Bid-overexpression regulates proliferation and phosphorylation of Akt and MAPKs in response to etoposide-induced DNA damage in hepatocellular carcinoma cells
- 医学院－已发表论文 
Background: Growing evidence supports BH3-interacting domain death agonist (Bid) playing a dual role in DNA damage response. However, the effects of Bid on hepatocellular carcinoma (HCC) cell proliferation in response to etoposide-induced DNA damage have not been sufficiently investigated. Methods: Using a stable Bid-overexpression HCC cell line, Bid/PLC/PRF/5, overexpression of Bid promoted loss of viability in response to etoposide-induced DNA damage. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]- and BrdU (5'-bromo-2'-deoxyuridine)- labeling assays revealed that etoposide-inhibited HCC cells grew in concentration- and time-dependent manners. The phosphorylations of Akt and mitogen-activated protein kinases (MAPKs) in response to etoposide-induced DNA damage were analyzed by Western blotting. Results: The survival rates of 100 mu M etoposide on the cells with control vector and Bid/PLC/PRF/5 at 48 hours amounted to 71% +/- 0.75% and 59% +/- 0.60% with MTT assay, and similar results of 85% +/- 0.08% and 63% +/- 0.14% with BrdU-labeling assay respectively. Moreover, overexpression of Bid sensitized the cells to apoptosis at a high dose of etoposide (causing irreparable damage). However, it had little effect on the proliferation at a low dose of etoposide (repairable damage). Furthermore, the phosphorylation status of Akt and MAPKs were investigated. Overexpression of Bid suppressed the activation of Akt with respect to etoposideinduced DNA damage. Similar to Akt, the levels of phosphorylated p38 and phosphorylated c-Jun were attenuated by Bid-overexpression. On the contrary, the level of phosphorylated ERK1/2 was sustained at a high level, especially in Bid/PLC/PRF/5 cells. Conclusion: Taken together, these results suggest that overexpression of Bid suppressed the activation of Akt, p38, and c-Jun, and promoted the activation of ERK1/2 induced by etoposide, suggesting that the promotion of ERK1/2 activation may have a negative effect on Bid-mediated HCC DNA damage induced by etoposide.