Drug-induced apoptosis in B-cell chronic lymphocytic leukemia: relationship between p53 gene mutation and bcl-2/bax proteins in drug resistance

Oncogene. 1996 Mar 7;12(5):1055-62.


We investigated the relationship among chemosensitivity to drug-induced apoptosis in vitro, the presence of p53 gene mutations, and the expression of bcl-2 and bax proteins in B-cells from B-cell chronic lymphocytic leukemia (B-CLL) patients. Apoptosis was induced with a camptothecin analogue, 9-amino-20(s)-camptothecin, or a purine analogue, fludarabine. Cell death was monitored by propidium iodide staining and FACS analysis. Drug-induced apoptosis in B-CLL cells was p53-independent. Immunoblot analysis of bcl-2 and bax expression revealed a correlation between drug-induced apoptosis and the ratio of endogenous levels of bcl-2 to bax proteins. B-CLL cells with none to low bcl-2/bax ratios were drug-sensitive as compared to cells with intermediate to high ratios that were drug-resistant (P = 0.015). Prior to drug treatment, bax protein migrated as a single species of 21 kDa. Following drug-induced apoptosis, anti-bax specific protein complexes of 36-42 kDa were up-regulated. Using two-dimensional gel electrophoresis, bax complexes were disrupted under reducing conditions to reveal homo- and heterodimers of 18 and 21 kDa suggesting that disulfide interactions were required for complex formation. The de novo appearance of the 18 kDa anti-bax specific protein together with its increased expression in drug-sensitive B-CLL B-cells undergoing cell death suggests a role for this protein in the regulation of apoptosis.

Publication types

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

MeSH terms

  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Apoptosis / physiology*
  • Drug Resistance, Neoplasm / physiology
  • Genes, p53 / genetics*
  • Humans
  • Leukemia, Lymphocytic, Chronic, B-Cell / drug therapy
  • Leukemia, Lymphocytic, Chronic, B-Cell / genetics
  • Leukemia, Lymphocytic, Chronic, B-Cell / metabolism*
  • Leukemia, Lymphocytic, Chronic, B-Cell / pathology*
  • Mercaptoethanol / pharmacology
  • Mutation*
  • Proto-Oncogene Proteins / drug effects
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-bcl-2
  • Up-Regulation
  • bcl-2-Associated X Protein


  • BAX protein, human
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-2-Associated X Protein
  • Mercaptoethanol