Effects of Ape1 overexpression on cellular resistance to DNA-damaging and anticancer agents.
In vitro biochemical studies indicate that Ape1 is the major mammalian enzyme responsible for repairing abasic lesions in DNA and a significant factor in the processing of specific 3'-replication-blocking termini. Toward addressing the role of Ape1 in cellular resistance to specific DNA-damaging and anticancer agents, we constructed a chinese hamster ovary (CHO) cell line, AA8-Ape1, that exhibits a 7-fold higher Ape1-dependent nuclease activity; this overexpression is abolished upon exposure to tetracycline (Tc). In comparison to the AA8 parental control, our data indicates that Ape1 activity is not rate-limiting for the repair of cytotoxic damages induced by the alkylating agent methyl methanesulfonate (MMS), the oxidizing agent hydrogen peroxide (H2O2), or ionizing radiation (IR). AA8-Ape1 cells did exhibit increased resistance to bleomycin following a chronic 3-day exposure, but not to more acute challenges of 1 h. Most notably, the AA8-Ape1 line displayed approximately 1.7-fold elevated resistance to the replication-blocking nucleoside analog dioxolane cytidine (L-OddC); this improved resistance was abrogated by the addition of Tc to the medium. These studies demonstrate that Ape1 is not rate-limiting in the repair of MMS- or H2O2-induced DNA damage, that Ape1 may dictate the sensitivity of bleomycin, depending on dosing scheme, and for the first time, that Ape1 can influence cellular resistance to the anticancer/antiviral antimetabolite L-OddC.
Schild
L J
LJ
Biology and Biotechnology Research Program, L441, Lawrence Livermore National Laboratory, Livermore, CA 94551-0808, USA.
Brookman
K W
KW
Thompson
L H
LH
Wilson
D M
DM
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002460:Cell Line; D006224:Cricetinae; D004249:DNA Damage; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D006801:Humans
D000970:Antineoplastic Agents; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase