Development of Comprehensive Ultraperformance Liquid Chromatography-High-Resolution Mass Spectrometry Assays to Quantitate Cisplatin-Induced DNA-DNA Cross-Links

Abstract

Cisplatin(CP) is a common antitumor drug that is usedto treatmany solid tumors. The activity of CP is attributed to the formationof DNA-DNA cross-links, which consist of 1,2-intra-, 1,3-intra-,and interstrand cross-links. To better understand how each intrastrandcross-link contributes to the activity of CP, we have developed comprehensiveultraperformance liquid chromatography-selective ion monitoring (UPLC-SIM)assays to quantify 1,2-GG-, 1,2-AG-, 1,3-GCG-, and 1,3-GTG-intrastrandcross-links. The limit of quantitation for the developed assays rangedfrom 5 to 50 fmol or as low as 6 cross-links per 10(8) nucleotides.To demonstrate the utility of the UPLC-SIM assays, we first performed in vitro cross-link formation kinetics experiments. We confirmedthat the 1,2-GG-intrastrand cross-links were the most abundant intrastrandcross-link and formed at a faster rate compared to 1,2-AG- and 1,3-intrastrandcross-links. Furthermore, we investigated the repair kinetics of intrastrandcross-links in CP-treated wild-type and nucleotide excision repair(NER)-deficient U2OS cells. We observed a slow decrease of both 1,2-and 1,3-intrastrand cross-links in wild-type cells and no evidenceof direct repair in the NER-deficient cells. Taken together, we havedemonstrated that our assays are capable of accurately quantifyingintrastrand cross-links in CP-treated samples and can be utilizedto better understand the activity of CP.