Cholesterol targeting alters lipid raft composition and cell survival in prostate cancer cells and xenografts
Liyan Zhuang, … , Keith R. Solomon, Michael R. Freeman
Liyan Zhuang, … , Keith R. Solomon, Michael R. Freeman
Published April 1, 2005
Citation Information: J Clin Invest. 2005;115(4):959-968. https://doi.org/10.1172/JCI19935.
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Article Oncology

Cholesterol targeting alters lipid raft composition and cell survival in prostate cancer cells and xenografts

Abstract

Lipid rafts are cholesterol- and sphingolipid-enriched microdomains in cell membranes that regulate phosphorylation cascades originating from membrane-bound proteins. In this study, we tested whether alteration of the cholesterol content of lipid rafts in prostate cancer (PCa) cell membranes affects cell survival mechanisms in vitro and in vivo. Simvastatin, a cholesterol synthesis inhibitor, lowered raft cholesterol content, inhibited Akt1 serine-threonine kinase (protein kinase Bα)/protein kinase B (Akt/PKB) pathway signaling, and induced apoptosis in caveolin- and PTEN-negative LNCaP PCa cells. Replenishing cell membranes with cholesterol reversed these inhibitory and apoptotic effects. Cholesterol also potentiated Akt activation in normal prostate epithelial cells, which were resistant to the apoptotic effects of simvastatin. Elevation of circulating cholesterol in SCID mice increased the cholesterol content and the extent of protein tyrosine phosphorylation in lipid rafts isolated from LNCaP/sHB xenograft tumors. Cholesterol elevation also promoted tumor growth, increased phosphorylation of Akt, and reduced apoptosis in the xenografts. Our results implicate membrane cholesterol in Akt signaling in both normal and malignant cells and provide evidence that PCa cells can become dependent on a cholesterol-regulated Akt pathway for cell survival.

Authors

Liyan Zhuang, Jayoung Kim, Rosalyn M. Adam, Keith R. Solomon, Michael R. Freeman

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Figure 3

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Cholesterol depletion inhibits Akt phosphorylation but does not induce a...
Cholesterol depletion inhibits Akt phosphorylation but does not induce apoptosis in PrECs. (A) Immunodetection of Akt in cell lysates following treatments. PrECs were treated with 20 ng/ml EGF, in the presence or absence of cholesterol complexes, under the following conditions: 1 hour of pretreatment with 2 μg/ml filipin (lane 2), 1 hour of pretreatment with 20 mM cyclodextrin (lane 3), 16 hours of pretreatment with 20 μM simvastatin (lane 4), 1 hour of pretreatment with vehicle (lane 5). After 1 hour of cholesterol pretreatment (lane 6), some groups were incubated with 2 μg/ml filipin (lane 7) or 20 mM cyclodextrin (lane 8). Other groups treated identically to conditions in lanes 7 and 8 were repleted (asterisk) with cholesterol for 1 hour (lanes 9 and 10). (B) PrECs were treated with varying concentrations of simvastatin or vehicle for 24 hours, and the extent of apoptosis was determined by DNA fragmentation. Values shown are means ± SD of triplicate determinations.