In vitro formation of DNA adducts by cisplatin, lobaplatin and oxaliplatin in calf thymus DNA in solution and in cultured human cells

Abstract

Two interesting representatives of a new generation of platinum-based cytostatic drugs that are currently being tested in clinical trials are lobaplatin [1,2-diaminomethylcyclobutane platinum(II) lactate] and oxaliplatin [1,2-diaminocyclohexane platinum (II) oxalate]. Since little is known about the DNA adduct formation of these compounds, we studied their formation in DNA in vitro in calf thymus DNA and in cells. The major adducts formed in vitro were the Pt-GG and Pt-AG intrastrand crosslinks. The latter adducts could be detected using a recently developed 32P-postlabelling method. Using both this assay and atomic absorption spectroscopy, it was shown that there is a substantially higher rate of the in vitro adduct formation by cisplatin, compared with lobaplatin and oxaliplatin. Platinum concentrations required to obtain 90% cell kill during a 2 h incubation of A2780 cells were 15 microM for cisplatin and oxaliplatin and 22 microM for lobaplatin. Using an antiserum originally raised against cisplatin-treated DNA, we were also able to detect platinum-DNA adducts induced by lobaplatin and oxaliplatin. Maximal nuclear staining for all three compounds was observed after a 4 h post-incubation period. The nuclear staining level induced by cisplatin was about 10-fold higher than after lobaplatin and oxaliplatin treatment. GG and AG adducts, measured by 32P-postlabelling, also showed maximum levels at about 4 h after treatment. Relative GG peak levels were 4:1:3 for cisplatin, lobaplatin and oxaliplatin, respectively. The ratios of GG over AG intrastrand crosslinks in the A2780 cells were not significantly different for the various compounds. In conclusion, the 32P-postlabelling technique has been shown to be appropriate for adduct analysis, not only for the classical Pt compounds cisplatin and carboplatin but also for novel platinum compounds like lobaplatin and oxaliplatin. Results indicated large differences in reactivity of the latter compounds to DNA in vitro, compared with cisplatin. This difference was smaller in cells, suggesting enhancement of adduct formation by certain cellular mechanisms and/or compounds. From these studies, no conclusions can be drawn with respect to the cytotoxicity of the different Pt-GG and Pt-AG intrastrand crosslinks formed by these compounds.

Improved Therapeutic Effectiveness by Combining Recombinant CXC Chemokine Ligand 10 with Cisplatin in Solid Tumors

“…DDP has been effective in inducing apoptosis in variety of tumor cell lines (40 -42). Its apoptosis-inducing effects are known to be correlated with DNA damage by forming DNA-Pt adducts and DNA strand breaks (40,41). Recently, evidence indicated that CXCL10 reduced microvessel density, leading to the observed increase in both tumor cell apoptosis and necrosis (43).…”

Effects of Spectator Ligands on the Specific Recognition of Intrastrand Platinum-DNA Cross-links by High Mobility Group Box and TATA-binding Proteins

“…As with cisplatin-DNA damage, the 1,2-intrastrand d(GpG) and d(ApG) cross-links formed by these closely related platinum compounds most likely contribute to their cytotoxicity. For example, oxaliplatin forms mainly 1,2-intrastand d(GpG) cross-links both in vitro and in cells (14,15). Therefore, understanding how these spectator ligands, ammonia in the case of cisplatin and 1,2-diaminocyclohexane in the case of oxaliplatin, affect the binding of cellular proteins to platinated DNA may help to distinguish the manner by which the proc-essing of their lesions in the cell can differ from that of cisplatin-damaged DNA.…”

Induction of JNK and c-Abl signalling by cisplatin and oxaliplatin in mismatch repair-proficient and -deficient cells

“…Following reaction with DNA, the adducts differ by virtue of the fact that the cisplatin adduct has two amino groups projecting into the major groove whereas the oxaliplatin adduct retains the bulkier DACH ring. The major adducts formed by oxaliplatin are the Pt-GG and Pt-AG intrastrand cross-links (Saris et al, 1996). Sedimentation analysis showed that oxaliplatin does not induce detectable interstand cross-links but forms DNA strand breaks (Woynarowski et al, 1997).…”

“…In contrast, cisplatin produces interstand crosslinks but no breaks. Oxaliplatin appears to be less reactive with cellular DNA than cisplatin, but is a comparably potent inhibitor of DNA and protein synthesis (Saris et al, 1996;Woynarowski et al, 1997).…”