O6-Benzylguanine potentiates BCNU but not busulfan toxicity in hematopoietic stem cells

Westerhof, G R; Down, Julian D.; Blokland, I.; Wood, Michelle; Boudewijn, A; Watson, Amanda J.; McGown, Alan T.; Ploemacher, Rob E.; Margison, Geoffrey P.

doi:10.1016/s0301-472x(01)00631-2

Cited by 15 publications

(14 citation statements)

References 14 publications

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“…Most studies have focused on the acute toxicities associated with O 6 -benzylguanine plus BCNU and demonstrate that myelosuppression probably leads to animal death with additional toxicities observed in the intestine and liver (Bibby et al, 1999;Reese et al, 2001;Westerhof et al, 2001). Our studies are consistent in that we observed pancytopenia immediately after treatment; however, treatment of mice with high-dose BCNU resulted in lymphocytosis and low hemoglobin and hematocrit between 3 and 6 months after treatment.…”

Section: Discussionsupporting

confidence: 88%

Role ofO⁶-Alkylguanine-DNA Alkyltransferase in Protecting against 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-Induced Long-Term Toxicities

Hansen

Nagasubramanian²,

Delaney³

et al. 2005

J Pharmacol Exp Ther

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O 6-alkylguanine-DNA alkyltransferase (AGT) protects from the mutagenic and toxic lesions induced by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and in many tumors, AGT overexpression provides a means of resistance. To circumvent this, O 6 -benzylguanine, an inactivator of AGT, has been developed and is currently in clinical development with BCNU; however, the potential long-term toxicities associated with this treatment are unknown. With the inactivation of AGT by O 6 -benzylguanine, a higher number of toxic and mutagenic O 6 -alkylguanine lesions introduced by methylating or chloroethylating agents would be expected. In this study, cohorts of mice were treated with vehicle, O 6 -benzylguanine (30 mg/kg), BCNU alone (low dose of 15 mg/kg or high dose of 50 mg/kg), or O 6 -benzylguanine (30 mg/kg) plus BCNU (15 mg/kg) and followed for 12 months post-treatment. Mice treated with O 6 -benzylguanine plus BCNU or high-dose BCNU died significantly earlier (p Ͻ 0.0001) than mice in the other three cohorts with a median survival of 8.3 (O 6 -benzylguanine plus BCNU) and 7.9 months (high-dose BCNU). Histopathologic sections of tissues revealed that the most common morphological diagnosis in animals treated with O 6 -benzylguanine plus BCNU (15 mg/kg) or BCNU (50 mg/kg) was cytomegaly in the lung with greater severity observed in mice receiving the combination O 6 -benzylguanine plus BCNU. Four of five mice analyzed in this cohort had alveolar histiocytosis, with one also having alveolar edema. In contrast, liver and kidney toxicity was only observed in mice treated with BCNU (50 mg/kg). These results suggest that O 6 -benzylguanine enhances long-term pulmonary toxicity associated with BCNU in mice.

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Section: Discussionsupporting

confidence: 88%

Role ofO⁶-Alkylguanine-DNA Alkyltransferase in Protecting against 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-Induced Long-Term Toxicities

Hansen

Nagasubramanian²,

Delaney³

et al. 2005

J Pharmacol Exp Ther

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“…Thus, it is possible, as previously described for busulfan, that nitrososulfamide analogs, especially compound 4, do not produce enough O 6 lesions to have a significant impact on the sensitivity of melanoma cells (Westerhof et al, 2001). Moreover, the activity, despite MGMT expression, that compound 4 retains on both melanoma cell lines, could also be attributed to the ability of bifunctional agents to form lethal crosslinks that are not repaired by MGMT, because this enzyme removes DNA adducts before they can be converted into DNA cross-links.…”

Section: Fotemustine Analogs Activity According To Mgmt Expressionmentioning

confidence: 90%

Cytotoxicity, DNA Damage, and Apoptosis Induced by New Fotemustine Analogs on Human Melanoma Cells in Relation to O⁶-Methylguanine DNA-Methyltransferase Expression

Passagne¹,

Evrard²,

Winum³

et al. 2003

J Pharmacol Exp Ther

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Fotemustine is a third generation chloroethylnitrosourea that has demonstrated significant antitumoral effects in malignant melanoma. However, its use is somewhat limited by its toxic side effects and chemoresistance caused by direct repair of O 6 -alkyl groups by the enzyme O 6 -methylguanine DNA-methyltransferase (MGMT). The aim of this work was to determine to what extent the expression of MGMT influences cytotoxicity, DNA damage, and apoptosis induced by new nitrososulfamide analogs of fotemustine (compounds 4 and 8), which have previously demonstrated interesting antiproliferative properties. We carried out complementary strategies that consisted of MGMT cDNA transfection in CAL77 MerϪ melanoma cells and of MGMT inhibition with O 6 -benzylguanine (BG) in A375 Merϩ melanoma cells. MGMT-transfected cells were 7 to 9 times less sensitive to fotemustine than parent cells, whereas no difference between the transfected and parent cells was observed for nitrososulfamide analogs. The cytotoxicity of these analogs vis à vis a MGMT-proficient A375 melanoma cell line was approximately 3 times greater than that of fotemustine. Coincubation of these cells with O 6 -benzylguanine significantly increased the cytotoxicity of fotemustine and compound 8, whereas BG had little effect on the cytotoxicity of compound 4. Furthermore, DNA fragmentation determined by a comet assay was greater with nitrososulfamide analogs than with fotemustine. O 6 -benzylguanine increased DNA fragmentation for fotemustine and compound 8, but not for compound 4, which induced comets with a typical apoptotic appearance. The ability of this compound to induce apoptosis in the absence of BG was confirmed by a specific enzyme-linked immunosorbent assay apoptotic assay using a single-stranded DNA monoclonal antibody.

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“…These studies suggest that, during repair of alkyl adducts, DNA alkyltransferase reacts with an intermediate formed before crosslink formation, generating a covalent link to DNA and thereby creating a very large adduct [Brent and Remack, 1988;Gonzaga and Brent, 1989]. Busulfan does not cause O6-alkyl adducts, therefore repair via DNA alkyltransferase is not relevant to the current model [Westerhof et al, 2001]. However, other proteins may be involved, possibly enzymes that participate in the initiation of DNA synthesis, which in turn would explain the block in replication of stem cells and their progeny [Morley et al, 1978;Kubota et al, 1983].…”

Section: Discussionmentioning

confidence: 92%

“…Previous work indicates that it does not elicit toxicity via alkylation at the O6 position of guanine in DNA [Westerhof et al, 2001], although no direct evidence has been obtained regarding the repair of these busulfan-induced lesions.…”

Section: Discussionmentioning

confidence: 96%

“…Evidence suggests that it does not elicit toxicity via alkylation at the O6 position of guanine in DNA [Westerhof et al, 2001], and that stem cell depletion is not explained by the distance or orientation of its two alkylating groups [Westerhof et al, 2000]. Busulfan suppresses hematopoietic stem cell and progenitor cell function via an apoptosis-independent mechanism [Meng et al, 2003].…”

Section: Introductionmentioning

confidence: 99%

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Different behavior of SCE‐eliciting lesions induced by low and high doses of busulfan

Morales-Ramı́rez

González-Beltrán

2007

Environ and Mol Mutagen

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Our previous studies suggested a dose-dependent transition in the types of DNA lesions induced by busulfan, as measured using the comet assay and by micronuclei analyses. The aim of the present study was to investigate the dose-dependent induction of different sister-chromatid exchange-eliciting lesions; lesions were distinguished by their efficiency in producing sister-chromatid exchange (SCE), and by their reparability during G1. Synchronously dividing murine salivary gland cells were assayed in vivo. Groups of mice were intraperitoneally injected with either 30 or 80 micromol busulfan/kg body weight solution at early or late G1. The rate of SCE/micromol busulfan/kg body weight obtained by exposure at late G1 with the high dose was twice that of the low dose. SCE induction during early G1 was higher than at late G1 with both doses; only the low-dose response was statistically significant. The frequency distribution of SCEs per cell demonstrated that cells exposed at the late G1 phase showed typical profiles that closely fit a Gaussian curve. However, an irregular profile was obtained for cells treated during early G1, which showed some cells with high-SCE frequency. Cells treated in early G1 have more time to repair lesions before DNA synthesis; therefore, the results suggest that instead of repair, secondary SCE-eliciting lesions during G1 were produced, especially at the lower dose. The results obtained in this study indicate that there are dose-dependent differences in the types of SCE-eliciting lesions induced by busulfan.

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O6-Benzylguanine potentiates BCNU but not busulfan toxicity in hematopoietic stem cells

Cited by 15 publications

References 14 publications

Role ofO⁶-Alkylguanine-DNA Alkyltransferase in Protecting against 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-Induced Long-Term Toxicities

Role ofO⁶-Alkylguanine-DNA Alkyltransferase in Protecting against 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-Induced Long-Term Toxicities

Cytotoxicity, DNA Damage, and Apoptosis Induced by New Fotemustine Analogs on Human Melanoma Cells in Relation to O⁶-Methylguanine DNA-Methyltransferase Expression

Different behavior of SCE‐eliciting lesions induced by low and high doses of busulfan

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O6-Benzylguanine potentiates BCNU but not busulfan toxicity in hematopoietic stem cells

Cited by 15 publications

References 14 publications

Role ofO6-Alkylguanine-DNA Alkyltransferase in Protecting against 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-Induced Long-Term Toxicities

Role ofO6-Alkylguanine-DNA Alkyltransferase in Protecting against 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-Induced Long-Term Toxicities

Cytotoxicity, DNA Damage, and Apoptosis Induced by New Fotemustine Analogs on Human Melanoma Cells in Relation to O6-Methylguanine DNA-Methyltransferase Expression

Different behavior of SCE‐eliciting lesions induced by low and high doses of busulfan

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Product

Resources

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Role ofO⁶-Alkylguanine-DNA Alkyltransferase in Protecting against 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-Induced Long-Term Toxicities

Role ofO⁶-Alkylguanine-DNA Alkyltransferase in Protecting against 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-Induced Long-Term Toxicities

Cytotoxicity, DNA Damage, and Apoptosis Induced by New Fotemustine Analogs on Human Melanoma Cells in Relation to O⁶-Methylguanine DNA-Methyltransferase Expression