Enhancing the Efficacy of Anti-tumor Immunotherapy by Targeting Tcell Metabolism

Tumor immunotherapy has become the fourth major type of cancer therapy, being used alone or in combination with surgery, radiotherapy or chemotherapy. In recent years, immunotherapies, especially immune checkpoint blockade (ICB) therapy and chimeric antigen receptor T-Cell (CAR-T), have achieved surprising curative effects in both preclinical studies and clinical practice. However, with the expansion of clinical cases and tumor types treated, the limitations of immunotherapy have gradually emerged. For example, the clinical positive response rate of ICB therapy is only 20%-30%, and is ineffective against or may even promote the progression and metastasis of certain types of tumors. CAR-T cells therapy is very effective against hematological tumors, but its application for treating solid tumors has encountered a bottleneck. Therefore, combination therapeutic strategies have emerged to overcome the drawbacks associated with the different treatments. At present, research on immunotherapy combined with radiotherapy, chemotherapy and targeted therapy is booming. Investigations about the metabolism of tumors and immune cells have become one of the hotspots in recent years. Regulating the metabolism of effector T cells in the tumor microenvironment represents an effective way to improve immunotherapy, resulting in the restoration or enhancement of the ability of effector T cells to produce an anti-tumor immune response. In this review, we discuss recent progress in this field, with an emphasis on the metabolic characteristics of tumor and immune cells, especially T cells in the tumor microenvironment. We also provide a snapshot of how T cell metabolic reprogramming can be regulated to restore or enhance the efficacy of tumor immunotherapy, as well as the challenges and solutions associated with this metabolic reprogramming.

Cellular and molecular regulation of innate inflammatory responses

Innate sensing of pathogens by pattern-recognition receptors （PRRs） plays essential roles in the innate discrimination between self and non-self components, leading to the generation of innate immune defense and inflammatory responses. The initiation, activation and resolution of innate inflammatory response are mediated by a complex network of interactions among the numerous cellular and molecular components of immune and non- immune system. While a controlled and beneficial innate inflammatory response is critical for the elimination of pathogens and maintenance of tissue homeostasis, dysregulated or sustained inflammation leads to pathological conditions such as chronic infection, inflammatory autoimmune diseases. In this review, we discuss some of the recent advances in our understanding of the cellular and molecular mechanisms for the establishment and reJzulation of innate immunity and inflammatory responses.

Platelets promote allergic asthma through the expression of CD154

Platelet activation is associated with multiple immune responses and the pathogenesis of various immune-related diseases. However, the exact role and the underlying mechanism of platelets in the progression of allergic asthma remain largely unclear. In this study, we demonstrate that during antigen sensitization, platelets can be activated by ovalbumin （OVA） aerosol viathe upregulation of CD154 （CD4OL） expression. Platelet transfer promoted allergic asthma progression by inducing more severe leukocyte infiltration and lung inflammation, elevated IgE production and strengthened T helper 2 （Th2） responses in asthma-induced mice. Accordingly, platelet depletion compromised allergic asthma progression. CdI54-deficient platelets failed to promote asthma development, indicating the requirement of CD154 for platelets to promote asthma progression. The mechanistic study showed that platelets inhibited the induction of Foxp3 ＋ regulatory T cells both in vivoand in vitroat least partially through CD154, providing an explanation for the increase of Th2 responses by platelet transfer. Our study reveals the previously unknown role of platelet CD154 in the promotion of asthma progression by polarizing Th2 responses and inhibiting regulatory T-cell generation and thus provides a potential clue for allergic disease interventions.

Apoptotic cell administration enhances pancreatic islet engraftment by induction of regulatory T cells and tolerogenic dendritic cells

cell transfer has been found to be able to facilitate engraftment of allograft. However, the underlying mechanisms remain to be fully understood. Here we demonstrate that intravenous administration of donor apoptotic splenocytes can promote pancreatic islet engraftment by inducing generation of tolerogenic dendritic cells （ToI-DCs） and expansion of CD4＋Foxp3＋ regulatory T cells （Tregs）. In vivo clearance of either dendritic cells （DCs） or Tregs prevented the induction of immune tolerance by apoptotic cell administration. Transient elimination of Tregs using anti-CD25, monoclonal antibody （mAb） abrogated the generation of ToI-DCs after administration of apoptotic splenocytes. Reciprocally, depletion of DCs within CD1 lc-DTR mice using diphtheria toxin （DT） prevented the generation of Tregs in the recipients with administration of apoptotic splenocytes. Induction of Tregs by ToI-DCs required direct cell contact between the two cell types, and programmed death 1 ligand （PD-L1） played important role in the Tregs expansion. Apoptotic cell administration failed to induce ToI-DCs in IL-lO-deficient and Smad3-deficient mice, suggesting that IL-10 and transforming growth factor-β （TGF-β） are needed to maintain DCs in the tolerogenic state. Therefore, we demonstrate that ToI-DCs promote the expansion of Tregs via PD-L1 on their surface and reciprocally Tregs facilitate ToI-DCs to maintain transplantation tolerance induced by apoptotic cells via secreting IL-IO and TGF-β.

Extracellular calcium elicits feedforward regulation of the roll-like receptor-triggered innate immune response

Despite the expanding knowledge on feedback regulation of Toll-like receptor （TLR） signaling, the feedforward regulation of TLR signaling for the proper innate response to invading microbes is not fully understood. Here, we report that extracellular calcium can coordinate the activation of the small GTPases Ras and Ras-proximate-1 （Rap1） upon TLR stimulation which favors activation of macrophages through a feedforward mechanism. We show that different doses of TLR agonists can trigger different levels of cytokine production, which can be potentiated by extracellular calcium but are impaired by the chelating reagent ethylene glycol tetraacetic acid （EGTA） or by knockdown of stromal interaction molecule 1 （STIM1）. Upon TLR engagement, GTP-bound Ras levels are increased and GTP-bound Rap1 is decreased, which can be reversed by EGTA-mediated removal of extracellular calcium. Furthermore, we demonstrate that Rap1 knockdown rescues the inhibitory effects of EGTA on the TLR-triggered innate response. Examination of the TLR signaling pathway reveals that extracellular calcium may regulate the TLR response via feedforward activation of the extracellular signal-regulated kinase signaling pathway. Our data suggest that an influx of extracellular calcium, mediated by STIM 1-operated calcium channels, may transmit the information about the intensity of extracellular TLR stimuli to initiate innate responses at an appropriate level. Our study may provide mechanistic insight into the feedforward regulation of the TLR-triggered innate immune response.

Inflammation-induced CD69^+ Kupffer cell feedback inhibits T cell proliferation via membrane-bound TGF-β1

Kupffer cells,tissue-resident macrophage lineage cell,are enriched in vertebrate liver.The mouse F4/80^+ Kupffer cells have been subclassified into two subpopulations according to their phenotype and function:CD68^+ subpopulation with potent reactive oxygen species(ROS) production and phagocytic capacities,and CD11b^+ subpopulation with a potent capacity to produce T helper 1 cytokines.In addition,CD11b^+ Kupffer cells/macrophages may be migrated from the bone marrow or spleen,especially in inflammatory conditions of the liver.For analyzing diverse Kupffer cell subsets,we infected mice with Listeria monocytogenes and analyzed the phenotype variations of hepatic Kupffer cells.During L.monocytogenes infection,hepatic CD69^+ Kupffer cells were significantly induced and expanded,and CD69^+ Kupffer cells expressed higher level of CD11 b,and particularly high level of membrane-bound TGF-β1(mTGF-β1) but lower level of F4/80.We also found that clodronate liposome administration did not eliminate hepatic CD69^+ Kupffer cell subset.We consider the hepatic CD69^+ Kupffer cell population corresponds to CD11b^+Kupffer cells,the bone marrow-derived population.Hepatic CD69^+ Kupffer cells suppressed Ag-nonspecific and OVA-specific CD4 T cell proliferation through mTGF-β1 both in vitro and in vivo,meanwhile,they did not interfere with activation of CD4 T cells.Thus,we have identified a new subset of inflammation-induced CD69^+ Kupffer cells which can feedback inhibit CD4 T cell response via cell surface TGF-β1 at the late stage of immune response against infection.CD69^+ Kupffer cells may contribute to protect host from pathological injure by preventing overactivation of immune response.

Ephedrine hydrochloride inhibits PGN-induced inflammatory responses by promoting IL-10 production and decreasing proinflammatory cytokine secretion via the PI3K/Akt/GSK3β pathway

Approaches for controlling inflammatory responses and reducing the mortality rate of septic patients remain clinically ineffective; new drugs need to be identified that can induce anti-inflammatory responses. Ephedrine hydrochloride （EH） is a compound that is widely used in cardiovascular diseases, especially to treat hypotension caused by either anesthesia or overdose of antihypertensive drugs. In this study, we reported that EH also plays an important role in the control of the inflammatory response. EH increased IL-IO and decreased proinflammatory cytokine （IL-6, tumor-necrosis factor （TNF）-a, IL-12 and IL-11~） expression in primary peritoneal macrophages and Raw264.7 cells treated with peptidoglycan （PGN）, a Gram-positive cell wall component. The anti-inflammatory role of EH was also demonstrated in an experimental mouse model of peritonitis induced by intraperitoneal PGN injection. The phosphatidylinositol 3-kinase （PI3K）/Akt pathway was found to be responsible for the EH-mediated increase in IL-IO production and decrease in IL-6 expression. Therefore, our results illustrated that EH can help maintain immune equilibrium and diminish host damage by balancing the production of pro- and anti-inflammatory cytokines after PGN challenge. EH may be a new potential anti-inflammatory drug that can be useful for treating severe invasive Gram-positive bacterial infection.

TLR4 inactivation protects from graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Graft-versus-host disease （GVHD） is the most common complication after hematopoietic stem cell transplantation. To clarify the role of Toll-like receptor 4 （TLR4）, which is a major receptor for bacterial lipopolysaccharides （LPS）, in the development of acute GVHD, we used a TLR4-knockout （TLR4-/-） mouse GVHD model and analyzed the underlying immunological mechanisms. When TLR4-/- mice were used as bone marrow and splenocyte cell graft donors or recipients, GVHD symptom occurrence and mortality were delayed compared to wild-type （TLR4＋/＋） mice. In addition, histopathological analyses revealed that in TLR4-/-→BALB/c chimeras, liver and small intestine tissue damage was reduced with minimal lymphocytic infiltration. In contrast to TLR4＋/＋, TLR4-/- mice dendritic cells did not express CD80, CD86, CD40, MHC-II or IL-12 during LPS induction and remained in an immature state. Furthermore, the ability of TLR4-/- mice spleen dendritic cells to promote allogeneic T-cell proliferation and, in particular, T-helper cell 1 （Th 1） development was obviously attenuated compared with TLR4＋/＋ mice dendritic cells, and the levels of interferon-T （IFN-γ） and IL-IO, Th2-cell specific cytokines, were significantly higher in the serum of TLR4-/-→BALB/c than in TLR4＋/＋→BALB/c chimeric mice. Overall, our data revealed that TLR4 may play a role in the pathogenesis of GVHD and that targeted TLR4 gene therapy might provide a new treatment approach to reduce the risk of GVHD.

nduced pluripotent stem cell （iPSCs） and their application n immunotherapy

The ever-improving technology to generate induced pluripotent stem cells （iPSCs） has increased their potential use as novel candidates for disease modeling, drug screening, regenerative medicine and cell therapy. Indeed, iPSCs offer extensive capacity for self-renewal without the ethical concerns faced by embryonic stem cells （ESCs）. With respect to potential applications in the immune system, many studies provide evidence to support that there are exclusive advantages to using iPSCs over other systems. Both hematopoietic stem cells and several types of mature immune cells have successfully been reprogrammed to iPSCs and vice versa, paving a path toward our ability to effectively model patient-specific diseases and provide potentially alternative cell sources for transfusion medicine. Despite these potential advances, some limitations regarding the use of iPSCs in the clinic still remain, including the immunogenicity of iPSCs and their derivatives, which is currently under debate in the field. In this review, we mainly focus on discussing the recent progress being made in the latest differentiation methods and clinical implications of iPSCs with respect to the immune system. Additionally, current issues regarding the clinical application of iPSCs are addressed, especially the controversy surrounding immunogenicity, along with various other perspectives.

Regional immunity in tissue homeostasis and diseases

The immune system functions in the organ/tissue of the body.The immune cell differentiation and function are influenced by the organ/tissue microenvironments in which they reside,and the interaction of immune cells with the organ/tissue microenvironments may affect and even determine the outcome of the immune responses(Hu and Pasare,2013;Zajac and Harrington,2014).It has been

LR members in inflammation-associated arcinogenesis

Chronic inflammation is regarded as an impor- tant factor in cancer progression. In addition to the immune surveillance function in the early stage of tumorigenesis, inflammation is also known as one of the hallmarks of cancer and can supply the tumor microenvironment with bioactive mole- cules and favor the development of other hallmarks of cancer, such as genetic instability and angiogen- esis, Moreover,

Genome-wide in vivo screen identifies host molecule in promoting cancer metastasis

Metastasis, the movement of tumor cells from a primary site to progressively colonize distant organs, is the leading cause of cancer mortality. Emerging evidences show that tumor- educated host microenvironment cooperates with tumor cells during the multiple stage of metastasis, making tumor cells evade immune attack, resistant to apoptosis, and proliferate in distant organ （Liu et al., 2016; Quail and Joyce, 2013）. This microenvironment consists of an elaborate array of inflammatory cells, flbroblastic cells, blood vessels, and the extracellular matrix （Joyce and Fearon, 2015; Liu and Cao, 2016）.