Gene Specific Damage and Repair of Platinum Adducts and Crosslinks

Abstract

We have developed techniques to study the DNA damage formation and repair of cisplatin lesions in individual genes. The frequency of intrastrand adducts and interstrand crosslinks can be determined in restriction fragments within genes or in non-transcribed gene regions. In hamster cells, intrastrand adducts are repaired faster from the essential dihydrofolate reductase (DHFR) gene than from an inactive region. In contrast, interstrand crosslinks are repaired at a similar rate from the active and inactive genomic regions. In an attempt to study the role of DNA repair in drug resistance, we have examined the repair of these lesions in certain important genes in cisplatin sensitive and resistant human ovarian cancer cells. The resistant cells repair interstrand crosslinks more efficiently than the sensitive ones from the DHFR gene, the multidrug resistance gene and from the inactive δglobin gene. However, these ovarian cancer cell lines do not differ in their ability to repair cisplatin intrastrand adducts from these genes.