text: Cisplatin interferes with DNA replication, which kills the fastest proliferating cells, which in theory are cancerous.   Following administration, one chloride ion is slowly displaced by water to give the aquo complex cis-[PtCl(NH)(HO)], in a process termed aquation.  Dissociation of the chloride is favored inside the cell because the intracellular chloride concentration is only 3–20% of the approximately 100 mM chloride concentration in the extracellular fluid.
  The water molecule in cis-[PtCl(NH)(HO)] is itself easily displaced by the N-heterocyclic bases on DNA. Guanine preferentially binds. A model compound has been prepared and crystals were examined by X-ray crystallography
  Subsequent to formation of [PtCl(guanine-DNA)(NH)], crosslinking can occur via displacement of the other chloride, typically by another guanine. Cisplatin crosslinks DNA in several different ways, interfering with cell division by mitosis. The damaged DNA elicits DNA repair mechanisms, which in turn activate apoptosis when repair proves impossible. In 2008, researchers were able to show that the apoptosis induced by cisplatin on human colon cancer cells depends on the mitochondrial serine-protease Omi/Htra2. Since this was only demonstrated for colon carcinoma cells, it remains an open question whether the Omi/Htra2 protein participates in the cisplatin-induced apoptosis in carcinomas from other tissues.
  Most notable among the changes in DNA are the 1,2-intrastrand cross-links with purine bases. These include 1,2-intrastrand d(GpG) adducts, which form nearly 90% of the adducts, and the less common 1,2-intrastrand d(ApG) adducts. Coordination chemists have obtained crystals of the products of reacting cisplain with small models of DNA. Here is a POVray plot of the platinum binding to a small model of DNA.
  1,3-intrastrand d(GpXpG) adducts occur but are readily excised by the nucleotide excision repair (NER). Other adducts include inter-strand crosslinks and nonfunctional adducts that have been postulated to contribute to cisplatin's activity. Interaction with cellular proteins, particularly HMG domain proteins, has also been advanced as a mechanism of interfering with mitosis, although this is probably not its primary method of action.