Diagnostic and prognostic value of scavenger receptor class B type 1 in clear cell renal cell carcinoma

Circ_0003146 upregulates SCARB1 expression by acting as a miR-1272 sponge to promote malignant behaviors of clear cell renal cell carcinoma

Circular RNAs (circRNAs) exhibit essential regulation in the malignant development of clear cell renal cell carcinoma (ccRCC). The aims of this study were to investigate the role and mechanism of circ_0003146 in the biologic behaviors of ccRCC. RNA level analysis was performed through reverse transcription-quantitative PCR assay. Cell proliferation was measured by EdU assay and cell counting kit-8 assay. The protein expression was analyzed using a western blot. Flow cytometry and caspase 3 activity assay were used to assess cell apoptosis. Cell migration and invasion were evaluated via wound healing assay and transwell assay. Circ_0003146 function in vivo was determined by xenograft tumor assay. Dual-luciferase reporter assay was applied for target relation analysis. Circ_0003146 upregulation was detected in ccRCC tissues and cells. Downregulation of circ_0003146 induced inhibition of proliferation, migration, invasion and EMT but the promotion of apoptosis in ccRCC cells. Tumor growth in vivo was inhibited after knockdown of circ_0003146. Circ_0003146 directly interacted with miR-1272, and the miR-1272 sponging effect was responsible for the function of circ_0003146. Scavenger receptor class B type 1 (SCARB1) was a target of miR-1272, and circ_0003146 regulated SCARB1 level by absorbing miR-1272. The regulation of circ_0003146 in ccRCC progression was achieved by upregulating SCARB1 in part. The current findings demonstrated that circ_0003146 contributed to the malignant progression of ccRCC via inducing SCARB1 upregulation by targeting miR-1272.

Establishment and characterization of a highly metastatic human osteosarcoma cell line from osteosarcoma lung metastases

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ZOSL-1 was the first report that isolated directly from lung metastases of OS.

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ZOSL-1 cells were highly metastatic, and the lung metastasis rate was 100% in vivo.

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ZOSL-1 cells were high expression in GNAS, SCARB1 and CXCR4 genes.

OS (Osteosarcoma) is the most common malignant tumor in adolescents, and lung metastasis limits its therapeutic outcome. The present study aimed to establish a highly metastatic human OS cell line directly from lung metastases and characterize its biological functions. In this study, epithelioid tumor cells with large nucleo-cytoplasmic ratio and abundant organelles were obtained by the tissue mass adherent and repeated digestion adherent method and named ZOSL-1 cells. ZOSL-1 cells had the potential to proliferate in vitro with a doubling time of 39.28 ± 3.04 h and migrate with or without a matrix. ZOSL-1 cells were tumorigenic in vivo, and had the ability to develop lung metastasis after intratibial injection. ZOSL-1 cells expressed the osteogenic-related genes osteocalcin and osteopontin. In addition, the expression of ZOSL-1 in Fas cell surface death receptor (FAS), CD44 molecule (CD44), GNAS complex locus (GNAS), scavenger receptor class B member 1 (SCARB1), C-X-C motif chemokine receptor 4 (CXCR4), cadherin 11 (CDH11), neurofibromin 2 (NF2) and ezrin (EZR) genes may be related to its transfer efficiency. Taken together, these results indicated the high metastatic capability and important biological functions of ZOSL-1 cells. ZOSL-1 establishment provided a relevant model for the study of osteosarcoma lung metastasis.

Targeted reduction of cholesterol uptake in cholesterol-addicted lymphoma cells blocks turnover of oxidized lipids to cause ferroptosis

Normal human cells can either synthesize cholesterol or take it up from lipoproteins to meet their metabolic requirements. In some malignant cells, de novo cholesterol synthesis genes are transcriptionally silent or mutated, meaning that cholesterol uptake from lipoproteins is required for survival. Recent data suggest that lymphoma cells dependent upon lipoprotein-mediated cholesterol uptake are also subject to ferroptosis, an oxygen- and iron-dependent cell death mechanism triggered by accumulation of oxidized lipids in cell membranes unless the lipid hydroperoxidase, glutathione peroxidase 4 (GPX4), reduces these toxic lipid species. To study mechanisms linking cholesterol uptake with ferroptosis and determine the potential role of the high-density lipoprotein (HDL) receptor as a target for cholesterol depleting therapy, we treated lymphoma cell lines known to be sensitive to the reduction of cholesterol uptake with HDL-like nanoparticles (HDL NPs). HDL NPs are a cholesterol-poor ligand that binds to the receptor for cholesterol-rich HDLs, scavenger receptor type B1 (SCARB1). Our data reveal that HDL NP treatment activates a compensatory metabolic response in treated cells toward increased de novo cholesterol synthesis, which is accompanied by nearly complete reduction in expression of GPX4. As a result, oxidized membrane lipids accumulate, leading to cell death through a mechanism consistent with ferroptosis. We obtained similar results in vivo after systemic administration of HDL NPs in mouse lymphoma xenografts and in primary samples obtained from patients with lymphoma. In summary, targeting SCARB1 with HDL NPs in cholesterol uptake-addicted lymphoma cells abolishes GPX4, resulting in cancer cell death by a mechanism consistent with ferroptosis.

Prognostic and clinicopathological significance of SR-B1 in solid tumors: A meta-analysis

BACKGROUND

The expression of cell surface receptors is abnormal in malignant tumors. The scavenger receptor class B type I (SR-B1) is an integral membrane glycoprotein receptor that facilitates the selective uptake of cholesterol by malignant cells. Accumulated studies investigated the prognostic role of SR-B1 in many solid tumors, such as breast cancer, lung cancer and so on. However, the conclusions remain undefined. Therefore, we conducted this meta-analysis to obtain more accurate evaluation of prognostic significance of SR-B1 in solid tumors.

MATERIALS AND METHODS

We searched PubMed, Embase, Web of science and Cochrane library for eligible studies published before November 2018. The included studies investigated the association between the SR-B1 level and clinicopathological features including survival outcomes in solid tumors. Hazard ratios (HRs) with 95% confidence intervals (CIs) were adopted to assess the survival outcomes and odds ratio (ORs) with 95% confidence intervals (CIs) were pooled to evaluated the clinicopathological features.

RESULTS

A total of 10 studies involving 2585 patients were included in this meta-analysis. The results showed that low SR-B1 level was significantly correlated with earlier tumor grade (pooled OR = 2.09, 95%CI = 1.28-3.43, P = 0.001), less nodal involvement (pooled OR = 2.07, 95%CI = 1.43-3.0, P < 0.001), less distant metastasis (OR = 19.8, 95%CI = 2.58-151.65, P = 0.004), smaller tumor size (OR = 2.34, 95%CI = 1.53-3.57, P < 0.001), earlier TNM stage (OR = 3.77, 95%CI = 1.67-8.48, P = 0.001), lower recurrence (HR = 1.98, 95%CI = 1.57-2.49, P = 0.000), and better OS (HR = 1.99, 95%CI = 1.70-2.31, P = 0.000).

CONCLUSION

The low expression of SR-B1 was significantly associated with better clinicopathological status and longer survival in patients with solid tumors. SR-B1 might act as a promising prognostic biomarker for solid tumors.

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.

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.

Scavenger receptor BI promotes cytoplasmic accumulation of lipoproteins in clear-cell renal cell carcinoma

Clear-cell renal cell carcinomas (ccRCCs) are characterized by inactivation of the von Hippel-Lindau (VHL) gene and intracellular lipid accumulation by unknown pathomechanisms. The immunochemical analysis of 356 RCCs revealed high abundance of apoA-I and apoB, as well as scavenger receptor BI (SR-BI) in the ccRCC subtype. Given the characteristic loss of VHL function in ccRCC, we used VHL-defective and VHL-proficient cells to study the potential influence of VHL on lipoprotein uptake. VHL-defective patient-derived ccRCC cells and cell lines (786O and RCC4) showed enhanced uptake as well as less resecretion and degradation of radio-iodinated HDL and LDL (¹²⁵I-HDL and ¹²⁵I-LDL, respectively) compared with the VHL-proficient cells. The ccRCC cells showed enhanced vascular endothelial growth factor (VEGF) and SR-BI expression compared with normal kidney epithelial cells. Uptake of ¹²⁵I-HDL and ¹²⁵I-LDL by patient-derived normal kidney epithelial cells as well as the VHL-reexpressing ccRCC cell lines, 786-O-VHL and RCC4-O-VHL cells, was strongly enhanced by VEGF treatment. The knockdown of the VEGF coreceptor, neuropilin-1 (NRP1), as well as blocking of SR-BI significantly reduced the uptake of lipoproteins into ccRCC cells in vitro. LDL stimulated proliferation of 786-O cells more potently than 786-O-VHL cells in a NRP1- and SR-BI-dependent manner. In conclusion, enhanced lipoprotein uptake due to increased activities of VEGF/NRP1 and SR-BI promotes lipid accumulation and proliferation of VHL-defective ccRCC cells.

SCARB1 rs5888 gene polymorphisms in coronary heart disease: A systematic review and a meta-analysis

BACKGROUND

Studies have suggested that high-density lipoprotein (HDL) stimulates scavenger receptor class B type 1 (SR-B1) to promote hepatic uptake of cholesterol. SR-B1 is encoded by scavenger receptor class B member 1 (SCARB1) gene in human. A rare mutation in SCARB1 gene has been associated with coronary heart disease (CHD). A polymorphism rs5888 of SCARB1 gene has been linked to CHD risk in humans.

OBJECTIVES

The objective was to investigate the relationship between the SCARB1 gene polymorphism rs5888 and risk of CHD.

METHODS

We searched databases of case-control studies and cohort studies on rs5888 polymorphism of SCARB1 gene and risk of CHD. Two reviewers independently screened literature, extracted data, and estimated potential bias of included studies. The quality of the studies was evaluated by recommendation of Newcastle-Ottawa Scale (NOS). Meta-analysis was performed with Stata 12.0 software.

RESULTS

Seven studies including 6360 subjects (cases: 2456, controls: 3904) were included in the final data combination. Meta-analysis showed T allele had a lower risk of CHD as compared to C allele in allele model (T vs. C: OR = 0.87, 95% CI: 0.70 to 1.09, P = 0.229). Moreover, we found that T allele or TT/TC had a lower risk of CHD as compared to C/CC in male in allele model (T vs. C: OR = 0.79, 95% CI: 0.61 to 1.01). However, no significant association was observed in women in all allele models.

CONCLUSIONS

Our findings suggested that polymorphism rs5888 had negative association with CHD, especially in male. However, the conclusion needs further verification with high quality studies with larger sample size and rigorous designs.