Most direct-acting and ultimate carcinogens are highly reactive electrophiles (have electron-deficient atoms) that can react with nucleophilic (electron-rich) sites in the cell.
These reactions are nonenzymatic and result in the formation of covalent adducts (addition products) between the chemical carcinogen and a nucleotide in DNA.
The electrophilic reactions may attack several electron-rich sites in the target cells, including DNA, RNA, and proteins, thus sometimes producing lethal damage.
In initiated cells, the interaction is obviously nonlethal, and, as expected, DNA is the primary target.
See also
carcinogenesis