title: Decreased nuclear matrix DNA topoisomerase II in human leukemia cells resistant to VM-26 and m-AMSA.
abstract: CEM leukemia cells selected for resistance to VM-26 (CEM/VM-1) are cross-resistant to various other DNA topoisomerase II inhibitors but not to Vinca alkaloids. Since DNA topoisomerase II is a major protein of the nuclear matrix, we asked if alterations in nuclear matrix topoisomerase II might be important in this form of multidrug resistance. Pretreatment of drug-sensitive CEM cells for 2 h with either 5 microM VM-26 or 3 microM m-AMSA reduced the specific activity of newly replicated DNA on the nuclear matrix by 75 and 50%, respectively, relative to that of the bulk DNA. However, neither VM-26 nor m-AMSA affected the relative specific activity of nascent DNA isolated from the nuclear matrices of drug-resistant CEM/VM-1 cells. The decatenating and unknotting activities of DNA topoisomerase II were 6- and 7-fold lower, respectively, in the nuclear matrix preparations from the CEM/VM-1 cells compared to parental CEM cells. Western blot analysis revealed that the amount of immunoreactive topoisomerase II in the nuclear matrices of the CEM/VM-1 cells was decreased 3.2-fold relative to that in CEM cells, but there was no significant difference in the amount of enzyme present in the nonmatrix (1.5 M salt soluble) fractions of nuclei from these cell lines. Increasing the NaCl concentration used in the matrix isolation procedure from 0.2 to 1.8 M resulted in a progressive decrease in the specific activity of topoisomerase II in matrices of CEM/VM-1 but not CEM cells, which suggested that the association of the enzyme with the matrix is altered in the resistant cells.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biochemistry, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27103.
authors.forename: D J
authors.initials: DJ
authors.lastname: Fernandes
authors.forename: M K
authors.initials: MK
authors.lastname: Danks
authors.forename: W T
authors.initials: WT
authors.lastname: Beck
mesh_terms: D000677:Amsacrine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology*; D003421:Crithidia / Q000187:drug effects / Q000201:enzymology*; D004247:DNA / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004351:Drug Resistance; D006801:Humans; D007938:Leukemia / Q000201:enzymology*; D011034:Podophyllotoxin / Q000031:analogs & derivatives*; D013713:Teniposide / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D000677:Amsacrine; C033073:4'-(9-acridinylamino)methanesulfon-o-anisidide; D004247:DNA; D013713:Teniposide; D004250:DNA Topoisomerases, Type II; D011034:Podophyllotoxin