The cholesterol transporter ABCG1 links cholesterol homeostasis and tumour immunity

The impact of lipids on the cancer–immunity cycle and strategies for modulating lipid metabolism to improve cancer immunotherapy

Lipids have been found to modulate tumor biology, including proliferation, survival, and metastasis. With the new understanding of tumor immune escape that has developed in recent years, the influence of lipids on the cancer-immunity cycle has also been gradually discovered. First, regarding antigen presentation, cholesterol prevents tumor antigens from being identified by antigen presenting cells. Fatty acids reduce the expression of major histocompatibility complex class I and costimulatory factors in dendritic cells, impairing antigen presentation to T cells. Prostaglandin E2 (PGE2) reduce the accumulation of tumor-infiltrating dendritic cells. Regarding T-cell priming and activation, cholesterol destroys the structure of the T-cell receptor and reduces immunodetection. In contrast, cholesterol also promotes T-cell receptor clustering and relative signal transduction. PGE2 represses T-cell proliferation. Finally, regarding T-cell killing of cancer cells, PGE2 and cholesterol weaken granule-dependent cytotoxicity. Moreover, fatty acids, cholesterol, and PGE2 can improve the activity of immunosuppressive cells, increase the expression of immune checkpoints and promote the secretion of immunosuppressive cytokines. Given the regulatory role of lipids in the cancer-immunity cycle, drugs that modulate fatty acids, cholesterol and PGE2 have been envisioned as effective way in restoring antitumor immunity and synergizing with immunotherapy. These strategies have been studied in both preclinical and clinical studies.

Clinical Significance of Lipid Transport Function of ABC Transporters in the Innate Immune System

ABC transporters are a large family of proteins that transport a variety of substrates across cell plasma membranes. Because of this, they are involved in many physiological processes. It is of interest to note that many ABC transporters are involved in the transport of various lipids. In addition, this function may be related to the innate immune system. The evidence that ABC transporters are involved in the regulation of the innate immune system through the transport of various substances greatly enhances the understanding of their clinical significance. ABC transporters are involved in the cellular homeostasis of cholesterol as well as in the regulation of its content in lipid rafts. Through these mechanisms, they can regulate the function of membrane proteins, including receptors of the innate immune system. By regulating lipid transport, some members of ABC transporters are involved in phagocytosis. In addition, ABC transporters are involved in the transport of lipopolysaccharide, lipid mediators of inflammation, and perform other functions in the innate immune system.

HDL metabolism and functions impacting on cell cholesterol homeostasis are specifically altered in patients with abdominal aortic aneurysm

Background

The etiopathogenesis of abdominal aortic aneurysm (AAA) is still unclarified, but vascular inflammation and matrix metalloproteases activation have a recognized role in AAA development and progression. Circulating lipoproteins are involved in tissue inflammation and repair, particularly through the regulation of intracellular cholesterol, whose excess is associated to cell damage and proinflammatory activation. We analyzed lipoprotein metabolism and function in AAA and in control vasculopathic patients, to highlight possible non-atherosclerosis-related, specific abnormalities.

Methods

We measured fluorometrically serum esterified/total cholesterol ratio, as an index of lecithin-cholesterol acyltransferase (LCAT) activity, and cholesteryl ester transfer protein (CETP) activity in patients referred to vascular surgery either for AAA (n=30) or stenotic aortic/peripheral atherosclerosis (n=21) having similar burden of cardiovascular risk factors and disease. We measured high-density lipoprotein (HDL)-cholesterol efflux capacity (CEC), through the ATP-binding cassette G1 (ABCG1) and A1 (ABCA1) pathways and serum cell cholesterol loading capacity (CLC), by radioisotopic and fluorimetric methods, respectively.

Results

We found higher LCAT (+23%; p < 0.0001) and CETP (+49%; p < 0.0001) activity in AAA sera. HDL ABCG1-CEC was lower (−16%; p < 0.001) and ABCA1-CEC was higher (+31.7%; p < 0.0001) in AAA. Stratification suggests that smoking may partly contribute to these modifications. CEC and CETP activity correlated with CLC only in AAA.

Conclusions

We demonstrated that compared to patients with stenotic atherosclerosis, patients with AAA had altered HDL metabolism and functions involved in their anti-inflammatory and tissue repair activity, particularly through the ABCG1-related intracellular signaling. Clarifying the relevance of this mechanism for AAA evolution might help in developing new diagnostic parameters and therapeutic targets for the early management of this condition.

Role of Lipids and Lipid Metabolism in Prostate Cancer Progression and the Tumor’s Immune Environment

Modulation of lipid metabolism during cancer development and progression is one of the hallmarks of cancer in solid tumors; its importance in prostate cancer (PCa) has been demonstrated in numerous studies. Lipid metabolism is known to interact with androgen receptor signaling, an established driver of PCa progression and castration resistance. Similarly, immune cell infiltration into prostate tissue has been linked with the development and progression of PCa as well as with disturbances in lipid metabolism. Immuno-oncological drugs inhibit immune checkpoints to activate immune cells’ abilities to recognize and destroy cancer cells. These drugs have proved to be successful in treating some solid tumors, but in PCa their efficacy has been poor, with only a small minority of patients demonstrating a treatment response. In this review, we first describe the importance of lipid metabolism in PCa. Second, we collate current information on how modulation of lipid metabolism of cancer cells and the surrounding immune cells may impact the tumor’s immune responses which, in part, may explain the unimpressive results of immune-oncological treatments in PCa.

Structural analysis of cholesterol binding and sterol selectivity by ABCG5/G8

The ATP-binding cassette (ABC) sterol transporters are responsible for maintaining cholesterol homeostasis in mammals by participating in reverse cholesterol transport (RCT) or transintestinal cholesterol efflux (TICE). The heterodimeric ABCG5/G8 carries out selective sterol excretion, preventing the abnormal accumulation of plant sterols in human bodies, while homodimeric ABCG1 contributes to the biogenesis and metabolism of high-density lipoproteins. A sterol-binding site on ABCG5/G8 was proposed at the interface of the transmembrane domain and the core of lipid bilayers. In this study, we have determined the crystal structure of ABCG5/G8 in a cholesterol-bound state. The structure combined with amino acid sequence analysis shows that in the proximity of the sterol-binding site, a highly conserved phenylalanine array supports functional implications for ABCG cholesterol/sterol transporters. Lastly, in silico docking analysis of cholesterol and stigmasterol (a plant sterol) suggests sterol-binding selectivity on ABCG5/G8, but not ABCG1. Together, our results provide a structural basis for cholesterol binding on ABCG5/G8 and the sterol selectivity by ABCG transporters.

High nuclear ABCG1 expression is a poor predictor for hepatocellular carcinoma patient survival

BACKGROUND

ATP-binding cassette transporter G1 (ABCG1) regulates cellular cholesterol homeostasis and plays a significant role in tumor immunity. But, for hepatocellular carcinoma (HCC), the role of ABCG1 has not been investigated. Thus, the aim of this study was to evaluate the prognostic value and clinicopathological significance of ABCG1 in HCC.

METHODS

One hundred and four adult patients with HCC were enrolled, and ABCG1 expression in paired HCC specimens was determined by immunohistochemistry. All these patients were stratified by ABCG1 expression, Kaplan-Meier analysis was used to compare the overall survival (OS) and recurrence-free survival (RFS), and Cox regression analysis was used to determine independent predictors of tumor recurrence.

RESULTS

Upregulation of ABCG1 was observed in HCC samples compared to matched tumor-adjacent tissues. Patients with high nuclear ABCG1 expression had lower OS and RFS (P = 0.012 and P = 0.020, respectively). High nuclear ABCG1 expression was related to larger tumor size (P = 0.004) and tumor recurrence (P = 0.027). Although ABCG1 was expressed in the cytoplasm, cytosolic expression could not predict the outcome in patients with HCC. A new stratification pattern was established based on the heterogenous ABCG1 expression pattern: high risk (High^nucleus/Low^cytosol), moderate risk (High^nucleus/High^cytosol or Low^nucleus/Low^cytosol), and low risk (Low^nucleus/High^cytosol). This ABCG1-based risk stratification could distinguish the different OS and RFS in patients with HCC. Multivariate Cox regression analysis indicated that ABCG1 high risk was an independent predictor of poor RFS (P = 0.015).

CONCLUSIONS

High nuclear ABCG1 expression indicates poor prognosis in patients with HCC. Asymmetric distribution of ABCG1 in the nucleus and cytoplasm may have an important role in tumor recurrence.

Lipid-loaded macrophages as new therapeutic target in cancer

Macrophages are main players of the innate immune system. They show great heterogeneity and play diverse functions that include support to development, sustenance of tissue homeostasis and defense against infections. Dysfunctional macrophages have been described in multiple pathologies including cancer. Indeed tumor-associated macrophages (TAMs) are abundant in most tumors and sustain cancer growth, promote invasion and mediate immune evasion. Importantly, lipid metabolism influences macrophage activation and lipid accumulation confers pathogenic features on macrophages. Notably, a subset of lipid-loaded macrophages has been recently identified in many tumor types. Lipid-loaded TAMs support tumor growth and progression and exert immune-suppressive activities. In this review, we describe the role of lipid metabolism in macrophage activation in physiology and pathology and we discuss the impact of lipid accumulation in macrophages in the context of cancer.

Metabolism and polarization regulation of macrophages in the tumor microenvironment

The occurrence and development of tumors depend on the tumor microenvironment (TME), which consists of various types of cellular and acellular components. Tumor-associated macrophages (TAMs) are the most abundant stromal cell types in the TME. The competition for nutrients between tumor cells and macrophages leads to a limited supply of nutrients, such as glucose, lipids, and amino acids, to immune cells, which affects the differentiation and function of macrophages. Other factors in the TME, such as cytokines, chemokines, and immune checkpoints, also affect the polarization and function of macrophages. Remodeling the tumor microenvironment induces changes in macrophage nutrient uptake and polarization status, which enhance anti-tumor immunity and oxidative stress resistance and suppress immune escape. This review summarizes the influence factors on tumor progression and immune function under different conditions of macrophages. It also demonstrates the metabolic heterogeneity and phenotypic plasticity of macrophages, which provides novel strategies for anti-tumor treatment.

Targeting Protein Translation in Melanoma by Inhibiting EEF-2 Kinase Regulates Cholesterol Metabolism though SREBP2 to Inhibit Tumour Development

Decreasing the levels of certain proteins has been shown to be important for controlling cancer but it is currently unknown whether proteins could potentially be targeted by the inhibiting of protein synthesis. Under this circumstance, targeting protein translation could preferentially affect certain pathways, which could then be of therapeutic advantage when treating cancer. In this report, eukaryotic elongation factor-2 kinase (EEF2K), which is involved in protein translation, was shown to regulate cholesterol metabolism. Targeting EEF2K inhibited key parts of the cholesterol pathway in cancer cells, which could be rescued by the addition of exogenous cholesterol, suggesting that it is a potentially important pathway modulated by targeting this process. Specifically, targeting EEF2K significantly suppressed tumour cell growth by blocking mRNA translation of the cholesterol biosynthesis transcription factor, sterol regulatory element-binding protein (SREBP) 2, and the proteins it regulates. The process could be rescued by the addition of LDL cholesterol taken into the cells via non-receptor-mediated-uptake, which negated the need for SREBP2 protein. Thus, the levels of SREBP2 needed for cholesterol metabolism in cancer cells are therapeutically vulnerable by targeting protein translation. This is the first report to suggest that targeting EEF2K can be used to modulate cholesterol metabolism to treat cancer.

Metabolism of tissue macrophages in homeostasis and pathology

Cellular metabolism orchestrates the intricate use of tissue fuels for catabolism and anabolism to generate cellular energy and structural components. The emerging field of immunometabolism highlights the importance of cellular metabolism for the maintenance and activities of immune cells. Macrophages are embryo- or adult bone marrow-derived leukocytes that are key for healthy tissue homeostasis but can also contribute to pathologies such as metabolic syndrome, atherosclerosis, fibrosis or cancer. Macrophage metabolism has largely been studied in vitro. However, different organs contain diverse macrophage populations that specialize in distinct and often tissue-specific functions. This context specificity creates diverging metabolic challenges for tissue macrophage populations to fulfill their homeostatic roles in their particular microenvironment and conditions their response in pathological conditions. Here, we outline current knowledge on the metabolic requirements and adaptations of macrophages located in tissues during homeostasis and selected diseases.

Lipid-Laden Macrophages and Inflammation in Atherosclerosis and Cancer: An Integrative View

Atherosclerotic arterial plaques and malignant solid tumors contain macrophages, which participate in anaerobic metabolism, acidosis, and inflammatory processes inherent in the development of either disease. The tissue-resident macrophage populations originate from precursor cells derived from the yolk sac and from circulating bone marrow-derived monocytes. In the tissues, they differentiate into varying functional phenotypes in response to local microenvironmental stimulation. Broadly categorized, the macrophages are activated to polarize into proinflammatory M1 and anti-inflammatory M2 phenotypes; yet, noticeable plasticity allows them to dynamically shift between several distinct functional subtypes. In atherosclerosis, low-density lipoprotein (LDL)-derived cholesterol accumulates within macrophages as cytoplasmic lipid droplets thereby generating macrophage foam cells, which are involved in all steps of atherosclerosis. The conversion of macrophages into foam cells may suppress the expression of given proinflammatory genes and thereby initiate their transcriptional reprogramming toward an anti-inflammatory phenotype. In this particular sense, foam cell formation can be considered anti-atherogenic. The tumor-associated macrophages (TAMs) may become polarized into anti-tumoral M1 and pro-tumoral M2 phenotypes. Mechanistically, the TAMs can regulate the survival and proliferation of the surrounding cancer cells and participate in various aspects of tumor formation, progression, and metastasis. The TAMs may accumulate lipids, but their type and their specific roles in tumorigenesis are still poorly understood. Here, we discuss how the phenotypic and functional plasticity of macrophages allows their multifunctional response to the distinct microenvironments in developing atherosclerotic lesions and in developing malignant tumors. We also discuss how the inflammatory reactions of the macrophages may influence the development of atherosclerotic plaques and malignant tumors, and highlight the potential therapeutic effects of targeting lipid-laden macrophages in either disease.

Structure and transport mechanism of the human cholesterol transporter ABCG1

The reverse cholesterol transport pathway is responsible for the maintenance of human cholesterol homeostasis, an imbalance of which usually leads to atherosclerosis. As a key component of this pathway, the ATP-binding cassette transporter ABCG1 forwards cellular cholesterol to the extracellular acceptor nascent high-density lipoprotein (HDL). Here, we report a 3.26-Å cryo-electron microscopy structure of cholesterol-bound ABCG1 in an inward-facing conformation, which represents a turnover condition upon ATP binding. Structural analyses combined with functional assays reveals that a cluster of conserved hydrophobic residues, in addition to two sphingomyelins, constitute a well-defined cholesterol-binding cavity. The exit of this cavity is closed by three pairs of conserved Phe residues, which constitute a hydrophobic path for the release of cholesterol in an acceptor concentration-dependent manner. Overall, we propose an ABCG1-driven cholesterol transport cycle initiated by sphingomyelin-assisted cholesterol recruitment and accomplished by the release of cholesterol to HDL.

Cholesterol-Lowering Intervention Decreases mTOR Complex 2 Signaling and Enhances Antitumor Immunity

PURPOSE

There is a need for strategies to prevent prostate cancer. Cholesterol-lowering interventions are employed widely and safely to reduce risk of cardiovascular disease and has been proposed for chemoprevention. Using preclinical models and a window-of-opportunity clinical trial, we describe an adaptive antitumor immunity resulting from cholesterol lowering.

EXPERIMENTAL DESIGN

Statins do not reliably lower serum cholesterol in mice. Therefore, oral ezetimibe was administered to mice to lower serum cholesterol to clinically relevant levels and evaluated the final adaptive immune response. T-lymphocytes-specific mTORC2 knockout mice were used to evaluate mTOR signaling and antitumor immunity. Pretreatment and posttreatment prostate tumors and lymphocytes were examined from a window-of-opportunity clinical trial where men with prostate cancer were treated with 2 to 6 weeks of aggressive cholesterol-lowering intervention prior to radical prostatectomy.

RESULTS

Mice treated with oral ezetimibe exhibited enhanced antitumor immunity against syngeneic cancers in a CD8+ lymphocyte-dependent manner, produced immunity that was transferrable through lymphocytes, and had enhanced central CD8+ T-cell memory. In mice and in patients undergoing prostatectomy, lowering serum cholesterol inhibited mTORC2 signaling in lymphocytes and increased infiltration of CD8+ lymphocytes into prostate tumors. T-lymphocyte-specific mTORC2 knockout mice demonstrated enhanced CD8+ lymphocyte function and antitumor capacity. In patients, cholesterol-lowering intervention prior to prostatectomy decreased the proliferation of normal prostate and low-grade adenocarcinomas.

CONCLUSIONS

Lowering serum cholesterol decreased signaling through mTORC2 and enhanced antitumor CD8+ T-cell memory. We provide a rationale for large-scale clinical testing of cholesterol lowering strategies for prostate cancer chemoprevention.

Circulating Lipid- and Inflammation-Based Risk (CLIR) Score: A Promising New Model for Predicting Outcomes in Complete Colorectal Liver Metastases Resection

BACKGROUND

Colorectal cancer liver metastasis (CRLM) is a determining factor affecting the survival of colorectal cancer (CRC) patients. This study aims at developing a novel prognostic stratification tool for CRLM resection.

METHODS

In this retrospective study, 666 CRC patients who underwent complete CRLM resection from two Chinese medical institutions between 2001 and 2016 were classified into the training (341 patients) and validation (325 patients) cohorts. The primary endpoint was overall survival (OS). Associations between clinicopathological variables, circulating lipid and inflammation biomarkers, and OS were explored. The five most significant prognostic factors were incorporated into the Circulating Lipid- and Inflammation-based Risk (CLIR) score. The predictive ability of the CLIR score and Fong's Clinical Risk Score (CRS) was compared by time-dependent receiver operating characteristic (ROC) analysis.

RESULTS

Five independent predictors associated with worse OS were identified in the training cohort: number of CRLMs >4, maximum diameter of CRLM >4.4 cm, primary lymph node-positive, serum lactate dehydrogenase (LDH) level >250.5 U/L, and serum low-density lipoprotein-cholesterol (LDL-C)/high-density lipoprotein-cholesterol (HDL-C) ratio >2.9. These predictors were included in the CLIR score and each factor was assigned one point. Median OS for the low (score 0-1)-, intermediate (score 2-3)-, and high (score 4-5)-risk groups was 134.0 months, 39.9 months, and 18.7 months in the pooled cohort. The CLIR score outperformed the Fong score with superior discriminatory capacities for OS and RFS, both in the training and validation cohorts.

CONCLUSIONS

The CLIR score demonstrated a promising ability to predict the long-term survival of CRC patients after complete hepatic resection.

Metabolism in tumor-associated macrophages

Macrophages functionally adapt to a diverse set of signals, a process that is critical for their role in maintaining or restoring tissue homeostasis. This process extends to cancer, where macrophages respond to a series of inflammatory and metabolic cues that direct a maladaptive healing response. Tumor-associated macrophages (TAMs) have altered glucose, amino acid, and lipid metabolic profiles, and interfering with this metabolic shift can blunt the ability of macrophages to promote tumor growth, metastasis, and the creation of an immunosuppressive microenvironment. Here we will review changes in metabolites and metabolic pathways in TAMs and link these with the phenotypic and functional properties of the cells. We will also discuss current strategies targeting TAM metabolism as a therapeutic intervention in cancer.

Construction of a ceRNA network in hepatocellular carcinoma and comprehensive analysis of immune infiltration patterns

BACKGROUND

Hepatocellular carcinoma (HCC) is a type of refractory malignant tumor with high fatality rate. Currently, immunotherapy and competitive endogenous RNA (ceRNA) are research hotspots in HCC, but the relationship between ceRNA and the immune microenvironment in HCC is unclear.

METHODS

Firstly, a differentially expressed circRNA-miRNA-mRNA network was constructed from the GEO database, and functional enrichment analysis was performed. Next, combine the TCGA database to construct a ceRNA prognosis-related subnetwork. Establish a risk prediction model based on the mRNA in the sub-network, and evaluate the impact of the model on the prognosis. Use clinical samples to verify the expression of genes in the model. Finally, we analyzed the distribution of tumor infiltrating immune cells (TIC) in HCC, and explored the correlation between mRNAs in the ceRNA sub-network and immune infiltration.

RESULTS

We used the HCC ceRNA network (including 12 circRNA, 5 miRNA, and 8 mRNA) as a starting point for the identification of target genes (PSMD10, ESR1 and PPARGC1A) in the ceRNA prognosis-related subnetwork to establish a risk prediction model and elucidated its important role in predicting the poor prognosis of HCC. The differences in mRNA expression verified by clinical samples are consistent with the database. In addition, we found that the mRNAs in the ceRNA prognosis subnetwork are closely related to different types of TICs and immune checkpoints.

CONCLUSIONS

This study is expected to serve as a reference for the study of mechanisms underlying liver cancer, the screening of prognostic markers and the evaluation of the immune response.

Metabolite transporters as regulators of macrophage polarization

Macrophages are myeloid immune cells, present in virtually all tissues which exhibit considerable functional plasticity and diversity. Macrophages are often subdivided into two distinct subsets described as classically activated (M1) and alternatively activated (M2) macrophages. It has recently emerged that metabolites regulate the polarization and function of macrophages by altering metabolic pathways. These metabolites often cannot freely pass the cell membrane and are therefore transported by the corresponding metabolite transporters. Here, we reviewed how glucose, glutamate, lactate, fatty acid, and amino acid transporters are involved in the regulation of macrophage polarization. Understanding the interactions among metabolites, metabolite transporters, and macrophage function under physiological and pathological conditions may provide further insights for novel drug targets for the treatment of macrophage-associated diseases. In Brief Recent studies have shown that the polarization and function of macrophages are regulated by metabolites, most of which cannot pass freely through biofilms. Therefore, metabolite transporters required for the uptake of metabolites have emerged seen as important regulators of macrophage polarization and may represent novel drug targets for the treatment of macrophage-associated diseases. Here, we summarize the role of metabolite transporters as regulators of macrophage polarization.

Diagnostic and prognostic value of ABC transporter family member ABCG1 gene in clear cell renal cell carcinoma

As the most common histologic subtype of renal cancer, clear cell renal cell carcinoma (ccRCC) poses a serious threat to public health. However, there are no specific molecular-targeted drugs for ccRCC at present. Human ATP-binding cassette (ABC) transporter family plays an important role in homeostasis maintenance. This study aimed to evaluate the potential diagnostic value of ABC genes in ccRCC. A total of 952 samples of ccRCC patients (707) and controls (245) from three different datasets were included for analysis. Receiver operating characteristic analysis and t-test were used to analyze the differential expression of ABC genes in ccRCC patients and control samples at mRNA level during screening and validations. The Cancer Genome Atlas (TCGA-ccRCC) dataset was utilized to investigate the correlation between ABC genes expression and prognostic value in ccRCC. We then investigated the interactions between ABCG1 and proteins in the Comparative Toxicogenomics Database (CTD). Finally, we found that ATP-binding cassette transporter G member 1 (ABCG1) was over-expressed in ccRCC patients compared with healthy samples at mRNA level. Cox regression analysis and Kaplan-Meier analysis showed that ccRCC patients with high ABCG1 expression had better overall survival (OS) than those patients with low expression (hazard ratio (HR) = 0.662, p = 0.007). This study demonstrated that ABCG1 is a potential diagnostic and prognostic biomarker in ccRCC and discussed the molecular mechanisms underlying the relationship between ccRCC and ABCG1, which might provide guidance for better management and treatment of ccRCC in the future.

Aberrant Cholesterol Metabolism in Ovarian Cancer: Identification of Novel Therapeutic Targets

Cholesterol is an essential substance in mammalian cells, and cholesterol metabolism plays crucial roles in multiple biological functions. Dysregulated cholesterol metabolism is a metabolic hallmark in several cancers, beyond the Warburg effect. Reprogrammed cholesterol metabolism has been reported to enhance tumorigenesis, metastasis and chemoresistance in multiple cancer types, including ovarian cancer. Ovarian cancer is one of the most aggressive malignancies worldwide. Alterations in metabolic pathways are characteristic features of ovarian cancer; however, the specific role of cholesterol metabolism remains to be established. In this report, we provide an overview of the key proteins involved in cholesterol metabolism in ovarian cancer, including the rate-limiting enzymes in cholesterol biosynthesis, and the proteins involved in cholesterol uptake, storage and trafficking. Also, we review the roles of cholesterol and its derivatives in ovarian cancer and the tumor microenvironment, and discuss promising related therapeutic targets for ovarian cancer.

Contradictory roles of lipid metabolism in immune response within the tumor microenvironment

Complex interactions between the immune system and tumor cells exist throughout the initiation and development of cancer. Although the immune system eliminates malignantly transformed cells in the early stage, surviving tumor cells evade host immune defense through various methods and even reprogram the anti-tumor immune response to a pro-tumor phenotype to obtain unlimited growth and metastasis. The high proliferation rate of tumor cells increases the demand for local nutrients and oxygen. Poorly organized vessels can barely satisfy this requirement, which results in an acidic, hypoxic, and glucose-deficient tumor microenvironment. As a result, lipids in the tumor microenvironment are activated and utilized as a primary source of energy and critical regulators in both tumor cells and related immune cells. However, the exact role of lipid metabolism reprogramming in tumor immune response remains unclear. A comprehensive understanding of lipid metabolism dysfunction in the tumor microenvironment and its dual effects on the immune response is critical for mapping the detailed landscape of tumor immunology and developing specific treatments for cancer patients. In this review, we have focused on the dysregulation of lipid metabolism in the tumor microenvironment and have discussed its contradictory roles in the tumor immune response. In addition, we have summarized the current therapeutic strategies targeting lipid metabolism in tumor immunotherapy. This review provides a comprehensive summary of lipid metabolism in the tumor immune response.

The inflammatory microenvironment and the urinary microbiome in the initiation and progression of bladder cancer

Accumulating evidence suggests that chronic inflammation may play a critical role in various malignancies, including bladder cancer. This hypothesis stems in part from inflammatory cells observed in the urethral microenvironment. Chronic inflammation may drive neoplastic transformation and the progression of bladder cancer by activating a series of inflammatory molecules and signals. Recently, it has been shown that the microbiome also plays an important role in the development and progression of bladder cancer, which can be mediated through the stimulation of chronic inflammation. In effect, the urinary microbiome can play a role in establishing the inflammatory urethral microenvironment that may facilitate the development and progression of bladder cancer. In other words, chronic inflammation caused by the urinary microbiome may promote the initiation and progression of bladder cancer. Here, we provide a detailed and comprehensive account of the link between chronic inflammation, the microbiome and bladder cancer. Finally, we highlight that targeting the urinary microbiome might enable the development of strategies for bladder cancer prevention and personalized treatment.

Dysregulation of cholesterol homeostasis in human lung cancer tissue and tumour-associated macrophages

Background

Based on reports on elevated cholesterol levels in cancer cells, strategies to lower cholesterol synthesis have been suggested as an antitumour strategy. However, cholesterol depletion has also been shown to induce tumour-promoting actions in tumour-associated macrophages (TAMs).

Methods

We performed lipidomic and transcriptomic analyses of human lung cancer material. To assess whether the TAM phenotype is shaped by secreted factors produced by tumour cells, primary human monocyte-derived macrophages were polarized towards a TAM-like phenotype using tumour cell-conditioned medium.

Findings

Lipidomic analysis of lung adenocarcinoma (n=29) and adjacent non-tumour tissues (n=22) revealed a significant accumulation of free cholesterol and cholesteryl esters within the tumour tissue. In contrast, cholesterol levels were reduced in TAMs isolated from lung adenocarcinoma tissues when compared with alveolar macrophages (AMs) obtained from adjacent non-tumour tissues. Bulk-RNA-Seq revealed that genes involved in cholesterol biosynthesis and metabolism were downregulated in TAMs, while cholesterol efflux transporters were upregulated. In vitro polarized TAM-like macrophages showed an attenuated lipogenic gene expression signature and exhibited lower cholesterol levels compared with non-polarized macrophages. A genome-wide comparison by bulk RNA-Seq confirmed a high similarity of ex vivo TAMs and in vitro TAM-like macrophages. Modulation of intracellular cholesterol levels by either starving, cholesterol depletion, or efflux transporter inhibition indicated that cholesterol distinctly shapes macrophage gene expression.

Interpretation

Our data show an opposite dysregulation of cholesterol homeostasis in tumour tissue vs. TAMs. Polarization of in vitro differentiated macrophages by tumour cell-conditioned medium recapitulates key features of ex vivo TAMs.

ATP-binding cassette (ABC) transporters in cancer: A review of recent updates

The ATP-binding cassette (ABC) transporter superfamily is one of the largest membrane protein families existing in wide spectrum of organisms from prokaryotes to human. ABC transporters are also known as efflux pumps because they mediate the cross-membrane transportation of various endo- and xenobiotic molecules energized by ATP hydrolysis. Therefore, ABC transporters have been considered closely to multidrug resistance (MDR) in cancer, where the efflux of structurally distinct chemotherapeutic drugs causes reduced itherapeutic efficacy. Besides, ABC transporters also play other critical biological roles in cancer such as signal transduction. During the past decades, extensive efforts have been made in understanding the structure-function relationship, transportation profile of ABC transporters, as well as the possibility to overcome MDR via targeting these transporters. In this review, we discuss the most recent knowledge regarding ABC transporters and cancer drug resistance in order to provide insights for the development of more effective therapies.

Transcriptional landscape of cellular networks reveal interactions driving the dormancy mechanisms in cancer

Primary cancer cells exert unique capacity to disseminate and nestle in distant organs. Once seeded in secondary sites, cancer cells may enter a dormant state, becoming resistant to current treatment approaches, and they remain silent until they reactivate and cause overt metastases. To illuminate the complex mechanisms of cancer dormancy, 10 transcriptomic datasets from the literature enabling 21 dormancy–cancer comparisons were mapped on protein–protein interaction networks and gene-regulatory networks to extract subnetworks that are enriched in significantly deregulated genes. The genes appearing in the subnetworks and significantly upregulated in dormancy with respect to proliferative state were scored and filtered across all comparisons, leading to a dormancy–interaction network for the first time in the literature, which includes 139 genes and 1974 interactions. The dormancy interaction network will contribute to the elucidation of cellular mechanisms orchestrating cancer dormancy, paving the way for improvements in the diagnosis and treatment of metastatic cancer.

Loss of fragile site-associated tumor suppressor promotes antitumor immunity via macrophage polarization

Common fragile sites (CFSs) are specific breakage-prone genomic regions and are present frequently in cancer cells. The (E2-independent) E3 ubiquitin-conjugating enzyme FATS (fragile site-associated tumor suppressor) has antitumor activity in cancer cells, but the function of FATS in immune cells is unknown. Here, we report a function of FATS in tumor development via regulation of tumor immunity. Fats^-/- mice show reduced subcutaneous B16 melanoma and H7 pancreatic tumor growth compared with WT controls. The reduced tumor growth in Fats^-/- mice is macrophage dependent and is associated with a phenotypic shift of macrophages within the tumor from tumor-promoting M2-like to antitumor M1-like macrophages. In addition, FATS deficiency promotes M1 polarization by stimulating and prolonging NF-κB activation by disrupting NF-κB/IκBα negative feedback loops and indirectly enhances both CD4⁺ T helper type 1 (Th1) and cytotoxic T lymphocyte (CTL) adaptive immune responses to promote tumor regression. Notably, transfer of Fats^-/- macrophages protects mice against B16 melanoma. Together, these data suggest that FATS functions as an immune regulator and is a potential target in cancer immunotherapy.

Extracellular matrix protein-1 secretory isoform promotes ovarian cancer through increasing alternative mRNA splicing and stemness

Extracellular matrix protein-1 (ECM1) promotes tumorigenesis in multiple organs but the mechanisms associated to ECM1 isoform subtypes have yet to be clarified. We report in this study that the secretory ECM1a isoform induces tumorigenesis through the GPR motif binding to integrin αXβ2 and the activation of AKT/FAK/Rho/cytoskeleton signaling. The ATP binding cassette subfamily G member 1 (ABCG1) transduces the ECM1a-integrin αXβ2 interactive signaling to facilitate the phosphorylation of AKT/FAK/Rho/cytoskeletal molecules and to confer cancer cell cisplatin resistance through up-regulation of the CD326-mediated cell stemness. On the contrary, the non-secretory ECM1b isoform binds myosin and blocks its phosphorylation, impairing cytoskeleton-mediated signaling and tumorigenesis. Moreover, ECM1a induces the expression of the heterogeneous nuclear ribonucleoprotein L like (hnRNPLL) protein to favor the alternative mRNA splicing generating ECM1a. ECM1a, αXβ2, ABCG1 and hnRNPLL higher expression associates with poor survival, while ECM1b higher expression associates with good survival. These results highlight ECM1a, integrin αXβ2, hnRNPLL and ABCG1 as potential targets for treating cancers associated with ECM1-activated signaling.

Extracellular matrix protein 1 (ECM1) has been associated with cancer but the underlying molecular mechanisms are not clear. Here, the authors show that while ECM1b isoform is a tumour suppressor, the secreted isoform ECM1a promotes tumourigenesis and chemoresistance through increasing stemness and alternative mRNA splicing in ovarian cancer.

The significances and clinical implications of cholesterol components in human breast cancer

Breast cancer is one the most common malignancies and leading cause of cancer-related mortality in women. Recent studies suggested that hypercholesterolemia may be the potential modifiable risk factors for breast cancer. Cholesterol was well-known for its strong association with cardiovascular disease for long. Moreover, solid evidence has been provided by different studies to illustrate the correlation between lipid and incidence in multiple cancers. Although the conclusion remains controversial or sometimes contrary, which may be due to the multifactorial nature of the disease and the disparity of ethnic population, it is critical to elucidate the relationship between specific cholesterol components in certain population and the exact underlying mechanism of the lipid-associated signaling pathway in breast cancer. The implications of dysregulated lipoproteins as therapeutic targets or options for breast cancer provide novel strategies for us in combating with this malignant disease, which may be achieved by manipulating lipid levels with pharmacological compounds.

The Role of ABC Transporters in Lipid Metabolism and the Comorbid Course of Chronic Obstructive Pulmonary Disease and Atherosclerosis

Chronic obstructive pulmonary disease (COPD) ranks among the leading causes of morbidity and mortality worldwide. COPD rarely occurs in isolation and is often combined with various diseases. It is considered that systemic inflammation underlies the comorbid course of COPD. The data obtained in recent years have shown the importance of violations of the cross-links of lipid metabolism and the immune response, which are links in the pathogenesis of both COPD and atherosclerosis. The role of lipid metabolism disorders in the pathogenesis of the comorbid course of COPD and atherosclerosis and the participation of ATP-binding cassette (ABC) transporters in these processes is discussed in this article. It is known that about 20 representatives of a large family of ABC transporters provide lipid homeostasis of cells by moving lipids inside the cell and in its plasma membrane, as well as removing lipids from the cell. It was shown that some representatives of the ABC-transporter family are involved in various links of the pathogenesis of COPD and atherosclerosis, which can determine their comorbid course.

Prognostic Value of Eight-Gene Signature in Head and Neck Squamous Carcinoma

Head and neck cancer (HNC) is the fifth most common cancer worldwide. In this study, we performed an integrative analysis of the discovery set and established an eight-gene signature for the prediction of prognosis in patients with head and neck squamous cell carcinoma (HNSCC). Univariate Cox analysis was used to identify prognosis-related genes (with P < 0.05) in the GSE41613, GSE65858, and TCGA-HNSC RNA-Seq datasets after data collection. We performed LASSO Cox regression analysis and identified eight genes (CBX3, GNA12, P4HA1, PLAU, PPL, RAB25, EPHX3, and HLF) with non-zero regression coefficients in TCGA-HNSC datasets. Survival analysis revealed that the overall survival (OS) of GSE41613 and GSE65858 datasets and the progression-free survival(DFS)of GSE27020 and GSE42743 datasets in the low-risk group exhibited better survival outcomes compared with the high-risk group. To verify that the eight-mRNA prognostic model was independent of other clinical features, KM survival analysis of the specific subtypes with different clinical characteristics was performed. Univariate and multivariate Cox regression analyses were used to identify three independent prognostic factors to construct a prognostic nomogram. Finally, the GSVA algorithm identified six pathways that were activated in the intersection of the TCGA-HNSC, GSE65858, and GSE41613 datasets, including early estrogen response, cholesterol homeostasis, oxidative phosphorylation, fatty acid metabolism, bile acid metabolism, and Kras signaling. However, the epithelial–mesenchymal transition pathway was inhibited at the intersection of the three datasets. In conclusion, the eight-gene prognostic signature proved to be a useful tool in the prognostic evaluation and facilitate personalized treatment of HNSCC patients.

Metabolic regulation in the immune response to cancer

Metabolic reprogramming in tumor‐immune interactions is emerging as a key factor affecting pro‐inflammatory carcinogenic effects and anticancer immune responses. Therefore, dysregulated metabolites and their regulators affect both cancer progression and therapeutic response. Here, we describe the molecular mechanisms through which microenvironmental, systemic, and microbial metabolites potentially influence the host immune response to mediate malignant progression and therapeutic intervention. We summarized the primary interplaying factors that constitute metabolism, immunological reactions, and cancer with a focus on mechanistic aspects. Finally, we discussed the possibility of metabolic interventions at multiple levels to enhance the efficacy of immunotherapeutic and conventional approaches for future anticancer treatments.

Targeting HDL in tumor microenvironment: New hope for cancer therapy

Epidemiological studies have shown that plasma HDL-C levels are closely related to the risk of prostate cancer, breast cancer, and other malignancies. As one of the key carriers of cholesterol regulation, high-density lipoprotein (HDL) plays an important role in tumorigenesis and cancer development through anti-inflammation, antioxidation, immune-modulation, and mediating cholesterol transportation in cancer cells and noncancer cells. In addition, the occurrence and progression of cancer are closely related to the alteration of the tumor microenvironment (TME). Cancer cells synthesize and secrete a variety of cytokines and other factors to promote the reprogramming of surrounding cells and shape the microenvironment suitable for cancer survival. By analyzing the effect of HDL on the infiltrating immune cells in the TME, as well as the relationship between HDL and tumor-associated angiogenesis, it is suggested that a moderate increase in the level of HDL in vivo with consequent improvement of the function of HDL in the TME and induction of intracellular cholesterol efflux may be a promising strategy for cancer therapy.

DNA methylome analysis identifies BMI-related epigenetic changes associated with non-small cell lung cancer susceptibility

Background

Body mass index (BMI) has been reported to be inversely associated with incident risk of non‐small cell lung cancer (NSCLC). However, the underlying mechanism is still unclear. This study aimed to investigate the role of DNA methylation in the relationship between BMI and NSCLC.

Methods

We carried out a genome‐wide DNA methylation study of BMI in peripheral blood among 2266 Chinese participants by using Illumina Methylation arrays. For the BMI‐related DNA methylation changes, their associations with NSCLC risk were further analyzed and their mediation effects on BMI‐NSCLC association were also evaluated.

Results

The methylation levels of four CpGs (cg12593793, cg17061862, cg11024682, and cg06500161, annotated to LMNA, ZNF143, SREBF1, and ABCG1, respectively) were found to be significantly associated with BMI. Methylation levels of cg12593793, cg11024682, and cg06500161 were observed to be inversely associated with NSCLC risk [OR (95%CI) =0.22 (0.16, 0.31), 0.39 (0.30, 0.50), and 0.66 (0.53, 0.82), respectively]. Additionally, cg11024682 in SREBF1 and cg06500161 in ABCG1 mediated 45.3% and 19.5% of the association between BMI and decreased NSCLC risk, respectively.

Conclusions

In this study, we identified four DNA methylation sites associated with BMI in the Chinese populations at the genome‐wide significant level. We also found that the BMI‐related methylations of SREBF1 and ABCG1 could mediate about a quintile‐to‐half of the effect of BMI on reduced NSCLC risk, which adds a potential mechanism underlying this association.

The construction and analysis of tumor-infiltrating immune cells and ceRNA networks in metastatic adrenal cortical carcinoma

Purpose: To construct and analyze tumor-infiltrating immune cell and ceRNA (competitive endogenous RNA) networks in metastatic adrenal cortical carcinoma (ACC).

Methods: A ceRNA network was established to identify the ceRNAs involved in metastasis of ACC based on 92 samples from TCGA, including 18 cases of metastasis and 74 cases of non-metastatic primary tumors. And the algorithm “cell type identification by estimating relative subsets of RNA transcripts (CIBERSORT)” was used to quantify the proportion of immune cells in ACC. In addition, predictive nomograms based on the types of important immune cells or ceRNAs were constructed to predict ACC prognosis. Moreover, we evaluated the relationships between metastatic ACC-specific immune cells and ceRNA networks to identify the potential immune gene characteristics.

Results: Ten prognostic biomarkers were identified as key members of the ceRNA network and three tumor-infiltrating immune cells were identified by CIBERSORT algorithm. Some important co-expression patterns between immune cells and ceRNAs network indicate significant correlation between Macrophages M0 and hsa-miR-130b-3p (P < 0.001), Macrophages M0 and H2AFX (P = 0.003).

Conclusions: The present study inferred that the metastasis-related ceRNAs of H2AFX, hsa-miR-130b-3p and Macrophages M0 might play important roles in ACC metastasis.

Comparative transcriptome and methylome analysis of the hindbrain in olive flounder (Paralichthys olivaceus) considering individual behavior-type and oxygen metabolism

In previous studies we employed multiple behavior assays, including propensity to feed, simulated trawl capture and escape response, to prove the presence of bold and shy personality (BP,SP) in olive flounder (Paralichthys olivaceus). However, the molecular mechanism of the different personality has not been elucidated. In this study, firstly, we found that the SP flounder had lower red blood cell count (RBC) and haemoglobin concentration (HBG) than BP flounder. Secondly, the transcriptomic profiles of the hindbrain in flounder with distinct personality were compared. A total of 144 differently expressed genes (DEGs) were identified, including 70 up-regulated and 74 down-regulated genes in SP flounder compared with BP flounder. Genes involved in hypoxia stress were detected in SP flounder, accompanied with down-regulation of ribosomal RNA synthesis. In addition, genes related with calcium signaling pathway, including endothelin, b-Fos, c-Fos and c-Jun were up-regulated in SP flounder. Furthermore, personality-related genes including UI, CCK, c-Fos showed significantly higher level in SP flounder than in BP flounder. GO enrichment analysis indicated that the GO categories "the tight junction pathway" and "lipid transport or localization pathway" were enriched in SP flounder, suggesting that the central nervous system homeostasis would be compromised. Thirdly, using a simple and scalable DNA methylation profiling method (MethylRAD), which allows for methylation analysis for DEGs in RNA-seq, we found that only part of gene expression was negatively associated with promoter methylation. Altogether, our study will not only lay a foundation for further studies on animal personality but also facilitate the selective breeding of olive flounder in aquaculture.

Using Elevated Cholesterol Synthesis as a Prognostic Marker in Wilms' Tumor: A Bioinformatic Analysis

Background

Wilms tumor is the most common renal malignancy of children. Identifying factors that could predict the prognosis of patients with Wilms tumor is clinically meaningful. Many studies found tumors with elevated cholesterol synthesis that are featured with dismal prognosis. Even in some clinical trials, people with excessive dietary cholesterol intake and high plasma low-density lipoprotein levels are observed to have increased risk for cancer. However, the role of cholesterol biosynthesis in Wilms tumor has not yet been well clarified.

Methods

RNA sequencing transcriptome data and all corresponding clinicopathological information used in our study were downloaded from the TARGET database. High-throughput sequencing (Fragments Per Kilobase of transcript per Million fragments mapped) data sets of 130 tumor samples and 6 normal samples were obtained for further analysis.

Results

Wilms tumor samples with higher activity of cholesterol synthesis are characterized with worse overall survival (P < 0.05). In addition, Wilms tumor samples with mitigated activity of cholesterol synthesis are featured with better dendritic cell (DC) function and cytolytic activity (P < 0.05). Furthermore, we constructed a prognosis model based on differential expressed cholesterol synthesis-related genes (DECSG), which could predict the OS of patients with Wilms tumor accurately. KEGG and GO analysis of differential expressed genes between tumor samples with high and low cholesterol synthesis indicated that DECSGs are highly enriched in “mitosis nuclear division,” “nuclear division,” “chromosome segregation,” “cell cycle,” “Spliceosome,” and “RNA transport.”

Conclusions

In conclusion, our study reported increased cholesterol synthesis in Wilms tumor predicts a worse prognosis and mitigated cytolytic activity, DC function, and MHC I signature in the tumor microenvironment. We also constructed a prognosis model for predicting the OS of patients with good accuracy, which is promising in clinical translation. Future studies should focus on the detailed mechanism that caused increasing cholesterol which promotes tumor progression and undermines patients' survival.

Mammalian ABCG-transporters, sterols and lipids: To bind perchance to transport?

Members of the ATP binding cassette (ABC) transporter family perform a critical function in maintaining lipid homeostasis in cells as well as the transport of drugs. In this review, we provide an update on the ABCG-transporter subfamily member proteins, which include the homodimers ABCG1, ABCG2 and ABCG4 as well as the heterodimeric complex formed between ABCG5 and ABCG8. This review focusses on progress made in this field of research with respect to their function in health and disease and the recognised transporter substrates. We also provide an update on post-translational regulation, including by transporter substrates, and well as the involvement of microRNA as regulators of transporter expression and activity. In addition, we describe progress made in identifying structural elements that have been recognised as important for transport activity. We furthermore discuss the role of lipids such as cholesterol on the transport function of ABCG2, traditionally thought of as a drug transporter, and provide a model of potential cholesterol binding sites for ABCG2.

Growth Hormone Upregulates Mediators of Melanoma Drug Efflux and Epithelial-to-Mesenchymal Transition In Vitro and In Vivo

Simple Summary

Growth hormone (GH) action is strongly implicated in the progression and therapy resistance in several types of solid tumors which overexpress the GH receptor (GHR). The aim of our study was to characterize the effects of GH and its downstream effector insulin-like growth factor 1 (IGF-1) on melanoma using in vitro and in vivo models. We confirmed an IGF-1-independent role of elevated circulating GH in upregulating key mechanisms of therapy resistance and malignancy with analyses conducted at the molecular and cellular level. We identified that GH upregulates key mechanisms of therapy resistance and metastases in melanoma tumors in an IGF-1 dependent and independent manner by upregulating multidrug efflux pumps and EMT transcription factors. Our study reveals that GH action renders an intrinsic drug resistance phenotype to the melanoma tumors—a clinically crucial property of GH verifiable in other human cancers with GHR expression.

Abstract

Growth hormone (GH) and the GH receptor (GHR) are expressed in a wide range of malignant tumors including melanoma. However, the effect of GH/insulin-like growth factor (IGF) on melanoma in vivo has not yet been elucidated. Here we assessed the physical and molecular effects of GH on mouse melanoma B16-F10 and human melanoma SK-MEL-30 cells in vitro. We then corroborated these observations with syngeneic B16-F10 tumors in two mouse lines with different levels of GH/IGF: bovine GH transgenic mice (bGH; high GH, high IGF-1) and GHR gene-disrupted or knockout mice (GHRKO; high GH, low IGF-1). In vitro, GH treatment enhanced mouse and human melanoma cell growth, drug retention and cell invasion. While the in vivo tumor size was unaffected in both bGH and GHRKO mouse lines, multiple drug-efflux pumps were up regulated. This intrinsic capacity of therapy resistance appears to be GH dependent. Additionally, epithelial-to-mesenchymal transition (EMT) gene transcription markers were significantly upregulated in vivo supporting our current and recent in vitro observations. These syngeneic mouse melanoma models of differential GH/IGF action can be valuable tools in screening for therapeutic options where lowering GH/IGF-1 action is important.

Lipoproteins and the Tumor Microenvironment

The tumor microenvironment (TME) plays a key role in enhancing the growth of malignant tumors and thus contributing to "aggressive phenotypes," supporting sustained tumor growth and metastasis. The precise interplay between the numerous components of the TME that contribute to the emergence of these aggressive phenotypes is yet to be elucidated and currently under intense investigation. The purpose of this article is to identify specific role(s) for lipoproteins as part of these processes that facilitate (or oppose) malignant growth as they interact with specific components of the TME during tumor development and treatment. Because of the scarcity of literature reports regarding the interaction of lipoproteins with the components of the tumor microenvironment, we were compelled to explore topics that were only tangentially related to this topic, to ensure that we have not missed any important concepts.

Metabolism in tumour-associated macrophages: a quid pro quo with the tumour microenvironment

Lung cancer is the leading cause of death from cancer worldwide. Recent studies demonstrated that the tumour microenvironment (TME) is pivotal for tumour progression, providing multiple targeting opportunities for therapeutic strategies. As one of the most abundant stromal cell types in the TME, tumour-associated macrophages (TAMs) exhibit high plasticity. Malignant cells alter their metabolic profiles to adapt to the limited availability of oxygen and nutrients in the TME, resulting in functional alteration of TAMs. The metabolic features of TAMs are strongly associated with their functional plasticity, which further impacts metabolic profiling in the TME and contributes to tumourigenesis and progression. Here, we review the functional determination of the TME by TAM metabolic alterations, including glycolysis as well as fatty acid and amino acid metabolism, which in turn are influenced by environmental changes. Additionally, we discuss metabolic reprogramming of TAMs to a tumouricidal phenotype as a potential antitumoural therapeutic strategy.

Tumour-associated macrophages (TAMs) display a high level of functional plasticity and altered metabolism symbolised by high sensitivity to the surrounding tumour microenvironment. The metabolism of TAMs provides novel therapeutic opportunities to treat cancer.https://bit.ly/31OqHhe

Role of cholesterol metabolism in the anticancer pharmacology of selective estrogen receptor modulators

Selective estrogen receptor modulators (SERMs) are a class of compounds that bind to estrogen receptors (ERs) and possess estrogen agonist or antagonist actions in different tissues. As such, they are widely used drugs. For instance, tamoxifen, the most prescribed SERM, is used to treat ERα-positive breast cancer. Aside from their therapeutic targets, SERMs have the capacity to broadly affect cellular cholesterol metabolism and handling, mainly through ER-independent mechanisms. Cholesterol metabolism reprogramming is crucial to meet the needs of cancer cells, and different key processes involved in cholesterol homeostasis have been associated with cancer progression. Therefore, the effects of SERMs on cholesterol homeostasis may be relevant to carcinogenesis, either by contributing to the anticancer efficacy of these compounds or, conversely, by promoting resistance to treatment. Understanding these aspects of SERMs actions could help to design more efficacious therapies. Herein we review the effects of SERMs on cellular cholesterol metabolism and handling and discuss their potential in anticancer pharmacology.

Lipid Metabolism and Cancer Immunotherapy: Immunosuppressive Myeloid Cells at the Crossroad

Cancer progression generates a chronic inflammatory state that dramatically influences hematopoiesis, originating different subsets of immune cells that can exert pro- or anti-tumor roles. Commitment towards one of these opposing phenotypes is driven by inflammatory and metabolic stimuli derived from the tumor-microenvironment (TME). Current immunotherapy protocols are based on the reprogramming of both specific and innate immune responses, in order to boost the intrinsic anti-tumoral activity of both compartments. Growing pre-clinical and clinical evidence highlights the key role of metabolism as a major influence on both immune and clinical responses of cancer patients. Indeed, nutrient competition (i.e., amino acids, glucose, fatty acids) between proliferating cancer cells and immune cells, together with inflammatory mediators, drastically affect the functionality of innate and adaptive immune cells, as well as their functional cross-talk. This review discusses new advances on the complex interplay between cancer-related inflammation, myeloid cell differentiation and lipid metabolism, highlighting the therapeutic potential of metabolic interventions as modulators of anticancer immune responses and catalysts of anticancer immunotherapy.

Lipoprotein-based drug delivery

Lipoproteins (LPs) are circulating heterogeneous nanoparticles produced by the liver and intestines. LPs play a major role in the transport of dietary and endogenous lipids to target cells through cell membrane receptors or cell surface-bound lipoprotein lipase. The stability, biocompatibility, and selective transport of LPs make them promising delivery vehicles for various therapeutic and imaging agents. This review discusses isolation, manufacturing, and drug loading techniques used for LP-based drug delivery, as well as recent applications for diagnosis and treatment of cancer, atherosclerosis, and other life-threatening diseases.

LC3-Associated Phagocytosis (LAP): A Potentially Influential Mediator of Efferocytosis-Related Tumor Progression and Aggressiveness

One aim of cancer therapies is to induce apoptosis of tumor cells. Efficient removal of the apoptotic cells requires coordinated efforts between the processes of efferocytosis and LC3-associated phagocytosis (LAP). However, this activity has also been shown to produce anti-inflammatory and immunosuppressive signals that can be utilized by live tumor cells to evade immune defense mechanisms, resulting in tumor progression and aggressiveness. In the absence of LAP, mice exhibit suppressed tumor growth during efferocytosis, while LAP-sufficient mice show enhanced tumor progression. Little is known about how LAP or its regulators directly affect efferocytosis, tumor growth and treatment responses, and identifying the mechanisms involved has the potential to lead to the discovery of novel approaches to target cancer cells. Also incompletely understood is the direct effect of apoptotic cancer cells on LAP. This is particularly important as induction of apoptosis by current cytotoxic cancer therapies can potentially stimulate LAP following efferocytosis. Herein, we highlight the current understanding of the role of LAP and its relationship with efferocytosis in the tumor microenvironment with a view to presenting novel therapeutic strategies.

Asaronic Acid Inhibited Glucose-Triggered M2-Phenotype Shift Through Disrupting the Formation of Coordinated Signaling of IL-4Rα-Tyk2-STAT6 and GLUT1-Akt-mTOR-AMPK

Macrophage polarization has been implicated in the pathogenesis of metabolic diseases such as obesity, diabetes, and atherosclerosis. Macrophages responsiveness to polarizing signals can result in their functional phenotype shifts. This study examined whether high glucose induced the functional transition of M2 macrophages, which was inhibited by asaronic acid, one of purple perilla constituents. J774A.1 murine macrophages were incubated with 40 ng/mL interleukin (IL)-4 or exposed to 33 mM glucose in the presence of 1-20 μΜ asaronic acid. In macrophages treated with IL-4 for 48 h, asaronic acid further accelerated cellular induction of the M2 markers of IL-10, arginase-1, CD163, and PPARγ via increased IL-4-IL-4Rα interaction and activated Tyk2-STAT6 pathway. Asaronic acid promoted angiogenic and proliferative capacity of M2-polarized macrophages, through increasing expression of VEGF, PDGF, and TGF-β. In glucose-loaded macrophages, there was cellular induction of IL-4, IL-4 Rα, arginase-1, and CD163, indicating that high glucose skewed naïve macrophages toward M2 phenotypes via an IL-4-IL-4Rα interaction. However, asaronic acid inhibited M2 polarization in diabetic macrophages in parallel with inactivation of Tyk2-STAT6 pathway and blockade of GLUT1-mediated metabolic pathway of Akt-mTOR-AMPKα. Consequently, asaronic acid deterred functional induction of COX-2, CTGF, α-SMA, SR-A, SR-B1, and ABCG1 in diabetic macrophages with M2 phenotype polarity. These results demonstrated that asaronic acid allayed glucose-activated M2-phenotype shift through disrupting coordinated signaling of IL-4Rα-Tyk2-STAT6 in parallel with GLUT1-Akt-mTOR-AMPK pathway. Thus, asaronic acid has therapeutic potential in combating diabetes-associated inflammation, fibrosis, and atherogenesis through inhibiting glucose-evoked M2 polarization.

Interferon-mediated reprogramming of membrane cholesterol to evade bacterial toxins

Plasma membranes of animal cells are enriched for cholesterol. Cholesterol-dependent cytolysins (CDCs) are pore-forming toxins secreted by bacteria that target membrane cholesterol for their effector function. Phagocytes are essential for clearance of CDC-producing bacteria; however, the mechanisms by which these cells evade the deleterious effects of CDCs are largely unknown. Here, we report that interferon (IFN) signals convey resistance to CDC-induced pores on macrophages and neutrophils. We traced IFN-mediated resistance to CDCs to the rapid modulation of a specific pool of cholesterol in the plasma membrane of macrophages without changes to total cholesterol levels. Resistance to CDC-induced pore formation requires the production of the oxysterol 25-hydroxycholesterol (25HC), inhibition of cholesterol synthesis and redistribution of cholesterol to an esterified cholesterol pool. Accordingly, blocking the ability of IFN to reprogram cholesterol metabolism abrogates cellular protection and renders mice more susceptible to CDC-induced tissue damage. These studies illuminate targeted regulation of membrane cholesterol content as a host defense strategy.

Lung Cancer Inhibition by Betulinic Acid Nanoparticles via Adenosine 5'-Triphosphate (ATP)-Binding Cassette Transporter G1 Gene Downregulation

BACKGROUND Despite scientific advancement in radiotherapy and chemotherapy, the 5-year survival rate of lung cancer patients is around 15%. The present study explored the anticancer potential of betulinic acid nanoparticles against lung cancer cells. MATERIAL AND METHODS The proliferative changes in lung cancer cells by betulinic acid nanoparticles were measured by MTT assay. Cell cycle analysis was performed by flow cytometry using propidium iodide stain. Transwell and wound healing assay were used for determination of HKULC2 cell metastatic potential. RESULTS The betulinic acid nanoparticle treatment significantly (P<0.05) reduced proliferation of HKULC2, H1299, and H23 cells. The proliferation of HKULC2, H1299, and H23 cells was reduced to 33%, 28% and 24%, respectively on treatment with 10 µM of betulinic acid nanoparticles. The results from flow cytometry showed that betulinic acid nanoparticle exposure lead to cell cycle arrest in G1 phase in HKULC2 cells. Treatment with betulinic acid nanoparticles markedly decreased migration potential of HKULC2 cells. The invasive ability of HKULC2 cells was also suppressed markedly on exposure to betulinic acid nanoparticles. Western blotting of HKULC2 cells showed that betulinic acid nanoparticles promoted the expression of p21 and p53 and downregulated CD133, ALDH, BCL2, MCL1, and c-Myc expression. Betulinic acid nanoparticles reduced the expression of ABCG1 protein markedly. CONCLUSIONS The present study demonstrated that betulinic acid nanoparticles inhibit proliferation, metastatic ability, and arrest cell cycle in lung cancer cells through downregulation of ABCG1 oncogene expression. Therefore, betulinic acid nanoparticles may be used as therapeutic agent for the treatment of lung cancer.

Cholesterol and beyond - The role of the mevalonate pathway in cancer biology

Cancer is a multifaceted global disease. Transformation of a normal to a malignant cell takes several steps, including somatic mutations, epigenetic alterations, metabolic reprogramming and loss of cell growth control. Recently, the mevalonate pathway has emerged as a crucial regulator of tumor biology and a potential therapeutic target. This pathway controls cholesterol production and posttranslational modifications of Rho-GTPases, both of which are linked to several key steps of tumor progression. Inhibitors of the mevalonate pathway induce pleiotropic antitumor-effects in several human malignancies, identifying the pathway as an attractive candidate for novel therapies. In this review, we will provide an overview about the role and regulation of the mevalonate pathway in certain aspects of cancer initiation and progression and its potential for therapeutic intervention in oncology.