Proteins binding to cisplatin-damaged DNA in human cell lines

Cisplatin (CDDP) is a highly effective, frequently used cancer chemotherapeutic drug employed in the treatment of several human malignancies including ovarian, testicular, and bladder cancers. A common problem encountered with cisplatin therapy is intrinsic or acquired resistance to this drug. While the mechanisms of resistance to cisplatin, and other chemotherapeutic agents, are not fully understood, one factor affecting the cellular response to CDDP may result from differences in the level of specific proteins that recognize CDDP-damaged DNA. We have developed a damaged DNA affinity precipitation technique that allows the direct visualization and characterization of cellular proteins that bind to cisplatin-damaged DNA. In the present study we have utilized this method to analyze proteins present in several mammalian cell lines that bind to cisplatin-damaged DNA. We demonstrate that HeLa cells, resistant to CDDP cytotoxicity, contain high levels of high-mobility-group proteins 1 and 2, which bind to CDDP-DNA. We also show that xeroderma pigmentosum cells of different genetic complementation groups contain variable levels of a 45-kDa protein that binds to CDDP-DNA. Thus, our results indicate that different human cell lines demonstrate qualitative and quantitative differences in the expression of cisplatin-damaged DNA binding proteins.