This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bobola, M. S. Articles by Silber, J. R. Search for Related Content PubMed PubMed Citation Articles by Bobola, M. S. Articles by Silber, J. R.

Human Glioma Cell Sensitivity to the Sequence-Specific Alkylating Agent Methyl-Lexitropsin

Authors' Affiliations: Departments of ¹ Neurological Surgery and ² Pathology, University of Washington; ³ Division of Neurosurgery, Department of Surgery, Children's Hospital and Regional Medical Center, Seattle, Washington; ⁴ Department of Chemistry and Biochemistry, University of North Carolina, Wilmington, North Carolina; and ⁵ Pharmaceutical Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania

Requests for reprints: John R. Silber, Department of Neurological Surgery, University of Washington, Seattle, WA 98105-6470. Phone: 206-685-8642; Fax: 206-543-8315; E-mail: jrsilber{at}u.washington.edu.

Purpose: Defining the cytotoxicity of individual adducts in DNA is necessary for mechanistic understanding of human brain tumor resistance to therapeutic alkylating agents and for design of DNA repair-related antiresistance strategies. Our purpose is to characterize the sensitivity of human glioma cells to methyl-lexitropsin (Me-lex), a sequence-specific alkylator that produces 3-methyladenine (3-meA) as the predominant (>90%) DNA lesion.

Experimental Design: We quantitated the Me-lex cytotoxicity of 10 human glioma cell lines that differ in O⁶-methylguanine (O⁶-meG)-DNA methyltransferase (MGMT) and mismatch repair activity. We used antisense suppression of alkyladenine DNA glycosylase (AAG) and Ape1 to assess the contribution of 3-meA and abasic sites to lethality and measured abasic sites.

Results: (a) The LD₁₀ for Me-lex varied widely among the cell lines. (b) MGMT-proficient lines were more resistant than MGMT-deficient lines, an unexpected finding because Me-lex produces very little O⁶-meG. (c) Suppression of AAG increased Me-lex killing and reduced abasic site content. (d) Suppression of Ape1 increased Me-lex killing and increased abasic site content. (e) Ablation of MGMT had no effect on Me-lex cytotoxicity.

Conclusions: (a) Me-lex is cytotoxic in human glioma cells and AAG promotes resistance, indicating that 3-meA is a lethal lesion in these cells. (b) Abasic sites resulting from 3-meA repair are cytotoxic and Ape1 promotes resistance to these derivative lesions. (c) A factor(s) associated with MGMT expression, other than repair of O⁶-meG, contributes to Me-lex resistance. (d) Me-lex may have clinical utility in the adjuvant therapy of gliomas. (e) AAG and Ape1 inhibitors may be useful in targeting alkylating agent resistance.