Expression of LXR‑β, ABCA1 and ABCG1 in human triple‑negative breast cancer tissues

Tumour-associated macrophage-derived DOCK7-enriched extracellular vesicles drive tumour metastasis in colorectal cancer via the RAC1/ABCA1 axis

BACKGROUND

Metastasis accounts for the majority of deaths among patients with colorectal cancer (CRC). Here, the regulatory role of tumour-associated macrophages (TAMs) in CRC metastasis was explored.

METHODS

Immunohistochemical (IHC) analysis of the TAM biomarker CD163 was conducted to evaluate TAM infiltration in CRC. Transwell assays and an ectopic liver metastasis model were established to evaluate the metastatic ability of tumour cells. RNA sequencing (RNA-seq) and liquid chromatography-mass spectrometry (LC-MS) were applied to identify the differentially expressed genes and proteins in CRC cells and in TAM-derived extracellular vesicles (EVs). Cholesterol content measurement, a membrane fluidity assay and filipin staining were performed to evaluate cholesterol efflux in CRC cells.

RESULTS

Our results showed that TAM infiltration is positively correlated with CRC metastasis. TAMs can facilitate the migration and invasion of MC-38 and CT-26 cells via EVs. According to the RNA-seq data, TAM-EVs increase cholesterol efflux and enhance membrane fluidity in CRC cells by regulating ABCA1 expression, thus affecting the motility of CRC cells. Mechanistically, DOCK7 packaged in TAM-EVs can activate RAC1 in CRC cells and subsequently upregulate ABCA1 expression by phosphorylating AKT and FOXO1. Moreover, IHC analysis of ABCA1 in patients with liver-metastatic CRC indicated that ABCA1 expression is significantly greater in metastatic liver nodules than in primary CRC tumours.

CONCLUSIONS

Overall, our findings suggest that DOCK7 delivered via TAM-EVs could regulate cholesterol metabolism in CRC cells and CRC cell metastasis through the RAC1/AKT/FOXO1/ABCA1 axis. DOCK7 could thus be a new therapeutic target for controlling CRC metastasis.

Exploring the Regulatory Roles of miR-21, miR-15, and miR-let-7 in ABC Transporter-Mediated Chemoresistance: Implications for Breast Cancer Etiology and Treatment

Breast cancer, a prevalent and aggressive malignancy among females worldwide, poses a significant challenge due to resistance to chemotherapy and tyrosine kinase inhibitors. In breast cancer, ABC transporters play a pivotal role by contributing to chemoresistance and drug efflux, a phenomenon observed also in various cancers. This study aims to elucidate the role of oncomiRs miR-15, miR-21, and miR-let-7 in breast cancer etiology and their impact on chemotherapy-resistant oncogenes ABCA1, ABCB1, and ABCC1. Blood samples from female breast cancer patients were analyzed to assess the expression levels of miRNAs and oncogenes by qPCR. Significantly, miR-21 exhibited a positive correlation with ABCA1 in newly diagnosed patients, while miR-15 and miR-let-7 displayed a positive correlation with ABCA1 in the metastasis group. Additionally, miR-let-7 demonstrated a negative correlation with ABCC1 in newly diagnosed patients. This study's findings provide valuable insights into the cancer etiology of these miRNAs and their interactions with ABCA1, ABCB1, and ABCC1. Targeting these interactions holds promise for mitigating drug efflux and chemoresistance in breast cancer, potentially enhancing current treatments and improving patient outcomes.

Multiplex immunohistochemistry defines two cholesterol metabolism patterns predicting immunotherapeutic outcomes in gastric cancer

BACKGROUND

The role of cholesterol metabolism in gastric cancer (GC) and its implications for tumor characteristics and immunotherapy response remain poorly understood. In this study, our aim was to investigate this role, identify associated metabolic subtypes, and assess their clinical implications in GC.

METHODS

We conducted a comprehensive analysis of cholesterol metabolism genes (CMGs) using transcriptomic data from TCGA and GEO. Based on 23 representative CMGs, we classified GC into metabolic subtypes. We evaluated clinical features and immune cell infiltration between these subtypes. Additionally, we identified a CMG signature and assessed its clinical relevance in GC. We retrospectively enrolled thirty-five GC patients receiving chemotherapy plus a PD-1 inhibitor to assess the CMG signature using multiplex immunohistochemistry.

RESULTS

Our analysis revealed two cholesterol metabolism subtypes in GC: Cholesterol Metabolism Type 1 (CMT1) and Cholesterol Metabolism Type 2 (CMT2). These subtypes exhibited distinct patterns: CMT1 indicated heightened cholesterol biosynthesis, while CMT2 showed abnormal cholesterol transport. CMT2 was associated with unfavorable clinical features, enriched malignant pathways, and a pro-tumor immune microenvironment. Furthermore, we developed a five-CMG prognostic signature (ABCA1, NR1H3, TSPO, NCEH1, and HMGCR) that effectively predicted the prognosis of patients with GC and their response to chemotherapy plus a PD-1 inhibitor. This signature was validated in a clinical cohort using multiplex immunohistochemistry.

CONCLUSION

Our results highlight the effectiveness of cholesterol metabolism patterns as biomarkers for predicting the prognosis and immunotherapy response in GC. The expression of cholesterol metabolism genes and the assessment of cholesterol metabolism patterns have the potential to predict the outcome of immunotherapy and guide treatment strategies.

Integrated analysis of single-cell and bulk RNA-sequencing reveals the poor prognostic value of ABCA1 in gastric adenocarcinoma

PURPOSE

ATP-binding cassette A1 (ABCA1) is a potential prognostic marker for various tumor types. However, the biological effects and prognostic value of ABCA1 in gastric adenocarcinoma (GAC) remain unknown.

METHODS

GAC-associated single-cell RNA and bulk RNA-sequencing (bulk-seq) data were obtained from the Gene Expression Omnibus and The Cancer Genome Atlas databases, respectively. The differential expression of ABCA1 between GAC and normal gastric tissues was analyzed based on the bulk-seq data. Additionally, the relationship between ABCA1 expression and various clinicopathological features was explored. Furthermore, Kaplan-Meier survival and Cox regression analyses were performed to establish the prognostic value of ABCA1. The relationships between ABCA1 expression and anti-tumor drug sensitivity and immune checkpoints were also explored. Finally, the biological functions of ABCA1 were evaluated at the single-cell level, and in vitro studies were performed to assess the effects of ABCA1 on GAC cell proliferation and invasion.

RESULTS

ABCA1 expression is significantly elevated in GAC samples compared with that in normal gastric tissues. Clinical features and survival analysis revealed that high ABCA1 expression is associated with poor clinical phenotypes and prognosis, whereas Cox analysis identified ABCA1 as an independent risk factor for patients with GAC. Furthermore, high ABCA1 expression suppresses sensitivity to various chemotherapeutic drugs, including cisplatin and mitomycin, while upregulating immune checkpoints. ABCA1-overexpressing macrophages are associated with adverse clinical phenotypes in GAC and express unique ligand-receptor pairs that drive GAC progression. In vitro, ABCA1-knockdown GAC cells exhibit significantly inhibited proliferative and invasive properties.

CONCLUSION

High ABCA1 expression promotes an adverse immune microenvironment and low survival rates in patients with GAC. Furthermore, ABCA1 and ABCA1-producing macrophages may serve as novel molecular targets in GAC treatment.

Drug metabolism-related gene ABCA1 augments temozolomide chemoresistance and immune infiltration abundance of M2 macrophages in glioma

Gliomas are the most prevalent primary tumor in the central nervous system, with an abysmal 5-year survival rate and alarming mortality. The current standard management of glioma is maximum resection of tumors followed by postoperative chemotherapy with temozolomide (TMZ) or radiotherapy. Low chemosensitivity of TMZ in glioma treatment eventuates limited therapeutic efficacy or treatment failure. Hence, overcoming the resistance of glioma to TMZ is a pressing question. Our research centered on identifying the drug metabolism-related genes potentially involved in TMZ-treated resistance of glioma through several bioinformatics datasets and cell experiments. One efflux transporter, ATP-binding cassette transporter subfamily A1 (ABCA1), was discovered with an upregulated expression level and signaled poor clinical outcomes for glioma patients. The transcript level of ABCA1 significantly elevated across the TMZ-resistant glioma cells in contrast with non-resistant cells. Over-expressed ABCA1 restrained the drug activity of TMZ, and ABCA1 knockdown improved the treatment efficacy. Meanwhile, the results of molecular docking between ABCA1 protein and TMZ showed a high binding affinity. Additionally, co-expression and immunological analysis revealed that ABCA1 facilitates the immune infiltration of M2 macrophages in glioma, thereby stimulating tumor growth and aggravating the poor survival of patients. Altogether, we discovered that the ABCA1 transporter was involved in TMZ chemoresistance and the immune infiltration of M2 macrophages in glioma. Treatment with TMZ after ABCA1 knockdown enhances the chemosensitivity, suggesting that inhibition of ABCA1 may be a potential strategy for improving the therapeutic efficacy of gliomas.

Increased plasma lipids in triple-negative breast cancer and impairment in HDL functionality in advanced stages of tumors

The association between plasma lipids and breast cancer (BC) has been extensively explored although results are still conflicting especially regarding the relationship with high-density lipoprotein cholesterol (HDLc) levels. HDL mediates cholesterol and oxysterol removal from cells limiting sterols necessary for tumor growth, inflammation, and metastasis and this may not be reflected by measuring HDLc. We addressed recently diagnosed, treatment-naïve BC women (n = 163), classified according to molecular types of tumors and clinical stages of the disease, in comparison to control women (CTR; n = 150) regarding plasma lipids and lipoproteins, HDL functionality and composition in lipids, oxysterols, and apo A-I. HDL was isolated by plasma discontinuous density gradient ultracentrifugation. Lipids (total cholesterol, TC; triglycerides, TG; and phospholipids, PL) were determined by enzymatic assays, apo A-I by immunoturbidimetry, and oxysterols (27, 25, and 24-hydroxycholesterol), by gas chromatography coupled with mass spectrometry. HDL-mediated cell cholesterol removal was determined in macrophages previously overloaded with cholesterol and ¹⁴C-cholesterol. Lipid profile was similar between CTR and BC groups after adjustment per age. In the BC group, lower concentrations of TC (84%), TG (93%), PL (89%), and 27-hydroxicholesterol (61%) were observed in HDL, although the lipoprotein ability in removing cell cholesterol was similar to HDL from CRT. Triple-negative (TN) BC cases presented higher levels of TC, TG, apoB, and non-HDLc when compared to other molecular types. Impaired HDL functionality was observed in more advanced BC cases (stages III and IV), as cholesterol efflux was around 28% lower as compared to stages I and II. The altered lipid profile in TN cases may contribute to channeling lipids to tumor development in a hystotype with a more aggressive clinical history. Moreover, findings reinforce the dissociation between plasma levels of HDLc and HDL functionality in determining BC outcomes.

Circular Sponge against miR-21 Enhances the Antitumor Activity of Doxorubicin against Breast Cancer Cells

Breast cancer is the most common type of cancer in women, with chemotherapy being the main strategy. However, its effectiveness is reduced by drug resistance mechanisms. miR-21 is upregulated in breast cancer that has been linked to drug resistance and carcinogenic processes. Our aim was to capture miR-21 with a circular sponge (Circ-21) and thus inhibit the carcinogenic processes and drug resistance mechanisms in which it participates. Proliferation, migration, colony formation, cell cycle, and poly [ADP-ribose] polymerase 1 (PARP-1) and vascular endothelial growth factor (VEGF) detection assays were performed with MCF7 breast cancer cells and MCF10A non-tumor cells. In addition, doxorubicin resistance tests and detection of drug resistance gene expression were performed in MCF7 cells. Reduction in proliferation, as well as migration and colony formation, increased PARP-1 expression, inhibition of VEGF expression and cell cycle arrest in G2/M phase were displayed in the Circ-21 MCF7, which were not observed in the MCF10A cells. Furthermore, in the MCF7 cells, the Circ-21 enhanced the antitumor activity of doxorubicin and decreased the expression of resistance genes: ABCA1, ABCC4, and ABCC5. Based on these results, the use of Circ-21 can be considered a first step for the establishment of an effective gene therapy in the treatment of breast cancer.

Alteration of cholesterol distribution at the plasma membrane of cancer cells: From evidence to pathophysiological implication and promising therapy strategy

Cholesterol-enriched domains are nowadays proposed to contribute to cancer cell proliferation, survival, death and invasion, with important implications in tumor progression. They could therefore represent promising targets for new anticancer treatment. However, although diverse strategies have been developed over the years from directly targeting cholesterol membrane content/distribution to adjusting sterol intake, all approaches present more or less substantial limitations. Those data emphasize the need to optimize current strategies, to develop new specific cholesterol-targeting anticancer drugs and/or to combine them with additional strategies targeting other lipids than cholesterol. Those objectives can only be achieved if we first decipher (i) the mechanisms that govern the formation and deformation of the different types of cholesterol-enriched domains and their interplay in healthy cells; (ii) the mechanisms behind domain deregulation in cancer; (iii) the potential generalization of observations in different types of cancer; and (iv) the specificity of some alterations in cancer vs. non-cancer cells as promising strategy for anticancer therapy. In this review, we will discuss the current knowledge on the homeostasis, roles and membrane distribution of cholesterol in non-tumorigenic cells. We will then integrate documented alterations of cholesterol distribution in domains at the surface of cancer cells and the mechanisms behind their contribution in cancer processes. We shall finally provide an overview on the potential strategies developed to target those cholesterol-enriched domains in cancer therapy.

Bioinformatic Prioritization and Functional Annotation of GWAS-Based Candidate Genes for Primary Open-Angle Glaucoma

Background: Primary open-angle glaucoma (POAG) is the most prevalent glaucoma subtype, but its exact etiology is still unknown. In this study, we aimed to prioritize the most likely ‘causal’ genes and identify functional characteristics and underlying biological pathways of POAG candidate genes. Methods: We used the results of a large POAG genome-wide association analysis study from GERA and UK Biobank cohorts. First, we performed systematic gene-prioritization analyses based on: (i) nearest genes; (ii) nonsynonymous single-nucleotide polymorphisms; (iii) co-regulation analysis; (iv) transcriptome-wide association studies; and (v) epigenomic data. Next, we performed functional enrichment analyses to find overrepresented functional pathways and tissues. Results: We identified 142 prioritized genes, of which 64 were novel for POAG. BICC1, AFAP1, and ABCA1 were the most highly prioritized genes based on four or more lines of evidence. The most significant pathways were related to extracellular matrix turnover, transforming growth factor-β, blood vessel development, and retinoic acid receptor signaling. Ocular tissues such as sclera and trabecular meshwork showed enrichment in prioritized gene expression (>1.5 fold). We found pleiotropy of POAG with intraocular pressure and optic-disc parameters, as well as genetic correlation with hypertension and diabetes-related eye disease. Conclusions: Our findings contribute to a better understanding of the molecular mechanisms underlying glaucoma pathogenesis and have prioritized many novel candidate genes for functional follow-up studies.

Suppression of the ABCA1 Cholesterol Transporter Impairs the Growth and Migration of Epithelial Ovarian Cancer

Simple Summary

Epithelial ovarian cancer (EOC) is the most lethal gynaecological cancer. Over 80% of cases have already spread at diagnosis, and these patients face a five-year survival rate of 35%. EOC cells often spread to the greater omentum, an abdominal fat pad. Here, EOC cells take-up cholesterols. Excessive amounts of cholesterol are lethal; thus, we proposed that the ABCA1 cholesterol transporter exports cholesterol from serous EOC cells to maintain cholesterol balance. Indeed, we found that reducing the level of ABCA1 could suppress serous EOC growth in two-dimensional as well as three-dimensional cell culture and also hindered their migration, a key process required for cancer spread. We also identified drugs that impair EOC cell growth by inhibiting cholesterol export. Our data demonstrate that disrupting the cholesterol balance by targeting ABCA1 may be an effective treatment strategy for EOC patients.

Abstract

Background: Epithelial ovarian cancer (EOC) is the most lethal gynaecological malignancy with over 80% of cases already disseminated at diagnosis and facing a dismal five-year survival rate of 35%. EOC cells often spread to the greater omentum where they take-up cholesterol. Excessive amounts of cholesterol can be cytocidal, suggesting that cholesterol efflux through transporters may be important to maintain homeostasis, and this may explain the observation that high expression of the ATP-binding cassette A1 (ABCA1) cholesterol transporter has been associated with poor outcome in EOC patients. Methods: ABCA1 expression was silenced in EOC cells to investigate the effect of inhibiting cholesterol efflux on EOC biology through growth and migration assays, three-dimensional spheroid culture and cholesterol quantification. Results: ABCA1 suppression significantly reduced the growth, motility and colony formation of EOC cell lines as well as the size of EOC spheroids, whilst stimulating expression of ABCA1 reversed these effects. In serous EOC cells, ABCA1 suppression induced accumulation of cholesterol. Lowering cholesterol levels using methyl-B-cyclodextrin rescued the effect of ABCA1 suppression, restoring EOC growth. Furthermore, we identified FDA-approved agents that induced cholesterol accumulation and elicited cytocidal effects in EOC cells. Conclusions: Our data demonstrate the importance of ABCA1 in maintaining cholesterol balance and malignant properties in EOC cells, highlighting its potential as a therapeutic target for this disease.

Effect of Cold Atmospheric Plasma on Epigenetic Changes, DNA Damage, and Possibilities for Its Use in Synergistic Cancer Therapy

Cold atmospheric plasma has great potential for use in modern medicine. It has been used in the clinical treatment of skin diseases and chronic wounds, and in laboratory settings it has shown effects on selective decrease in tumour-cell viability, reduced tumour mass in animal models and stem-cell proliferation. Many researchers are currently focusing on its application to internal structures and the use of plasma-activated liquids in tolerated and effective human treatment. There has also been analysis of plasma's beneficial synergy with standard pharmaceuticals to enhance their effect. Cold atmospheric plasma triggers various responses in tumour cells, and this can result in epigenetic changes in both DNA methylation levels and histone modification. The expression and activity of non-coding RNAs with their many important cell regulatory functions can also be altered by cold atmospheric plasma action. Finally, there is ongoing debate whether plasma-produced radicals can directly affect DNA damage in the nucleus or only initiate apoptosis or other forms of cell death. This article therefore summarises accepted knowledge of cold atmospheric plasma's influence on epigenetic changes, the expression and activity of non-coding RNAs, and DNA damage and its effect in synergistic treatment with routinely used pharmaceuticals.

Lipid Metabolism Disorders in the Comorbid Course of Nonalcoholic Fatty Liver Disease and Chronic Obstructive Pulmonary Disease

Non-alcoholic fatty liver disease (NAFLD) is currently among the most common liver diseases. Unfavorable data on the epidemiology of metabolic syndrome and obesity have increased the attention of clinicians and researchers to the problem of NAFLD. The research results allow us to emphasize the systemicity and multifactoriality of the pathogenesis of liver parenchyma lesion. At the same time, many aspects of its classification, etiology, and pathogenesis remain controversial. Local and systemic metabolic disorders are also a part of the pathogenesis of chronic obstructive pulmonary disease and can influence its course. The present article analyzes the metabolic pathways mediating the links of impaired lipid metabolism in NAFLD and chronic obstructive pulmonary disease (COPD). Free fatty acids, cholesterol, and ceramides are involved in key metabolic and inflammatory pathways underlying the pathogenesis of both diseases. Moreover, inflammation and lipid metabolism demonstrate close links in the comorbid course of NAFLD and COPD.

Characterization and prognostic value of LXR splice variants in triple-negative breast cancer

Activity of liver x receptor (LXR), the homeostatic regulator of cholesterol metabolism, is elevated in triple-negative breast cancer (BCa) relative to other BCa subtypes, driving drug resistance and metastatic gene signatures. The loci encoding LXRα and LXRβ produce multiple alternatively spliced proteins, but the true range of variants and their relevance to cancer remain poorly defined. Here, we report seven LXR splice variants, three of which have not previously been reported and five that were prognostic for disease-free survival. Expression of full-length LXRα splice variants was associated with poor prognosis, consistent with a role as an oncogenic driver of triple-negative tumor pathophysiology. Contrary to this was the observation that high expression of truncated LXRα splice variants or any LXRβ splice variant was associated with longer survival. These findings indicate that LXR isoform abundance is an important aspect of understanding the link between dysregulated cholesterol metabolism and cancer pathophysiology.

Cytoplasmic LXR expression is an independent marker of poor prognosis for patients with early stage primary breast cancer

Purpose

The aim of this study was to investigate the expression of liver X receptors α/β (LXR) in primary breast cancer (BC) tissues and to analyze its correlations with clinicopathological parameters including patient survival.

Methods

In a well-characterized cohort of 305 primary BC, subcellular distribution of LXR was evaluated by immunohistochemistry. Correlations with clinicopathological characteristics as well as with patient outcome were analyzed.

Results

LXR was frequently localized in both nuclei and cytoplasms of BC cells, with stronger staining in nuclei. Total and nuclear LXR expression was positively correlated with ER and PR status. Overall survival analysis demonstrated that cytoplasmic LXR was significantly correlated with poor survival and appeared as an independent marker of poor prognosis, in stage I but not in stage II–III tumors

Conclusion

Altogether, these data suggest that cytoplasmic LXR could be defined as a prognostic marker in early stage primary BC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-021-03670-y.

Participation of ABCA1 Transporter in Pathogenesis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is the important medical and social problem. According to modern concepts, COPD is a chronic inflammatory disease, macrophages play a key role in its pathogenesis. Macrophages are heterogeneous in their functions, which is largely determined by their immunometabolic profile, as well as the features of lipid homeostasis, in which the ATP binding cassette transporter A1 (ABCA1) plays an essential role. The objective of this work is the analysis of the ABCA1 protein participation and the function of reverse cholesterol transport in the pathogenesis of COPD. The expression of the ABCA1 gene in lung tissues takes the second place after the liver, which indicates the important role of the carrier in lung function. The participation of the transporter in the development of COPD consists in provision of lipid metabolism, regulation of inflammation, phagocytosis, and apoptosis. Violation of the processes in which ABCA1 is involved may be a part of the pathophysiological mechanisms, leading to the formation of a heterogeneous clinical course of the disease.

The Role of the ATP-Binding Cassette A1 (ABCA1) in Human Disease

Cholesterol homeostasis is essential in normal physiology of all cells. One of several proteins involved in cholesterol homeostasis is the ATP-binding cassette transporter A1 (ABCA1), a transmembrane protein widely expressed in many tissues. One of its main functions is the efflux of intracellular free cholesterol and phospholipids across the plasma membrane to combine with apolipoproteins, mainly apolipoprotein A-I (Apo A-I), forming nascent high-density lipoprotein-cholesterol (HDL-C) particles, the first step of reverse cholesterol transport (RCT). In addition, ABCA1 regulates cholesterol and phospholipid content in the plasma membrane affecting lipid rafts, microparticle (MP) formation and cell signaling. Thus, it is not surprising that impaired ABCA1 function and altered cholesterol homeostasis may affect many different organs and is involved in the pathophysiology of a broad array of diseases. This review describes evidence obtained from animal models, human studies and genetic variation explaining how ABCA1 is involved in dyslipidemia, coronary heart disease (CHD), type 2 diabetes (T2D), thrombosis, neurological disorders, age-related macular degeneration (AMD), glaucoma, viral infections and in cancer progression.

Aberrant DNA Methylation of ABC Transporters in Cancer

ATP-binding cassette (ABC) transporters play a crucial role in multidrug resistance (MDR) of cancers. They function as efflux pumps, resulting in limited effectiveness or even failure of therapy. Increasing evidence suggests that ABC transporters are also involved in tumor initiation, progression, and metastasis. Tumors frequently show multiple genetic and epigenetic abnormalities, including changes in histone modification and DNA methylation. Alterations in the DNA methylation status of ABC transporters have been reported for a variety of cancer types. In this review, we outline the current knowledge of DNA methylation of ABC transporters in cancer. We give a brief introduction to structure, function, and gene regulation of ABC transporters that have already been investigated for their DNA methylation status in cancer. After giving an overview of the applied methodologies and the CpGs analyzed, we summarize and discuss the findings on aberrant DNA methylation of ABC transporters by cancer types. We conclude our review with the discussion of the potential to target aberrant DNA methylation of ABC transporters for cancer therapy.

ABCA8 is regulated by miR-374b-5p and inhibits proliferation and metastasis of hepatocellular carcinoma through the ERK/ZEB1 pathway

Background

ATP binding cassette subfamily A member 8 (ABCA8) belongs to the ATP binding cassette (ABC) transporter superfamily. ABCA8 is a transmembrane transporter responsible for the transport of organics, such as cholesterol, and drug efflux. Some members of the ABC subfamily, such as ABCA1, may inhibit cancer development. However, the mechanism of ABCA8 in the process of cancer activation is still ambiguous.

Methods

The expression of ABCA8 in human hepatocellular carcinoma (HCC) tissues and cell lines was examined using qPCR, immunoblotting, and immunohistochemical staining. The effects of ABCA8 on the proliferation and metastasis of HCC were examined using in vitro and in vivo functional tests. A luciferase reporter assay was performed to explore the binding between microRNA-374b-5p (miR-374b-5p) and the ABCA8 3′-untranslated region (UTR).

Results

ABCA8 was frequently down-regulated in HCC and this down-regulation was negatively correlated with prognosis. The overexpression of ABCA8 inhibited growth and metastasis in HCC, whereas the knockdown of ABCA8 exerted the antithetical effects both in vivo and in vitro. ABCA8 was down-regulated by miR-374b-5p; this down-regulation can induce epithelial transformation to mesenchyme via the ERK/ZEB1 signaling pathway and promote HCC progression.

Conclusion

We exposed the prognostic value of ABCA8 in HCC, and illuminated a novel pathway in ABCA8-regulated inhibition of HCC tumorigenesis and metastasis. These findings may lead to a new targeted therapy for HCC through the regulation of ABCA8, and miR-374b-5p.

Cholesterol, Oxysterols and LXRs in Breast Cancer Pathophysiology

Breast cancer is the most frequent cancer among women. In 2018, it is estimated that 627,000 women died from breast cancer. This is approximately 15% of all cancer deaths among women (WHO 2018). Breast cancer is a multifactorial chronic disease. While important progress has been made to treat patients, many questions regarding aspects of this disease relating to carcinogenesis are still open. During carcinogenesis, cells exhibit cholesterol homeostasis deregulation. This results in an accumulation of intracellular cholesterol, which is required to sustain their high growth rate. Cholesterol efflux and influx are two metabolic pathways that are necessary to prevent cholesterol accumulation in the cells. Liver X receptors (LXRs) are nuclear receptors that, upon activation, induce the expression of ABC transporters, responsible for promoting cholesterol efflux, and the expression of IDOL (inducible degrader of low-density lipoprotein receptor), in charge of reducing cholesterol influx. Oxysterols, oxygenated derivatives of cholesterol formed through different pathways, have been discovered as LXR-specific ligands. Some oxysterols are involved in tumor formation while others are considered anti-tumor agents. In the present review, we discuss the involvement of cholesterol, oxysterols and LXRs in breast cancer pathophysiology, with an emphasis on the biological effects of LXR ligands.