Dataset Information

Supraphysiological androgen levels induce cellular senescence in human prostate cancer cells through the Src-Akt pathway.

ABSTRACT:

Background

Prostate cancer (PCa) is the second leading cause of cancer mortality of men in Western countries. The androgen receptor (AR) and AR-agonists (androgens) are required for the development and progression of the normal prostate as well as PCa. However, it is discussed that in addition to their tumor promoting activity, androgens may also exhibit tumor suppressive effects. A biphasic growth response to androgens a growth-promoting and -inhibition has been observed that suggests that administration of supraphysiological androgen levels mediates growth reduction in AR expressing PCa cells.

Methods

Detection of senescence markers, three dimensional interphase fluorescence in situ hybridization (3D-iFISH), qRT-PCR, Western blotting, detection of GFP fusions, prostatectomy, ex vivo culturing.

Results

Here, we describe that supraphysiological levels of androgens induce cell cycle arrest and markers of cellular senescence in human PCa cells, which may in part explain the growth inhibitory role of androgens. The expression of the senescence associated beta galactosidase is observed by treatment with the natural androgen DHT or the less metabolized synthetic androgen R1881. The induction of senescence marker was detected in human PCa cell lines as well as in human primary PCa tissue derived from prostatectomy treated ex vivo. Using interphase FISH (iFISH) suggests that the androgen-induced cellular senescence is associated with localizing the genomic E2F1 locus to senescence associated heterochromatic foci. Analysis of different signaling pathways in LNCaP cells suggest that the p16-Rb-E2F1 pathway is essential for the induction of cellular senescence since treatment with siRNA directed against p16 reduces the level of androgen-induced cellular senescence. Based on the rapid induction of androgen-mediated cellular senescence we identified the Src-PI3K-Akt-signaling pathway and autophagy being in part involved in androgen regulation.

Conclusions

Taken together, our data suggest that AR-agonists at supraphysiological levels mediate induction of cellular senescence in human PCa cells, which may have a protective anti-cancer role. These results provide also new insights for understanding androgen-mediated regulation of PCa growth.

SUBMITTER: Roediger J

PROVIDER: S-EPMC4171558 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Publications

Supraphysiological androgen levels induce cellular senescence in human prostate cancer cells through the Src-Akt pathway.

Roediger Julia J Hessenkemper Wiebke W Bartsch Sophie S Manvelyan Marina M Huettner Soeren S SS Liehr Thomas T Esmaeili Mohsen M Foller Susan S Petersen Iver I Grimm Marc-Oliver MO Baniahmad Aria A

Molecular cancer 20140912

<h4>Background</h4>Prostate cancer (PCa) is the second leading cause of cancer mortality of men in Western countries. The androgen receptor (AR) and AR-agonists (androgens) are required for the development and progression of the normal prostate as well as PCa. However, it is discussed that in addition to their tumor promoting activity, androgens may also exhibit tumor suppressive effects. A biphasic growth response to androgens a growth-promoting and -inhibition has been observed that suggests t ...[more]

PMID: 25216853

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Project description:The bipolar androgen therapy (BAT) to treat prostate cancer includes cycles of supraphysiological androgen levels (SAL) under continuous androgen deprivation therapy (ADT). We showed previously that SAL induces cellular senescence in androgen-sensitive PCa cells and ex vivo in PCa tumor samples from patients that underwent radical prostatectomy. Here, we show that SAL induces cellular senescence in both, castration sensitive (CSPC) LNCaP and castration resistant PCa (CRPC) C4-2 cells through the cell cycle inhibitor p15. Treatment with the Akt inhibitor (Akti) potently inhibited SAL-induced expression of p15 and cellular senescence in both cell lines. Proximity ligation assays (PLA) combined with high-resolution laser-scanning microscopy indicate that SAL promotes interaction of endogenous androgen receptor (AR) with endogenous Akt in cytoplasm as well as in nucleus after 72 hours hormone treatment. This suggests that the AR interacts with Akt also in a long-term manner. Transcriptome sequencing (RNA-seq) comparing the SAL-induced transcriptomes of LNCaP with C4-2 cells as well as of Akti treated cells revealed landscapes for cell senescence. Interestingly, one of the identified genes is the lncRNASAT1. SAL treatment of native patient tumor samples ex vivo results in upregulation of lncRNASAT1. The lncRNASAT1 is down-regulated in PCa tumor tissues compared to non-tumor tissues of same patients indicating a tumor suppressive function. Knockdown indicates that the lncRNASAT1 is crucial for SAL-induced cancer cell senescence and regulates LNCaP cell proliferation being an upstream factor for pAkt and for p15. Further, knockdown of lncRNASAT1 inhibits LNCaP cell proliferation by low androgen levels but enhances proliferation by SAL. This suggests that lncRNASAT1 serves as a tumor suppressor with SAL. Interestingly, immunoprecipitation of AR detected lncRNASAT1 as an AR interacting partner that regulates AR target gene expression. Thus, we identified a novel pathway of androgen signaling as the AR- lncRNASAT1- Akt- p15INK4b- axis to mediate SAL-induced cellular senescence.

Project description:Background: Both supraphysiological and subphysiological testosterone levels are associated with increased cardiovascular risk. Testosterone consumption at supraphysiological doses has been linked to increased blood pressure, left ventricular hypertrophy, vascular dysfunction, and increased levels of inflammatory markers. Activation of the NLRP3 inflammasome contributes to the production of proinflammatory cytokines, leading to cardiovascular dysfunction. We hypothesized that supraphysiological levels of testosterone, via generation of mitochondrial reactive oxygen species (mROS), activates the NLRP3 inflammasome and promotes vascular dysfunction. Methods: Male, 12 week-old C57Bl/6J (WT) and NLRP3 knockout (NLRP3-/-) mice were used. Mice were treated with testosterone propionate [TP (10 mg/kg) in vivo] or vehicle for 30 days. In addition, vessels were incubated with testosterone [Testo (10-6 M, 2 h) in vitro]. Testosterone levels, blood pressure, vascular function (thoracic aortic rings), pro-caspase-1/caspase-1 and interleukin-1? (IL-1?) expression, and generation of reactive oxygen species were determined. Results: Testosterone increased contractile responses and reduced endothelium-dependent vasodilation, both in vivo and in vitro. These effects were not observed in arteries from NLRP3-/- mice. Aortas of TP-treated WT mice (in vivo), as well as aortas from WT mice incubated with testo (in vitro), exhibited increased mROS levels and increased caspase-1 and IL-1? expression. These effects were not observed in arteries from NLRP3-/- mice. Flutamide [Flu, 10-5 M, androgen receptor (AR) antagonist], carbonyl cyanide m-chlorophenyl hydrazone (CCCP, 10-6 M, mitochondrial uncoupler) and MCC950 (MCC950, 10-6 M, a NLRP3 receptor inhibitor) prevented testosterone-induced mROS generation. Conclusion: Supraphysiological levels of testosterone induce vascular dysfunction via mROS generation and NLRP3 inflammasome activation. These events may contribute to increased cardiovascular risk.

Dataset Information

Supraphysiological androgen levels induce cellular senescence in human prostate cancer cells through the Src-Akt pathway.

Background

Methods

Results

Conclusions

Publications

Supraphysiological androgen levels induce cellular senescence in human prostate cancer cells through the Src-Akt pathway.

Similar Datasets

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