The DNA repair enzyme O-6-alkylguanine DNA-alkyltransferase (OGAT) and a deficient mismatch repair system play a critical role in the resistance to chemotherapeutic agents that generate adducts at the O-6-position of guanine. However, DNA adducts different from O-6-methylguanine might be also involved in cytotoxicity induced by methylating agents. Because the loss of p53 function is generally associated with tumor cell resistance to anticancer chemotherapy, we have investigated whether wild-type p53 might affect chemosensitivity of leukemia cells endowed with high OGAT levels to the methylating agent temozolomide (TZM). The effect of poly(ADP-ribose) polymerase (PADPRP) inhibition, which potentiates the cytotoxic effects of N-7-methylguanine and N-3-methylguanine, was also assessed in OGAT-proficient cells, either susceptible or tolerant to O-6-methylguanine. OGAT-proficient and p53 null HL60 cells were transfected with the human p53 cDNA (p53+ cells). Treatment with TZM concentrations not toxic for the cells transduced with the control vector (p53-cells), induced apoptosis in p53 + cells. These cells were characterized by a lower level of bcl-2 protein than p53- cells, whereas bar and OGAT expression was comparable in both lines. Inhibition of PADPRP potentiated the cytotoxic and apoptotic effects of TZM in either p53- or p53+ HL60 cells. Furthermore, PADPRP inhibitors potentiated apoptosis induced by TZM in Jurkat cells, which possess a mutated p53 gene and are tolerant to O-6-methylguanine adducts. The analysis of cell cycle indicated that the drug combination of TZM and PADPRP inhibitors provoked G1 arrest only in p53+ cells. Conversely, G1 arrest was not observed in p53+ cells exposed to TZM alone. It is possible to speculate that PADPRP inhibitors might affect the repair of DNA adducts that are processed differently from O-6 methylguanine and induce a different pattern of cell cycle distribution. In conclusion, the results show that p53 increases apoptosis by TZM in OGAT-proficient cells and suggest the potential role of PADPRP inhibitors in enhancing TZM activity against leukemias independently of DNA repair systems.

Tentori L., L.P. (1998). Role of wild-type p53 on the antineoplastic activity of temozolomide alone or combined with inhibitors of poly(ADP-Ribose) polymerase. JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS, 285(2), 884-893.

Role of wild-type p53 on the antineoplastic activity of temozolomide alone or combined with inhibitors of poly(ADP-Ribose) polymerase

TENTORI, LUCIO;BONMASSAR, ENZO;GRAZIANI, GRAZIA
1998

Abstract

The DNA repair enzyme O-6-alkylguanine DNA-alkyltransferase (OGAT) and a deficient mismatch repair system play a critical role in the resistance to chemotherapeutic agents that generate adducts at the O-6-position of guanine. However, DNA adducts different from O-6-methylguanine might be also involved in cytotoxicity induced by methylating agents. Because the loss of p53 function is generally associated with tumor cell resistance to anticancer chemotherapy, we have investigated whether wild-type p53 might affect chemosensitivity of leukemia cells endowed with high OGAT levels to the methylating agent temozolomide (TZM). The effect of poly(ADP-ribose) polymerase (PADPRP) inhibition, which potentiates the cytotoxic effects of N-7-methylguanine and N-3-methylguanine, was also assessed in OGAT-proficient cells, either susceptible or tolerant to O-6-methylguanine. OGAT-proficient and p53 null HL60 cells were transfected with the human p53 cDNA (p53+ cells). Treatment with TZM concentrations not toxic for the cells transduced with the control vector (p53-cells), induced apoptosis in p53 + cells. These cells were characterized by a lower level of bcl-2 protein than p53- cells, whereas bar and OGAT expression was comparable in both lines. Inhibition of PADPRP potentiated the cytotoxic and apoptotic effects of TZM in either p53- or p53+ HL60 cells. Furthermore, PADPRP inhibitors potentiated apoptosis induced by TZM in Jurkat cells, which possess a mutated p53 gene and are tolerant to O-6-methylguanine adducts. The analysis of cell cycle indicated that the drug combination of TZM and PADPRP inhibitors provoked G1 arrest only in p53+ cells. Conversely, G1 arrest was not observed in p53+ cells exposed to TZM alone. It is possible to speculate that PADPRP inhibitors might affect the repair of DNA adducts that are processed differently from O-6 methylguanine and induce a different pattern of cell cycle distribution. In conclusion, the results show that p53 increases apoptosis by TZM in OGAT-proficient cells and suggest the potential role of PADPRP inhibitors in enhancing TZM activity against leukemias independently of DNA repair systems.
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore BIO/14
eng
Con Impact Factor ISI
3 aminobenzamide; 6 o alkylguanine dna alkyltransferase; 6 o benzylguanine; 7 methylguanine; protein bax; protein p53; temozolomide; antineoplastic activity; article; cell strain hl 60; controlled study; dna adduct; dna repair; flow cytometry; human; human cell; immunoblotting; leukemia cell; leukemia cell line; priority journal; protein expression; reverse transcription polymerase chain reaction; Antineoplastic Agents, Alkylating; Apoptosis; Benzamides; Dacarbazine; Enzyme Inhibitors; Guanine; HL-60 Cells; Humans; O(6)-Methylguanine-DNA Methyltransferase; Poly(ADP-ribose) Polymerases; Tumor Suppressor Protein p53
Tentori L., L.P. (1998). Role of wild-type p53 on the antineoplastic activity of temozolomide alone or combined with inhibitors of poly(ADP-Ribose) polymerase. JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS, 285(2), 884-893.
Tentori, L; Lacal, Pm; Benincasa, E; Franco, D; Faraoni, I; Bonmassar, E; Graziani, G
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2108/52881
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