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-methyl-adenine-inducing agents, such as MeOSO2(CH2)(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) combincd 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-I inhibitors (25 muM NU and 4 mM 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 muM 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.
Tentori, L., Portarena, I., Vernole, P., Gold, B., Graziani, G. (2002). 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 CHEMOTHERAPY AND PHARMACOLOGY, 49(3), 217-224 [10.1007/s00280-001-0409-z].
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
TENTORI, LUCIO;VERNOLE, PATRIZIA;GRAZIANI, GRAZIA
2002-01-01
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-methyl-adenine-inducing agents, such as MeOSO2(CH2)(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) combincd 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-I inhibitors (25 muM NU and 4 mM 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 muM 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
