Increased gene-specific repair of cisplatin interstrand cross-links in cisplatin-resistant human ovarian cancer cell lines.

Abstract

We have studied several aspects of DNA damage formation and repair in human ovarian cancer cell lines which have become resistant to cisplatin through continued exposure to the anticancer drug. The Cells in culture were treated with cisplatin, and the two main DNA lesions formed, intrastrand adducts and interstrand cross-links, were quantitated before and after repair incubation. This quantitation was done for total genomic lesions and at the level of individual genes. In the overall genome, the initial frequency of both cisplatin lesions assayed was higher in the parental than in the derivative resistant cell lines. Nonetheless, the total genomic repair of each of these lesions was not increased in the resistant cells. These differences in initial lesion frequency between parental and resistant cell lines were not observed at the gene level. Resistant and parental cells had similar initial frequencies of intrastrand adducts and interstrand cross-links in the dihydrofolate reductase (DHFR) gene and in several other genes after cisplatin treatment of the cells. There was no increase in the repair efficiency of intrastrand adducts in the DHFR gene in resistant cell lines compared with the parental partners. However, a marked and consistent repair difference between parental and resistant cells was observed for the gene-specific repair of cisplatin interstrand cross-links. DNA interstrand cross-links were removed from three genes, the DHFR, multidrug resistance (MDR1), and b-globin genes, much more efficiently in the resistant cell lines than in the parental cell lines. Our findings suggest that acquired cellular resistance to cisplatin may be associated with increased gene-specific DNA repair efficiency of a specific lesion, the interstrand cross-link.The metal coordination complex cisplatin has been widely used in the treatment of ovarian, testicular, head and neck, bladder, and small-cell lung carcinomas (19). DNA is thought to be the most critical target for the antitumor action of cisplatin, although the compound can also react with other biologically important molecules such as RNA and proteins (25, 29). The major lesions produced by cisplatin are DNA intrastrand adducts (IA) between adjacent purines GpG or ApG. Minor lesions include IA between two guanine residues separated by one nucleotide residue (GpXpG), interstrand cross-links (ICL) between two adjacent guanine residues on opposite DNA strands, and DNA-protein crosslinks (13,27). The lesions of most therapeutic significance are thought to be IA and ICL.Platinum-based chemotherapy is the standard treatment in the initial therapy of advanced-stage ovarian cancer. Although up to 80% of patients will have an early favorable response to therapy, less than 20% of individuals will experience long-term disease-free survival (33). As a result of primary or acquired resistance, most ovarian cancer patients will eventually relapse with cisplatin-resistant disease (5). Attempts to overcome drug resistance are central to both clinical and basic molecular research ...

Role of the human ERCC-1 gene in gene-specific repair of cisplatin-induced DNA damage

“…This is in accordance with a previous report proposing that ERCC-1 is more important for the repair of MMC induced crosslinks than UV induced damage (32). Furthermore, it was shown that overexpression of the human ERCC-1 gene may inhibit a pathway specific to the repair of ICL (33), and that acquired cellular resistance to cisplatin may be associated with increased gene-specific repair efficiency of interstrand crosslinks (34).…”

Tyrosinase-related protein 2 as a mediator of melanoma specific resistance to cis-diamminedichloroplatinum(II): therapeutic implications

“…They are multifaceted and complex, and can include the involvement of membrane-associated e ux pumps, the up-regulation of cellular detoxifying thiols, enhanced DNA repair activity and the inhibition of apoptotic pathways (Ishikawa et al, 1994;Andrews et al, 1985;Lai et al, 1988Lai et al, , 1989Chu, 1994;Chu and Chang, 1990;Zhen et al, 1992;Miyake et al, 1998;Citro et al, 1998). In many malignancies, drug resistance is acquired through prolonged and repeated exposure to a chemotherapeutic agent.…”

DNA damage by anti-cancer agents resolved at the nucleotide level of a single copy gene: evidence for a novel binding site for cisplatin in cells

“…Repair studies at the nucleotide level are also particularly important in the investigation of anti-cancer drugs. For example Zhen et al (35), using Southern blotting, have found differences in the gene specific repair of cisplatin interstrand, but not intrastrand, crosslinks which seemed to correlate with the degree of resistance to the drug. Further studies on nucleotide-specific lesions will help to identify molecules capable of creating lesions which are resistant to repair.…”