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Polyphenols from green tea inhibit the growth of melanoma cells through inhibition of class I histone deacetylases and induction of DNA damage.

Prasad R, Katiyar SK - Genes Cancer (2015)

Bottom Line: GTPs-induced decrease in the levels of class I HDAC proteins is mediated through proteasomal degradation.Valproic acid, an inhibitor of HDACs, exhibited a similar pattern of reduced viability and induction of death of melanoma cells.Treatment of A375 and Hs294t cells with GTPs resulted in a decrease in the levels of cyclins and cyclin dependent kinases of G1 phase of cell cycle whereas upregulated the levels of tumor suppressor proteins (Cip1/WAF1/p21, p16 and p53).

View Article: PubMed Central - PubMed

Affiliation: Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL, USA.

ABSTRACT
Melanoma is the leading cause of skin cancer-related deaths. We have examined the effect of green tea polyphenols (GTPs), a natural mixture of epicatechin monomers, on melanoma cancer cell growth and the molecular mechanism underlying these effects using different human melanoma cell lines as an in vitro model. Treatment of melanoma cell lines (A375, Hs294t, SK-Mel28 and SK-Mel119) with GTPs significantly inhibited the cell viability as well as colony formation ability of melanoma cells in a dose-dependent manner. These effects of GTPs were associated with a significant inhibition of histone deacetylase (HDAC) activity, reduction in the levels of class I HDAC proteins, enhancement of histone acetyltransferase (HAT) activity and induction of DNA damage, as detected by Comet assay, in melanoma cells. GTPs-induced decrease in the levels of class I HDAC proteins is mediated through proteasomal degradation. Valproic acid, an inhibitor of HDACs, exhibited a similar pattern of reduced viability and induction of death of melanoma cells. Treatment of A375 and Hs294t cells with GTPs resulted in a decrease in the levels of cyclins and cyclin dependent kinases of G1 phase of cell cycle whereas upregulated the levels of tumor suppressor proteins (Cip1/WAF1/p21, p16 and p53).

No MeSH data available.


Related in: MedlinePlus

Effect of MG132 (a proteasome inhibitor) on GTPs-induced inhibition of class I HDACs expression in A375 and Hs294t cells(A) Treatment of melanoma cells with MG132 inhibits the effect of GTPs on HDAC protein expressions. A375 and Hs294t cells were treated with GTPs (60 μg/ml) with and without the treatment of MG132 for 48 h, then cells were harvested and nuclear lysates were subjected to western blot analysis. (B) A375 and Hs294t cells were treated with various concentrations of valproic acid (0, 10, 20 and 40 mM) for 24 and 48 h, and cell viability was determined using an MTT assay. Data on cell viability are presented in terms of percent of control group (non-valproic acid-treated) as the mean ±SD of 6 replicates. (C) Treatment of melanoma cells with valproic acid induces cell death. Cell death was determined using a trypan blue exclusion assay. Data are presented in terms of the percent cell death as the mean ± SD from three separate experiments. Significant difference versus non-valproic acid treated controls, *P<0.05, †P<0.01, ¶P<0.001.
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Figure 6: Effect of MG132 (a proteasome inhibitor) on GTPs-induced inhibition of class I HDACs expression in A375 and Hs294t cells(A) Treatment of melanoma cells with MG132 inhibits the effect of GTPs on HDAC protein expressions. A375 and Hs294t cells were treated with GTPs (60 μg/ml) with and without the treatment of MG132 for 48 h, then cells were harvested and nuclear lysates were subjected to western blot analysis. (B) A375 and Hs294t cells were treated with various concentrations of valproic acid (0, 10, 20 and 40 mM) for 24 and 48 h, and cell viability was determined using an MTT assay. Data on cell viability are presented in terms of percent of control group (non-valproic acid-treated) as the mean ±SD of 6 replicates. (C) Treatment of melanoma cells with valproic acid induces cell death. Cell death was determined using a trypan blue exclusion assay. Data are presented in terms of the percent cell death as the mean ± SD from three separate experiments. Significant difference versus non-valproic acid treated controls, *P<0.05, †P<0.01, ¶P<0.001.

Mentions: To determine whether GTPs reduce the levels of HDAC proteins in melanoma cells through proteasome-mediated degradation, A375 and Hs294t cells were treated with GTPs (60μg/ml) with and without treatment with MG132 (5, 10 and 20 μM conc.), an inhibitor of proteasomal degradation, for 48 h. Cells were harvested and nuclear lysates were prepared for western blot analysis. Western blot analysis revealed that the levels of class I HDAC proteins were higher in the cells treated with GTPs + MG132 as compared with levels in the cells treated with GTPs alone (Figure 6A). These results indicate that proteasome-mediated degradation of HDACs may be a possible mechanism through which GTPs reduce the levels of class I HDACs proteins in both melanoma cell lines.


Polyphenols from green tea inhibit the growth of melanoma cells through inhibition of class I histone deacetylases and induction of DNA damage.

Prasad R, Katiyar SK - Genes Cancer (2015)

Effect of MG132 (a proteasome inhibitor) on GTPs-induced inhibition of class I HDACs expression in A375 and Hs294t cells(A) Treatment of melanoma cells with MG132 inhibits the effect of GTPs on HDAC protein expressions. A375 and Hs294t cells were treated with GTPs (60 μg/ml) with and without the treatment of MG132 for 48 h, then cells were harvested and nuclear lysates were subjected to western blot analysis. (B) A375 and Hs294t cells were treated with various concentrations of valproic acid (0, 10, 20 and 40 mM) for 24 and 48 h, and cell viability was determined using an MTT assay. Data on cell viability are presented in terms of percent of control group (non-valproic acid-treated) as the mean ±SD of 6 replicates. (C) Treatment of melanoma cells with valproic acid induces cell death. Cell death was determined using a trypan blue exclusion assay. Data are presented in terms of the percent cell death as the mean ± SD from three separate experiments. Significant difference versus non-valproic acid treated controls, *P<0.05, †P<0.01, ¶P<0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Figure 6: Effect of MG132 (a proteasome inhibitor) on GTPs-induced inhibition of class I HDACs expression in A375 and Hs294t cells(A) Treatment of melanoma cells with MG132 inhibits the effect of GTPs on HDAC protein expressions. A375 and Hs294t cells were treated with GTPs (60 μg/ml) with and without the treatment of MG132 for 48 h, then cells were harvested and nuclear lysates were subjected to western blot analysis. (B) A375 and Hs294t cells were treated with various concentrations of valproic acid (0, 10, 20 and 40 mM) for 24 and 48 h, and cell viability was determined using an MTT assay. Data on cell viability are presented in terms of percent of control group (non-valproic acid-treated) as the mean ±SD of 6 replicates. (C) Treatment of melanoma cells with valproic acid induces cell death. Cell death was determined using a trypan blue exclusion assay. Data are presented in terms of the percent cell death as the mean ± SD from three separate experiments. Significant difference versus non-valproic acid treated controls, *P<0.05, †P<0.01, ¶P<0.001.
Mentions: To determine whether GTPs reduce the levels of HDAC proteins in melanoma cells through proteasome-mediated degradation, A375 and Hs294t cells were treated with GTPs (60μg/ml) with and without treatment with MG132 (5, 10 and 20 μM conc.), an inhibitor of proteasomal degradation, for 48 h. Cells were harvested and nuclear lysates were prepared for western blot analysis. Western blot analysis revealed that the levels of class I HDAC proteins were higher in the cells treated with GTPs + MG132 as compared with levels in the cells treated with GTPs alone (Figure 6A). These results indicate that proteasome-mediated degradation of HDACs may be a possible mechanism through which GTPs reduce the levels of class I HDACs proteins in both melanoma cell lines.

Bottom Line: GTPs-induced decrease in the levels of class I HDAC proteins is mediated through proteasomal degradation.Valproic acid, an inhibitor of HDACs, exhibited a similar pattern of reduced viability and induction of death of melanoma cells.Treatment of A375 and Hs294t cells with GTPs resulted in a decrease in the levels of cyclins and cyclin dependent kinases of G1 phase of cell cycle whereas upregulated the levels of tumor suppressor proteins (Cip1/WAF1/p21, p16 and p53).

View Article: PubMed Central - PubMed

Affiliation: Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL, USA.

ABSTRACT
Melanoma is the leading cause of skin cancer-related deaths. We have examined the effect of green tea polyphenols (GTPs), a natural mixture of epicatechin monomers, on melanoma cancer cell growth and the molecular mechanism underlying these effects using different human melanoma cell lines as an in vitro model. Treatment of melanoma cell lines (A375, Hs294t, SK-Mel28 and SK-Mel119) with GTPs significantly inhibited the cell viability as well as colony formation ability of melanoma cells in a dose-dependent manner. These effects of GTPs were associated with a significant inhibition of histone deacetylase (HDAC) activity, reduction in the levels of class I HDAC proteins, enhancement of histone acetyltransferase (HAT) activity and induction of DNA damage, as detected by Comet assay, in melanoma cells. GTPs-induced decrease in the levels of class I HDAC proteins is mediated through proteasomal degradation. Valproic acid, an inhibitor of HDACs, exhibited a similar pattern of reduced viability and induction of death of melanoma cells. Treatment of A375 and Hs294t cells with GTPs resulted in a decrease in the levels of cyclins and cyclin dependent kinases of G1 phase of cell cycle whereas upregulated the levels of tumor suppressor proteins (Cip1/WAF1/p21, p16 and p53).

No MeSH data available.


Related in: MedlinePlus