Epigallocatechin-3-gallate and trichostatin A synergistically inhibit human lymphoma cell proliferation through epigenetic modification of p16INK4a

Abstract

DNA methylation and histone deacetylation play important roles in the occurrence and development of cancers by inactivating the expression of tumor suppressors, including p16(INK4a), a cyclin-dependent kinase inhibitor. The present study investigated the effect of epigallocatechin-3-gallate (EGCG) alone or in combination with trichostatin A (TSA) on p16(INK4a) gene expression and growth in human malignant lymphoma CA46 cells. CA46 cell viability and cell cycle were analyzed; methylation of the p16(INK4a) gene was assessed by nested methylation-specific PCR (n-MSP). p16(INK4a )mRNA and protein expression was determined by real-time quantitative PCR and western blot analyses, respectively. Both EGCG and TSA alone inhibited CA46 cell proliferation; the combined treatment (6 µg/ml EGCG and 15 ng/ml TSA) significantly reduced CA46 cell proliferation from 24 to 96 h (all P<0.001). Cells treated with 24 µg/ml EGCG or the combination treatment (6 µg/ml EGCG and 15 ng/ml TSA) had lower proliferative indices when compared to the other groups. Co-treatment with EGCG and TSA decreased p16(INK4a) gene methylation, which coincided with increased p16(INK4a) mRNA and protein expression. Thus, EGCG and TSA synergistically reactivate p16(INK4a) gene expression in part through reducing promoter methylation, which may decrease CA46 cell proliferation.

Epigenetic reactivation of p21CIP1/WAF1 and KLOTHO by a combination of bioactive dietary supplements is partially ERα-dependent in ERα-negative human breast cancer cells

“…Dietary EGCG has been shown to reactivate several known key TSGs in various cancer cell lines (Fang et al, 2003; Nandakumar et al, 2011). Similarly, EGCG in combination with TSA, a HDAC inhibitor, synergistically reactivates p16 INK4a and ERα expressions in human lymphoma and breast cancer cells, respectively, through active chromatin modifications (Li et al, 2010; Wu et al, 2013). Therefore, the focus of the present study was to investigate the effect of the combinations of dietary DNMT and HDAC inhibitors toward the epigenetic reactivation of key TSGs and its ERα dependence in ERα-negative human breast cancer cells.…”

Implications of Genetic and Epigenetic Alterations of CDKN2A (p16 INK4a ) in Cancer

“…Co-treatment with EGCG and TSA decreased the DNA methylation of CDKN2A , which coincided with increased CDKN2A mRNA and protein expression. Thus, EGCG and TSA synergistically induced CDKN2A expression by reducing promoter methylation, which might decrease CA46 lymphoma cell proliferation ( Wu et al, 2013 ).…”

Epigenetic regulation by selected dietary phytochemicals in cancer chemoprevention

“…Studies conducted by Li et al [49] showed that a combination of EGCG with an HDAC inhibitor reactivates estrogen receptor-α (ERα) expression in ERα-negative human breast cancer cells through a process associated with chromatin modifications. EGCG in combination with TSA, a HDAC inhibitor, synergistically reactivates p16 INK4a expression, in part, through a reduction of promoter expression in CA46 human lymphoma cells [50]. Similarly, EGCG in combination with sodium butyrate synergistically inhibits cell cycle arrest and induces cellular apoptosis through down regulation of HDAC1, DNMT1 and inhibition of HDAC activities in colon cancer cells [51].…”