title: Removal of uracil by uracil DNA glycosylase limits pemetrexed cytotoxicity: overriding the limit with methoxyamine to inhibit base excision repair.
abstract: Uracil DNA glycosylase (UDG) specifically removes uracil bases from DNA, and its repair activity determines the sensitivity of the cell to anticancer agents that are capable of introducing uracil into DNA. In the present study, the participation of UDG in the response to pemetrexed-induced incorporation of uracil into DNA was studied using isogenic human tumor cell lines with or without UDG (UDG(+/+)/UDG(-/-)). UDG(-/-) cells were very sensitive to pemetrexed. Cell killing by pemetrexed was associated with genomic uracil accumulation, stalled DNA replication, and catastrophic DNA strand breaks. By contrast, UDG(+/+) cells were >10 times more resistant to pemetrexed due to the rapid removal of uracil from DNA by UDG and subsequent repair of the resultant AP sites (abasic sites) via the base excision repair (BER). The resistance to pemetrexed in UDG(+/+) cells could be reversed by the addition of methoxyamine (MX), which binds to AP sites and interrupts BER pathway. Furthermore, MX-bound AP sites induced cell death was related to their cytotoxic effect of dual inactivation of UDG and topoisomerase IIα, two genes that are highly expressed in lung cancer cells in comparison with normal cells. Thus, targeting BER-based therapy exhibits more selective cytotoxicity on cancer cells through a synthetic lethal mechanism.
authors.affiliation: Department of Medicine, Division of Hematology/Oncology, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Bulgar
authors.forename: L D
authors.initials: LD
authors.lastname: Weeks
authors.forename: Y
authors.initials: Y
authors.lastname: Miao
authors.forename: S
authors.initials: S
authors.lastname: Yang
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: C
authors.initials: C
authors.lastname: Guo
authors.forename: S
authors.initials: S
authors.lastname: Markowitz
authors.forename: N
authors.initials: N
authors.lastname: Oleinick
authors.forename: S L
authors.initials: SL
authors.lastname: Gerson
authors.forename: L
authors.initials: L
authors.lastname: Liu
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004247:DNA / Q000235:genetics; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects*; D004250:DNA Topoisomerases, Type II / Q000235:genetics; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D055786:Gene Knockout Techniques; D005971:Glutamates / Q000494:pharmacology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D006898:Hydroxylamines / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D000068437:Pemetrexed; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics*; D014498:Uracil / Q000378:metabolism; D051981:Uracil-DNA Glycosidase / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D005971:Glutamates; D006898:Hydroxylamines; D000068437:Pemetrexed; D014498:Uracil; D006147:Guanine; D004247:DNA; C005214:methoxyamine; D051981:Uracil-DNA Glycosidase; D004250:DNA Topoisomerases, Type II