Involvement of Ca2+ influx in the mechanism of tamoxifen-induced apoptosis in HepG2 human hepatoblastoma cells

Cancer Lett. 1999 Dec 1;147(1-2):115-23. doi: 10.1016/s0304-3835(99)00284-0.

Abstract

The signaling mechanism of tamoxifen (TAM)-induced apoptosis was investigated in HepG2 human hepatoblastoma cells which do not express the estrogen receptor (ER). TAM induced cytotoxicity and DNA fragmentation, a hallmark of apoptosis, in a dose-dependent manner. TAM increased the intracellular concentration of Ca2+. This effect was completely inhibited by the extracellular Ca2+ chelation with EGTA. TAM also induced a Mn2+ influx, indicating that TAM activated Ca2+ influx pathways. This action of TAM was significantly inhibited by flufenamic acid (FA), a known non-selective cation channel blocker. Quantitative analysis of apoptosis by flow cytometry revealed that treatment with either FA or BAPTA, an intracellular Ca2+ chelator, significantly inhibited TAM-induced apoptosis. These results suggest that intracellular Ca2+ signals may play a central role in the mechanism of the TAM-induced apoptotic cell death in ER-negative HepG2 cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Calcium / metabolism*
  • Calcium Channel Blockers / pharmacology
  • Cell Survival / drug effects
  • Chelating Agents / pharmacology
  • DNA Fragmentation
  • Dose-Response Relationship, Drug
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology
  • Extracellular Space / metabolism
  • Flufenamic Acid / pharmacology
  • Fluorescent Dyes
  • Fura-2
  • Hepatoblastoma / metabolism*
  • Hepatoblastoma / pathology
  • Humans
  • Intracellular Fluid / drug effects
  • Intracellular Fluid / metabolism
  • Ion Channels / drug effects
  • Liver Neoplasms / metabolism*
  • Liver Neoplasms / pathology
  • Manganese / pharmacokinetics
  • Membrane Potentials / drug effects
  • Receptors, Estrogen
  • Signal Transduction / drug effects
  • Tamoxifen / antagonists & inhibitors
  • Tamoxifen / pharmacology*
  • Tumor Cells, Cultured

Substances

  • Calcium Channel Blockers
  • Chelating Agents
  • Fluorescent Dyes
  • Ion Channels
  • Receptors, Estrogen
  • Tamoxifen
  • Manganese
  • Egtazic Acid
  • Flufenamic Acid
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Calcium
  • Fura-2