Apoptotic and genotoxic effects of a methyl sulfonate ester that selectively generates N3-methyladenine and poly(ADP-ribose) polymerase inhibitors in normal peripheral blood lymphocytes

Cancer Chemother Pharmacol. 2002 Mar;49(3):217-24. doi: 10.1007/s00280-001-0409-z. Epub 2002 Jan 22.

Abstract

Selective N3-adenine methylation represents a novel strategy for tumors with a phenotype of poor responsiveness to a number of anticancer agents currently used in the clinic. Resistance to N3-methyladenine-inducing agents, such as MeOSO(2)(CH(2))(2)-lexitropsin (Me-Lex), is due to high levels of N-methylpurine glycosylase (MPG). However, tumor cells with high MPG activity can be rendered susceptible to Me-Lex using poly(ADP-ribose) polymerase-1 (PARP-1) inhibitors.

Purpose: To evaluate the potential toxicity of Me-Lex, used as single agent or combined with PARP-1 inhibitors, in normal peripheral blood lymphocytes (PBL).

Methods: PBL either resting or activated with phytohemagglutinin (PHA), obtained from healthy donors, were treated with graded concentrations of Me-Lex with or without PARP-1 inhibitor (3-aminobenzamide, AB, or NU1025, NU). MPG activity, apoptosis and sister chromatid exchanges (SCE) were evaluated.

Results: (a) Me-Lex was cytotoxic mainly in PHA-activated PBL with low MPG activity; (b) combined treatment with Me-Lex and AB induced apoptotic effects as early as 24 h after drug exposure both in non-stimulated and PHA-activated PBL. When concentrations of PARP-1 inhibitors (25 microM NU and 4 m M AB) that produced a twofold increase in Me-Lex cytotoxicity in tumor cells were compared, NU induced a less-pronounced increase in apoptosis in PBL treated with Me-Lex; (c) Me-Lex at concentrations that allowed cytogenetic analysis did not induce a significant number of SCE; (d) PARP-1 inhibitors provoked a dose-dependent increase in SCE, but 25 microM NU was devoid of genotoxic effects and did not significantly increase SCE in PBL treated with Me-Lex.

Conclusions: Me-Lex showed preferential cytotoxicity against mitogen-activated PBL. Our results also indicated that for each PARP-1 inhibitor it is necessary to define the concentration devoid of genotoxic effects in normal cells, but still capable of enhancing the efficacy of DNA-damaging agents in tumor cells.

Publication types

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

MeSH terms

  • Alkylating Agents / toxicity
  • Apoptosis / drug effects*
  • Cell Division / drug effects
  • Cell Survival / drug effects
  • Enzyme Inhibitors / toxicity*
  • Flow Cytometry
  • Humans
  • Jurkat Cells
  • Lymphocyte Activation / drug effects
  • Lymphocytes / cytology
  • Lymphocytes / drug effects*
  • Lymphocytes / immunology
  • Mutagens / toxicity*
  • Netropsin / analogs & derivatives*
  • Netropsin / toxicity*
  • Poly(ADP-ribose) Polymerase Inhibitors*
  • Reference Values
  • Tumor Cells, Cultured

Substances

  • Alkylating Agents
  • Enzyme Inhibitors
  • Mutagens
  • Poly(ADP-ribose) Polymerase Inhibitors
  • methyl lexitropsin
  • Netropsin