Potentiating the antitumour response of CD8(+) T cells by modulating cholesterol metabolism. Nature. 2016;531:651-655. [PMID: 26982734 DOI: 10.1038/nature17412]

Reconstructing the blood metabolome and genotype using long-range chromatin interactions

BACKGROUND

-Maintenance of tight controls on circulating blood metabolites is crucial to normal, healthy tissue and organismal function. A number of single nucleotide polymorphisms (SNPs) have been associated with changes in the levels of blood metabolites. However, the impacts of the metabolite-associated SNPs are largely unknown because they fall within non-coding regions of the genome.

OBJECTIVE

-We aimed to identify genes and tissues that are linked to changes in circulating blood metabolites by characterizing genome-wide spatial regulatory interactions involving blood metabolite-associated SNPs.

METHOD

-We systematically integrated chromatin interaction (Hi-C), expression quantitative trait loci (eQTL), gene ontology, drug interaction, and literature-supported connections to deconvolute the genetic regulatory influences of 145 blood metabolite-associated SNPs.

FINDINGS

-We identified 577 genes that are regulated by 130 distal and proximal metabolite-associated SNPs across 48 different human tissues. The affected genes are enriched in categories that include metabolism, enzymes, plasma proteins, disease development, and potential drug targets. Our results suggest that regulatory interactions in other tissues contribute to the modulation of blood metabolites.

CONCLUSIONS

-The spatial SNP-gene-metabolite associations identified in this study expand on the list of genes and tissues that are influenced by metabolic-associated SNPs and improves our understanding of the molecular mechanisms underlying pathologic blood metabolite levels.

The future of cancer immunotherapy: microenvironment-targeting combinations

Immunotherapy holds the potential to induce durable responses, but only a minority of patients currently respond. The etiologies of primary and secondary resistance to immunotherapy are multifaceted, deriving not only from tumor intrinsic factors, but also from the complex interplay between cancer and its microenvironment. In addressing frontiers in clinical immunotherapy, we describe two categories of approaches to the design of novel drugs and combination therapies: the first involves direct modification of the tumor, while the second indirectly enhances immunogenicity through alteration of the microenvironment. By systematically addressing the factors that mediate resistance, we are able to identify mechanistically-driven novel approaches to improve immunotherapy outcomes.

Lipid metabolism alteration contributes to and maintains the properties of cancer stem cells

Lipids, the basic components of the cell membrane, execute fundamental roles in almost all the cell activities including cell-cell recognition, signalling transduction and energy supplies. Lipid metabolism is elementary for life sustentation that balances activity between synthesis and degradation. An accumulating amount of data has indicated abnormal lipid metabolism in cancer stem cells (CSCs), and that the alteration of lipid metabolism exerts a great impact on CSCs' properties such as the capability of self-renewal, differentiation, invasion, metastasis, and drug sensitivity and resistance. CSCs' formation and maintenance cannot do without the regulation of fatty acids and cholesterol. In normal cells and embryonic development, fatty acids and cholesterol metabolism are regulated by some important signalling pathways (such as Hedgehog, Notch, Wnt signalling pathways); these signalling pathways also play crucial roles in initiating and/or maintaining CSCs' properties, and such signalling is shown to be commonly modulated by the abnormal lipid metabolism in CSCs; on the other hand, the altered lipid metabolism in turn modifies the cell signalling and generates additional impacts on CSCs. Metabolic rewiring is considered as an ideal hallmark of CSCs, and metabolic alterations would be promising therapeutic targets of CSCs for aggressive tumors. In this review, we summarize the most updated findings of lipid metabolic abnormalities in CSCs and prospect the potential applications of targeting lipid metabolism for anticancer treatment.

The Pivotal Role of the Dysregulation of Cholesterol Homeostasis in Cancer: Implications for Therapeutic Targets

Cholesterol plays an important role in cellular homeostasis by maintaining the rigidity of cell membranes, providing a medium for signaling transduction, and being converted into other vital macromolecules, such as sterol hormones and bile acids. Epidemiological studies have shown the correlation between cholesterol content and cancer incidence worldwide. Accumulating evidence has shown the emerging roles of the dysregulation of cholesterol metabolism in cancer development. More specifically, recent reports have shown the distinct role of cholesterol in the suppression of immune cells, regulation of cell survival, and modulation of cancer stem cells in cancer. Here, we provide a comprehensive review of the epidemiological analysis, functional roles, and mechanistic action of cholesterol homeostasis in regard to its contribution to cancer development. Based on the existing data, cholesterol homeostasis is identified to be a new key player in cancer pathogenesis. Lastly, we also discuss the therapeutic implications of natural compounds and cholesterol-lowering drugs in cancer prevention and treatment. In conclusion, intervention in cholesterol metabolism may offer a new therapeutic avenue for cancer treatment.

Structural insights into the inhibition mechanism of human sterol O-acyltransferase 1 by a competitive inhibitor

Sterol O-acyltransferase 1 (SOAT1) is an endoplasmic reticulum (ER) resident, multi-transmembrane enzyme that belongs to the membrane-bound O-acyltransferase (MBOAT) family. It catalyzes the esterification of cholesterol to generate cholesteryl esters for cholesterol storage. SOAT1 is a target to treat several human diseases. However, its structure and mechanism remain elusive since its discovery. Here, we report the structure of human SOAT1 (hSOAT1) determined by cryo-EM. hSOAT1 is a tetramer consisted of a dimer of dimer. The structure of hSOAT1 dimer at 3.5 Å resolution reveals that a small molecule inhibitor CI-976 binds inside the catalytic chamber and blocks the accessibility of the active site residues H460, N421 and W420. Our results pave the way for future mechanistic study and rational drug design targeting hSOAT1 and other mammalian MBOAT family members.

Structure of nevanimibe-bound tetrameric human ACAT1

Cholesterol is an essential component of mammalian cell membranes, constituting up to 50% of plasma membrane lipids. By contrast, it accounts for only 5% of lipids in the endoplasmic reticulum (ER)¹. The ER enzyme sterol O-acyltransferase 1 (also named acyl-coenzyme A:cholesterol acyltransferase, ACAT1) transfers a long-chain fatty acid to cholesterol to form cholesteryl esters that coalesce into cytosolic lipid droplets. Under conditions of cholesterol overload, ACAT1 maintains the low cholesterol concentration of the ER and thereby has an essential role in cholesterol homeostasis^2,3. ACAT1 has also been implicated in Alzheimer's disease⁴, atherosclerosis⁵ and cancers⁶. Here we report a cryo-electron microscopy structure of human ACAT1 in complex with nevanimibe⁷, an inhibitor that is in clinical trials for the treatment of congenital adrenal hyperplasia. The ACAT1 holoenzyme is a tetramer that consists of two homodimers. Each monomer contains nine transmembrane helices (TMs), six of which (TM4-TM9) form a cavity that accommodates nevanimibe and an endogenous acyl-coenzyme A. This cavity also contains a histidine that has previously been identified as essential for catalytic activity⁸. Our structural data and biochemical analyses provide a physical model to explain the process of cholesterol esterification, as well as details of the interaction between nevanimibe and ACAT1, which may help to accelerate the development of ACAT1 inhibitors to treat related diseases.

Blocking ACAT-1 Activity for Tumor Therapy with Fluorescent Hyperstar Polymer-Encapsulated Avasimible

Targeting the distinct cholesterol metabolism of tumor cells is proposed as a novel way to treat tumors. Blocking acyl-CoA cholesterol acyltransferase-1 (ACAT-1) by the inhibitor avasimible (Ava), which elevates intracellular free cholesterol levels, is shown to effectively induce apoptosis. However, Ava faces disadvantages of poor water solubility, a short half-life, and no capability for fluorescence detection, which have greatly limited its application. Herein, a fluorescent hyperstar polymer (FHSP) is developed to encapsulate Ava to improve its ability to inhibit HeLa cells and K562 cells. The results of this study show that the obtained Ava-FHSP micelles possess a high drug loading capacity of 22.7% and bright green fluorescence. Ava and Ava-FHSP are cytotoxic to both HeLa and K562 cells and cause reductions in cell size, nuclear lysis, and chromatin condensation and hindered proliferation of both cell types by causing S phase cell cycle arrest. Further mechanistic analysis indicates that Ava-FHSP reduces the protein and messenger RNA expression of ACAT-1 and significantly increases intracellular free cholesterol levels, which can increase endoplasmic reticulum stress and finally cause cell apoptosis. All these results suggest that this fluorescent hyperstar polymer represents a potential therapeutic tumor strategy by changing the cholesterol metabolism of tumor cells.

Screening for the Next-Generation T Cell Therapies

In a recently published Cell paper, Roth et al. report a CRISPR-based platform for developing T cell therapies that strategically combine a tumor-specific TCR with novel protein factors that potentiate antitumor function.

High Serum Levels of Cholesterol Increase Antitumor Functions of Nature Killer Cells and Reduce Growth of Liver Tumors in Mice

BACKGROUND AND AIMS

The relationship between serum cholesterol level and development of hepatocellular carcinoma (HCC) remains unclear. We investigated the effects of serum cholesterol level on development of liver tumors in mice.

METHODS

We performed studies with C57BL/6J mice, mice with disruption of the low-density lipoprotein receptor gene (Ldlr^-/-mice), and mice with conditional deletion of nature killer (NK) cells (NK^dele mice). Some C57BL/6J and NK^dele mice were given injections of diethylinitrosamine to induce liver tumor formation. Mice were placed on a normal diet (ND) or high-cholesterol diet (HCD) to induce high serum levels of cholesterol. We also studied mice with homozygous disruption of ApoE (ApoE^-/- mice), which spontaneously develop high serum cholesterol. C57BL/6J and NK^dele mice on the ND or HCD were implanted with Hep1-6 (mouse hepatoma) cells and growth of xenograft tumors and lung metastases were monitored. Blood samples were collected from mice and analyzed by biochemistry and flow cytometry; liver and tumor tissues were collected and analyzed by histology, immunohistochemistry, and RNA-sequencing analysis. NK cells were isolated from mice and analyzed for cholesterol content, lipid raft formation, immune signaling, and changes in functions. We obtained matched tumor tissues and blood samples from 30 patients with HCC and blood samples from 40 healthy volunteers; levels of cholesterol and cytotoxicity of NK cells were measured.

RESULTS

C57BL/6J mice on HCD and ApoE^-/- mice with high serum levels of cholesterol developed fewer and smaller liver tumors and lung metastases after diethylinitrosamine injection or implantation of Hep1-6 cells than mice on ND. Liver tumors from HCD-fed mice and ApoE^-/- mice had increased numbers of NK cells compared to tumors from ND-fed mice. NK^dele mice or mice with antibody-based depletion for NK cells showed similar tumor number and size in ND and HCD groups after diethylinitrosamine injection or implantation of Hep1-6 cells. NK cells isolated from C57BL/6J mice fed with HCD had increased expression of NK cell-activating receptors (natural cytotoxicity triggering receptor 1 and natural killer group 2, member D), markers of effector function (granzyme B and perforin), and cytokines and chemokines compared with NK cells from mice on ND; these NK cells also had enhanced cytotoxic activity against mouse hepatoma cells, accumulated cholesterol, increased lipid raft formation, and immune signaling activation. NK cells isolated from HCD-fed Ldlr^-/- mice did not have increased cholesterol content or cytotoxic activity against mouse hepatoma cells compared with ND-fed Ldlr^-/- mice. Serum levels of cholesterol correlated with number and activity of NK cells isolated from human HCCs.

CONCLUSIONS

Mice with increased serum levels of cholesterol due to an HCD or genetic disruption of ApoE develop fewer and smaller tumors after injection of hepatoma cells or a chemical carcinogen. We found cholesterol to accumulate in NK cells and activate their effector functions against hepatoma cells. Strategies to increase cholesterol uptake by NK cells can be developed for treatment of HCC.

High-intensity interval training in allogeneic adoptive T-cell immunotherapy - a big HIT?

Background

Adoptive transfer of virus-specific T cells (VSTs) represents a prophylactic and curative approach for opportunistic viral infections and reactivations after transplantation. However, inadequate frequencies of circulating memory VSTs in the T-cell donor’s peripheral blood often result in insufficient enrichment efficiency and purity of the final T-cell product, limiting the effectiveness of this approach.

Methods

This pilot study was designed as a cross-over trial and compared the effect of a single bout (30 min) of high-intensity interval training (HIT) with that of 30 min of continuous exercise (CONT) on the frequency and function of circulating donor VSTs. To this end, we used established immunoassays to examine the donors’ cellular immune status, in particular, with respect to the frequency and specific characteristics of VSTs restricted against Cytomegalovirus (CMV)-, Epstein–Barr-Virus (EBV)- and Adenovirus (AdV)-derived antigens. T-cell function, phenotype, activation and proliferation were examined at different time points before and after exercise to identify the most suitable time for T-cell donation. The clinical applicability was determined by small-scale T-cell enrichment using interferon- (IFN-) γ cytokine secretion assay and virus-derived overlapping peptide pools.

Results

HIT proved to be the most effective exercise program with up to fivefold higher VST response. In general, donors with a moderate fitness level had higher starting and post-exercise frequencies of VSTs than highly fit donors, who showed significantly lower post-exercise increases in VST frequencies. Both exercise programs boosted the number of VSTs against less immunodominant antigens, specifically CMV (IE-1), EBV (EBNA-1) and AdV (Hexon, Penton), compared to VSTs against immunodominant antigens with higher memory T-cell frequencies.

Conclusion

This study demonstrates that exercise before T-cell donation has a beneficial effect on the donor’s cellular immunity with respect to the proportion of circulating functionally active VSTs. We conclude that a single bout of HIT exercise 24 h before T-cell donation can significantly improve manufacturing of clinically applicable VSTs. This simple and economical adjuvant treatment proved to be especially efficient in enhancing virus-specific memory T cells with low precursor frequencies.

Protein arginine methyltransferase 5 promotes cholesterol biosynthesis-mediated Th17 responses and autoimmunity

Protein arginine methyltransferase 5 (PRMT5) catalyzes symmetric dimethylation (SDM) of arginine, a posttranslational modification involved in oncogenesis and embryonic development. However, the role and mechanisms by which PRMT5 modulates Th cell polarization and autoimmune disease have not yet been elucidated. Here, we found that PRMT5 promoted SREBP1 SDM and the induction of cholesterol biosynthetic pathway enzymes that produce retinoid-related orphan receptor (ROR) agonists that activate RORγt. Specific loss of PRMT5 in the CD4+ Th cell compartment suppressed Th17 differentiation and protected mice from developing experimental autoimmune encephalomyelitis (EAE). We also found that PRMT5 controlled thymic and peripheral homeostasis in the CD4+ Th cell life cycle and invariant NK (iNK) T cell development and CD8+ T cell maintenance. This work demonstrates that PRMT5 expression in recently activated T cells is necessary for the cholesterol biosynthesis metabolic gene expression program that generates RORγt agonistic activity and promotes Th17 differentiation and EAE. These results point to Th PRMT5 and its downstream cholesterol biosynthesis pathway as promising therapeutic targets in Th17-mediated diseases.

The Agpat4/LPA axis in colorectal cancer cells regulates antitumor responses via p38/p65 signaling in macrophages

Lipid metabolic reprogramming plays an essential role in regulating the progression of colorectal cancer (CRC). However, the effect of lysophosphatidic acid (LPA) metabolism on CRC development is incompletely characterized. Here, we compared the mRNA levels of human CRC tissues to those of paracarcinoma tissues and focused on the notably enriched LPA metabolic pathways. We identified and verified that 1-acylglycerol-3-phosphate O-acyltransferase 4 (Agpat4) was aberrantly expressed in CRC tissues and predicted poor survival in CRC patients. Manipulating Agpat4 expression in CRC cells did not affect the growth or migration of CRC cells in vitro, whereas Agpat4 silencing suppressed CRC cell growth in subcutaneous and peritoneal xenograft models. Mechanistically, Agpat4 silencing-induced LPA release from CRC cells and polarized macrophages to an M1-like phenotype through LPA receptors 1 and 3. This M1 activation, characterized by elevated p38/p65 signaling and increased proinflammatory cytokines, promoted the infiltration and activation of CD4⁺ and CD8⁺ T cells in the tumor microenvironment. Modulation of the Agpat4/LPA/p38/p65 axis regulated macrophage polarization, T-cell activity and CRC progression. Notably, combined therapy with LPA and regular chemotherapy drugs synergistically suppressed CRC development. Taken together, our results showed that the Agpat4/LPA axis in CRC cells regulated p38/p65 signaling-dependent macrophage polarization, T-cell activation, and CRC progression. The Agpat4/LPA/p38/p65 axis might represent a potential target for therapy in the clinic.

Signaling networks in immunometabolism

Adaptive immunity is essential for pathogen and tumor eradication, but may also trigger uncontrolled or pathological inflammation. T cell receptor, co-stimulatory and cytokine signals coordinately dictate specific signaling networks that trigger the activation and functional programming of T cells. In addition, cellular metabolism promotes T cell responses and is dynamically regulated through the interplay of serine/threonine kinases, immunological cues and nutrient signaling networks. In this review, we summarize the upstream regulators and signaling effectors of key serine/threonine kinase-mediated signaling networks, including PI3K–AGC kinases, mTOR and LKB1–AMPK pathways that regulate metabolism, especially in T cells. We also provide our perspectives about the pending questions and clinical applicability of immunometabolic signaling. Understanding the regulators and effectors of immunometabolic signaling networks may uncover therapeutic targets to modulate metabolic programming and T cell responses in human disease.

The association and joint effect of serum cholesterol, glycemic status with the risk of incident cancer among middle-aged and elderly population in china cardiometabolic disease and cancer cohort (4C)-study

The associations between different combinations of metabolic abnormalities and the risk of all and site-specific cancers remain unclear. We aimed to estimate the association and interplay between serum cholesterol, glycemic status and risk of cancer in the China Cardiometabolic Disease and Cancer Cohort (4C)-Study, a nationwide, multicenter, prospective, population-based study. The investigation was performed in 137,884 participants during 2014-2016. Incident cancer was defined as the first occurrence of any type cancer of all sites during follow-up. After 510,164 person-years of follow-up, 1,710 were detected as incident cancer after exclusion of participants diagnosed as cancer within 6 months from baseline. A relatively low level of LDL cholesterol (<100 mg/dl) was related to a significant higher risk of incident cancer [1.20 (1.08-1.34); P=0.0007]. Diabetic individuals have a significantly higher risk of incident cancer, especially those with poorly glycemic control. Diabetic participants with both lower levels of LDL cholesterol and poorly glycemic control were at a higher risk of incident cancer [1.42 (1.10-1.81); P=0.006]. Our study showed a positive association of cancer risk with low-level LDL cholesterol and diabetes and found that participants with both lower levels of LDL cholesterol and poorly controlled diabetes had the higher risk of incident cancer, which indicates the compelling need of achieving glycemic control goal and maintaining appropriate LDL cholesterol levels.

Immunometabolism in the development of rheumatoid arthritis

In rheumatoid arthritis (RA), breakdown of self-tolerance and onset of clinical disease are separated in time and space, supporting a multi-hit model in which emergence of autoreactive T cells is a pinnacle pathogenic event. Determining factors in T cell differentiation and survival include antigen recognition, but also the metabolic machinery that provides energy and biosynthetic molecules for cell building. Studies in patients with RA have yielded a disease-specific metabolic signature, which enables naive CD4 T cells to differentiate into pro-inflammatory helper T cells that are prone to invade into tissue and elicit inflammation through immunogenic cell death. A typifying property of RA CD4 T cells is the shunting of glucose away from glycolytic breakdown and mitochondrial processing toward the pentose phosphate pathway, favoring anabolic over catabolic reactions. Key defects have been localized to the mitochondria and the lysosome; including instability of mitochondrial DNA due to the lack of the DNA repair nuclease MRE11A and inefficient lysosomal tethering of AMPK due to deficiency of N-myristoyltransferase 1 (NMT1). The molecular taxonomy of the metabolically reprogrammed RA T cells includes glycolytic enzymes (glucose-6-phosphate dehydrogenase, phosphofructokinase), DNA repair molecules (MRE11A, ATM), regulators of protein trafficking (NMT1), and the membrane adapter protein TSK5. As the mechanisms determining abnormal T cell behavior in RA are unraveled, opportunities will emerge to interject autoimmune T cells by targeting their metabolic checkpoints.

Structural understanding of T cell receptor triggering

The T cell receptor (TCR) is one of the most complicated receptors in mammalian cells, and its triggering mechanism remains mysterious. As an octamer complex, TCR comprises an antigen-binding subunit (TCRαβ) and three CD3 signaling subunits (CD3ζζ, CD3δε, and CD3γε). Engagement of TCRαβ with an antigen peptide presented on the MHC leads to tyrosine phosphorylation of the immunoreceptor tyrosine-based activation motif (ITAM) in CD3 cytoplasmic domains (CDs), thus translating extracellular binding kinetics to intracellular signaling events. Whether conformational change plays an important role in the transmembrane signal transduction of TCR is under debate. Attracted by the complexity and functional importance of TCR, many groups have been studying TCR structure and triggering for decades using diverse biochemical and biophysical tools. Here, we synthesize these structural studies and discuss the relevance of the conformational change model in TCR triggering.

Enforced PGC-1α expression promotes CD8 T cell fitness, memory formation and antitumor immunity

Memory CD8 T cells can provide long-term protection against tumors, which depends on their enhanced proliferative capacity, self-renewal and unique metabolic rewiring to sustain cellular fitness. Specifically, memory CD8 T cells engage oxidative phosphorylation and fatty acid oxidation to fulfill their metabolic demands. In contrast, tumor-infiltrating lymphocytes (TILs) display severe metabolic defects, which may underlie their functional decline. Here, we show that overexpression of proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), the master regulator of mitochondrial biogenesis (MB), favors CD8 T cell central memory formation rather than resident memory generation. PGC-1α-overexpressing CD8 T cells persist and mediate more robust recall responses to bacterial infection or peptide vaccination. Importantly, CD8 T cells with enhanced PGC-1α expression provide stronger antitumor immunity in a mouse melanoma model. Moreover, TILs overexpressing PGC-1α maintain higher mitochondrial activity and improved expansion when rechallenged in a tumor-free host. Altogether, our findings indicate that enforcing mitochondrial biogenesis promotes CD8 T cell memory formation, metabolic fitness, and antitumor immunity in vivo.

Inhibition of Cholesterol Esterification Enzyme Enhances the Potency of Human Chimeric Antigen Receptor T Cells against Pancreatic Carcinoma

This study aimed to assess the effectiveness of inhibiting cholesterol acyltransferase 1 (ACAT-1) in chimeric antigen receptor T (CAR-T) cells on potentiating the antitumor response against mesothelin (MSLN)-expressing pancreatic carcinoma (PC) cells. We engineered ACAT-1-inhibited CAR-T cells (CAR-T-1847 and CAR-T-1848) using the targeting MSLN CAR lentiviral vector and small interfering RNA (siRNA) targeting the conserved region of the ACAT-1 gene, and characterized the efficacy of these modified CAR-T cells in terms of the cytotoxicity and cytokine release of both MSLN-positive and MSLN-negative PC cells using in vitro methods and in vivo mouse xenografts. The ACAT-1-inhibited CAR-T-1847 and CAR-T-1848 cells showed a higher cytotoxicity at effector-to-target cell (E:T) ratios of 8:1 and 10:1, respectively, and induced a higher secretion of proinflammatory cytokines interleukin-2 (IL-2) and interferon-gamma (IFNγ) in vitro. In addition, bioluminescence imaging of tumor xenografts of ACAT-1-inhibited targeting MSLN CAR-T cells in MSLN-positive PC mice in vivo showed significant tumor regression, which is consistent with the in vitro observations. Our findings demonstrate a novel immunotherapeutic strategy involving the transplantation of ACAT-1-inhibited targeting MSLN CAR-T cells and the feasibility of enhancing the antitumor potency of CAR-T through the novel strategy.

CD8+ T cells regulate liver injury in obesity-related nonalcoholic fatty liver disease

Nonalcoholic steatohepatitis (NASH) has increased in Western countries due to the prevalence of obesity. Current interests are aimed at identifying the type and function of immune cells that infiltrate the liver and key factors responsible for mediating their recruitment and activation in NASH. We investigated the function and phenotype of CD8⁺ T cells under obese and nonobese NASH conditions. We found an elevation in CD8 staining in livers from obese human subjects with NASH and cirrhosis that positively correlated with α-smooth muscle actin, a marker of hepatic stellate cell (HSC) activation. CD8⁺ T cells were elevated 3.5-fold in the livers of obese and hyperlipidemic NASH mice compared with obese hepatic steatosis mice. Isolated hepatic CD8⁺ T cells from these mice expressed a cytotoxic IL-10-expressing phenotype, and depletion of CD8⁺ T cells led to significant reductions in hepatic inflammation, HSC activation, and macrophage accumulation. Furthermore, hepatic CD8⁺ T cells from obese and hyperlipidemic NASH mice activated HSCs in vitro and in vivo. Interestingly, in the lean NASH mouse model, depletion and knockdown of CD8⁺ T cells did not impact liver inflammation or HSC activation. We demonstrated that under obese/hyperlipidemia conditions, CD8⁺ T cell are key regulators of the progression of NASH, while under nonobese conditions they play a minimal role in driving the disease. Thus, therapies targeting CD8⁺ T cells may be a novel approach for treatment of obesity-associated NASH.NEW & NOTEWORTHY Our study demonstrates that CD8⁺ T cells are the primary hepatic T cell population, are elevated in obese models of NASH, and directly activate hepatic stellate cells. In contrast, we find CD8⁺ T cells from lean NASH models do not regulate NASH-associated inflammation or stellate cell activation. Thus, for the first time to our knowledge, we demonstrate that hepatic CD8⁺ T cells are key players in obesity-associated NASH.

Cholesterol metabolism in cancer: mechanisms and therapeutic opportunities

Cholesterol metabolism produces essential membrane components as well as metabolites with a variety of biological functions. In the tumour microenvironment, cell-intrinsic and cell-extrinsic cues reprogram cholesterol metabolism and consequently promote tumourigenesis. Cholesterol-derived metabolites play complex roles in supporting cancer progression and suppressing immune responses. Preclinical and clinical studies have shown that manipulating cholesterol metabolism inhibits tumour growth, reshapes the immunological landscape and reinvigorates anti-tumour immunity. Here, we review cholesterol metabolism in cancer cells, its role in cancer progression and the mechanisms through which cholesterol metabolites affect immune cells in the tumour microenvironment. We also discuss therapeutic strategies aimed at interfering with cholesterol metabolism, and how the combination of such approaches with existing anti-cancer therapies can have synergistic effects, thus offering new therapeutic opportunities.

Impaired lipid biosynthesis hinders anti-tumor efficacy of intratumoral iNKT cells

Dysfunction of invariant natural killer T (iNKT) cells in tumor microenvironment hinders their anti-tumor efficacy, and the underlying mechanisms remain unclear. Here we report that iNKT cells increase lipid biosynthesis after activation, and that is promoted by PPARγ and PLZF synergically through enhancing transcription of Srebf1. Among those lipids, cholesterol is required for the optimal IFN-γ production from iNKT cells. Lactic acid in tumor microenvironment reduces expression of PPARγ in intratumoral iNKT cells and consequently diminishes their cholesterol synthesis and IFN-γ production. Importantly, PPARγ agonist pioglitazone, a thiazolidinedione drug for type 2 diabetes, successfully restores IFN-γ production in tumor-infiltrating iNKT cells from both human patients and mouse models. Combination of pioglitazone and alpha-galactosylceramide treatments significantly enhances iNKT cell-mediated anti-tumor immune responses and prolongs survival of tumor-bearing mice. Our studies provide a strategy to augment the anti-tumor efficacy of iNKT cell-based immunotherapies via promoting their lipid biosynthesis.

Lipid metabolism has been linked to iNKT function largely as it impacts processing and presentation of lipids they recognize. Here the authors show that iNKT-intrinsic lipid biosynthesis is important for their function but is impaired in tumors, and its restoration with PPARγ agonist drugs promotes anti-tumor iNKT response.

PD-1/PD-L1-dependent immune response in colorectal cancer

Colorectal cancer (CRC) is still considered as the third most frequent cancer in the world. Microsatellite instability (MSI), inflammation, and microRNAs have been demonstrated as the main contributing factors in CRC. Subtype 1 CRC is defined by NK cells infiltration, induction of Th1 lymphocyte and cytotoxic T cell responses as well as upregulation of immune checkpoint proteins including programmed cell death-1 (PD-1). Based on the diverse features of CRC, such as the stage and localization of the tumor, several treatment approaches are available. However, the efficiency of these treatments may be decreased due to the development of diverse resistance mechanisms. It has been proven that monoclonal antibodies (mAbs) can increase the effectiveness of CRC treatments. Nowadays, several mAbs including nivolumab and pembrolizumab have been approved for the treatment of CRC. Immune checkpoint receptors including PD-1 can be inhibited by these antibodies. Combination therapy gives an opportunity for advanced treatment for CRC patients. In this review, an update has been provided on the molecular mechanisms involved in MSI colorectal cancer immune microenvironment by focusing on PD-ligand 1 (PD-L1) and treatment of patients with advanced immunotherapy, which were examined in the different clinical trial phases. Considering induced expression of PD-L1 by conventional chemotherapeutics, we have summarized the role of PD-L1 in CRC, the chemotherapy effects on the PD-1/PD-L1 axis and novel combined approaches to enhance immunotherapy of CRC by focusing on PD-L1.

Role of de novo cholesterol synthesis enzymes in cancer

Despite extensive research in the cancer field, cancer remains one of the most prevalent diseases. There is an urgent need to identify specific targets that are safe and effective for the treatment of cancer. In recent years, cancer metabolism has come into the spotlight in cancer research. Lipid metabolism, especially cholesterol metabolism, plays a critical role in membrane synthesis as well as lipid signaling in cancer. This review focuses on the contribution of the de novo cholesterol synthesis pathway to tumorigenesis, cancer progression and metastasis. In conclusion, cholesterol metabolism could be an effective target for novel anticancer treatment.

Steroidal glycoalkaloids from Solanum lyratum inhibit the pro-angiogenic activity of A549-derived exosomes

In this study, seven previously undescribed steroidal glycoalkaloids, compounds 1-7, were isolated from Solanum lyratum, along with two known ones (8 and 9). Comprehensive spectroscopy techniques were used to determine their structures. Although 1-8 only showed a weak inhibitory effect on the proliferation of the tumor-derived vascular endothelial cells, however, in a former study we found both total steroidal glycoalkaloids from Solanum lyratum (TSGS) and 9 significantly inhibited tumor angiogenesis and its mechanism was linked to its ability to interfere with cell membrane lipid rafts. Lipid rafts are closely related to the functions of tumor-derived exosomes, a vital factor in cancer progression. Thus, we investigated the impacts of TSGS and 9 on the functions of A549-derived exosomes. Our results indicated that A549-derived exosomes can significantly enhance the angiogenesis abilities of human umbilical vein endothelial cells, whereas the intervention of TSGS or 9 significantly inhibited this activity of A549-derived exosomes. These findings suggest that TSGS and 9 exert anti-tumor angiogenesis by inhibiting the pro-angiogenic activity of A549-derived exosomes.

Raman and FTIR spectroscopy in determining the chemical changes in healthy brain tissues and glioblastoma tumor tissues

Glioblastoma, also called glioblastoma multiforme (GBM), is a particularly malignant form of primary brain tumor. This cancer accounts for 12-15% of all brain tumors. Despite the advances in neurosurgery, radio and chemotherapy the average survival rate is only 12.1-16.6 months. This is due not only to the late diagnosis of the disease, but also to ineffective treatment methods which result from the still low knowledge about the causes of glioblastoma development. Therefore, it is very important to look for new diagnostic methods of detection of the smallest features of cancer. Raman and infrared spectroscopy (FTIR) can be such methods. In this paper we discuss the chemical composition of sample glioblastoma brain tissues and marginal brain tissues using these two spectroscopy methods. Raman and FTIR spectra of cancer brain tissues showed that the highest differences in the chemical composition, compared to the control brain tissue, occur in the areas corresponding to lipids, collagen and proteins. Moreover, Raman spectroscopy also showed significant changes in the cancer tissues in the phosphatidylcholine and sphingomyelin. Interestingly, FTIR spectra after Kramers-Kronig transformations showed signals only for three peaks which corresponded to the vibrations of lipid function groups. Adjustment of the Lorenz function for these three peaks showed that only in the case of cancerous tissues the number of matching lines is different, compared to the control and marginal tissues. Therefore, we assume that lipids could be a spectroscopic marker for brain tumor. Furthermore, principal component analysis (PCA) showed that chemical changes seen between cancer and control tissues are significant and it is possible to differentiate the infected tissue from the healthy one. Interestingly, the PCA analysis also showed that adjacent brain tissues have different chemical composition than the control tissues.

Enzyme-instructed assembly of a cholesterol conjugate promotes pro-inflammatory macrophages and induces apoptosis of cancer cells

Enzyme-instructed assembly that promotes pro-inflammatory macrophages and induces the apoptosis of cancer cells provides a unique method for combination therapy.

Commentary on: Combination of Metabolic Intervention and T Cell Therapy Enhances Solid Tumor Immunotherapy

Metabolism is a common cellular feature. Cancer creates a suppressive microenvironment resulting in inactivation of antigen-specific T cells by metabolic reprogramming. Development of approaches that enhance and sustain physiologic properties of T cell metabolism to prevent T cell inactivation and promote effector function in the tumor microenvironment is an urgent need for improvement of cell-based cancer immunotherapies.

Tumor microenvironmental influences on dendritic cell and T cell function: A focus on clinically relevant immunologic and metabolic checkpoints

Cancer immunotherapy is fast becoming one of the most promising means of treating malignant disease. Cancer vaccines, adoptive cell transfer therapies, and immune checkpoint blockade have all shown varying levels of success in the clinical management of several cancer types in recent years. However, despite the clinical benefits often achieved by these regimens, an ongoing problem for many patients is the inherent or acquired resistance of their cancer to immunotherapy. It is now appreciated that dendritic cells and T lymphocytes both play key roles in antitumor immune responses and that the tumor microenvironment presents a number of barriers to the function of these cells that can ultimately limit the success of immunotherapy. In particular, the engagement of several immunologic and metabolic checkpoints within the hostile tumor microenvironment can severely compromise the antitumor functions of these important immune populations. This review highlights work from both preclinical and clinical studies that has shaped our understanding of the tumor microenvironment and its influence on dendritic cell and T cell function. It focuses on clinically relevant targeted and immunotherapeutic strategies that have emerged from these studies in an effort to prevent or overcome immune subversion within the tumor microenvironment. Emphasis is also placed on the potential of next-generation combinatorial regimens that target metabolic and immunologic impediments to dendritic cell and T lymphocyte function as strategies to improve antitumor immune reactivity and the clinical outcome of cancer immunotherapy going forward.

The antimetastatic activity of orlistat is accompanied by an antitumoral immune response in mouse melanoma

PURPOSE

Fatty acid synthase (FASN), the multifunctional enzyme responsible for endogenous fatty acid synthesis, is highly expressed and associated with poor prognosis in several human cancers, including melanoma. Our group has previously shown that pharmacological inhibition of FASN with orlistat decreases proliferation, promotes apoptosis, and reduces the metastatic spread of B16-F10 cells in experimental models of melanoma. While most of the orlistat antitumor properties seem to be closely related to direct effects on malignant cells, its impact on the host immune system is still unknown.

METHODS

The effects of orlistat on the phenotype and activation status of infiltrating leukocytes in primary tumors and metastatic lymph nodes were assessed using a model of spontaneous melanoma metastasis (B16-F10 cells/C57BL/6 mice). Cells from the primary tumors and lymph nodes were mechanically dissociated and immune cells phenotyped by flow cytometry. The expression of IL-12p35, IL-12p40, and inducible nitric oxide synthase (iNOS) was analyzed by qRT-PCR and production of nitrite (NO₂^-) evaluated in serum samples with the Griess method.

RESULTS

Orlistat-treated mice exhibited a 25% reduction in the number of mediastinal lymph node metastases (mean 3.96 ± 0.78, 95% CI 3.63-4.28) compared to the controls (mean 5.7 ± 1.72; 95% CI 5.01-6.43). The drug elicited an antitumor immune response against experimental melanomas by increasing maturation of intratumoral dendritic cells (DC), stimulating the expression of cytotoxicity markers in CD8 T lymphocytes and natural killer (NK) cells, as well as reducing regulatory T cells (Tregs). Moreover, the orlistat-treatment increased serum levels of nitric oxide (NO) concentrations.

CONCLUSION

Taken together, these findings suggest that orlistat supports an antitumor response against experimental melanomas by increasing CD80/CD81-positive and IL-12-positive DC populations, granzyme b/NKG2D-positive NK populations, and perforin/granzyme b-positive CD8 T lymphocytes as well as reducing Tregs counts within experimental melanomas.

LXR-inverse agonism stimulates immune-mediated tumor destruction by enhancing CD8 T-cell activity in triple negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive subtype that is untreatable with hormonal or HER2-targeted therapies and is also typically unresponsive to checkpoint-blockade immunotherapy. Within the tumor microenvironment dysregulated immune cell metabolism has emerged as a key mechanism of tumor immune-evasion. We have discovered that the Liver-X-Receptors (LXRα and LXRβ), nuclear receptors known to regulate lipid metabolism and tumor-immune interaction, are highly activated in TNBC tumor associated myeloid cells. We therefore theorized that inhibiting LXR would induce immune-mediated TNBC-tumor clearance. Here we show that pharmacological inhibition of LXR activity induces tumor destruction primarily through stimulation of CD8+ T-cell cytotoxic activity and mitochondrial metabolism. Our results imply that LXR inverse agonists may be a promising new class of TNBC immunotherapies.

A Critical Role of PCSK9 in Mediating IL-17-Producing T Cell Responses in Hyperlipidemia

We previously demonstrated that atherogenic Ldlr ^-/- Apobec1 ^-/- (LDb) double knockout mice lacking both low-density lipoprotein receptor (LDLR) and apolipoprotein B mRNA-editing catalytic polypeptide-1 (Apobec1) had increased serum IL-17 levels, with T cell programming shifted towards Th17 cells. In this study, we assessed the role of proprotein convertase subtilisin/kexin type 9 (PCSK9) in T cell programming and atherogenesis. We deleted the Pcsk9 gene from LDb mice to generate Ldlr ^-/- Apobec1 ^-/- Pcsk9 ^-/- (LTp) triple knockout mice. Atherosclerosis in the aortic sinus and aorta were quantitated. Lymphoid cells were analyzed by flow cytometry, ELISA and real-time PCR. Despite of dyslipidemia, LTp mice developed barely detectable atherosclerotic lesions. The IL-17, was very low in plasma and barely detectable in the aortic sinus in the LTp mice. In the spleen, the number of CD4⁺CD8^- cells and splenocytes were much lower in the LDb mice than LTp mice, whereas, the IL-17-producing cells of γδTCR⁺ T cells and effector memory CD4⁺ T cells (CD44^hiCD4⁺) in the spleen were significantly higher in the LDb mice than in the LTp mice. The Rorc mRNA expression levels were elevated in LDb mice compared to LTp mice. When re-stimulated with an anti-CD3 Ab, CD44^hiCD4⁺ T cells from LDb mice secreted more IL-17 than those from LTp mice. T cells from LDb mice (with PCSK9) produce more IL-17 at basal and stimulated conditions when compared with LTp mice (without PCSK9). Despite the dyslipidemic profile and the lack of LDLR, atherogenesis is markedly reduced in LTp mice. These results suggest that PCSK9 is associated with changes in T cell programming that contributes to the development of atherosclerosis.

Efficacy of adoptive therapy with tumor-infiltrating lymphocytes and recombinant interleukin-2 in advanced cutaneous melanoma: a systematic review and meta-analysis

Adoptive cell therapy (ACT) using autologous tumor-infiltrating lymphocytes (TIL) has been tested in advanced melanoma patients at various centers. We conducted a systematic review and meta-analysis to assess its efficacy on previously treated advanced metastatic cutaneous melanoma. The PubMed electronic database was searched from inception to 17 December 2018 to identify studies administering TIL-ACT and recombinant interleukin-2 (IL-2) following non-myeloablative chemotherapy in previously treated metastatic melanoma patients. Objective response rate (ORR) was the primary end point. Secondary end points were complete response rate (CRR), overall survival (OS), duration of response (DOR) and toxicity. Pooled estimates were derived from fixed or random effect models, depending on the amount of heterogeneity detected. Analysis was carried out separately for high dose (HD) and low dose (LD) IL-2. Sensitivity analyses were carried out. Among 1211 records screened, 13 studies (published 1988 - 2016) were eligible for meta-analysis. Among 410 heavily pretreated patients (some with brain metastasis), 332 received HD-IL-2 and 78 LD-IL-2. The pooled overall ORR estimate was 41% [95% confidence interval (CI) 35% to 48%], and the overall CRR was 12% (95% CI 7% to 16%). For the HD-IL-2 group, the ORR was 43% (95% CI 36% to 50%), while for the LD-IL-2 it was 35% (95% CI 25% to 45%). Corresponding pooled estimates for CRR were 14% (95% CI 7% to 20%) and 7% (95% CI 1% to 12%). The majority of HD-IL-2 complete responders (27/28) remained in remission during the extent of follow-up after CR (median 40 months). Sensitivity analyses yielded similar results. Higher number of infused cells was associated with a favorable response. The ORR for HD-IL-2 compared favorably with the nivolumab/ipilimumab combination following anti-PD-1 failure. TIL-ACT therapy, especially when combined with HD-IL-2, achieves durable clinical benefit and warrants further investigation. We discuss the current position of TIL-ACT in the therapy of advanced melanoma, particularly in the era of immune checkpoint blockade therapy, and review future opportunities for improvement of this approach.

Cholesterol membrane content has a ubiquitous evolutionary function in immune cell activation: the role of HDL

PURPOSE OF REVIEW

Cellular cholesterol content influences the structure and function of lipid rafts, plasma membrane microdomains essential for cell signaling and activation. HDL modulate cellular cholesterol efflux, thus limiting cholesterol accumulation and controlling immune cell activation. Aim of this review is to discuss the link between HDL and cellular cholesterol metabolism in immune cells and the therapeutic potential of targeting cholesterol removal from cell membranes.

RECENT FINDINGS

The inverse relationship between HDL-cholesterol (HDL-C) levels and the risk of cardiovascular disease has been recently challenged by observations linking elevated levels of HDL-C with increased risk of all-cause mortality, infections and autoimmune diseases, paralleled by the failure of clinical trials with HDL-C-raising therapies. These findings suggest that improving HDL function might be more important than merely raising HDL-C levels. New approaches aimed at increasing the ability of HDL to remove cellular cholesterol have been assessed for their effect on immune cells, and the results have suggested that this could be a new effective approach.

SUMMARY

Cholesterol removal from plasma membrane by different means affects the activity of immune cells, suggesting that approaches aimed at increasing the ability of HDL to mobilize cholesterol from cells would represent the next step in HDL biology.

Galectin-3 modulation of T-cell activation: mechanisms of membrane remodelling

Galectin-3 (Gal3) is a multifaceted protein which belongs to a family of lectins and binds β-galactosides. Gal3 expression is altered in many types of cancer, with increased expression generally associated with poor prognosis. Although the mechanisms remain unknown, Gal3 has been implicated in several biological processes involved in cancer progression, including suppression of T cell-mediated immune responses. Extracellular Gal3 binding to the plasma membrane of T cells alters membrane organization and the formation of an immunological synapse. Its multivalent capacity allows Gal3 to interact specifically with different membrane proteins and lipids, influencing endocytosis, trafficking and T cell receptor signalling. The ability of Gal3 to inhibit T cell responses may provide a mechanism by which Gal3 aids in cancer progression. In this review, we seek to give an overview of the mechanisms by which Gal3 alters the spatial organization of cell membranes and how these processes impact on T cell activation.

Potentiation of Kras peptide cancer vaccine by avasimibe, a cholesterol modulator

Background

No effective approaches to target mutant Kras have yet been developed. Immunoprevention using KRAS-specific antigenic peptides to trigger T cells capable of targeting tumor cells relies heavily on lipid metabolism. To facilitate better TCR/peptide/MHC interactions that result in better cancer preventive efficacy, we combined KVax with avasimibe, a specific ACAT1 inhibitor, tested their anti-cancer efficacy in mouse lung cancer models, where Kras mutation was induced before vaccination.

Methods

Control of tumor growth utilizing a multi-peptide Kras vaccine was tested in combination with avasimibe in a syngeneic lung cancer mouse model and a genetically engineered mouse model (GEMM). Activation of immune responses after administration of Kras vaccine and avasimibe was also assessed by flow cytometry, ELISpot and IHC.

Findings

We found that Kras vaccine combined with avasimibe significantly decreased the presence of regulatory T cells in the tumor microenvironment and facilitated CD8+ T cell infiltration in tumor sites. Avasimibe also enhanced the efficacy of Kras vaccines target mutant Kras. Whereas the Kras vaccine significantly increased antigen-specific intracellular IFN-γ and granzyme B levels in CD8+ T cells, avasimibe significantly increased the number of tumor-infiltrating CD8+ T cells. Additionally, modulation of cholesterol metabolism was found to specifically impact in T cells, and not in cancer cells.

Interpretation

Avasimibe complements the efficacy of a multi-peptide Kras vaccine in controlling lung cancer development and growth. This treatment regimen represents a novel immunoprevention approach to prevent lung cancer.

LXRβ controls glioblastoma cell growth, lipid balance, and immune modulation independently of ABCA1

Cholesterol is a critical component of membranes and a precursor for hormones and other signaling molecules. Previously, we showed that unlike astrocytes, glioblastoma cells do not downregulate cholesterol synthesis when plated at high density. In this report, we show that high cell density induces ABCA1 expression in glioblastoma cells, enabling them to get rid of excess cholesterol generated by an activated cholesterol biosynthesis pathway. Because oxysterols are agonists for Liver X Receptors (LXRs), we investigated whether increased cholesterol activates LXRs to maintain cholesterol homeostasis in highly-dense glioblastoma cells. We observed that dense cells had increased oxysterols, which activated LXRβ to upregulate ABCA1. Cells with CRISPR-mediated knockdown of LXRβ, but not ABCA1, had decreased cell cycle progression and cell survival, and decreased feedback repression of the mevalonate pathway in densely-plated glioma cells. LXRβ gene expression poorly correlates with ABCA1 in glioblastoma patients, and expression of each gene correlates with poor patient prognosis in different prognostic subtypes. Finally, gene expression and lipidomics analyses cells revealed that LXRβ regulates the expression of immune response gene sets and lipids known to be involved in immune modulation. Thus, therapeutic targeting of LXRβ in glioblastoma might be effective through diverse mechanisms.

Combined effects of avasimibe immunotherapy, doxorubicin chemotherapy, and metal-organic frameworks nanoparticles on breast cancer

CD8⁺ T cells play a vital role in cancer immunotherapy and can be shaped by metabolism. Avasimibe is an acyl coenzyme A-cholesterol acyltransferase (ACAT) inhibitor, which has been clinically verified safe in other phase Ⅲ clinical trials. It can potentiate the killing function of CD8⁺ T cells by modulating cholesterol metabolism. Doxorubicin (DOX) is an anticancer drug widely used in many cancers to induce tumor cell apoptosis. Unfortunately, DOX also can induce toxic and side effects in many organs, compromising its usage and efficacy. Herein, we report the combinational usage of avasimibe and a safe pH sensitive nano-drug delivery system composing of DOX and metal-organic frameworks nanoparticles (MNPs). Our findings demonstrated that DOX-MNPs treatment inhibited tumor growth with good safety profile and avasimibe treatment combined DOX-MNPs treatment exhibited a better efficacy than monotherapies in 4T1 breast cancer therapy.

Generating stem-like memory T cells with antioxidants for adoptive cell transfer immunotherapy of cancer

Among the multiple factors that are responsible for the success of adoptive cell transfer (ACT) immunotherapy for cancer, the differentiation status of the in vitro expanded T cell product at the time of transfer seems to play a major role. In particular, less differentiated memory CD8⁺ T cells endowed with self-renewing capacity and multipotency exert the most potent antitumor activity. To this aim, expansion protocols that generate sufficient numbers of tumor-specific CD8⁺ T cells with superior capacity to persist in vivo following ACT are needed. We describe a procedure for the differentiation of TCF-1⁺ stem-like CD8⁺ memory T cells from peripheral blood naïve precursors that takes advantage of the use of antioxidants, in particular N-acetylcysteine (NAC), in combination with T cell receptor stimulation and proinflammatory cytokines. We additionally describe how to conduct in vitro assays to test the stem-like features of the generated cells at the phenotypic, functional and metabolic level. Balancing the oxidative metabolism by the addition of antioxidants during in vitro manipulation of CD8⁺ T cells results in the generation of cell products with potent antitumor characteristics following ACT.

Role of Neutral Sphingomyelinase-2 (NSM 2) in the Control of T Cell Plasma Membrane Lipid Composition and Cholesterol Homeostasis

The activity of neutral sphingomyelinase-2 (NSM2) to catalyze the conversion of sphingomyelin (SM) to ceramide and phosphocholine at the cytosolic leaflet of plasma membrane (PM) is important in T cell receptor (TCR) signaling. We recently identified PKCζ as a major NSM2 downstream effector which regulates microtubular polarization. It remained, however, unclear to what extent NSM2 activity affected overall composition of PM lipids and downstream effector lipids in antigen stimulated T cells. Here, we provide a detailed lipidomics analyses on PM fractions isolated from TCR stimulated wild type and NSM2 deficient (ΔNSM) Jurkat T cells. This revealed that in addition to that of sphingolipids, NSM2 depletion also affected concentrations of many other lipids. In particular, NSM2 ablation resulted in increase of lyso-phosphatidylcholine (LPC) and lyso-phosphatidylethanolamine (LPE) which both govern PM biophysical properties. Crucially, TCR dependent upregulation of the important T cell signaling lipid diacylglycerol (DAG), which is fundamental for activation of conventional and novel PKCs, was abolished in ΔNSM cells. Moreover, NSM2 activity was found to play an important role in PM cholesterol transport to the endoplasmic reticulum (ER) and production of cholesteryl esters (CE) there. Most importantly, CE accumulation was essential to sustain human T cell proliferation. Accordingly, inhibition of CE generating enzymes, the cholesterol acetyltransferases ACAT1/SOAT1 and ACAT2/SOAT2, impaired TCR driven expansion of both CD4⁺ and CD8⁺ T cells. In summary, our study reveals an important role of NSM2 in regulating T cell functions by its multiple effects on PM lipids and cholesterol homeostasis.

Donor single nucleotide polymorphism in ACAT1 affects the incidence of graft-versus-host disease after bone marrow transplantation

Acyl-coenzyme A: cholesterol acyltransferase 1 (ACAT1) is an enzyme that converts cholesterol to cholesteryl esters. A recent in vivo study reported that inhibiting ACAT1 enzyme activity upregulates the membrane cholesterol levels of T cells, enhancing their cytotoxic function. In the present study, we investigated whether the presence of the ACAT1 single nucleotide polymorphism rs11545566 in transplant donors affected the risk of graft-versus-host disease (GVHD) in 116 adult patients who underwent bone marrow transplantation from human leukocyte antigen-identical sibling donors, and who received GVHD prophylaxis with short-term methotrexate and cyclosporine. The frequencies of the AA, AG, and GG genotypes in the donors were 31%, 45%, and 24%, respectively. The cumulative incidences of grade II-IV acute GVHD on day 100 in patients whose donors had AA vs. non-AA genotypes were 6% and 18%, respectively, and those of extensive chronic GVHD at 2 years were 7% and 32%, respectively. Multivariate analyses demonstrated that donor rs11545566 non-AA genotypes showed a trend toward a higher incidence of grade II-IV acute GVHD (P = 0.079), and were significantly associated with a higher incidence of extensive chronic GVHD (P = 0.021). These results suggest that donor ACAT1 rs11545566 genotype may be predictive of GVHD.

Targeting T cell metabolism in the tumor microenvironment: an anti-cancer therapeutic strategy

T cells play important roles in anti-tumor immunity. Emerging evidence has revealed that distinct metabolic changes impact the activation and differentiation of T cells. Tailoring immune responses by manipulating cellular metabolic pathways and the identification of new targets may provide new options for cancer immunotherapy. In this review, we focus on recent advances in the metabolic reprogramming of different subtypes of T cells and T cell functions. We summarize how metabolic pathways accurately regulate T cell development, differentiation, and function in the tumor microenvironment. Because of the similar metabolism in activated T cells and tumor cells, we also describe the effect of the tumor microenvironment on T cell metabolism reprogramming, which may provide strategies for maximal anti-cancer effects and enhancing the immunity of T cells. Thus, studies of T lymphocyte metabolism can not only facilitate the basic research of immune metabolism, but also provide potential targets for drug development and new strategies for clinical treatment of cancer.

SCP2-mediated cholesterol membrane trafficking promotes the growth of pituitary adenomas via Hedgehog signaling activation

Background

Metabolic reprogramming is an important characteristic of tumors. In the progression of pituitary adenomas (PA), abnormal glucose metabolism has been confirmed by us before. However, whether cholesterol metabolism is involved in the process of PA remains unclear. This study aimed to investigate whether abnormal cholesterol metabolism could affect the progression of PA.

Methods

We analyzed the expression of sterol carrier protein 2 (SCP2) in 40 surgical PA samples. In vitro experiments and xenograft models were used to assess the effects of SCP2 and cholesterol on proliferation of PA. The incidence of hypercholesterolemia between 140 PA patients and 100 heathy controls were compared.

Results

We found an upregulation of SCP2 in PA samples, especially in tumors with high proliferation index. Forced expression of SCP2 promoted PA cell lines proliferation in vitro. Furthermore, SCP2 regulated cholesterol trafficking from cytoplasm to membrane in GH3 cells, and extracellularly treating GH3 cells and primary PA cells with methyl-β-cyclodextrin/cholesterol complex to mimic membrane cholesterol concentration enhanced cell proliferation, which suggested a proliferative effect of cholesterol. Mechanistically, cholesterol induced activation of PKA/SUFU/GLI1 signaling via smoothened receptor, which was well-known as Hedgehog signaling, resulting in inhibiting apoptosis and promoting cell cycle. Accordingly, activation of Hedgehog signaling was also confirmed in primary PA cells and surgical PA samples. In vivo, SCP2 overexpression and high cholesterol diet could promote tumor growth. Intriguingly, the incidence of hypercholesterolemia was significantly higher in PA patients than healthy controls.

Conclusions

Our data indicated that dysregulated cholesterol metabolism could promote PA growth by activating Hedgehog signaling, supporting a potential tumorigenic role of cholesterol metabolism in PA progression.

Cholesterol Esterification Enzyme Inhibition Enhances Antitumor Effects of Human Chimeric Antigen Receptors Modified T Cells

Chimeric antigen receptor-modified T cell (CART) therapy has been demonstrated to have significant effect on hematologic tumor in patients. However, many persistent obstacles and challenges still limit the application. It is known that CD8 T cells are a key component of antitumor immunity. An avasimibe-induced inhibition of cholesterol esterification has been shown to improve the antitumor response of CD8 T cells in mice. In this study, using human CD19-directed CART cells as effector cells and CD19-overexpressing K562 cells as target cells, we detected whether cholesterol acyltransferase inhibition by avasimibe can enhance the antitumor effect of human CART cells. After avasimibe treatment, the infection rate was dropped by up to 50% (P<0.05). The cytotoxic effect of CART cells was significantly increased than the control group in a dose-dependent manner. Moreover, the level of secreted interferon-γ increased in almost half of the cases (P<0.05); the ratio of CD8CD4 T cells was increased among the total T cells and the CART cells in some of cases (P<0.05). Our study suggests that inhibition of cholesterol acyltransferase can promote the antitumor effect of CART cells, and provides a new option for a combination therapy by regulating T-cell metabolism to enhance antitumor effects.

Atractylodes macrocephala polysaccharides regulate the innate immunity of colorectal cancer cells by modulating the TLR4 signaling pathway

Background

It has been well-recognized that the polysaccharides from Atractylodes macrocephala (PAM) are immune system enhancers, which can facilitate the proliferation of lymphocytes and stimulate immune cells. Nevertheless, the antitumor effects of PAM and their molecular mechanisms remain unclear.

Aim

Our research aimed to evaluate the anti-cancer effects of PAM on colorectal cancer (CRC).

Methods

We tested the effects of PAM on the growth and proliferation of CRC cells and macrophages by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The pro-inflammatory cytokines expression and secretion was analyzed by real-time RT-PCR and ELISA assay. We also used MC38 cells xenograft model to test the anti-cancer effects of PAM in vivo.

Results

We found that although PAM treatment did not significantly affect the growth of CRC cells or enhance the proliferation of bone marrow-derived macrophages (BMDMs), it could enhance the phagocytosis of BMDMs by CRC cells. Biochemical tests and immunoblotting assays revealed that exposing BMDMs to PAM promoted the production of interleukin-6 (IL-6), interferon λ (IFN λ), tumor necrosis factor α (TNF-α), and nitric oxide (NO) through the MyD88/TLR4-dependent signaling pathway. One noteworthy observation is that PAM treatment could significantly prevent tumorigenesis of MC38 cells in C57BL/6J mice and increase the survival duration of mice with tumors, without influence on the weight of those mice. However, the anti-cancer effects of PAM were compromised in TLR4 KO mice, further suggesting that TLR4 signaling plays a vital role in the anti-cancer effects of PAM.

Conclusion

Therefore, PAM may prove to be a potential candidate in cancer immunotherapy.

Immunity, Hypoxia, and Metabolism-the Ménage à Trois of Cancer: Implications for Immunotherapy

It is generally accepted that metabolism is able to shape the immune response. Only recently we are gaining awareness that the metabolic crosstalk between different tumor compartments strongly contributes to the harsh tumor microenvironment (TME) and ultimately impairs immune cell fitness and effector functions. The major aims of this review are to provide an overview on the immune system in cancer; to position oxygen shortage and metabolic competition as the ground of a restrictive TME and as important players in the anti-tumor immune response; to define how immunotherapies affect hypoxia/oxygen delivery and the metabolic landscape of the tumor; and vice versa, how oxygen and metabolites within the TME impinge on the success of immunotherapies. By analyzing preclinical and clinical endeavors, we will discuss how a metabolic characterization of the TME can identify novel targets and signatures that could be exploited in combination with standard immunotherapies and can help to predict the benefit of new and traditional immunotherapeutic drugs.