Irofulven cytotoxicity depends on transcription-coupled nucleotide excision repair and is correlated with XPG expression in solid tumor cells.
BACKGROUND
Irofulven is a novel alkylating agent with promising clinical activity, particularly toward ovarian and hormone-refractory prostate cancers. To facilitate additional clinical development, we have aimed to identify biological markers associated with sensitivity to the compound.


METHODS
Fibroblasts derived from patients with xeroderma pigmentosum or Cockayne's syndrome along with a panel of 20 human cancer cell lines (eight different tumor types) were examined to establish the importance of nucleotide excision repair proteins in the sensitivity to irofulven.


RESULTS
Human cells deficient in nucleotide excision repair are up to 30-fold more sensitive to the cytotoxic effects of irofulven compared with repair-proficient controls, clearly indicating that nucleotide excision repair plays a crucial role in the sensitivity to the drug. Interestingly, our results show that irofulven-induced lesions are recognized by transcription-coupled repair but not by global genome repair. Another unique feature is the pronounced sensitivity of XPD and XPB helicase-deficient cells to the drug. Comparison of the IC50 values for irofulven, cisplatin, and ecteinascidin 743 with the expression levels of ERCC1, XPD, and XPG genes in different solid tumor cell lines shows no correlation between the expression levels of any of the three nucleotide excision repair proteins and the sensitivity to ecteinascidin 743. In contrast, expression of the XPG endonuclease was correlated with the cytotoxicity for irofulven and, to a lesser degree, for cisplatin. Importantly, XPG expression was also correlated with cellular nucleotide excision repair activity.


CONCLUSIONS
Increasing evidence indicates that compromised nucleotide excision repair activity is frequent in several solid tumor types. The results presented here suggest that XPG expression in such tumors may be a useful marker to predict their sensitivity to irofulven.
Koeppel
Florence
F
Group of Biology and Pharmacogenetics of Human Tumors, Centre National de la Recherche Scientifique, UMR 8113, Institut Gustave-Roussy, Villejuif, France.
Poindessous
Virginie
V
Lazar
Vladimir
V
Raymond
Eric
E
Sarasin
Alain
A
Larsen
Annette K
AK
D018906:Antineoplastic Agents, Alkylating / Q000633:toxicity; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D003057:Cockayne Syndrome / Q000235:genetics / Q000473:pathology; D017931:DNA Primers; D004260:DNA Repair / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D004720:Endonucleases; D006801:Humans; D009687:Nuclear Proteins; D012717:Sesquiterpenes / Q000633:toxicity*; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*; D014983:Xeroderma Pigmentosum / Q000235:genetics / Q000473:pathology; D000099250:DNA Excision Repair Protein ERCC-5
D018906:Antineoplastic Agents, Alkylating; D017931:DNA Primers; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D004720:Endonucleases; D009687:Nuclear Proteins; D012717:Sesquiterpenes; D014157:Transcription Factors; D000099250:DNA Excision Repair Protein ERCC-5; C102714:irofulven