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Enhancement of Apoptotic and Autophagic Induction by a Novel Synthetic C-1 Analogue of 7-deoxypancratistatin in Human Breast Adenocarcinoma and Neuroblastoma Cells with Tamoxifen
19:44

Enhancement of Apoptotic and Autophagic Induction by a Novel Synthetic C-1 Analogue of 7-deoxypancratistatin in Human Breast Adenocarcinoma and Neuroblastoma Cells with Tamoxifen

Published on: May 30, 2012

Estrogen receptor-dependent and estrogen receptor-independent pathways for tamoxifen and 4-hydroxytamoxifen-induced

Maria Obrero1, David V Yu, David J Shapiro

  • 1Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.

The Journal of Biological Chemistry
|September 24, 2002
PubMed

Insights

Tamoxifen (TAM) and its metabolite 4-hydroxytamoxifen (OHT) induce cancer cell death via estrogen receptor (ER)-dependent and ER-independent pathways. This novel finding reveals new therapeutic strategies for cancer treatment.

Area of Science:

  • Cell Biology
  • Pharmacology
  • Cancer Research

Background:

  • Tamoxifen (TAM) is a widely used cancer therapeutic agent, primarily functioning by competing with estrogens for estrogen receptor (ER) binding.
  • The precise mechanisms underlying TAM's therapeutic efficacy, particularly its role in programmed cell death, are not fully elucidated.

Purpose of the Study:

  • To investigate the distinct pathways through which TAM and its active metabolite, 4-hydroxytamoxifen (OHT), induce programmed cell death.
  • To differentiate between ER-dependent and ER-independent mechanisms of cell death triggered by TAM and OHT.

Main Methods:

  • Utilized various concentrations of TAM and OHT in both ER-positive and ER-negative cancer cell lines.
  • Employed ER ligands (17beta-estradiol, raloxifene, ICI 182,780) and a p38 inhibitor (SB203580) to dissect signaling pathways.
  • Assessed hallmarks of apoptosis, including Bax translocation, cytochrome c release, poly(ADP-ribose) polymerase cleavage, and DNA laddering.

Main Results:

  • TAM and OHT induce programmed cell death through both ER-dependent and ER-independent pathways.
  • The ER-independent pathway is activated at higher concentrations (10-20 micromolar) and occurs in ER-negative cells.
  • The ER-dependent pathway, triggered by submicromolar concentrations, involves stress kinase pathways and diverges from classical caspase-dependent apoptosis.

Conclusions:

  • Tamoxifen and 4-hydroxytamoxifen possess novel activities beyond ER antagonism, including the direct induction of programmed cell death.
  • Understanding these distinct cell death pathways offers potential for developing more effective and targeted cancer therapies.
  • The ER-dependent cell death pathway initiated by OHT appears to bypass key caspase activation steps, representing a unique mode of apoptosis induction.

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