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Onco Targets Ther. 2012;5:279-86. doi: 10.2147/OTT.S36087. Epub 2012 Oct 17.

Bid-overexpression regulates proliferation and phosphorylation of Akt and MAPKs in response to etoposide-induced DNA damage in hepatocellular carcinoma cells.

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1
Fisheries College, Jimei University, Fujian, China.

Abstract

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 μM 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 etoposide-induced 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.

KEYWORDS:

BH3-interacting domain death agonist; HCC; mitogen-activated protein kinases

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