Repair of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea-induced damage by mammalian cell extracts.
The repair of damage induced by the alkylating antitumor drug 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) was investigated using an in vitro excision repair system. Hamster cell extracts prepared from the parental CHO-9 cell line and the ERCC1 mutant 43-3B were both proficient in the repair of CCNU-induced damage. The in vitro repair of CCNU damage was faster than the repair of UV damage and plasmid substrates were rapidly and efficiently incised after incubation with either CHO-9 or 43-3B extracts. 7-Methylguanine (7-meG) and 3-methyladenine (3-meA) glycosylases were active to a similar extent in the CHO-9 and 43-3B extracts. The data indicate that most damage induced by CCNU is repaired via the ERCC1-independent base excision repair pathway, initiating with removal of chloroethylated and hydroxyethylated bases by N-glycosylases. Yet, the sensitive phenotype of 43-3B cells suggests that the ERCC1 gene product is required for the removal of a small subset of CCNU-induced lesions that are important for drug cytotoxicity.
Cappelli
E
E
CSTA-Mutagenesis laboratory, Istituto Nazionale per la Ricerca sul Cancro-IST, Genova, Italy.
Redaelli
A
A
Rivano
M E
ME
Abbondandolo
A
A
Frosina
G
G
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000633:toxicity*; D016466:CHO Cells / Q000737:chemistry / Q000201:enzymology; D002457:Cell Extracts / Q000494:pharmacology*; D006224:Cricetinae; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D004260:DNA Repair; D004268:DNA-Binding Proteins; D004720:Endonucleases; D008130:Lomustine / Q000633:toxicity*; D008780:Methyltransferases / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism / Q000494:pharmacology; D019853:O(6)-Methylguanine-DNA Methyltransferase; D011506:Proteins / Q000378:metabolism / Q000494:pharmacology
D018906:Antineoplastic Agents, Alkylating; D002457:Cell Extracts; D004268:DNA-Binding Proteins; D009711:Nucleotides; D011506:Proteins; D008130:Lomustine; D004247:DNA; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase; D004720:Endonucleases