RT Journal Article SR Electronic T1 Cytotoxicity, DNA Damage, and Apoptosis Induced by New Fotemustine Analogs on Human Melanoma Cells in Relation to O6-Methylguanine DNA-Methyltransferase Expression JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 816 OP 823 DO 10.1124/jpet.103.051938 VO 307 IS 2 A1 Isabelle Passagne A1 Alexandre Evrard A1 Jean-Yves Winum A1 Philippe Depeille A1 Pierre Cuq A1 Jean-Louis Montero A1 Didier Cupissol A1 Laurence Vian YR 2003 UL http://jpet.aspetjournals.org/content/307/2/816.abstract AB Fotemustine is a third generation chloroethylnitrosourea that has demonstrated significant antitumoral effects in malignant melanoma. However, its use is somewhat limited by its toxic side effects and chemoresistance caused by direct repair of O6-alkyl groups by the enzyme O6-methylguanine DNA-methyltransferase (MGMT). The aim of this work was to determine to what extent the expression of MGMT influences cytotoxicity, DNA damage, and apoptosis induced by new nitrososulfamide analogs of fotemustine (compounds 4 and 8), which have previously demonstrated interesting antiproliferative properties. We carried out complementary strategies that consisted of MGMT cDNA transfection in CAL77 Mer- melanoma cells and of MGMT inhibition with O6-benzylguanine (BG) in A375 Mer+ melanoma cells. MGMT-transfected cells were 7 to 9 times less sensitive to fotemustine than parent cells, whereas no difference between the transfected and parent cells was observed for nitrososulfamide analogs. The cytotoxicity of these analogs vis à vis a MGMT-proficient A375 melanoma cell line was approximately 3 times greater than that of fotemustine. Coincubation of these cells with O6-benzylguanine significantly increased the cytotoxicity of fotemustine and compound 8, whereas BG had little effect on the cytotoxicity of compound 4. Furthermore, DNA fragmentation determined by a comet assay was greater with nitrososulfamide analogs than with fotemustine. O6-benzylguanine increased DNA fragmentation for fotemustine and compound 8, but not for compound 4, which induced comets with a typical apoptotic appearance. The ability of this compound to induce apoptosis in the absence of BG was confirmed by a specific enzyme-linked immunosorbent assay apoptotic assay using a single-stranded DNA monoclonal antibody. The American Society for Pharmacology and Experimental Therapeutics