Involvement of activator protein-1 (AP-1) in induction of apoptosis by vitamin E succinate in human breast cancer cells

Mol Carcinog. 1997 Jul;19(3):180-90.

Abstract

The purpose of this study was to document induction of apoptosis by vitamin E succinate (VES; RRR-alpha-tocopheryl succinate) in human breast cancer cells in culture and to characterize potential c-jun involvement. VES at 18.8 microM (10 micrograms/mL) induced DNA synthesis arrest, reduced total cell numbers, and induced apoptosis in estrogen receptor-positive and estrogen-responsive MCF-7 human breast cancer cells. VES at 10 micrograms/mL induced apoptosis in greater than 60% of cells within 3 d of treatment. Apoptosis was documented by detection of fragmented or condensed nuclei in 4',6-diamindino-2-phenylindole-stained cells, detection of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeled DNA, and DNA laddering. Analyses of mRNA and protein levels of candidate molecules involved in apoptosis showed that MCF-7 cells treated with VES exhibited elevated and persistent expression of c-jun. MCF-7 cells stably transfected with a dominant-negative interfering mutant c-jun, TAM-67, and expressing high levels of mutant jun exhibited approximately 50% blockage of VES-mediated apoptosis. In addition to increased c-jun expression after VES treatment, VES-treated MCF-7 cells exhibited elevated activator protein-1 (AP-1) binding activity. Comparisons of AP-1 binding factors by super-shift analyses with jun-specific antibodies in cells sensitive to VES-induced apoptosis (empty-vector control 7-1 cells) and cells resistant to VES-induced apoptosis (TAM-67-containing TAM-9 cells) showed that the sensitive cells expressed c-jun and jun D and the resistant cells TAM-67 AP-1 binding proteins after VES treatment. These studies suggested that c-jun may be involved in the apoptotic process initiated by VES treatment of human MCF-7 breast cancer cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Apoptosis / drug effects*
  • Apoptosis / physiology*
  • Blotting, Northern
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology*
  • DNA, Neoplasm / metabolism
  • Humans
  • Mutation
  • Neoplasms, Hormone-Dependent / drug therapy
  • Neoplasms, Hormone-Dependent / metabolism
  • Neoplasms, Hormone-Dependent / pathology
  • Proto-Oncogene Proteins c-fos / biosynthesis
  • Proto-Oncogene Proteins c-fos / metabolism
  • Proto-Oncogene Proteins c-jun / biosynthesis
  • Proto-Oncogene Proteins c-jun / metabolism
  • RNA, Messenger / metabolism
  • Receptors, Estrogen / physiology
  • Tocopherols
  • Transcription Factor AP-1 / metabolism
  • Transcription Factor AP-1 / physiology*
  • Transfection
  • Tumor Cells, Cultured
  • Vitamin E / analogs & derivatives*
  • Vitamin E / pharmacology

Substances

  • DNA, Neoplasm
  • Proto-Oncogene Proteins c-fos
  • Proto-Oncogene Proteins c-jun
  • RNA, Messenger
  • Receptors, Estrogen
  • Transcription Factor AP-1
  • Vitamin E
  • Tocopherols