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Valproic acid induces autophagy by suppressing the Akt/mTOR pathway in human prostate cancer cells

View Article: PubMed Central - PubMed

ABSTRACT

Previous studies have demonstrated that the chronic administration of valproic acid (VPA) suppresses angiogenesis in vivo; however, the mechanisms implicated in VPA-induced autophagy remain unclear. The current study aimed to assess VPA-induced autophagy in three prostate cancer cell lines (PC3, DU145 and LNCaP), in addition to analyzing the Akt/mammalian target of rapamycin (mTOR) signal pathway. Prostate cancer cell lines were cultured with various doses of VPA. Cell cycle was analyzed using flow cytometry, and autophagy markers [1A/1B-light chain 3 (LC3)-II and Beclin-1] were examined using transmission electron microscopy, fluorescent microscopy and western blotting. Activation of the Akt/mTOR signal pathway was also assessed by western blotting. The results demonstrated that VPA induced autophagosomes and suppressed the Akt/mTOR signal pathway. This was confirmed by detection of increased LC3-II and Beclin-1 in VPA-treated cells compared with untreated controls. Phosphorylated forms of Akt (PC3, P=0.048; DU145, P=0.045; LNCaP, P=0.039) and mTOR (PC3, P=0.012; DU145, P=0.41; LNCaP, P=0.35) were significantly reduced following VPA treatment. These results suggest that VPA may function as a histone deacetylase inhibitor, suppressing the growth of prostate cancer cells by modulating autophagy pathways, including inhibition of the Akt/mTOR pathway. Further experiments are required to determine the significance of all involved pathways regarding VPA-induced growth inhibition.

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VPA induces cell cycle arrest primarily at the G0-G1 phase. (A) Cells were treated with various concentrations of VPA (1.2, 2.5 and 5.0 mmol/l) for 48 h, and were subsequently fixed and stained with propidium iodide. Cell cycle distribution was assessed by flow cytometry. When the DNA curve was measured, the cell number formed a G1 percentage peak. Subsequent to VPA treatment, the percentage of cells in the G0-G1 phase were significantly increased in a dose-dependent manner in PC3 and DU145 cells. VPA caused cell cycle arrest in PC3 and DU145 cell lines. (B) Histograms represent the percentage of cells arrested at the G0-G1 phase. The percentage of cells in the G0-G1 phase were increased in a dose-dependent manner in PC3 and DU145 cells. The G0-G1 phase of the three VPA treatment groups was significantly longer compared with the control groups in the two cell lines. *P<0.05. VPA, valproic acid.
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f1-ol-0-0-4880: VPA induces cell cycle arrest primarily at the G0-G1 phase. (A) Cells were treated with various concentrations of VPA (1.2, 2.5 and 5.0 mmol/l) for 48 h, and were subsequently fixed and stained with propidium iodide. Cell cycle distribution was assessed by flow cytometry. When the DNA curve was measured, the cell number formed a G1 percentage peak. Subsequent to VPA treatment, the percentage of cells in the G0-G1 phase were significantly increased in a dose-dependent manner in PC3 and DU145 cells. VPA caused cell cycle arrest in PC3 and DU145 cell lines. (B) Histograms represent the percentage of cells arrested at the G0-G1 phase. The percentage of cells in the G0-G1 phase were increased in a dose-dependent manner in PC3 and DU145 cells. The G0-G1 phase of the three VPA treatment groups was significantly longer compared with the control groups in the two cell lines. *P<0.05. VPA, valproic acid.

Mentions: To further understand the mechanism underlying VPA-induced cell growth inhibition, the impact of VPA on the regulation of cell cycle distribution was investigated using flow cytometry. As presented in Fig. 1, the results demonstrated that VPA was able to induce cell cycle arrest in the DU145 and LNCaP cell lines. The cell number percentage in the G0-G1 phase significantly increased in a dose-dependent manner compared with control groups (PC3, P=0.035; DU145, P=0.037).


Valproic acid induces autophagy by suppressing the Akt/mTOR pathway in human prostate cancer cells
VPA induces cell cycle arrest primarily at the G0-G1 phase. (A) Cells were treated with various concentrations of VPA (1.2, 2.5 and 5.0 mmol/l) for 48 h, and were subsequently fixed and stained with propidium iodide. Cell cycle distribution was assessed by flow cytometry. When the DNA curve was measured, the cell number formed a G1 percentage peak. Subsequent to VPA treatment, the percentage of cells in the G0-G1 phase were significantly increased in a dose-dependent manner in PC3 and DU145 cells. VPA caused cell cycle arrest in PC3 and DU145 cell lines. (B) Histograms represent the percentage of cells arrested at the G0-G1 phase. The percentage of cells in the G0-G1 phase were increased in a dose-dependent manner in PC3 and DU145 cells. The G0-G1 phase of the three VPA treatment groups was significantly longer compared with the control groups in the two cell lines. *P<0.05. VPA, valproic acid.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4998110&req=5

f1-ol-0-0-4880: VPA induces cell cycle arrest primarily at the G0-G1 phase. (A) Cells were treated with various concentrations of VPA (1.2, 2.5 and 5.0 mmol/l) for 48 h, and were subsequently fixed and stained with propidium iodide. Cell cycle distribution was assessed by flow cytometry. When the DNA curve was measured, the cell number formed a G1 percentage peak. Subsequent to VPA treatment, the percentage of cells in the G0-G1 phase were significantly increased in a dose-dependent manner in PC3 and DU145 cells. VPA caused cell cycle arrest in PC3 and DU145 cell lines. (B) Histograms represent the percentage of cells arrested at the G0-G1 phase. The percentage of cells in the G0-G1 phase were increased in a dose-dependent manner in PC3 and DU145 cells. The G0-G1 phase of the three VPA treatment groups was significantly longer compared with the control groups in the two cell lines. *P<0.05. VPA, valproic acid.
Mentions: To further understand the mechanism underlying VPA-induced cell growth inhibition, the impact of VPA on the regulation of cell cycle distribution was investigated using flow cytometry. As presented in Fig. 1, the results demonstrated that VPA was able to induce cell cycle arrest in the DU145 and LNCaP cell lines. The cell number percentage in the G0-G1 phase significantly increased in a dose-dependent manner compared with control groups (PC3, P=0.035; DU145, P=0.037).

View Article: PubMed Central - PubMed

ABSTRACT

Previous studies have demonstrated that the chronic administration of valproic acid (VPA) suppresses angiogenesis in vivo; however, the mechanisms implicated in VPA-induced autophagy remain unclear. The current study aimed to assess VPA-induced autophagy in three prostate cancer cell lines (PC3, DU145 and LNCaP), in addition to analyzing the Akt/mammalian target of rapamycin (mTOR) signal pathway. Prostate cancer cell lines were cultured with various doses of VPA. Cell cycle was analyzed using flow cytometry, and autophagy markers [1A/1B-light chain 3 (LC3)-II and Beclin-1] were examined using transmission electron microscopy, fluorescent microscopy and western blotting. Activation of the Akt/mTOR signal pathway was also assessed by western blotting. The results demonstrated that VPA induced autophagosomes and suppressed the Akt/mTOR signal pathway. This was confirmed by detection of increased LC3-II and Beclin-1 in VPA-treated cells compared with untreated controls. Phosphorylated forms of Akt (PC3, P=0.048; DU145, P=0.045; LNCaP, P=0.039) and mTOR (PC3, P=0.012; DU145, P=0.41; LNCaP, P=0.35) were significantly reduced following VPA treatment. These results suggest that VPA may function as a histone deacetylase inhibitor, suppressing the growth of prostate cancer cells by modulating autophagy pathways, including inhibition of the Akt/mTOR pathway. Further experiments are required to determine the significance of all involved pathways regarding VPA-induced growth inhibition.

No MeSH data available.


Related in: MedlinePlus