The HDL receptor SR-BI is associated with human prostate cancer progression and plays a possible role in establishing androgen independence

Adaptations of membrane trafficking in cancer and tumorigenesis

Membrane trafficking, a fundamental cellular process encompassing the transport of molecules to specific organelles, endocytosis at the plasma membrane and protein secretion, is crucial for cellular homeostasis and signalling. Cancer cells adapt membrane trafficking to enhance their survival and metabolism, and understanding these adaptations is vital for improving patient responses to therapy and identifying therapeutic targets. In this Review, we provide a concise overview of major membrane trafficking pathways and detail adaptations in these pathways, including COPII-dependent endoplasmic reticulum (ER)-to-Golgi vesicle trafficking, COPI-dependent retrograde Golgi-to-ER trafficking and endocytosis, that have been found in cancer. We explore how these adaptations confer growth advantages or resistance to cell death and conclude by discussing the potential for utilising this knowledge in developing new treatment strategies and overcoming drug resistance for cancer patients.

Lipid Metabolism as a Potential Target of Liver Cancer

Hepatocellular carcinoma (HCC) stands as a severe malignant tumor with a profound impact on overall health, often accompanied by an unfavorable prognosis. Despite some advancements in the diagnosis and treatment of this disease, improving the prognosis of HCC remains a formidable challenge. It is noteworthy that lipid metabolism plays a pivotal role in the onset, development, and progression of tumor cells. Existing research indicates the potential application of targeting lipid metabolism in the treatment of HCC. This review aims to thoroughly explore the alterations in lipid metabolism in HCC, offering a detailed account of the potential advantages associated with innovative therapeutic strategies targeting lipid metabolism. Targeting lipid metabolism holds promise for potentially enhancing the prognosis of HCC.

Deficiency of SR-B1 reduced the tumor load of colitis-induced or APCmin /+ -induced colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is one of the most common tumors in the world. Cholesterol plays an important role in the pathogenesis of tumors. One of the cholesterol transporters, scavenger receptor class B type 1 (SR-B1), a multi-ligand membrane receptor protein, is expressed in the intestines which also highly expressed in various tumors. But the potential mechanism of SR-B1 in CRC development has not been reported.

AIMS

This study aimed to clarify the importance of SR-B1 in the development and prognosis of CRC as much as possible to provide a possible strategy in CRC treatment.

MATERIALS & METHODS

In this study, we used SR-B1 gene knockdown mice to study the effect of SR-B1 on colitis-induced or APCmin/+ -induced CRC. The expression of related molecules were detected through the immunohistochemistry and hematoxylin-eosin staining, western blot analysis, and Flow cytometry. The gene expression and microbiota in microenvironment of CRC mice were analyzed through eukaryotic mRNA sequencing and 16S rRNA high-throughput sequencing.

RESULTS

The results showed that SR-B1 knockdown reduced the tumor load of colitis-induced or APCmin/+ -induced CRC. SR-B1 knockdown improved the immune microenvironment by affecting the level of tumor-associated macrophage (TAM), mononuclear myeloid-derived suppressor cells (M-MDSCs), granulocytic myeloid-derived suppressor cells (G-MDSCs), programmed cell death-ligand 1 (PD-L1), and human leukocyte antigen class I-B (HLA-B), and also reduced the level of low-density lipoprotein receptor (LDL-R), and increased the level of ATP binding cassette transporter A1 (ABCA1) to regulate the cholesterol metabolism, and regulated the expression of related genes and intestinal microbiota. SR-B1 knockdown can also trigger the anti-CRC effect of anti-PD 1 in colitis-induced CRC.

DISCUSSION

SR-B1 deficiency significantly improved the immunity in tumor microenvironment of colitis-induced or APCmin/+ -induced CRC. In addition, the microbiota changes caused by SR-B1 deficiency favor improving the immune response to chemotherapeutic drugs and anti-PD1 therapy. The mechanism of action of SR-B1 deficiency on the development of CRC still needs further in-depth research.

CONCLUSION

This study provides a new treatment strategy for treating CRC by affecting the expression of SR-B1 in intestine.

SCARB1 in extracellular vesicles promotes NPC metastasis by co-regulating M1 and M2 macrophage function

Distant metastasis is currently the main factor affecting the prognosis of nasopharyngeal carcinoma (NPC), and understanding the mechanisms of metastasis and identifying reliable therapeutic targets are critical for improving prognosis and achieving clinical translation. Macrophages, as important immune cells in the tumor microenvironment (TME), have been shown to regulate metastasis. And extracellular vesicles (EVs) secreted by stromal cells and tumor cells play the important role in intercellular communication in the tumor microenvironment. However, the role of NPC-EVs on macrophages and their function in regulating macrophages to affect metastasis has not been fully clarified. In this study, we report that NPC-EVs can be uptake by macrophages and alter macrophage polarization, for the first time, we identified the genes implicated in these regulatory functions: SCARB1, HAAO, and CYP1B1. Moreover, we found that SCARB1 was positively associated with metastasis and poor prognosis of NPC. Interestingly, we found that SCARB1-rich EVs promoted M1 macrophages ferroptosis to decrease M1 macrophages infiltration by upregulating the HAAO level while decreasing phagocytosis of M2 macrophages by upregulating the CYP1B1 level. Finally, we identified the SCARB1-binding gene KLF9, which is involved in the transcription of HAAO and CYP1B1. Our findings showed that SCARB1-EVs promoted metastasis by co-regulating M1 and M2 macrophage function. The related mechanism will provide a new therapeutic strategy to help patients with NPC improve their prognosis.

The Role of Cholesterol in Chronic Lymphocytic Leukemia Development and Pathogenesis

Cholesterol has many critical functions in cells. It is a key component of membranes and cell-signalling processes, and it functions as a chemical precursor in several biochemical pathways, such as Vitamin D and steroid synthesis. Cholesterol has also been implicated in the development and progression of various cancers, in which it is thought to promote cell proliferation, migration, and invasion. Chronic lymphocytic leukemia (CLL) is an example of a lipid-avid cancer that relies on lipid metabolism, rather than glycolysis, to fuel cell proliferation. However, data regarding the role of cholesterol in CLL are conflicting. Studies have shown that dyslipidaemia is more common among CLL patients than age-matched healthy controls, and that CLL patients who take cholesterol-lowering drugs, such as statins, appear to have improved survival rates. Therefore, defining the roles of cholesterol in CLL may highlight the importance of monitoring and managing hyperlipidaemia as part of the routine management of patients with CLL. In this review, we discuss the roles of cholesterol in the context of CLL by examining the literature concerning the trafficking, uptake, endogenous synthesis, and intracellular handling of this lipid. Data from clinical trials investigating various classes of cholesterol and lipid-lowering drugs in CLL are also discussed.

89Zr-Labeled High-Density Lipoprotein Nanoparticle PET Imaging Reveals Tumor Uptake in Patients with Esophageal Cancer

Nanomedicine holds promise for the delivery of therapeutic and imaging agents to improve cancer treatment outcomes. Preclinical studies have demonstrated that high-density lipoprotein (HDL) nanoparticles accumulate in tumor tissue on intravenous administration. Whether this HDL-based nanomedicine concept is feasible in patients is unexplored. Using a multimodal imaging approach, we aimed to assess tumor uptake of exogenously administered HDL nanoparticles in patients with esophageal cancer. Methods: The HDL mimetic CER-001 was radiolabeled using ⁸⁹Zr to allow for PET/CT imaging. Patients with primary esophageal cancer staged T2 and above were recruited for serial ⁸⁹Zr-HDL PET/CT imaging before starting chemoradiation therapy. In addition, patients underwent routine ¹⁸F-FDG PET/CT and 3-T MRI scanning (diffusion-weighted imaging/intravoxel incoherent motion imaging and dynamic contrast-enhanced MRI) to assess tumor glucose metabolism, tumor cellularity and microcirculation perfusion, and tumor vascular permeability. Tumor biopsies were analyzed for the expression of HDL scavenger receptor class B1 and macrophage marker CD68 using immunofluorescence staining. Results: Nine patients with adenocarcinoma or squamous cell carcinoma underwent all study procedures. After injection of ⁸⁹Zr-HDL (39.2 ± 1.2 [mean ± SD] MBq), blood-pool SUV_mean decreased over time (11.0 ± 1.7, 6.5 ± 0.6, and 3.3 ± 0.5 at 1, 24, and 72 h, respectively), whereas liver and spleen SUV_mean remained relatively constant (4.1 ± 0.6, 4.0 ± 0.8, and 4.3 ± 0.8 at 1, 24, and 72 h, respectively, for the liver; 4.1 ± 0.3, 3.4 ± 0.3, and 3.1 ± 0.4 at 1, 24, and 72 h, respectively, for the spleen) and kidney SUV_mean markedly increased over time (4.1 ± 0.9, 9.3 ± 1.4, and 9.6 ± 2.0 at 1, 24, and 72 h, respectively). Tumor uptake (SUV_peak) increased over time (3.5 ± 1.1 and 5.5 ± 2.1 at 1 and 24 h, respectively [P = 0.016]; 5.7 ± 1.4 at 72 h [P = 0.001]). The effective dose of ⁸⁹Zr-HDL was 0.523 ± 0.040 mSv/MBq. No adverse events were observed after the administration of ⁸⁹Zr-HDL. PET/CT and 3-T MRI measures of tumor glucose metabolism, tumor cellularity and microcirculation perfusion, and tumor vascular permeability did not correlate with tumor uptake of ⁸⁹Zr-HDL, suggesting that a specific mechanism mediated the accumulation of ⁸⁹Zr-HDL. Immunofluorescence staining of clinical biopsies demonstrated scavenger receptor class B1 and CD68 positivity in tumor tissue, establishing a potential cellular mechanism of action. Conclusion: To our knowledge, this was the first ⁸⁹Zr-HDL study in human oncology. ⁸⁹Zr-HDL PET/CT imaging demonstrated that intravenously administered HDL nanoparticles accumulated in tumors of patients with esophageal cancer. The administration of ⁸⁹Zr-HDL was safe. These findings may support the development of HDL nanoparticles as a clinical delivery platform for drug agents. ⁸⁹Zr-HDL imaging may guide drug development and serve as a biomarker for individualized therapy.

Cholesterol: An important actor on the cancer immune scene

Based on the structural and signaling roles of cholesterol, which are necessary for immune cell activity, high concentrations of cholesterol and its metabolites not only trigger malignant cell activities but also impede immune responses against cancer cells. To proliferate and evade immune responses, tumor cells overcome environmental restrictions by changing their metabolic and signaling pathways. Overexpression of mevalonate pathway enzymes and low-density lipoprotein receptor cause elevated cholesterol synthesis and uptake, respectively. Accordingly, cholesterol can be considered as both a cause and an effect of cancer. Variations in the effects of blood cholesterol levels on the outcome of different types of cancer may depend on the stage of cancer. However, positive effects of cholesterol-lowering drugs have been reported in the treatment of patients with some malignancies.

Cholesterol homeostasis and cancer: a new perspective on the low-density lipoprotein receptor

BACKGROUND

Disturbance of cholesterol homeostasis is considered as one of the manifestations of cancer. Cholesterol plays an essential role in the pleiotropic functions of cancer cells, including mediating membrane trafficking, intracellular signal transduction, and production of hormones and steroids. As a single transmembrane receptor, the low-density lipoprotein receptor (LDLR) can participate in intracellular cholesterol uptake and regulate cholesterol homeostasis. It has recently been found that LDLR is aberrantly expressed in a broad range of cancers, including colon cancer, prostate cancer, lung cancer, breast cancer and liver cancer. LDLR has also been found to be involved in various signaling pathways, such as the MAPK, NF-κB and PI3K/Akt signaling pathways, which affect cancer cells and their surrounding microenvironment. Moreover, LDLR may serve as an independent prognostic factor for lung cancer, breast cancer and pancreatic cancer, and is closely related to the survival of cancer patients. However, the role of LDLR in some cancers, such as prostate cancer, remains controversial. This may be due to the lack of normal feedback regulation of LDLR expression in cancer cells and the severe imbalance between LDLR-mediated cholesterol uptake and de novo biosynthesis of cholesterol.

CONCLUSIONS

The imbalance of cholesterol homeostasis caused by abnormal LDLR expression provides new therapeutic opportunities for cancer. LDLR interferes with the occurrence and development of cancer by modulating cholesterol homeostasis and may become a novel target for the development of anti-cancer drugs. Herein, we systematically review the contribution of LDLR to cancer progression, especially its dysregulation and underlying mechanism in various malignancies. Besides, potential targeting and immunotherapeutic options are proposed.

New dawn for cancer cell death: Emerging role of lipid metabolism

BACKGROUND

Resistance to cell death, a protective mechanism for removing damaged cells, is a "Hallmark of Cancer" that is essential for cancer progression. Increasing attention to cancer lipid metabolism has revealed a number of pathways that induce cancer cell death.

SCOPE OF REVIEW

We summarize emerging concepts regarding lipid metabolic reprogramming in cancer that is mainly involved in lipid uptake and trafficking, de novo synthesis and esterification, fatty acid synthesis and oxidation, lipogenesis, and lipolysis. During carcinogenesis and progression, continuous metabolic adaptations are co-opted by cancer cells, to maximize their fitness to the ever-changing environmental. Lipid metabolism and the epigenetic modifying enzymes interact in a bidirectional manner which involves regulating cancer cell death. Moreover, lipids in the tumor microenvironment play unique roles beyond metabolic requirements that promote cancer progression. Finally, we posit potential therapeutic strategies targeting lipid metabolism to improve treatment efficacy and survival of cancer patient.

MAJOR CONCLUSIONS

The profound comprehension of past findings, current trends, and future research directions on resistance to cancer cell death will facilitate the development of novel therapeutic strategies targeting the lipid metabolism.

Rhenium(I) conjugates as tools for tracking cholesterol in cells

Cholesterol is vital to control membrane integrity and fluidity, but is also a precursor to produce steroid hormones, bile acids, and vitamin D. Consequently, altered cholesterol biology has been linked to many diseases, including metabolic syndromes and cancer. Defining the intracellular pools of cholesterol and its trafficking within cells is essential to understand both normal cell physiology and mechanisms of pathogenesis. We have synthesized a new cholesterol mimic (ReTEGCholestanol), comprising a luminescent rhenium metal complex and a cholestanol targeting unit, linked using a tetraethylene glycol (TEG) spacer. ReTEGCholestanol demonstrated favourable imaging properties and improved water solubility when compared to a cholesterol derivative, and structurally related probes lacking the TEG linker. A non-malignant and three malignant prostate cell lines were used to characterize the uptake and intracellular distribution of ReTEGCholestanol. The ReTEGCholestanol complex was effectively internalized and mainly localized to late endosomes/lysosomes in non-malignant PNT1a cells, while in prostate cancer cells it also accumulated in early endosomes and multivesicular bodies, suggesting disturbed cholesterol biology in the malignant cells. The ReTEGCholestanol is a novel imaging agent for visualizing endosomal uptake and trafficking, which may be used to define cholesterol related biology including membrane integration and altered lipid trafficking/processing.

Use of paclitaxel carried in lipid core nanoparticles in patients with late-stage solid cancers with bone metastases: Lack of toxicity and therapeutic benefits

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LDE-PTX at 175 mg/m²/3wk dose was devoid of toxicity at > 3rd line treatment.

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Among 18 LDE-PTX treated patients, 9 had PFS > 6 months and 2 had PFS > 1 yr.

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LDE-PTX diminished bone pain and improved quality of life in all treated patients.

^{Patients with heavily pretreated, late-stage cancer and bone metastasis are usually poor candidates for further chemotherapy. Previously, we showed that association to lipid nanoparticles (LDE) drastically decreases the toxicity of anti-cancer drugs. Here, we tested the hypothesis that paclitaxel (PTX) carried in LDE could benefit end-of-life patients with painful bone metastases that had been previously treated with conventional PTX. Methods: Eighteen consecutive patients with late-stage cancer, 8 with breast, 5 with prostate and 5 with lung carcinoma, aged 59±9 years, were included in this study. All were receiving opioid medication. LDE-PTX was administered at 175 mg/m 2 every 3 weeks until disease progression. Clinical imaging examinations and serum biochemistry determinations were performed to monitor disease progression. Intensity of bone pain, use of opioid medications and occurrence of pathological bone fractures were also evaluated. Results: In total, 104 chemotherapy cycles were performed and none of the patients showed clinical and laboratorial toxicities or pathological bone fractures. In all patients, pain was reduced so as to allow substitution of non-opioid for opioid medication. Median progression-free survival (PFS) was four months (95% CI 2.4-5.5), but in five patients PFS was longer than 6 months. Conclusions: Absence of observable clinical and laboratorial toxicities from LDE-PTX treatment, improvement of bone pain and the possible effect on PFS in some patients, despite previous use of conventional PTX, suggest that LDEPTX merits further clinical investigation.}

HDL as Bidirectional Lipid Vectors: Time for New Paradigms

The anti-atherogenic properties of high-density lipoproteins (HDL) have been explained mainly by reverse cholesterol transport (RCT) from peripheral tissues to the liver. The RCT seems to agree with most of the negative epidemiological correlations between HDL cholesterol levels and coronary artery disease. However, therapies designed to increase HDL cholesterol failed to reduce cardiovascular risk, despite their capacity to improve cholesterol efflux, the first stage of RCT. Therefore, the cardioprotective role of HDL may not be explained by RCT, and it is time for new paradigms about the physiological function of these lipoproteins. It should be considered that the main HDL apolipoprotein, apo AI, has been highly conserved throughout evolution. Consequently, these lipoproteins play an essential physiological role beyond their capacity to protect against atherosclerosis. We propose HDL as bidirectional lipid vectors carrying lipids from and to tissues according to their local context. Lipid influx mediated by HDL appears to be particularly important for tissue repair right on site where the damage occurs, including arteries during the first stages of atherosclerosis. In contrast, the HDL-lipid efflux is relevant for secretory cells where the fusion of intracellular vesicles drastically enlarges the cytoplasmic membrane with the potential consequence of impairment of cell function. In such circumstances, HDL could deliver some functional lipids and pick up not only cholesterol but an integral part of the membrane in excess, restoring the viability of the secretory cells. This hypothesis is congruent with the beneficial effects of HDL against atherosclerosis as well as with their capacity to induce insulin secretion and merits experimental exploration.

Lipid Metabolism and Epigenetics Crosstalk in Prostate Cancer

Prostate cancer (PCa) is the most commonly diagnosed malignant neoplasm in men in the Western world. Localized low-risk PCa has an excellent prognosis thanks to effective local treatments; however, despite the incorporation of new therapeutic strategies, metastatic PCa remains incurable mainly due to disease heterogeneity and the development of resistance to therapy. The mechanisms underlying PCa progression and therapy resistance are multiple and include metabolic reprogramming, especially in relation to lipid metabolism, as well as epigenetic remodelling, both of which enable cancer cells to adapt to dynamic changes in the tumour. Interestingly, metabolism and epigenetics are interconnected. Metabolism can regulate epigenetics through the direct influence of metabolites on epigenetic processes, while epigenetics can control metabolism by directly or indirectly regulating the expression of metabolic genes. Moreover, epidemiological studies suggest an association between a high-fat diet, which can alter the availability of metabolites, and PCa progression. Here, we review the alterations of lipid metabolism and epigenetics in PCa, before focusing on the mechanisms that connect them. We also discuss the influence of diet in this scenario. This information may help to identify prognostic and predictive biomarkers as well as targetable vulnerabilities.

Tissue cholesterol metabolism and prostate cancer aggressiveness: Ethno-geographic variations

BACKGROUND

Prostate cancer (PCa) is more frequent and more aggressive in populations of African descent than in Caucasians. Since the fatty acid composition of peri-prostatic adipose tissue (PPAT) has been shown to differ according to the ethno-geographic origin and is involved in PCa aggressiveness, we aimed to analyze the cholesterol content of PPAT from Caucasian and African-Caribbean patients, in correlation with markers of disease aggressiveness and cholesterol metabolism in cancer tissues.

METHODS

The quantification of cholesterol in PPAT was analyzed in 52 Caucasian and 52 African-Caribbean PCa patients, with in each group 26 indolent tumors (ISUP Group1 and pT2) and 26 potentially aggressive tumors (ISUP Group 3-5 and/or pT3). The expression of proteins involved in cholesterol metabolism was analyzed by immunohistochemistry on cancer tissue samples included in tissue microarrays.

RESULTS

The amount of cholesterol esters was lower in PPAT from African-Caribbean patients compared with Caucasians, without any correlation with markers of disease aggressiveness. In cancer tissues from African-Caribbean patients, the expression of ABCA1 (involved in cholesterol efflux) was decreased, and that of SREBP-2 (involved in cholesterol uptake) was increased. In both groups of patients, SREBP-2 expression was strongly associated with that of Zeb1, a key player in the epithelial-to-mesenchymal transition (EMT) process.

CONCLUSION

These results suggest that cholesterol metabolism differs according to the ethno-geographic origin, in both PPAT and cancer tissues. In African-Caribbeans, the orientation towards accumulation of cholesterol in cancer cells is associated with a more frequent state of EMT, which may promote PCa aggressiveness in this population.

Prostate Cancer-Focus on Cholesterol

Prostate cancer (PC) is the most common malignancy in men. Common characteristic involved in PC pathogenesis are disturbed lipid metabolism and abnormal cholesterol accumulation. Cholesterol can be further utilized for membrane or hormone synthesis while cholesterol biosynthesis intermediates are important for oncogene membrane anchoring, nucleotide synthesis and mitochondrial electron transport. Since cholesterol and its biosynthesis intermediates influence numerous cellular processes, in this review we have described cholesterol homeostasis in a normal cell. Additionally, we have illustrated how commonly deregulated signaling pathways in PC (PI3K/AKT/MTOR, MAPK, AR and p53) are linked with cholesterol homeostasis regulation.

Inhibition of Scavenger Receptor Class B Type 1 (SR-B1) Expression and Activity as a Potential Novel Target to Disrupt Cholesterol Availability in Castration-Resistant Prostate Cancer

There have been several studies that have linked elevated scavenger receptor class b type 1 (SR-B1) expression and activity to the development and progression of castration-resistant prostate cancer (CRPC). SR-B1 facilitates the influx of cholesterol to the cell from lipoproteins in systemic circulation. This influx of cholesterol may be important for many cellular functions, including the synthesis of androgens. Castration-resistant prostate cancer tumors can synthesize androgens de novo to supplement the loss of exogenous sources often induced by androgen deprivation therapy. Silencing of SR-B1 may impact the ability of prostate cancer cells, particularly those of the castration-resistant state, to maintain the intracellular supply of androgens by removing a supply of cholesterol. SR-B1 expression is elevated in CRPC models and has been linked to poor survival of patients. The overarching belief has been that cholesterol modulation, through either synthesis or uptake inhibition, will impact essential signaling processes, impeding the proliferation of prostate cancer. The reduction in cellular cholesterol availability can impede prostate cancer proliferation through both decreased steroid synthesis and steroid-independent mechanisms, providing a potential therapeutic target for the treatment of prostate cancer. In this article, we discuss and highlight the work on SR-B1 as a potential novel drug target for CRPC management.

Cholesterol Metabolic Reprogramming in Cancer and Its Pharmacological Modulation as Therapeutic Strategy

Cholesterol is a ubiquitous sterol with many biological functions, which are crucial for proper cellular signaling and physiology. Indeed, cholesterol is essential in maintaining membrane physical properties, while its metabolism is involved in bile acid production and steroid hormone biosynthesis. Additionally, isoprenoids metabolites of the mevalonate pathway support protein-prenylation and dolichol, ubiquinone and the heme a biosynthesis. Cancer cells rely on cholesterol to satisfy their increased nutrient demands and to support their uncontrolled growth, thus promoting tumor development and progression. Indeed, transformed cells reprogram cholesterol metabolism either by increasing its uptake and de novo biosynthesis, or deregulating the efflux. Alternatively, tumor can efficiently accumulate cholesterol into lipid droplets and deeply modify the activity of key cholesterol homeostasis regulators. In light of these considerations, altered pathways of cholesterol metabolism might represent intriguing pharmacological targets for the development of exploitable strategies in the context of cancer therapy. Thus, this work aims to discuss the emerging evidence of in vitro and in vivo studies, as well as clinical trials, on the role of cholesterol pathways in the treatment of cancer, starting from already available cholesterol-lowering drugs (statins or fibrates), and moving towards novel potential pharmacological inhibitors or selective target modulators.

Influence of cholesterol on cancer progression and therapy

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Abnormality in blood cholesterol level is significantly correlated with risk of different cancers.

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Majority of tumor tissue from cancer patient exhibits overexpression of LDLR and ACAT for supporting rapid cancer cell proliferation.

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Alteration of the cholesterol metabolism in cancer cells hampers therapeutic response.

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Targeting cholesterol metabolism for treatment of cancer with other conventional chemotherapeutic drugs appears to be beneficial.

Cholesterol is a fundamental molecule necessary for the maintenance of cell structure and is vital to various normal biological functions. It is a key factor in lifestyle-related diseases including obesity, diabetes, cardiovascular disease, and cancer. Owing to its altered serum chemistry status under pathological states, it is now being investigated to unravel the mechanism by which it triggers various health complications. Numerous clinical studies in cancer patients indicate an alteration in blood cholesterol level (either decreased or increased) in comparison to normal healthy individuals. This article elaborates on our understanding as to how cholesterol is being hijacked in the malignancy for the development, survival, stemness, progression, and metastasis of cancerous cells. Also, it provides a glimpse of how cholesterol derived entities, alters the signaling pathway towards their advantage. Moreover, deregulation of the cholesterol metabolism pathway has been often reported to hamper various treatment strategies in different cancer. In this context, attempts have been made to bring forth its relevance in being targeted, in pre-clinical and clinical studies for various treatment modalities. Thus, understanding the role of cholesterol and deciphering associated molecular mechanisms in cancer progression and therapy are of relevance towards improvement in the management of various cancers.

LDL, HDL and endocrine-related cancer: From pathogenic mechanisms to therapies

Cholesterol is essential for a variety of functions in endocrine-related cells, including hormone and steroid production. We have reviewed the progress to date in research on the role of the main cholesterol-containing lipoproteins; low-density lipoprotein (LDL) and high-density lipoprotein (HDL), and their impact on intracellular cholesterol homeostasis and carcinogenic pathways in endocrine-related cancers. Neither LDL-cholesterol (LDL-C) nor HDL-cholesterol (HDL-C) was consistently associated with endocrine-related cancer risk. However, preclinical studies showed that LDL receptor plays a critical role in endocrine-related tumor cells, mainly by enhancing circulating LDL-C uptake and modulating tumorigenic signaling pathways. Although scavenger receptor type BI-mediated uptake of HDL could enhance cell proliferation in breast, prostate, and ovarian cancer, these effects may be counteracted by the antioxidant and anti-inflammatory properties of HDL. Moreover, 27-hydroxycholesterol a metabolite of cholesterol promotes tumorigenic processes in breast and epithelial thyroid cancer. Furthermore, statins have been reported to reduce the incidence of breast, prostate, pancreatic, and ovarian cancer in large clinical trials, in part because of their ability to lower cholesterol synthesis. Overall, cholesterol homeostasis deregulation in endocrine-related cancers offers new therapeutic opportunities, but more mechanistic studies are needed to translate the preclinical findings into clinical therapies.

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.

Uptake of high-density lipoprotein by scavenger receptor class B type 1 is associated with prostate cancer proliferation and tumor progression in mice

High-density lipoprotein (HDL) metabolism is facilitated in part by scavenger receptor class B, type 1 (SR-B1) that mediates HDL uptake into cells. Higher levels of HDL have been associated with protection in other diseases, however, its role in prostate cancer is not definitive. SR-B1 is up-regulated in prostate cancer tissue, suggesting a possible role of this receptor in tumor progression. Here, we report that knockout (KO) of SR-B1 in both human and mouse prostate cancer cell lines through CRISPR/Cas9-mediated genome editing reduces HDL uptake into the prostate cancer cells and reduces their proliferation in response to HDL. In vivo studies using syngeneic SR-B1 WT (SR-B1+/+) and SR-B1 KO (SR-B1-/-) prostate cancer cells in WT and apolipoprotein-AI KO (apoA1-KO) C57BL/6J mice revealed that WT hosts, containing higher levels of total and HDL-cholesterol, grew larger tumors than apoA1-KO hosts with lower levels of total and HDL-cholesterol. Furthermore, SR-B1-/- prostate cancer cells formed smaller tumors in WT hosts than SR-B1+/+ cells in the same host model. Increased tumor volume was overall associated with reduced survival. We conclude that knocking out SR-B1 in prostate cancer tumors reduces HDL-associated increases in prostate cancer cell proliferation and disease progression.

Development of synthetic high-density lipoprotein-based ApoA-I mimetic peptide-loaded docetaxel as a drug delivery nanocarrier for breast cancer chemotherapy

In this study, a synthetic high-density lipoprotein (sHDL), peptide-based nanocarrier loaded with docetaxel (DTX) was constructed, against breast cancer. The thermodynamic and molecular dynamic analyses were conducted to examine the stability of nanoparticles synthesized from mimetic peptide 5 A and various types of phospholipids. Furthermore, the cellular uptake and in vivo fluorescence imaging analysis experiments, with scavenger receptor B-I (SR-BI) were carried out to examine the tumor-targeting ability of sHDL. The nanoparticles were investigated for their pharmacodynamic and cytotoxic effects to show their effectivity as anti-tumor agents. The results showed that the synthesized sHDL nanoparticles exhibited a high payload of DTX, sustained drug release properties, and excellent biocompatibility. Moreover, DTX-sHDL nanoparticles enhanced the uptake of DTX, increased the cytotoxicity against MCF-7 cells, and reduced the off-target side-effects to normal cells. Finally, experiments in 4T1 cell line-bearing mice indicate that inhibition of tumor growth by DTX-sHDL nanoparticles was superior to that of free DTX group. Thus, the sHDL nanoparticles are a promising drug delivery vehicle for improving the efficacy of anti-cancer drugs.

Cholesterol metabolism in cancer: mechanisms and therapeutic opportunities

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

SR-BI as a target of natural products and its significance in cancer

Scavenger receptor class B type I (SR-BI) protein is an integral membrane glycoprotein. SR-BI is emerging as a multifunctional protein, which regulates autophagy, efferocytosis, cell survival and inflammation. It is well known that SR-BI plays a critical role in lipoprotein metabolism by mediating cholesteryl esters selective uptake and the bi-directional flux of free cholesterol. Recently, SR-BI has also been identified as a potential marker for cancer diagnosis, prognosis, or even a treatment target. Natural products are a promising source for the discovery of new drug leads. Multiple natural products were identified to regulate SR-BI protein expression. There are still a number of challenges in modulating SR-BI expression in cancer and in using natural products for modulation of such protein expression. In this review, our purpose is to discuss the relationship between SR-BI protein and cancer, and the molecular mechanisms regulating SR-BI expression, as well as to provide an overview of natural products that regulate SR-BI expression.

Metabolism of cholesterol and progesterone is differentially regulated in primary trophoblastic subtypes and might be disturbed in recurrent miscarriages

During pregnancy, extravillous trophoblasts (EVTs) invade the maternal decidua and remodel the local vasculature to establish blood supply for the growing fetus. Compromised EVT function has been linked to aberrant pregnancy associated with maternal and fetal morbidity and mortality. However, metabolic features of this invasive trophoblast subtype are largely unknown. Using primary human trophoblasts isolated from first trimester placental tissues, we show that cellular cholesterol homeostasis is differentially regulated in EVTs compared with villous cytotrophoblasts. Utilizing RNA-sequencing, gene set-enrichment analysis, and functional validation, we provide evidence that EVTs display increased levels of free and esterified cholesterol. Accordingly, EVTs are characterized by increased expression of the HDL-receptor, scavenger receptor class B type I, and reduced expression of the LXR and its target genes. We further reveal that EVTs express elevated levels of hydroxy-delta-5-steroid dehydrogenase 3 beta- and steroid delta-isomerase 1 (HSD3B1) (a rate-limiting enzyme in progesterone synthesis) and are capable of secreting progesterone. Increasing cholesterol export by LXR activation reduced progesterone secretion in an ABCA1-dependent manner. Importantly, HSD3B1 expression was decreased in EVTs of idiopathic recurrent spontaneous abortions, pointing toward compromised progesterone metabolism in EVTs of early miscarriages. Here, we provide insights into the regulation of cholesterol and progesterone metabolism in trophoblastic subtypes and its putative relevance in human miscarriage.

SR-BI Interactome Analysis Reveals a Proviral Role for UGGT1 in Hepatitis C Virus Entry

Hepatitis C virus (HCV) entry is mediated by multiple co-receptors including scavenger receptor class B, type I (SR-BI). To elucidate the interactome of human SR-BI, we performed immunoprecipitation (IP) experiment coupled with mass spectrometry (MS) analysis. UDP-glucose:glycoprotein glucosyltransferase 1 (UGGT1), a key component of calnexin cycle involved in protein glycosylation, was identified as a SR-BI-interacting protein. Silencing UGGT1 or N-glycosylation inhibitor treatment reduced SR-BI protein level. Further study demonstrated that human SR-BI was N-glycosylated at nine asparagines. Moreover, HCV entry and infection were reduced by the absence of UGGT1. Interestingly, silencing SR-BI reduced protein stability of UGGT1 and protein quality control function mediated by UGGT1. Our finding not only identified UGGT1 as a HCV host factor, but also identified a UGGT1-mediated protein folding function for SR-BI.

The role of high-density lipoproteins in antitumor drug delivery

High-density lipoproteins (HDLs) are the smallest lipoprotein with the highest level of protein in their surface. The main role of HDLs are reverse transport of cholesterol from peripheral tissues to the liver. More recently, HDLs have been considered as a new drug delivery system because of their small size, proper surface properties, long circulation time, biocompatibility, biodegradability, and low immune stimulation. Delivery of anticancer drug to the tumor tissue is a major obstacle against successful chemotherapy, which is because of the toxicity and poor aqueous solubility of these drugs. Loading chemotherapeutic drugs in the lipid core of HDLs can overcome the aforementioned problems and increase the efficiency of drug delivery. In this review, we discuss the use of HDLs particles in drug delivery to the tumor tissue and explain some barriers and limitations that exist in the use of HDLs as an ideal delivery vehicle.

Role of cholesterol homeostasis and its efflux pathways in cancer progression

Tumor cells show high avidity for cholesterol in order to support their inherent nature to divide and proliferate. This results in the rewiring of cholesterol homeostatic pathways by influencing not only de novo synthesis but also uptake or efflux pathways of cholesterol. Recent findings have pointed towards the importance of cholesterol efflux in tumor pathogenesis. Cholesterol efflux is the first and foremost step in reverse cholesterol transport and any perturbation in this pathway may lead to the accumulation of intracellular cholesterol, thereby altering the cellular equilibrium. This review addresses the different mechanisms of cholesterol efflux from the cell and highlights their role and regulation in context to tumor development. There are four different routes by which cholesterol can be effluxed from the cell namely, 1) passive diffusion of cholesterol to mature HDL particles, 2) SR-B1 mediated facilitated diffusion, 3) Active efflux to apo A1 via ABCA1 and 4) ABCG1 mediated efflux to mature HDL. These molecular players facilitating cholesterol efflux are engaged in a complex interplay with different signaling pathways. Thus, an understanding of the efflux pathways, their regulation and cross-talk with signaling molecules may provide novel prognostic markers and therapeutic targets to combat the onset of carcinogenesis.

Clinical relevance of cholesterol homeostasis genes in colorectal cancer

Accumulation of cholesterol is a well-known feature in cancer. Preclinical studies suggest the contribution of various cholesterol regulators in CRC. However, their clinical relevance remains poorly understood. The aim of the present study is to evaluate the expression of these modulators in CRC and elucidate their diagnostic and prognostic value. mRNA levels of HMGCR, SREBF2, NR1H3 and NR1H2 were downregulated in tumors in local and TCGA cohort. The expression of LDLR, ABCA1 and SCARB1 was not consistent in the two cohorts. Western Blot analysis showed the increased levels of LDLR and reduced levels of LXR in early stage patients. Tumoral SREBP2 levels were enhanced in early stage whereas decreased in late stage. The individual expression of HMGCR, SREBF2, NR1H3 and NR1H2 did not have the potential to be used as independent prognostic marker, however, the combined expression of these genes associated with poor clinical outcome independent of lymph node metastasis, distant metastasis and advanced stage. This work sheds light on deregulation of cholesterol uptake and efflux pathways and provides novel leads in the development of biomarkers and therapeutic regimens that can detect and target CRC at initial stages.

The SR-B1 Receptor as a Potential Target for Treating Glioblastoma

Purpose

The goal of these studies was to provide proof of concept for a novel targeted therapy for Glioblastoma Multiforme (GBM). Methods. These studies involve the evaluation of reconstituted high density lipoprotein (rHDL) nanoparticles (NPs) as delivery agents for the drug, mammalian Target of Rapamycin (mTOR) inhibitor Everolimus (EVR) to GBM cells. Cytotoxicity studies and assessment of downstream effects, including apoptosis, migration, and cell cycle events, were probed, in relation to the expression of scavenger receptor B type 1 (SR-B1) by GBM cells.

Results

Findings from cytotoxicity studies indicate that the rHDL/EVR formulation was 185 times more potent than free EVR against high SR-B1 expressing cell line (LN 229). Cell cycle analysis revealed that rHDL/EVR treated LN229 cells had a 5.8 times higher apoptotic cell population than those treated with EVR. The sensitivity of GBM cells to EVR treatment was strongly correlated with SR-B1 expression.

Conclusions

These studies present strong proof of concept regarding the efficacy of delivering EVR and likely other agents, via a biocompatible transport system, targeted to the SR-B1 receptor that is upregulated in most cancers, including GBM. Targeting the SR-B1 receptor could thus lead to effective personalized therapy of GBM.

Upregulation of Scavenger Receptor B1 Is Required for Steroidogenic and Nonsteroidogenic Cholesterol Metabolism in Prostate Cancer

Aberrant cholesterol metabolism is increasingly appreciated to be essential for prostate cancer initiation and progression. Transcript expression of the high-density lipoprotein-cholesterol receptor scavenger receptor B1 (SR-B1) is elevated in primary prostate cancer. Hypothesizing that SR-B1 expression may help facilitate malignant transformation, we document increased SR-B1 protein and transcript expression in prostate cancer relative to normal prostate epithelium that persists in lethal castration-resistant prostate cancer (CRPC) metastasis. As intratumoral steroid synthesis from the precursor cholesterol can drive androgen receptor (AR) pathway activity in CRPC, we screened androgenic benign and cancer cell lines for sensitivity to SR-B1 antagonism. Benign cells were insensitive to SR-B1 antagonism, and cancer line sensitivity inversely correlated with expression levels of full-length and splice variant AR. In androgen-responsive CRPC cell model C4-2, SR-B1 antagonism suppressed cholesterol uptake, de novo steroidogenesis, and AR activity. SR-B1 antagonism also suppressed growth and viability and induced endoplasmic reticulum stress and autophagy. The inability of exogenous steroids to reverse these effects indicates that AR pathway activation is insufficient to overcome cytotoxic stress caused by a decrease in the availability of cholesterol. Furthermore, SR-B1 antagonism decreased cholesterol uptake, growth, and viability of the AR-null CRPC cell model PC-3, and the small-molecule SR-B1 antagonist block lipid transport-1 decreased xenograft growth rate despite poor pharmacologic properties. Overall, our findings show that SR-B1 is upregulated in primary and castration-resistant disease and is essential for cholesterol uptake needed to drive both steroidogenic and nonsteroidogenic biogenic pathways, thus implicating SR-B1 as a novel and potentially actionable target in CRPC. SIGNIFICANCE: These findings highlight SR-B1 as a potential target in primary and castration-resistant prostate cancer that is essential for cholesterol uptake needed to drive steroidogenic and nonsteroidogenic biogenic pathways.

Loss of SR-BI Down-Regulates MITF and Suppresses Extracellular Vesicle Release in Human Melanoma

Melanoma is a skin tumor with a high tendency for metastasis and thus is one of the deadliest cancers worldwide. Here, we investigated the expression of the scavenger receptor class B type 1 (SR-BI), a high-density lipoprotein (HDL) receptor, and tested for its role in melanoma pigmentation as well as extracellular vesicle release. We first analyzed the expression of SR-BI in patient samples and found a strong correlation with MITF expression as well as with the melanin synthesis pathway. Hence, we asked whether SR-BI could also play a role for the secretory pathway in metastatic melanoma cells. Interestingly, gain- and loss-of-function of SR-BI revealed regulation of the proto-oncogene MET. In line, SR-BI knockdown reduced expression of the small GTPase RABB22A, the ESCRT-II protein VPS25, and SNAP25, a member of the SNARE complex. Accordingly, reduced overall extracellular vesicle generation was detected upon loss of SR-BI. In summary, SR-BI expression in human melanoma enhances the formation and transport of extracellular vesicles, thereby contributing to the metastatic phenotype. Therapeutic targeting of SR-BI would not only interfere with cholesterol uptake, but also with the secretory pathway, therefore suppressing a key hallmark of the metastatic program.

Immunohistochemical Labeling of Low-Density Lipoprotein Receptor and Scavenger Receptor Class B Type 1 Are Increased in Canine Lymphoma

Altered lipid metabolism is a well-documented hallmark of neoplastic transformation and impacts disease progression. Two major lipoprotein receptors, the low-density lipoprotein receptor (LDL-R) and scavenger receptor class B, type 1 (SR-BI) are overexpressed in a number of cancer types in people. These receptors serve to deliver cholesterol to the tumor cells and have been used to target drug therapies. In this study, we performed a retrospective analysis of LDL-R and SR-B1 expression in canine lymphoma using archived formalin-fixed tissue samples. Cases were immunophenotyped and classified according to World Health Organization (WHO) standards prior to immunostaining for the LDL_R and SR-B1. A total of 45 cases were evaluated; 21 high grade B (HGB), 11 low grade B (LGB), 7 high grade T (HGT), and 6 low grade T (LGT) lymphomas. One sided Wilcoxon rank sum tests were used to compare staining intensity between neoplastic and hyperplastic lymphoid tissue. The relationships between histological score and tumor grade and score and stage at presentation were assessed using non-parametric Kruskal-Wallis tests. Neoplastic lymphoid tissue expressed higher levels of both receptors compared to reactive lymph nodes. Median LDL-R score was 85.0 (interquartile range = 101.7), Median SR-B1 score was 209.0 (interquartile range 105.2). No relationship between LDL-R or SR-B1 staining score and tumor grade or phenotype was found. Serum cholesterol concentration was compared between dogs with high and low grade tumors using a two sample T-test, and correlations between cholesterol concentration and histological score, and between the score for the two receptors were determined using a Spearman correlation. The high expression level of these lipoprotein receptors on most of the tumors could underlie the lack of relationship between score and tumor grade. The overexpression of LDL-R and SR-B1 in canine lymphoma holds therapeutic potential particularly in dogs that overexpress one or both of these receptors, and this warrants further investigation.

High-Density Lipoprotein Components and Functionality in Cancer: State-of-the-Art

Cancer is the second leading cause of death in western countries, and thus represents a major global public health issue. Whilst it is well-recognized that diet, obesity, and smoking are risk factors for cancer, the role of low levels of high-density lipoprotein cholesterol (HDL-C) in cancer is less well appreciated. Conflicting evidence suggests that serum HDL-C levels may be either positively or negatively associated with cancer incidence and mortality. Such disparate associations are supported in part by the multitude of high-density lipoprotein (HDL) functions that can all have an impact on cancer cell biology. The aim of this review is to provide a comprehensive overview of the crosstalk between HDLs and cancer, focusing on the molecular mechanisms underlying this association.

Reconstituted HDL: Drug Delivery Platform for Overcoming Biological Barriers to Cancer Therapy

Drug delivery to malignant tumors is limited by several factors, including off-target toxicities and suboptimal benefits to cancer patient. Major research efforts have been directed toward developing novel technologies involving nanoparticles (NPs) to overcome these challenges. Major obstacles, however, including, opsonization, transport across cancer cell membranes, multidrug-resistant proteins, and endosomal sequestration of the therapeutic agent continue to limit the efficiency of cancer chemotherapy. Lipoprotein-based drug delivery technology, "nature's drug delivery system," while exhibits highly desirable characteristics, it still needs substantial investment from private/government stakeholders to promote its eventual advance to the bedside. Consequently, this review focuses specifically on the synthetic (reconstituted) high-density lipoprotein rHDL NPs, evaluating their potential to overcome specific biological barriers and the challenges of translation toward clinical utilization and commercialization. This highly robust drug transport system provides site-specific, tumor-selective delivery of anti-cancer agents while reducing harmful off-target effects. Utilizing rHDL NPs for anti-cancer therapeutics and tumor imaging revolutionizes the future strategy for the management of a broad range of cancers and other diseases.

Serum cholesterol and prostate cancer risk in the Finnish randomized study of screening for prostate cancer

BACKGROUND

Hypercholesterolemia has been associated with advanced stage prostate cancer (PCa), but the role of lipid parameters such as HDL and triglycerides is unclear. We examined PCa risk by lipid parameters in a population nested within the Finnish Randomized Study of Screening for Prostate Cancer (FinRSPC).

METHODS

Cholesterol measurements were available on 17,696 men. During the 17-year median follow-up, 2404 PCa cases were diagnosed. Cox regression model was used to estimate hazard ratios (HR) and their 95% confidence intervals (95% CI) for overall PCa risk and stratified by Gleason grade and tumor stage. We compared normolipidemic and hyperlipidemic men on four cholesterol parameters total cholesterol (TC), HDL, LDL, and triglycerides (TG), analyzed as time-dependent variables.

RESULTS

TC in the highest tertile (above 5.1 mmol/l) and LDL above 3 mmol/l were associated with increased risk of Gleason 8-10 cancer (HR 1.42, 95% CI 1.04-1.95 and HR 1.38, 95% CI 1.02-1.86, respectively). Further, overall PCa risk was elevated in the 3-year lag time analysis by TC in the highest two tertiles (HR 1.27, 95% CI 1.05-1.54 for TC above 4.4 mmol/l, and HR 1.26, 95% CI 1.05-1.51 for TC above 5.1 mmol/l) and HDL in the highest tertile (HR 1.33, 95% CI 1.08-1.64) and above 1 mmol/l (HR 1.29, 95% CI 1.01-1.65). In contrast, TC in the highest tertile was associated with a decreased risk of PCa with 20-year lag time. The risk associations for overall PCa grew stronger with added lag time but were observed only in the FinRSPC control arm. Statin use did not modify the risk association.

CONCLUSIONS

Hypercholesterolemia may increase overall PCa risk in short-term, inverse risk association was observed with 20-years' time lag. Similar risk increase of overall PCa was also observed for elevated HDL, conflicting with previous findings on the subject.

Individual Comparison of Cholesterol Metabolism in Normal and Tumour Areas in Radical Prostatectomy Specimens from Patients with Prostate Cancer: Results of the CHOMECAP Study

BACKGROUND

Deregulation of cholesterol metabolism represents a hallmark of prostate cancer (PCa) and promotes its development.

OBJECTIVE

To compare cholesterol metabolism on individual paired normal and tumour prostate tissues obtained from patients with PCa.

DESIGN, SETTING, AND PARTICIPANTS

Between 2008 and 2012, normal and tumour paired tissue samples were collected from radical prostatectomy specimens from a cohort of 69 patients treated for localised PCa.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Tumour and normal tissues were subjected to gene analysis, sterol measurement, and immunohistochemistry. The Wilcoxon paired test and Spearman test were applied for comparison and correlation analyses, respectively. Principal component analysis was also carried out to investigate relationships between quantitative variables.

RESULTS AND LIMITATIONS

Overall, cholesterol concentrations were not significantly different between tissue pairs. However, tumour samples were significantly associated with downregulated de novo cholesterol synthesis, but exhibited 54.7% overexpression of SCARB1 that could increase high-density lipoprotein uptake in PCa. Tumour tissues showed different trafficking of available cholesterol, with significantly lower ACAT1, and an altered efflux via APOE. Furthermore, cholesterol metabolism in tumour tissues was characterised by higher accumulation of 7α-hydroxycholesterol (OHC), 7βOHC, and 7-ketosterol, and a lower level of 27OHC.

CONCLUSIONS

Focusing on individually paired prostate tissues, our results highlighted several differences between normal and tumour samples linked to a metabolic shift in cholesterol flux. PCa samples exhibited a specific tissue signature characterised by higher SCARB1 expression, higher accumulation of OHC species, and clear downregulation of de novo cholesterol synthesis.

PATIENT SUMMARY

Comparing normal and tumour tissues from the same prostates, our study identified a set of alterations in prostate cancer samples in terms of their use of cholesterol. These included higher cholesterol uptake, accumulation of oxidised cholesterol derivatives, and autonomous cellular production of cholesterol. Together, these data provide promising clinical targets to fight prostate cancer.

Role of SR-BI in atherosclerosis, malignancies, and infectious diseases

Scavenger receptor class B type I (SR-BI) is a high-affinity receptor for high-density lipoprotein (HDL). The primary role of this receptor is the selective uptake of HDLs in the liver through reverse cholesterol transport. SR-BI interacts with HDL to regulate lipid metabolism and affects various vascular cell functions involved in atherosclerosis (As). In addition, SR-BI is involved in the development of malignant tumors and infectious diseases. This article reviews the function and potential therapeutic targets of SR-BI in As, malignancies, and infectious diseases.

Sprouty2 loss-induced IL6 drives castration-resistant prostate cancer through scavenger receptor B1

Metastatic castration-resistant prostate cancer (mCRPC) is a lethal form of treatment-resistant prostate cancer and poses significant therapeutic challenges. Deregulated receptor tyrosine kinase (RTK) signalling mediated by loss of tumour suppressor Sprouty2 (SPRY2) is associated with treatment resistance. Using pre-clinical human and murine mCRPC models, we show that SPRY2 deficiency leads to an androgen self-sufficient form of CRPC Mechanistically, HER2-IL6 signalling axis enhances the expression of androgen biosynthetic enzyme HSD3B1 and increases SRB1-mediated cholesterol uptake in SPRY2-deficient tumours. Systemically, IL6 elevated the levels of circulating cholesterol by inducing host adipose lipolysis and hepatic cholesterol biosynthesis. SPRY2-deficient CRPC is dependent on cholesterol bioavailability and SRB1-mediated tumoral cholesterol uptake for androgen biosynthesis. Importantly, treatment with ITX5061, a clinically safe SRB1 antagonist, decreased treatment resistance. Our results indicate that cholesterol transport blockade may be effective against SPRY2-deficient CRPC.

Low scavenger receptor class B type I expression is associated with gastric adenocarcinoma tumor aggressiveness

Scavenger receptor class B type I (SR-BI), a well-documented high-density lipoprotein receptor, has been implicated in the development and progression of human cancer. However, little is known regarding the expression profile and clinical value of SR-BI in gastric adenocarcinoma. In the present study immunohistochemistry analysis was performed on a well-annotated gastric adenocarcinoma tissue microarray to investigate the association between SR-BI expression and clinicopathological parameters or patient outcome. The results revealed that SR-BI expression was detected in 69% of the 84 gastric adenocarcinomas. Moreover, a significant association was observed between low SR-BI expression and poor histological grade, higher Tumor-Node-Metastasis T stage, higher N stage and diffuse type carcinoma. Low SR-BI expression was also significantly associated with a shorter overall survival time in patients with gastric adenocarcinoma, although it was not an independent prognostic factor. Overall, the results of the present study demonstrated that SR-BI was possibly involved in gastric carcinogenesis and could be used as a biomarker to predict malignancy of gastric adenocarcinoma.

Lipoproteins for therapeutic delivery: recent advances and future opportunities

The physiological role(s) of mammalian plasma lipoproteins is to transport hydrophobic molecules (primarily cholesterol and triacylglycerols) to their respective destinations. Lipoproteins have also been studied as drug-delivery agents due to their advantageous payload capacity, long residence time in the circulation and biocompatibility. The purpose of this review is to briefly discuss current findings with the focus on each type of formulation's potential for clinical applications. Regarding utilizing lipoprotein type formulation for cancer therapeutics, their potential for tumor-selective delivery is also discussed.

High Density Lipoproteins Inhibit Oxidative Stress-Induced Prostate Cancer Cell Proliferation

Recent evidence suggests that oxidative stress can play a role in the pathogenesis and the progression of prostate cancer (PCa). Reactive oxygen species (ROS) generation is higher in PCa cells compared to normal prostate epithelial cells and this increase is proportional to the aggressiveness of the phenotype. Since high density lipoproteins (HDL) are known to exert antioxidant activities, their ability to reduce ROS levels and the consequent impact on cell proliferation was tested in normal and PCa cell lines. HDL significantly reduced basal and H₂O₂-induced oxidative stress in normal, androgen receptor (AR)-positive and AR-null PCa cell lines. AR, scavenger receptor BI and ATP binding cassette G1 transporter were not involved. In addition, HDL completely blunted H₂O₂-induced increase of cell proliferation, through their capacity to prevent the H₂O₂-induced shift of cell cycle distribution from G0/G1 towards G2/M phase. Synthetic HDL, made of the two main components of plasma-derived HDL (apoA-I and phosphatidylcholine) and which are under clinical development as anti-atherosclerotic agents, retained the ability of HDL to inhibit ROS production in PCa cells. Collectively, HDL antioxidant activity limits cell proliferation induced by ROS in AR-positive and AR-null PCa cell lines, thus supporting a possible role of HDL against PCa progression.

Up-regulation of SR-BI promotes progression and serves as a prognostic biomarker in clear cell renal cell carcinoma

Background

Scavenger receptor class B type I (SR-BI) has been reported to be involved in carcinogenesis of several human cancers. However, it is currently unknown whether SR-BI plays a role in clear cell renal cell carcinoma (ccRCC). Here, we aimed to evaluate a tumor promotive mechanism for SR-BI in ccRCC.

Methods

The expression of SR-BI was evaluated by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blot and immunohistochemistry (IHC) in ccRCC tissues and cell lines. Lipid droplets in ccRCC tissues and normal kidney tissues were examined by Oil Red O (ORO) and hematoxylin-eosin (HE) staining. The correlation between SR-BI mRNA levels and clinicopathological features was analyzed by Pearson’s chi-square test or Fisher’s exact test. Kaplan-Meier analysis and Cox model were used to evaluate the difference in progression-free survival (PFS) associated with expression of SR-BI. Inhibition of SR-BI was conducted by using small interfering RNA (siRNA). In vitro assays were performed to assess the impact of SR-BI knockdown on cell biological behaviors. High density lipoprotein (HDL)-cholesterol content in ccRCC cells and extracellular media was also measured after transfection with siRNA.

Results

The expression of SR-BI was markedly up-regulated in ccRCC tissues and tumor cell lines. ORO and HE staining revealed huge amounts of lipid droplets accumulation in ccRCC. Clinical analysis showed that over-expression of SR-BI was positively associated with tumor size, grade, distant metastasis and inversely correlated with PFS. Furthermore, SR-BI was proved to be an independent prognostic marker in ccRCC patients. The inhibition of SR-BI attenuated the tumorous behaviors of ccRCC cells, expression of metastasis and AKT pathway related proteins. The content of HDL-cholesterol was reduced in cells while increased in extracellular media after transfection with si-SR-BI.

Conclusions

Our results demonstrate that SR-BI functions as an oncogene and promotes progression of ccRCC. SR-BI may serve as a potential prognostic biomarker and therapeutic target for ccRCC.

HDL nanoparticles targeting sonic hedgehog subtype medulloblastoma

Medulloblastoma is the most common paediatric malignant brain cancer and there is a need for new targeted therapeutic approaches to more effectively treat these malignant tumours, which can be divided into four molecular subtypes. Here, we focus on targeting sonic hedgehog (SHH) subtype medulloblastoma, which accounts for approximately 25% of all cases. The SHH subtype relies upon cholesterol signalling for tumour growth and maintenance of tumour-initiating cancer stem cells (CSCs). To target cholesterol signalling, we employed biomimetic high-density lipoprotein nanoparticles (HDL NPs) which bind to the HDL receptor, scavenger receptor type B-1 (SCARB1), depriving cells of natural HDL and their cholesterol cargo. We demonstrate uptake of HDL NPs in SCARB1 expressing medulloblastoma cells and depletion of cholesterol levels in cancer cells. HDL NPs potently blocked proliferation of medulloblastoma cells, as well as hedgehog-driven Ewing sarcoma cells. Furthermore, HDL NPs disrupted colony formation in medulloblastoma and depleted CSC populations in medulloblastoma and Ewing sarcoma. Altogether, our findings provide proof of principle for the development of a novel targeted approach for the treatment of medulloblastoma using HDL NPs. These findings present HDL-mimetic nanoparticles as a promising therapy for sonic hedgehog (SHH) subtype medulloblastoma and possibly other hedgehog-driven cancers.

SR-B1: A Unique Multifunctional Receptor for Cholesterol Influx and Efflux

The scavenger receptor, class B type 1 (SR-B1), is a multiligand membrane receptor protein that functions as a physiologically relevant high-density lipoprotein (HDL) receptor whose primary role is to mediate selective uptake or influx of HDL-derived cholesteryl esters into cells and tissues. SR-B1 also facilitates the efflux of cholesterol from peripheral tissues, including macrophages, back to liver. As a regulator of plasma membrane cholesterol content, SR-B1 promotes the uptake of lipid soluble vitamins as well as viral entry into host cells. These collective functions of SR-B1 ultimately affect programmed cell death, female fertility, platelet function, vasculature inflammation, and diet-induced atherosclerosis and myocardial infarction. SR-B1 has also been identified as a potential marker for cancer diagnosis and prognosis. Finally, the SR-B1-linked selective HDL-cholesteryl ester uptake pathway is now being evaluated as a gateway for the delivery of therapeutic and diagnostic agents. In this review, we focus on the regulation and functional significance of SR-B1 in mediating cholesterol movement into and out of cells.

Cholesterol uptake and regulation in high-grade and lethal prostate cancers

Lethal prostate cancers have higher expression of squalene monooxygenase (SQLE), the second rate-limiting enzyme of cholesterol synthesis. Preclinical studies suggested that aberrant cholesterol regulators, receptors and transporters contribute to cholesterol accumulation uniformly. We assessed their association with features of aggressive cancers. In the prospective prostate cancer cohorts within the Health Professional Follow-up Study, the Physicians' Health Study and the Swedish Watchful Waiting Study, tumor mRNA expression profiling was performed. Lethal disease was defined as mortality or metastases from prostate cancer (n = 266) in contrast to non-lethal disease without metastases after >8 years of follow-up (n = 476). Associations with Gleason grade were additionally assessed using The Cancer Genome Atlas primary prostate cancer dataset (n = 333). Higher Gleason grade was associated with lower LDLR expression, lower SOAT1 and higher SQLE expression. Besides high SQLE expression, cancers that became lethal despite primary treatment were characterized by low LDLR expression (odds ratio for highest versus lowest quintile, 0.37; 95% CI 0.18-0.76) and by low SOAT1 expression (odds ratio, 0.41; 95% CI 0.21-0.83). The association of LDLR expression and lethality was not present in tumors with high IDOL expression. ABCA1, PCSK9 or SCARB1 expressions were not associated with Gleason grade or lethal cancer. In summary, prostate cancers that progress to lethal disease rely on de novo cholesterol synthesis (via SQLE), rather than transcellular uptake (via LDLR) or cholesterol esterification (via SOAT1). These results may help design pharmacotherapy for high-risk patients.