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The importance of LDL and cholesterol metabolism for prostate epithelial cell growth.

ABSTRACT: Cholesterol-lowering treatment has been suggested to delay progression of prostate cancer by decreasing serum LDL. We studied in vitro the effect of extracellular LDL-cholesterol on the number of prostate epithelial cells and on the expression of key regulators of cholesterol metabolism. Two normal prostatic epithelial cell lines (P96E, P97E), two in vitro immortalized epithelial cell lines (PWR-1E, RWPE-1) and two cancer cell lines (LNCaP and VCaP) were grown in cholesterol-deficient conditions. Cells were treated with 1-50 µg/ml LDL-cholesterol and/or 100 nM simvastatin for seven days. Cell number relative to control was measured with crystal violet staining. Changes in mRNA and protein expression of key effectors in cholesterol metabolism (HMGCR, LDLR, SREBP2 and ABCA1) were measured with RT-PCR and immunoblotting, respectively. LDL increased the relative cell number of prostate cancer cell lines, but reduced the number of normal epithelial cells at high concentrations. Treatment with cholesterol-lowering simvastatin induced up to 90% reduction in relative cell number of normal cell lines but a 15-20% reduction in relative number of cancer cells, an effect accompanied by sharp upregulation of HMGCR and LDLR. These effects were prevented by LDL. Compared to the normal cells, prostate cancer cells showed high expression of cholesterol-producing HMGCR but failed to express the major cholesterol exporter ABCA1. LDL increased relative cell number of cancer cell lines, and these cells were less vulnerable than normal cells to cholesterol-lowering simvastatin treatment. Our study supports the importance of LDL for prostate cancer cells, and suggests that cholesterol metabolism in prostate cancer has been reprogrammed to increased production in order to support rapid cell growth.

SUBMITTER: Murtola TJ

PROVIDER: S-EPMC3384647 | biostudies-other | 2012

REPOSITORIES: biostudies-other

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The importance of LDL and cholesterol metabolism for prostate epithelial cell growth.

Murtola Teemu J TJ Syvälä Heimo H Pennanen Pasi P Bläuer Merja M Solakivi Tiina T Ylikomi Timo T Tammela Teuvo L J TL

PloS one 20120627 6

Cholesterol-lowering treatment has been suggested to delay progression of prostate cancer by decreasing serum LDL. We studied in vitro the effect of extracellular LDL-cholesterol on the number of prostate epithelial cells and on the expression of key regulators of cholesterol metabolism. Two normal prostatic epithelial cell lines (P96E, P97E), two in vitro immortalized epithelial cell lines (PWR-1E, RWPE-1) and two cancer cell lines (LNCaP and VCaP) were grown in cholesterol-deficient conditions ...[more]

PMID: 22761797

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Project description:BackgroundProstate cancer growth is driven by androgen receptor signaling, and advanced disease is initially treatable by depleting circulating androgens. However, prostate cancer cells inevitably adapt, resulting in disease relapse with incurable castrate-resistant prostate cancer. Androgen deprivation therapy has many side effects, including hypercholesterolemia, and more aggressive and castrate-resistant prostate cancers typically feature cellular accumulation of cholesterol stored in the form of cholesteryl esters. As cholesterol is a key substrate for de novo steroidogenesis in prostate cells, this study hypothesized that castrate-resistant/advanced prostate cancer cell growth is influenced by the availability of extracellular, low-density lipoprotein (LDL)-derived, cholesterol, which is coupled to intracellular cholesteryl ester homeostasis.MethodsC4-2B and PC3 prostate cancer cells were cultured in media supplemented with fetal calf serum (FCS), charcoal-stripped FCS (CS-FCS), lipoprotein-deficient FCS (LPDS), or charcoal-stripped LPDS (CS-LPDS) and analyzed by a variety of biochemical techniques. Cell viability and proliferation were measured by MTT assay and Incucyte, respectively.ResultsReducing lipoprotein availability led to a reduction in cholesteryl ester levels and cell growth in C4-2B and PC3 cells, with concomitant reductions in PI3K/mTOR and p38MAPK signaling. This reduced growth in LPDS-containing media was fully recovered by supplementation of exogenous low-density lipoprotein (LDL), but LDL only partially rescued growth of cells cultured with CS-LPDS. This growth pattern was not associated with changes in androgen receptor signaling but rather increased p38MAPK and MEK1/ERK/MSK1 activation. The ability of LDL supplementation to rescue cell growth required cholesterol esterification as well as cholesteryl ester hydrolysis activity. Further, growth of cells cultured in low androgen levels (CS-FCS) was suppressed when cholesteryl ester hydrolysis was inhibited.ConclusionsOverall, these studies demonstrate that androgen-independent prostate cancer cell growth can be influenced by extracellular lipid levels and LDL-cholesterol availability and that uptake of extracellular cholesterol, through endocytosis of LDL-derived cholesterol and subsequent delivery and storage in the lipid droplet as cholesteryl esters, is required to support prostate cancer cell growth. This provides new insights into the relationship between extracellular cholesterol, intracellular cholesterol metabolism, and prostate cancer cell growth and the potential mechanisms linking hypercholesterolemia and more aggressive prostate cancer.

Project description:Dyslipidemia is described as a hallmark of metabolic syndrome, promoting a stage of metabolic inflammation (metainflammation) that could lead to misbalances in energetic metabolism, contributing to insulin resistance, and modifying intracellular cholesterol pathways and the renin-angiotensin system (RAS) in pancreatic islets. Low-density lipoprotein (LDL) hypercholesterolemia could disrupt the tissue communication between Langerhans β-cells and hepatocytes, wherein extracellular vesicles (EVs) are secreted by β-cells, and exposition to LDL can impair these phenomena. β-cells activate compensatory mechanisms to maintain insulin and metabolic homeostasis; therefore, the work aimed to characterize the impact of LDL on β-cell cholesterol metabolism and the implication on insulin secretion, connected with the regulation of cellular communication mediated by EVs on hepatocytes. Our results suggest that β-cells can endocytose LDL, promoting an increase in de novo cholesterol synthesis targets. Notably, LDL treatment increased mRNA levels and insulin secretion; this hyperinsulinism condition was associated with the transcription factor PDX-1. However, a compensatory response that maintains basal levels of intracellular calcium was described, mediated by the overexpression of calcium targets PMCA1/4, SERCA2, and NCX1, together with the upregulation of the unfolded protein response (UPR) through the activation of IRE1 and PERK arms to maintain protein homeostasis. The LDL treatment induced metainflammation by IL-6, NF-κB, and COX-2 overexpression. Furthermore, LDL endocytosis triggered an imbalance of the RAS components. LDL treatment increased the intracellular levels of cholesterol on lipid droplets; the adaptive β-cell response was portrayed by the overexpression of cholesterol transporters ABCA1 and ABCG1. Therefore, lipotoxicity and hyperinsulinism induced by LDL were regulated by the natural compound auraptene, a geranyloxyn coumarin modulator of cholesterol-esterification by ACAT1 enzyme inhibition. EVs isolated from β-cells impaired insulin signaling via mTOR/p70S6Kα in hepatocytes, a phenomenon regulated by auraptene. Our results show that LDL overload plays a novel role in hyperinsulinism, mechanisms associated with a dysregulation of intracellular cholesterol, lipotoxicity, and the adaptive UPR, which may be regulated by coumarin-auraptene; these conditions explain the affectations that occur during the initial stages of insulin resistance.

Project description:Cholesterol efflux relates to cardiovascular disease but cannot predict cellular cholesterol mass changes. We asked whether influx and net flux assays provide additional insights.Adapt a bidirectional flux assay to cells where efflux has clinical correlates and examine the association of influx, efflux, and net flux to serum triglycerides (TGs). Apolipoprotein B-depleted (high-density lipoprotein-fraction) serum from individuals with unfavorable lipids (median [interquartile range]; high-density lipoprotein-cholesterol=39 [32-42], low-density lipoprotein-cholesterol=109 [97-137], TGs=258 [184-335] mg/dL; n=13) promoted greater ATP-binding cassette transporter A1-mediated [1,2-(3H)] cholesterol efflux (3.8±0.3%/4 hour versus 1.2±0.4%/4 hour; P<0.0001) from cyclic 3',5'-amp(CTP-amp)-treated J774 macrophages than from individuals with favorable lipids (high-density lipoprotein-cholesterol=72 [58-88], low-density lipoprotein-cholesterol=111 [97-131], TGs=65 [56-69] mg/dL; n=10). Thus, high TGs associated with more ATP-binding cassette transporter A1 acceptors. Efflux of cholesterol mass (?g free cholesterol/mg cell protein per 8 hour) to serum was also higher (7.06±0.33 versus 5.83±0.48; P=0.04). However, whole sera from individuals with unfavorable lipids promoted more influx (5.14±0.65 versus 2.48±0.85; P=0.02) and lower net release of cholesterol mass (1.93±0.46 versus 3.36±0.47; P=0.04). The pattern differed when mass flux was measured using apolipoprotein B-depleted serum rather than serum. Although individuals with favorable lipids tended to have greater influx than those with unfavorable lipids, efflux to apolipoprotein B-depleted serum was markedly higher (6.81±0.04 versus 2.62±0.14; P<0.0001), resulting in an efflux:influx ratio of ?3-fold. Thus both serum and apolipoprotein B-depleted serum from individuals with favorable lipids promoted greater net cholesterol mass release despite increased ATP-binding cassette transporter A1-mediated efflux in samples of individuals with high TGs/unfavorable lipids.When considering the efficiency of serum specimens to modulate cell cholesterol content, both influx and efflux need to be measured.

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The importance of LDL and cholesterol metabolism for prostate epithelial cell growth.

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The importance of LDL and cholesterol metabolism for prostate epithelial cell growth.

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