Potentiation of 2-chlorodeoxyadenosine activity by bryostatin 1 in the resistant chronic lymphocytic leukemia cell line (WSU-CLL): association with increased ratios of dCK/5'-NT and Bax/Bcl-2

Biol Chem. 1998 Oct;379(10):1253-61. doi: 10.1515/bchm.1998.379.10.1253.

Abstract

The activities of 2-chlorodeoxyadenosine (2-CdA) metabolizing enzymes, deoxycytidine kinase (dCK) and cytosolic 5'-nucleotidase (5'-NT) were measured in control and bryostatin 1 treated CLL cells using an EBV-negative WSU-CLL cell line. This cell line was established from a patient with CLL resistant to fludarabine. The results revealed a significant increase in dCK activity in bryostatin 1 treated cells at 48 and 72 h compared with the control. 5'-NT activity decreased significantly at 48 h. The ratio of dCK to 5'-NT activity was significantly increased in bryostatin 1 treated WSU-CLL cells after 48 h. WSU-CLL cells treated with bryostatin 1 exhibited an increase in the percentage of apoptotic and dead cells from control levels of 16% to 40%. This percentage was further increased to 67% following the addition of 11.2 microM 2-CdA to WSU-CLL cells pretreated with bryostatin 1. Results from Western blot analysis indicate that WSU-CLL cells express high levels of Bcl-2, Bcl-xL and c-myc, and a low level of Bax. p53 in untreated WSU-CLL cells is undetectable. WSU-CLL cells treated with bryostatin 1 showed a significant increase in the ratio of Bax to Bcl-2. To demonstrate that the bryostatin 1 mediated enhancement of 2-CdA efficacy was not restricted to in vitro cell culture, we have studied the tumor growth delay of WSU-CLL xenografts treated with placebo, bryostatin 1, 2-CdA, and bryostatin 1 followed by 2-CdA. SCID mice given bryostatin 1 at 75 microg x kg(-1) x d(-1) for 5 days followed by 30 mg x kg(-1) x d(-1) 2-CdA for 5 days in two cycles, had significantly improved tumor growth delay (P = 0.05). We conclude that bryostatin 1 is not only capable of inducing apoptosis by itself, but also sensitizes de novo resistant WSU-CLL cells to the chemo-therapeutic effects of 2-CdA. The bryostatin 1-induced increased ratio of dCK/5'-NT activity and an increased ratio of Bax/Bcl-2 are at least two mechanisms through which this natural compound is able to potentiate the anti-tumor activity of 2-CdA in otherwise resistant CLL cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5'-Nucleotidase / metabolism*
  • Animals
  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects
  • Bryostatins
  • Cell Division / drug effects
  • Cladribine / pharmacology*
  • Deoxycytidine Kinase / metabolism*
  • Drug Synergism
  • Female
  • Humans
  • Lactones / pharmacology*
  • Leukemia, Lymphocytic, Chronic, B-Cell / enzymology
  • Leukemia, Lymphocytic, Chronic, B-Cell / metabolism
  • Leukemia, Lymphocytic, Chronic, B-Cell / pathology*
  • Macrolides
  • Mice
  • Mice, Inbred ICR
  • Mice, SCID
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Proto-Oncogene Proteins c-myc / metabolism
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / metabolism
  • bcl-2-Associated X Protein

Substances

  • Antineoplastic Agents
  • BAX protein, human
  • Bax protein, mouse
  • Bryostatins
  • Lactones
  • Macrolides
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Proto-Oncogene Proteins c-myc
  • Tumor Suppressor Protein p53
  • bcl-2-Associated X Protein
  • bryostatin 1
  • Cladribine
  • Deoxycytidine Kinase
  • 5'-Nucleotidase