Theophylline and cisplatin synergize in down regulation of BCL-2 induction of apoptosis in human granulosa cells transformed by a mutated p53 (p53 val135) and Ha-ras oncogene

Int J Oncol. 2000 Aug;17(2):227-35. doi: 10.3892/ijo.17.2.227.

Abstract

Cisplatin is in common use in ovarian cancer therapy, although it is also implicated in cytotoxicity in normal tissue. We have examined the effect of cisplatin alone and in combination with theophylline, a phoshodiesterase inhibitor, on modulation of Bcl-2/Bax expression and induction of apoptosis in human granulosa cells transformed by stable transfection with mutant p53 plus Ha-ras. Theophylline elicited cell death only at relatively high concentrations with an EC50 of 200 microg/ml. Cisplatin exerted its lethal effect with an EC50 of 7 microM. In the presence of 15 or 50 microg/ml of theophylline (in the range used against asthma in humans), the EC50 for cisplatin was reduced to 2 microM or 1.2 microM, respectively. Using fluorescence-activated cell sorting analysis of DNA stained cells and the terminal deoxy-nucleotide tranferase-mediated dUTP nick end-labeling method, we found that even at concentrations of 0. 3 and 1 microM cisplatin, theophylline at 15 and 50 microg/ml increased the incidence of apoptosis in these cells by 3-5-fold, while theophylline alone induced extremely low apoptosis. Neither drug had any measurable effect on Bax protein expression. In contrast Bcl-2 protein expression levels were markedly reduced by theophylline and cisplatin in a dose-dependent manner. The combination of theophylline and cisplatin resulted in a further dramatic reduction in Bcl-2, under-scoring the pronounced synergy of these two drugs. These observations suggest that suppression of Bcl-2 expression may play an important role in mediating the synergistic effect of cisplatin and theophylline on induction of apoptosis in ovarian cancer cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Antineoplastic Agents / therapeutic use
  • Apoptosis / drug effects*
  • Apoptosis / physiology
  • Cisplatin / pharmacology*
  • Cisplatin / therapeutic use
  • Drug Therapy, Combination
  • Female
  • Genes, ras / drug effects
  • Genes, ras / physiology
  • Granulosa Cells / drug effects
  • Granulosa Cells / metabolism
  • Humans
  • Neoplasm Proteins / drug effects*
  • Neoplasm Proteins / metabolism
  • Ovarian Neoplasms / drug therapy
  • Ovarian Neoplasms / metabolism
  • Phosphodiesterase Inhibitors / pharmacology*
  • Phosphodiesterase Inhibitors / therapeutic use
  • Proto-Oncogene Proteins c-bcl-2 / drug effects*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Theophylline / pharmacology*
  • Theophylline / therapeutic use
  • Tumor Cells, Cultured / drug effects
  • Tumor Suppressor Protein p53 / drug effects
  • Tumor Suppressor Protein p53 / metabolism

Substances

  • Antineoplastic Agents
  • Neoplasm Proteins
  • Phosphodiesterase Inhibitors
  • Proto-Oncogene Proteins c-bcl-2
  • Tumor Suppressor Protein p53
  • Theophylline
  • Cisplatin