Epigallocatechin Gallate Enhances Inhibition Effect of DDP on the Proliferation of Gastric Cancer BGC-823 Cells by Regulating p19Arf-p53-p21Cip1 Signaling Pathway.

OBJECTIVE: To indicate the effect of Epigallocatechin gallate (EGCG) and Cisplatin (DDP) on proliferation of gastric cancer BGC-823 cells and the relative underlying mechanism. METHODS: Cultured BGC-823 cells were treated by 5 µg/mL DDP, 25 µg/mL EGCG and combined 5 µg/mL DDP with 25 µg/mL EGCG, a blank group was used as control. Cell morphology was observed by 4',6-diamidino-2-phenylindole (DAPI) staining. The ability of cell proliferation was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)assay. The cell cloning rate was determined by colony formation assay. The ability of cell migration was detected by cell scratch test. The cell cycle distributions and apoptosis were analyzed by flow cytometry, The expression of p19Arf, p53, p21Cip1 mRNA was determined by RT-qPCR. The protein levels of p19Arf, p53, p21Cip1 were measured by Western blot. RESULTS: Compared with DDP or EGCG treatment alone, EGCG combined with DDP treatment significantly caused nuclear shrinkage, reduced the proliferation rate, the ability of cell clone and migration. EGCG combined with DDP treatment caused cell cycle arrest in G1 phase in BGC-823 cells, increase of apoptosis (21.3%) vs EGCG (7.25%) and DDP (3.86%) single-use group (p <0.01), up-regulated gene and protein expressions of p19Arf, p53, p21Cip1 (p <0.01). CONCLUSION: EGCG can enhance the effect of DDP on inhibiting BGC-823 cell proliferation and inducing apoptosis via activating the p19Arf-p53-p21Cip1 signaling pathway.

Acetyl-11-keto-ß-boswellic acid triggers premature senescence via induction of DNA damage accompanied by impairment of DNA repair genes in hepatocellular carcinoma cells in vitro and in vivo.

Cellular senescence, a state of irreversible growth arrest, occurs in all somatic cells and causes the cells to exhaust replicative capacity. Recently, cellular senescence has been emerging as one of the principal mechanisms of tumor suppression, which can be induced by low doses of therapeutic drugs in cancer cells. Acetyl-11-keto-ß-boswellic acid (AKBA), an active ingredient isolated from the plant Boswellia serrata, has been identified to induce apoptosis in hepatocellular carcinoma (HCC) cells. In this study, we found that low concentrations of AKBA treatment triggered cell growth arrest at G0/G1 phase with features of premature cellular senescence phenotype in both HCC cell lines HepG2 and SMMC7721, as observed by enlarged and flattened morphology, significant increase in cells with senescence-associated ß-galactosidase staining, and decrease in cell proliferation and DNA synthesis. Furthermore, cellular senescence induced by AKBA occurred via activation of DNA damage response and impairment of DNA repair, as evidenced by strong induction of γH2AX and p53, and downregulated expressions of multiple DNA repair associated genes. Induction of p53 by AKBA caused a significant increase in p21CIP1 , which had a critical involvement in the induction of cellular senescence. Additionally, in vivo study demonstrated that induction of senescence contributed to the anticancer efficacy of AKBA. Therefore, our findings suggested that induction of premature senescence by AKBA through DNA damage response accompanied by impairment of DNA repair genes defines a novel mechanism contributing to its growth suppression in HCC cells.

[Epigallocatechin gallate induces CHD5 gene demethylation to promote acute myeloid leukemia cell apoptosis in vitro by regulating p19Arf-p53-p21Cip1 signaling pathway].

OBJECTIVE: To investigate the mechanism by which epigallocatechin gallate (EGCG) induces CHD5 gene demethylation and promotes the apoptosis of acute myeloid leukemia KG-1 and THP-1 cell lines. METHODS: KG-1 and THP-1 cells treated with 25, 50, 75, 100 or 150 µg/mL EGCG for 48 h were examined for CHD5 gene methylation using MSP and for cell proliferation using MTT assay. The changes in cell cycle and apoptosis of the two cell lines after treatment with EGCG for 48 h were detected using flow cytometry. The mRNA and protein expressions of DNMT1, CHD5, p19Arf, p53 and p21Cip1 in the cells were detected using RT-quantitative PCR and Western blot. RESULTS: EGCG dose-dependently reversed hypermethylation of CHD5 gene and reduced the cell viability in both KG-1 and THP-1 cells (P < 0.05). EGCG treatment caused obvious cell cycle arrest in G1 phase, significantly increased cell apoptosis, downregulated the expression of DNMT1 and upregulated the expressions of CHD5, p19Arf, p53 and p21Cip1 in KG-1 and THP-1 cells (P < 0.05). CONCLUSIONS: EGCG reduces hypermethylation of CHD5 gene in KG-1 and THP-1 cells by downregulating DNMT1 to restore its expression, which results in upregulated expressions of p19Arf, p53 and p21Cip1 and induces cell apoptosis.