BNIP3 protects HepG2 cells against etoposide-induced cell death under hypoxia by an autophagy-independent pathway

Biochem Pharmacol. 2010 Oct 15;80(8):1160-9. doi: 10.1016/j.bcp.2010.07.009. Epub 2010 Jul 15.


Tumor hypoxia is a common characteristic of most solid tumors and is correlated with poor prognosis for patients partly because hypoxia promotes resistance to cancer therapy. Hypoxia selects cancer cells that are resistant to apoptosis and allows the onset of mechanisms that promote cancer cells survival including autophagy. Previously, we showed that human hepatoma HepG2 cells were protected under hypoxia against the etoposide-induced apoptosis. In this study, respective putative contribution of autophagy and BNIP3 in the protection conferred by hypoxia against the etoposide-induced apoptosis was investigated. We report that autophagy is induced by etoposide, a process that is not affected by hypoxic conditions. Using Atg5 siRNA, we show that etoposide-induced autophagy promotes apoptotic cell death under normoxia but not under hypoxia. Then, we investigated whether the hypoxia-induced protein BNIP3 could explain the different effect of autophagy on cell death under hypoxia or normoxia. We show that the silencing of BNIP3 does not affect autophagy whatever the pO(2) but participates in the protective effect of hypoxia against etoposide-induced apoptosis. Together, these results suggest that autophagy might be involved in etoposide-induced cell death only under normoxia and that BNIP3 is a major effector of the protective mechanism conferred by hypoxia to protect cancer cells against etoposide-induced apoptotic cell death.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Autophagy / physiology*
  • Cell Hypoxia / physiology*
  • Etoposide / pharmacology*
  • Gene Expression Regulation, Neoplastic
  • Hep G2 Cells
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • Oxygen Consumption
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • RNA Interference
  • Vacuoles


  • Antineoplastic Agents
  • BNIP3 protein, human
  • Membrane Proteins
  • Neoplasm Proteins
  • Proto-Oncogene Proteins
  • Etoposide