The role of DNA polymerase eta in translesion synthesis past platinum-DNA adducts in human fibroblasts.
Cisplatin, a widely used chemotherapeutic agent, has been implicated in the induction of secondary tumors in cancer patients. This drug is presumed to be mutagenic because of error-prone translesion synthesis of cisplatin adducts in DNA. Oxaliplatin is effective in cisplatin-resistant tumors, but its mutagenicity in humans has not been reported. The polymerases involved in bypass of cisplatin and oxaliplatin adducts in vivo are not known. DNA polymerase eta is the most efficient polymerase for bypassing platinum adducts in vitro. We evaluated the role of polymerase eta in translesion synthesis past platinum adducts by determining cytotoxicity and induced mutation frequencies at the hypoxanthine guanine phosphoribosyltransferase (HPRT) locus in diploid human fibroblasts. Normal human fibroblasts (NHF1) were compared with xeroderma pigmentosum variant (XPV) cells (polymerase eta-null) after treatment with cisplatin. In addition, XPV cells complemented for polymerase eta expression were compared with the isogenic cells carrying the empty expression vector. Cytotoxicity and induced mutagenicity experiments were measured in parallel in UVC-irradiated fibroblasts. We found that equitoxic doses of cisplatin induced mutations in fibroblasts lacking polymerase eta at frequencies 2- to 2.5-fold higher than in fibroblasts with either normal or high levels of polymerase eta. These results indicate that polymerase eta is involved in error-free translesion synthesis past some cisplatin adducts. We also found that per lethal event, cisplatin was less mutagenic than UVC. Treatment with a wide range of cytotoxic doses of oxaliplatin did not induce mutations above background levels in cells either expressing or lacking polymerase eta, suggesting that oxaliplatin is nonmutagenic in human fibroblasts.
Bassett
Ekaterina
E
Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7525, USA.
King
Nicole M
NM
Bryant
Miriam F
MF
Hector
Suzanne
S
Pendyala
Lakshmi
L
Chaney
Stephen G
SG
Cordeiro-Stone
Marila
M
D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D002945:Cisplatin / Q000378:metabolism / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis* / Q000235:genetics; D018736:DNA Adducts / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000096:biosynthesis / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D016368:Frameshift Mutation; D017353:Gene Deletion; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D008297:Male; D009944:Organoplatinum Compounds / Q000378:metabolism / Q000494:pharmacology*; D000077150:Oxaliplatin; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics / Q000473:pathology; D000099270:Y-Family DNA Polymerases
D000970:Antineoplastic Agents; D002945:Cisplatin; D004247:DNA; D018736:DNA Adducts; D004259:DNA-Directed DNA Polymerase; D007041:Hypoxanthine Phosphoribosyltransferase; D009944:Organoplatinum Compounds; D000077150:Oxaliplatin; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases