SUMMARY Impaired insulin-mediated suppression of hepatic glucose production (HGP) plays a major role in the pathogenesis of type 2 diabetes (T2D), yet the molecular mechanism by which this occurs remains unknown. Using a novel in vivo metabolomics approach, we show that the major mechanism by which insulin suppresses HGP is through reductions in hepatic acetyl CoA by suppression of lipolysis in white adipose tissue (WAT) leading to reductions in pyruvate carboxylase flux. This mechanism was confirmed in mice and rats with genetic ablation of insulin signaling and mice lacking adipose triglyceride lipase. Insulin’s ability to suppress hepatic acetyl CoA, PC activity, and lipolysis was lost in high-fat-fed rats, a phenomenon reversible by IL-6 neutralization and inducible by IL-6 infusion. Taken together, these data identify WAT-derived hepatic acetyl CoA as the main regulator of HGP by insulin and link it to inflammation-induced hepatic insulin resistance associated with obesity and T2D.

Summary Protein kinase B (a.k.a. AKT) and the mechanistic target of rapamycin (mTOR) are central regulators of T cell differentiation, proliferation, metabolism and survival. Here, we show that during chronic murine lymphocytic choriomeningitis virus (LCMV) infection, activation of AKT and mTOR are impaired in antiviral cytotoxic T lymphocytes (CTLs), resulting in enhanced activity of the transcription factor FoxO1. Blockade of inhibitory receptor programmed cell death protein 1 (PD-1) in vivo increased mTOR activity in virus-specific CTLs, and its therapeutic effects were abrogated by the mTOR inhibitor rapamycin. FoxO1 functioned as a transcriptional activator of PD-1 that promoted the differentiation of terminally exhausted CTLs. Importantly, FoxO1 null CTLs failed to persist and control chronic viral infection. Collectively, this study identifies that CTLs adapt to persistent infection through a positive feedback pathway (PD-1→FoxO1→PD-1) that functions to both desensitize virus-specific CTLs to antigen and to support their survival during chronic viral infection.

Summary Human melanomas exhibit relatively high somatic mutation burden compared to other malignancies. These somatic mutations may produce neoantigens that are recognized by the immune system, leading to an anti-tumor response. By irradiating a parental mouse melanoma cell line carrying three driver mutations with UVB and expanding a single cell clone, we generated a mutagenized model that exhibits high somatic mutation burden. When inoculated at low cell numbers in immunocompetent C57BL/6J mice, YUMMER1.7 (YUMM Exposed to Radiation) regresses after a brief period of growth. This regression phenotype is dependent on T cells as YUMMER1.7 tumors grow significantly faster in immunodeficient Rag1−/− mice and C57BL/6J mice depleted of CD4 and CD8 T cells. Interestingly, regression can be overcome by injecting higher cell numbers of YUMMER1.7, which results in tumors that grow without effective rejection. Mice that have previously rejected YUMMER1.7 tumors develop immunity against higher doses of YUMMER1.7 tumor challenge. In addition, escaping YUMMER1.7 tumors are sensitive to anti-CTLA-4 and anti-PD-1 therapy, establishing a new model for the evaluation of immune checkpoint inhibition and anti-tumor immune responses.

More than 10% of the world’s population is chronically infected with HIV, HCV or HBV, which cause severe disease and death. These viruses persist in part because continuous antigenic stimulation causes deterioration of virus-specific cytotoxic T lymphocyte (CTL) function and survival. Additionally, antiviral CTLs autonomously suppress their responses to limit immunopathology by upregulating inhibitory receptors such as Programmed cell death 1 (PD-1). Identification and blockade of the pathways that induce CTL dysfunction may facilitate clearance of chronic viral infections. We have identified that the prostaglandin E2 (PGE2) receptors EP2 and EP4 are upregulated on virus-specific CTLs during chronic LCMV infection and suppress CTL survival and function. We showed that the combined blockade of PGE2 and PD-1 signaling was therapeutic in terms of improving viral control and augmenting the numbers of functional virus-specific CTLs. Thus, PGE2 inhibition is both independent candidate therapeutic target and a promising adjunct therapy to PD-1 blockade for treatment of HIV and other chronic viral infections.

During the course of many chronic viral infections, the antiviral T cell response becomes attenuated through a process that is regulated in part by the host. While elevated expression of the immunosuppressive cytokine IL-10 is involved in the suppression of viral-specific T cell responses, the relevant cellular sources of IL-10, as well as the pathways responsible for IL-10 induction, remain unclear. In this study, we traced IL-10 production over the course of chronic lymphocytic choriomeningitis virus (LCMV) infection in an IL-10 reporter mouse line. Using this model, we demonstrated that virus-specific T cells with reduced inflammatory function, particularly Th1 cells, display elevated and sustained IL-10 expression during chronic LCMV infection. Furthermore, ablation of IL-10 from the T cell compartment partially restored T cell function and reduced viral loads in LCMV-infected animals. We found that viral persistence is needed for sustained IL-10 production by Th1 cells and that the transcription factor BLIMP-1 is required for IL-10 expression by Th1 cells. Restimulation of Th1 cells from LCMV-infected mice promoted BLIMP-1 and subsequent IL-10 expression, suggesting that constant antigen exposure likely induces the BLIMP-1/IL-10 pathway during chronic viral infection. Together, these data indicate that effector T cells self-limit their responsiveness during persistent viral infection via an IL-10-dependent negative feedback loop.

Perry et al. show that myeloid-targeted immunotherapy with a combination of anti-CD40 and CSF-1R inhibition synergistically induces a proinflammatory microenvironment that suppresses CPI-resistant tumors in a TNF-α– and IFN-γ–dependent manner.

SUMMARY Obesity is associated with colon cancer pathogenesis, but the underlying mechanism is actively debated. Here, we confirm that diet-induced obesity promotes tumor growth in two murine colon cancer models and show that this effect is reversed by an orally administered controlled-release mitochondrial protonophore (CRMP) that acts as a liver-specific uncoupler of oxidative phosphorylation. This agent lowered circulating insulin, and the reduction of tumor growth was abrogated by an insulin infusion raising plasma insulin to the level of high-fat-fed mice. We also demonstrate that hyperinsulinemia increases glucose uptake and oxidation in vivo in tumors and that CRMP reverses these effects. This study provides evidence that perturbations of whole-organism energy balance or hepatic energy metabolism can influence neoplastic growth. Furthermore, the data show that glucose uptake and utilization by cancers in vivo are not necessarily constitutively high but rather may vary according to the hormonal milieu.

Background Epidermal Growth Factor Receptor (EGFR) tyrosine kinase inhibitors (TKIs) like erlotinib are effective for treating patients with EGFR mutant lung cancer; however, drug resistance inevitably emerges. Approaches to combine immunotherapies and targeted therapies to overcome or delay drug resistance have been hindered by limited knowledge of the effect of erlotinib on tumor-infiltrating immune cells. Methods Using mouse models, we studied the immunological profile of mutant EGFR-driven lung tumors before and after erlotinib treatment. Results We found that erlotinib triggered the recruitment of inflammatory T cells into the lungs and increased maturation of alveolar macrophages. Interestingly, this phenotype could be recapitulated by tumor regression mediated by deprivation of the EGFR oncogene indicating that tumor regression alone was sufficient for these immunostimulatory effects. We also found that further efforts to boost the function and abundance of inflammatory cells, by combining erlotinib treatment with anti-PD-1 and/or a CD40 agonist, did not improve survival in an EGFR-driven mouse model. Conclusions Our findings lay the foundation for understanding the effects of TKIs on the tumor microenvironment and highlight the importance of investigating targeted and immuno-therapy combination strategies to treat EGFR mutant lung cancer. Electronic supplementary material The online version of this article (10.1186/s40425-019-0643-8) contains supplementary material, which is available to authorized users.