DNA damage and repair in L1210 cells exposed to 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea.

The DNA of L1210 cells exposed to low concentrations of 1-(2-chloroethyl)=3-cyclohexyl-1-nitrosourea has been analyzed for the presence of single-strand breaks. DNA from 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea-treated cells both sediments more slowly than control DNA on alkaline sucrose gradients andshows a greater extent of strand separation of the DNA helix in alkali. These effects are a typical result of exposure of cellular DNA to alkylating agents or ionizing radiation. The extent of DNA damage caused by 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea has been related to the same amount of damage resulting from exposure of cells to low doses of gamma-irradiation. The rate and extent of repair of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea-induced damage is slow and incomplete, compared with the repair of gamma-irradiation damage to DNA. It is concluded that 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea behaves as a weak alkylating agent, a property that may explain its antitumor properties.