title: Formation of DNA adducts by the anticancer drug carboplatin: different nucleotide sequence preferences in vitro and in cells.
abstract: We have studied the formation of adducts upon carboplatin treatment of isolated DNA and in cells. The major adduct formed in vitro, determined with atomic absorption spectroscopy and enzyme-linked immunosorbent assay, was the intrastrand cross-link cis-Pt(NH3)2d(pGpG)(Pt-GG) (58%). cis-Pt-(NH3)2d(pApG) (Pt-AG) (11%), cis-Pt(NH3)2d(GMP)2 (G-Pt-G) (9%), and monofunctionally bound platinum (cis-Pt(NH3)3dGMP (Pt-G), 22%) were formed in smaller amounts. These relative occurrences of the adducts, average values found between 1 and 16 h of incubation, are comparable with those after incubation with cisplatin. The formation of carboplatin-DNA adducts was slow, and about 230-fold more carboplatin than cisplatin (molar dose) was required to obtain equal levels of platination after 4 h of incubation. However, less than 20 times more carboplatin was needed to obtain equal levels of cytotoxicity after 1 h of exposure of CHO cells. The percentages of the carboplatin-DNA adducts after 7-12 h postincubation of the cells (determined with ELISA), Pt-GG (30%), Pt-AG (16%), G-Pt-G (40%), and Pt-G (14%), were different from those of the in vitro data. After 12 h postincubation, the number of interstrand cross-links (determined by alkaline elution) amounted to about 10% of the G-Pt-G adducts and 3-4% of the total amount of adducts. The immunocytochemical detection (with antiserum NKI-A59) of the platinum-DNA modifications showed a pattern similar to that found for the various bifunctional adducts: the initially low levels slowly increased to maximum values within 7-12 h and then slowly decreased. In conclusion, carboplatin forms the same bifunctional adducts as cisplatin.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Molecular Carcinogenesis, The Netherlands Cancer Institute (Antoni van Leeuwenhoek Huis), Amsterdam.
authors.forename: F A
authors.initials: FA
authors.lastname: Blommaert
authors.forename: H C
authors.initials: HC
authors.lastname: van Dijk-Knijnenburg
authors.forename: F J
authors.initials: FJ
authors.lastname: Dijt
authors.forename: L
authors.initials: L
authors.lastname: den Engelse
authors.forename: R A
authors.initials: RA
authors.lastname: Baan
authors.forename: F
authors.initials: F
authors.lastname: Berends
authors.forename: A M
authors.initials: AM
authors.lastname: Fichtinger-Schepman
mesh_terms: D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D016190:Carboplatin / Q000378:metabolism / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000378:metabolism / Q000633:toxicity; D006224:Cricetinae; D004247:DNA / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D018736:DNA Adducts / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D007700:Kinetics; D008297:Male; D012474:Salmon; D013054:Spectrophotometry, Atomic; D013094:Spermatozoa
chemical_list: D018736:DNA Adducts; D004247:DNA; D016190:Carboplatin; D002945:Cisplatin