Compacting effect of BBR3464, a new-generation trisplatinum anticancer agent, on DNA

BBR3464 is a trinuclear platinum compound of formula [{trans-PtCl(NH(3))(2)}(2)-mu-trans-Pt(NH(3))(2){NH(2)(CH(2))(6)NH(2)}(2)](4+). It is a new-generation platinum chemotherapeutic agent that exhibits cytotoxicity at ten to thousand times lower dose limit compared to the well-known platinum drug cisplatin, in cisplatin-sensitive as well as in cisplatin-resistant cells. DNA is thought to be the primary cellular target of BBR3464. In this work, we have applied high-resolution atomic force microscopy (AFM) for the first time, to obtain direct information on BBR3464-induced structural changes of DNA. It is found that the DNA molecules get compacted after treatment with BBR3464, for the drug:DNA molar ratio and the drug treatment period of 0.01 and 48 h, respectively. These values of molar ratio and incubation period have been obtained previously, as a result of biochemical optimization studies carried out for achieving maximum drug effects. The DNA structural changes, as observed in AFM topographs, have been correlated to the bulk level spectroscopic information. A remark on the significance of BBR3464-induced DNA compaction with respect to the available AFM reports on DNA modification by cisplatin has been made.