Long-term ethanol exposure causes human liver cancer cells to become resistant to mitomycin c treatment through the inactivation of bad-mediated apoptosis

Ching Shui Huang, Yi Ru Lee, Ching Shyang Chen, Shih Hsin Tu, Ying Jan Wang, Chia Hwa Lee, Li Ching Chen, Hui Wen Chang, Chien Hsi Chang, Chih-Ming Su, Chih Hsiung Wu, Yuan Soon Ho

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Abstract

The aim of this study was to test whether long-term ethanol consumption confers therapeutic resistance to human liver cancer patients infected with hepatitis B virus (HBV). Chronic ethanol-treated cells were established by consecutively culturing a human hepatocellular carcinoma cell line, Hep 3B, which contains integrated HBV sequences, for 20-40 passages with or without 10mM ethanol (designated as E20-E40 and C20-C40, respectively). Flow cytometry analysis demonstrated that a growth promoting effect of long-term ethanol treatment was induced in the E40 cells through preferential acceleration of S-phase in these cells. Lower protein expression levels of p16, p21/Cip1, and p27/Kip1 were detected in the ethanol-treated E40 cells. We further demonstrated that long-term ethanol-treated E40 cells develop drug resistance in response to mitomycin C (MMC) treatment (>8 μM). Immunoblot analysis revealed that caspase-8-mediated mitochondrial apoptotic signals (such as Bad) were inactivated in the MMC-resistant E40 cells. Immunoprecipitation experiments demonstrated that the sequestration of phosphorylated Bad (Ser-112) through its binding with 14-3-3 was detected more profoundly in the MMC-resistant E40 cells. Next, we examined the therapeutic efficacy of MMC (10mg MMC/kg body weight, three times per week) in severe combined immunodeficient (SCID) mice bearing E40- and C40-xenografted tumors. Significant reductions (>3-fold) in tumor growth were detected in MMC-treated C40-xenografted mice. In vivo and in vitro studies demonstrated that AKT-and extracellular signal-regulated kinase (ERK)-mediated survival factors inhibited the Bad-induced mitochondrial apoptotic signals that were involved in E40 tumor cells and that conferred resistance to MMC.

Original languageEnglish
Pages (from-to)728-738
Number of pages11
JournalMolecular Carcinogenesis
Volume49
Issue number8
DOIs
Publication statusPublished - Aug 2010

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Keywords

  • Apoptosis
  • Bad phosphorylation
  • Ethanol consumption
  • Liver cancer
  • Mitomycin C

ASJC Scopus subject areas

  • Cancer Research
  • Molecular Biology

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