Journal Article

Fisetin induces autophagic cell death through suppression of mTOR signaling pathway in prostate cancer cells

Yewseok Suh, Farrukh Afaq, Naghma Khan, Jeremy J. Johnson, Fatima H. Khusro and Hasan Mukhtar

in Carcinogenesis

Volume 31, issue 8, pages 1424-1433
Published in print August 2010 | ISSN: 0143-3334
Published online June 2010 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgq115
Fisetin induces autophagic cell death through suppression of mTOR signaling pathway in prostate cancer cells

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The mammalian target of rapamycin (mTOR) kinase is an important component of PTEN/PI3K/Akt signaling pathway, which is frequently deregulated in prostate cancer (CaP). Recent studies suggest that targeting PTEN/PI3K/Akt and mTOR signaling pathway could be an effective strategy for the treatment of hormone refractory CaP. Here, we show that the treatment of androgen-independent and PTEN-negative human CaP PC3 cells with fisetin, a dietary flavonoid, resulted in inhibition of mTOR kinase signaling pathway. Treatment of cells with fisetin inhibited mTOR activity and downregulated Raptor, Rictor, PRAS40 and GβL that resulted in loss of mTOR complexes (mTORC)1/2 formation. Fisetin also activated the mTOR repressor TSC2 through inhibition of Akt and activation of AMPK. Fisetin-mediated inhibition of mTOR resulted in hypophosphorylation of 4EBP1 and suppression of Cap-dependent translation. We also found that fisetin treatment leads to induction of autophagic-programmed cell death rather than cytoprotective autophagy as shown by small interfering RNA Beclin1-knockdown and autophagy inhibitor. Taken together, we provide evidence that fisetin functions as a dual inhibitor of mTORC1/2 signaling leading to inhibition of Cap-dependent translation and induction of autophagic cell death in PC3 cells. These results suggest that fisetin could be a useful chemotherapeutic agent in treatment of hormone refractory CaP.

Journal Article.  6903 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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