Garcinol, an Acetyltransferase Inhibitor, Suppresses Proliferation of Breast Cancer Cell Line MCF-7 Promoted by 17β-Estradiol

Abstract

The acetyltransferase inhibitor garcinol, a polyisoprenylated benzophenone, is extracted from the rind of the fruit of Garcinia indica, a plant found extensively in tropical regions. Anti-cancer activity has been suggested but there is no report on its action via inhibiting acetylation against cell proliferation, cell cycle progression, and apoptosis-inhibtion induced by estradiol (<TEX>$E_2$</TEX>) in human breast cancer MCF-7 cells. The main purposes of this study were to investigate the effects of the acetyltransferase inhibitor garcinol on cell proliferation, cell cycle progression and apoptosis inhibition in human breast cancer MCF-7 cells treated with estrogen, and to explore the significance of changes in acetylation levels in this process. We used a variety of techniques such as CCK-8 analysis of cell proliferation, FCM analysis of cell cycling and apoptosis, immunofluorescence analysis of NF-<TEX>${\kappa}B$</TEX>/p65 localization, and RT-PCR and Western blotting analysis of ac-H3, ac-H4, ac-p65, cyclin D1, Bcl-2 and Bcl-xl. We found that on treatment with garcinol in MCF-7 cells, <TEX>$E_2$</TEX>-induced proliferation was inhibited, cell cycle progression was arrested at G0/G1 phase, and the cell apoptosis rate was increased. Expression of ac-H3, ac-H4 and NF-<TEX>${\kappa}B$</TEX>/ac-p65 proteins in <TEX>$E_2$</TEX>-treated MCF-7 cells was increased, this being inhibited by garcinol but not ac-H4.The nuclear translocation of NF-<TEX>${\kappa}B$</TEX>/p65 in <TEX>$E_2$</TEX>-treated MCF-7 cells was also inhibited, along with cyclin D1, Bcl-2 and Bcl-xl in mRNA and protein expression levels. These results suggest that the effect of <TEX>$E_2$</TEX> on promoting proliferation and inhibiting apoptosis is linked to hyperacetylation levels of histones and nonhistone NF-<TEX>${\kappa}B$</TEX>/p65 in MCF-7 cells. The acetyltransferase inhibitor garcinol plays an inhibitive role in MCF-7 cell proliferation promoted by <TEX>$E_2$</TEX>. Mechanisms are probably associated with decreasing ac-p65 protein expression level in the NF-<TEX>${\kappa}B$</TEX> pathway, thus down-regulating the expression of cyclin D1, Bcl-2 and Bcl-xl.