title: Human glioma cell sensitivity to the sequence-specific alkylating agent methyl-lexitropsin.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  We quantitated the Me-lex cytotoxicity of 10 human glioma cell lines that differ in O(6)-methylguanine (O(6)-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 LD(10) 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 O(6)-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 O(6)-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.
authors.affiliation: Department of Neurological Surgery, University of Washington, Seattle, WA 98105, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Bobola
authors.forename: Sridhar
authors.initials: S
authors.lastname: Varadarajan
authors.forename: Nolan W
authors.initials: NW
authors.lastname: Smith
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Goff
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Kolstoe
authors.forename: A
authors.initials: A
authors.lastname: Blank
authors.forename: Barry
authors.initials: B
authors.lastname: Gold
authors.forename: John R
authors.initials: JR
authors.lastname: Silber
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001932:Brain Neoplasms / Q000473:pathology*; D045744:Cell Line, Tumor; D018736:DNA Adducts / Q000378:metabolism; D053843:DNA Mismatch Repair; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D005910:Glioma / Q000473:pathology*; D006801:Humans; D009429:Netropsin / Q000031:analogs & derivatives* / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000737:chemistry; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D018736:DNA Adducts; D016376:Oligonucleotides, Antisense; C110963:methyl lexitropsin; D009429:Netropsin