efficacy and safety of different CPM for the treatment of insomnia. CONCLUSION: CPM plays a positive role in the treatment of insomnia and can provide evidence support for clinicians and patients. INPLASY REGISTRATION NUMBER: INPLASY2020120121.