BACKGROUND: The tumor suppressor gene PTEN is a major negative regulator of the PI3K/Akt cellular survival pathway. Overexpression of PTEN by adenoviral transfection increases doxorubicin-induced apoptosis. Whereas doxorubicin-induced apoptosis can be potentiated by the histone deacetylase (HDAC) inhibitor Trichostatin A (TSA), the mechanisms underlying this process remain unclear. The aim of this work was to investigate whether changes in PTEN expression are involved in TSA/doxorubicin-induced apoptosis. METHODS: We treated 293 T cells with TSA and doxorubicin, detected apoptosis by using Hoechst 33342 staining, and examined changes of PTEN and Egr-1 expression by quantitative real-time polymerase chain reaction (PCR). Luciferase reporter assay was used to evaluate the promoter activity of PTEN and Western blot and enzyme-linked immunosorbent assay (ELISA) were used to confirm changes in the expression of PTEN. The chromatin immunoprecipitation (ChIP) assay was performed to estimate the acetylation level of PTEN promoter. RESULTS: Doxorubicin-induced apoptosis was enhanced by TSA, whereas small interfering RNA (siRNA) targeting PTEN inhibited TSA/doxorubicin-induced apoptosis. Also, TSA promoted Egr-1 expression, which is the main transcription factor of PTEN, and this resulted in up-regulation of PTEN expression, which consequently potentiated apoptosis. Moreover, histone acetyltransferase p300 was able to synergistically activate PTEN transcription with Egr-1, implicating the role of histone acetylation in the regulation of PTEN expression. CONCLUSIONS: TSA promoted doxorubicin-induced apoptosis through a mechanism that involved the stimulation of Egr-1 expression, acetylation of core histones at the PTEN promoter, and consequently induction of PTEN transcription. These findings provide a theoretical basis for the therapeutic application of combined treatment of TSA/doxorubicin for cancer.
BACKGROUND: The tumor suppressor gene PTEN is a major negative regulator of the PI3K/Akt cellular survival pathway. Overexpression of PTEN by adenoviral transfection increases doxorubicin-induced apoptosis. Whereas doxorubicin-induced apoptosis can be potentiated by the histone deacetylase (HDAC) inhibitor Trichostatin A (TSA), the mechanisms underlying this process remain unclear. The aim of this work was to investigate whether changes in PTEN expression are involved in TSA/doxorubicin-induced apoptosis. METHODS: We treated 293 T cells with TSA and doxorubicin, detected apoptosis by using Hoechst 33342 staining, and examined changes of PTEN and Egr-1 expression by quantitative real-time polymerase chain reaction (PCR). Luciferase reporter assay was used to evaluate the promoter activity of PTEN and Western blot and enzyme-linked immunosorbent assay (ELISA) were used to confirm changes in the expression of PTEN. The chromatin immunoprecipitation (ChIP) assay was performed to estimate the acetylation level of PTEN promoter. RESULTS:Doxorubicin-induced apoptosis was enhanced by TSA, whereas small interfering RNA (siRNA) targeting PTEN inhibited TSA/doxorubicin-induced apoptosis. Also, TSA promoted Egr-1 expression, which is the main transcription factor of PTEN, and this resulted in up-regulation of PTEN expression, which consequently potentiated apoptosis. Moreover, histone acetyltransferase p300 was able to synergistically activate PTEN transcription with Egr-1, implicating the role of histone acetylation in the regulation of PTEN expression. CONCLUSIONS:TSA promoted doxorubicin-induced apoptosis through a mechanism that involved the stimulation of Egr-1 expression, acetylation of core histones at the PTEN promoter, and consequently induction of PTEN transcription. These findings provide a theoretical basis for the therapeutic application of combined treatment of TSA/doxorubicin for cancer.
Authors: Su Dao Xiong; Kang Yu; Xin Hua Liu; Li Hui Yin; Alexander Kirschenbaum; Shen Yao; Goutham Narla; Analisa DiFeo; Jian Buo Wu; Yong Yuan; Shuk-Mei Ho; Ying Wai Lam; Alice C Levine Journal: Int J Cancer Date: 2009-08-15 Impact factor: 7.396