Cytotoxicity, calmodulin and DNA lesions in cells treated with streptozotocin.

Streptozotocin is a nitrosourea-derivative containing a methyl group instead of a haloethyl group. Treatment of human adenocarcinoma cells with streptozotocin induces DNA lesions. The presence of the lesions is visualized during cell lysis in dilute alkali as changes in fragmentation of prelabelled DNA. The increase in DNA fragmentation is paralleled by increased cytotoxicity. Furthermore prolonged duration of treatment reduces the level of DNA fragmentation. The repair of the DNA lesions is prevented by treating the cells with W-7, an inhibitor of calmodulin.