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Histone deacetylases (HDACs) in XPC gene silencing and bladder cancer.

Xu XS, Wang L, Abrams J, Wang G - J Hematol Oncol (2011)

Bottom Line: Bladder cancer is strongly associated with exposure to environmental carcinogens.The results of our immunohistochemistry (IHC) staining studies further revealed a strong correlation between the over-expression of HDAC4 and increased bladder cancer occurrence (p < 0.001) as well as a marginal significance of increasing incidence of HDAC4 positivity seen with an increase in severity of bladder cancer (p = 0.08).In addition, the results of our caspase 3 activation studies demonstrated that prior treatment with VPA increased the anticancer drug cisplatin-induced activation of caspase 3 in both HTB4 and HTB9 cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Environmental Health Sciences, Wayne State University, 259 Mack Avenue, Detroit, MI 48201, USA.

ABSTRACT
Bladder cancer is one of the most common malignancies and causes hundreds of thousands of deaths worldwide each year. Bladder cancer is strongly associated with exposure to environmental carcinogens. It is believed that DNA damage generated by environmental carcinogens and their metabolites causes development of bladder cancer. Nucleotide excision repair (NER) is the major DNA repair pathway for repairing bulk DNA damage generated by most environmental carcinogens, and XPC is a DNA damage recognition protein required for initiation of the NER process. Recent studies demonstrate reduced levels of XPC protein in tumors for a majority of bladder cancer patients. In this work we investigated the role of histone deacetylases (HDACs) in XPC gene silencing and bladder cancer development. The results of our HDAC inhibition study revealed that the treatment of HTB4 and HTB9 bladder cancer cells with the HDAC inhibitor valproic acid (VPA) caused an increase in transcription of the XPC gene in these cells. The results of our chromatin immunoprecipitation (ChIP) studies indicated that the VPA treatment caused increased binding of both CREB1 and Sp1 transcription factors at the promoter region of the XPC gene for both HTB4 and HTB9 cells. The results of our immunohistochemistry (IHC) staining studies further revealed a strong correlation between the over-expression of HDAC4 and increased bladder cancer occurrence (p < 0.001) as well as a marginal significance of increasing incidence of HDAC4 positivity seen with an increase in severity of bladder cancer (p = 0.08). In addition, the results of our caspase 3 activation studies demonstrated that prior treatment with VPA increased the anticancer drug cisplatin-induced activation of caspase 3 in both HTB4 and HTB9 cells. All of these results suggest that the HDACs negatively regulate transcription of the XPC gene in bladder cancer cells and contribute to the severity of bladder tumors.

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The cisplatin-induced caspase 3 activity in both untreated and VPA-treated HTB4 and HTB9 bladder cancer cells. The VPA treatment (5 mM) was done 24 hours prior to the cisplatin treatment. The cells were treated with cisplatin at the indicated concentrations for 3 hours and then cultured in the cell culture incubator for 40 hours before the cells were harvested and the caspase 3 activity was measured. The caspase 3 activity was measured as nanomole of AMC/minute/mg of protein. (* statistical difference to that of the untreated cells with p value < 0.01).
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Figure 5: The cisplatin-induced caspase 3 activity in both untreated and VPA-treated HTB4 and HTB9 bladder cancer cells. The VPA treatment (5 mM) was done 24 hours prior to the cisplatin treatment. The cells were treated with cisplatin at the indicated concentrations for 3 hours and then cultured in the cell culture incubator for 40 hours before the cells were harvested and the caspase 3 activity was measured. The caspase 3 activity was measured as nanomole of AMC/minute/mg of protein. (* statistical difference to that of the untreated cells with p value < 0.01).

Mentions: Extensive studies have demonstrated the cisplatin-induced apoptosis as major mechanism in cell killing [16,39,56-58]. Because of the important function of XPC protein in the cisplatin-caused apoptosis [16] and the role HDACs in XPC gene silencing, we further investigated the effect of the HDAC inhibitor VPA in cisplatin-induced apoptosis of bladder cancer cells. The HTB4 and HTB9 bladder cancer cells were treated with VPA (5 mM) for 48 hours before they were treated with cisplatin. The cells were harvested 40 hours after the cisplatin treatment and the caspase-3 activity was determined (Figure 5). The caspase-3 activity was also determined from the HBT4 and HTB9 cells that were treated with cisplatin but without the prior VPA treatment (Figure 5). The cisplatin treatment itself caused an increase in caspase-3 activity in both HTB4 and HTB9 bladder cancer cells at high concentrations (20 μM and 40 μM) but not at lower concentrations (5 μM and 10 μM) (Figure 5). When these cells were treated with VPA prior to the cisplatin treatment, however, the caspase-3 activity was significantly increased at lower concentrations as well (Figure 5). For example, when treated only with cisplatin at 10 μM, the caspase 3 activity was increased by a 1.5 and 2 fold in the HTB4 and HTB9 cells respectively; when the cells were treated with 5 mM VPA prior to the cisplatin treatment, however, the 10 μM cisplatin treatment resulted in a 7.3 and 6.6 fold increase of the caspase-3 activity in the HTB4 and HTB9 cells respectively (Figure 5). These results suggest that the prior treatment of HTB4 and HTB9 bladder cancer cells with the HDAC inhibitor VPA sensitizes these bladder cancer cells to the anticancer drug cisplatin.


Histone deacetylases (HDACs) in XPC gene silencing and bladder cancer.

Xu XS, Wang L, Abrams J, Wang G - J Hematol Oncol (2011)

The cisplatin-induced caspase 3 activity in both untreated and VPA-treated HTB4 and HTB9 bladder cancer cells. The VPA treatment (5 mM) was done 24 hours prior to the cisplatin treatment. The cells were treated with cisplatin at the indicated concentrations for 3 hours and then cultured in the cell culture incubator for 40 hours before the cells were harvested and the caspase 3 activity was measured. The caspase 3 activity was measured as nanomole of AMC/minute/mg of protein. (* statistical difference to that of the untreated cells with p value < 0.01).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108377&req=5

Figure 5: The cisplatin-induced caspase 3 activity in both untreated and VPA-treated HTB4 and HTB9 bladder cancer cells. The VPA treatment (5 mM) was done 24 hours prior to the cisplatin treatment. The cells were treated with cisplatin at the indicated concentrations for 3 hours and then cultured in the cell culture incubator for 40 hours before the cells were harvested and the caspase 3 activity was measured. The caspase 3 activity was measured as nanomole of AMC/minute/mg of protein. (* statistical difference to that of the untreated cells with p value < 0.01).
Mentions: Extensive studies have demonstrated the cisplatin-induced apoptosis as major mechanism in cell killing [16,39,56-58]. Because of the important function of XPC protein in the cisplatin-caused apoptosis [16] and the role HDACs in XPC gene silencing, we further investigated the effect of the HDAC inhibitor VPA in cisplatin-induced apoptosis of bladder cancer cells. The HTB4 and HTB9 bladder cancer cells were treated with VPA (5 mM) for 48 hours before they were treated with cisplatin. The cells were harvested 40 hours after the cisplatin treatment and the caspase-3 activity was determined (Figure 5). The caspase-3 activity was also determined from the HBT4 and HTB9 cells that were treated with cisplatin but without the prior VPA treatment (Figure 5). The cisplatin treatment itself caused an increase in caspase-3 activity in both HTB4 and HTB9 bladder cancer cells at high concentrations (20 μM and 40 μM) but not at lower concentrations (5 μM and 10 μM) (Figure 5). When these cells were treated with VPA prior to the cisplatin treatment, however, the caspase-3 activity was significantly increased at lower concentrations as well (Figure 5). For example, when treated only with cisplatin at 10 μM, the caspase 3 activity was increased by a 1.5 and 2 fold in the HTB4 and HTB9 cells respectively; when the cells were treated with 5 mM VPA prior to the cisplatin treatment, however, the 10 μM cisplatin treatment resulted in a 7.3 and 6.6 fold increase of the caspase-3 activity in the HTB4 and HTB9 cells respectively (Figure 5). These results suggest that the prior treatment of HTB4 and HTB9 bladder cancer cells with the HDAC inhibitor VPA sensitizes these bladder cancer cells to the anticancer drug cisplatin.

Bottom Line: Bladder cancer is strongly associated with exposure to environmental carcinogens.The results of our immunohistochemistry (IHC) staining studies further revealed a strong correlation between the over-expression of HDAC4 and increased bladder cancer occurrence (p < 0.001) as well as a marginal significance of increasing incidence of HDAC4 positivity seen with an increase in severity of bladder cancer (p = 0.08).In addition, the results of our caspase 3 activation studies demonstrated that prior treatment with VPA increased the anticancer drug cisplatin-induced activation of caspase 3 in both HTB4 and HTB9 cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Environmental Health Sciences, Wayne State University, 259 Mack Avenue, Detroit, MI 48201, USA.

ABSTRACT
Bladder cancer is one of the most common malignancies and causes hundreds of thousands of deaths worldwide each year. Bladder cancer is strongly associated with exposure to environmental carcinogens. It is believed that DNA damage generated by environmental carcinogens and their metabolites causes development of bladder cancer. Nucleotide excision repair (NER) is the major DNA repair pathway for repairing bulk DNA damage generated by most environmental carcinogens, and XPC is a DNA damage recognition protein required for initiation of the NER process. Recent studies demonstrate reduced levels of XPC protein in tumors for a majority of bladder cancer patients. In this work we investigated the role of histone deacetylases (HDACs) in XPC gene silencing and bladder cancer development. The results of our HDAC inhibition study revealed that the treatment of HTB4 and HTB9 bladder cancer cells with the HDAC inhibitor valproic acid (VPA) caused an increase in transcription of the XPC gene in these cells. The results of our chromatin immunoprecipitation (ChIP) studies indicated that the VPA treatment caused increased binding of both CREB1 and Sp1 transcription factors at the promoter region of the XPC gene for both HTB4 and HTB9 cells. The results of our immunohistochemistry (IHC) staining studies further revealed a strong correlation between the over-expression of HDAC4 and increased bladder cancer occurrence (p < 0.001) as well as a marginal significance of increasing incidence of HDAC4 positivity seen with an increase in severity of bladder cancer (p = 0.08). In addition, the results of our caspase 3 activation studies demonstrated that prior treatment with VPA increased the anticancer drug cisplatin-induced activation of caspase 3 in both HTB4 and HTB9 cells. All of these results suggest that the HDACs negatively regulate transcription of the XPC gene in bladder cancer cells and contribute to the severity of bladder tumors.

Show MeSH
Related in: MedlinePlus