Design and mechanism of action of a novel cytotoxic 1,2,3-triazene-containing heterocycle, 3,5-dimethyl-pyrido-1,2,3,5-tetrazepin-4-one (PYRZ), in the human epithelial ovarian cancer cell line NIH:OVCAR-3 in vitro

Abstract

Summary The mechanism of action of the novel heterocycle 3,5-dimethyl-pyrido-1,2,3,5-tetrazepin-4-one (PYRZ), structurally related to temozolomide, was studied in the human ovarian tumour cell line OVCAR-3. Our results showed that, despite its marked structural similarities to temozolomide, PYRZ presents properties that are atypical of 1,2,3-triazene-containing alkylating agents. In a Maxam-Gilbert DNA sequencing assay, PYRZ showed background levels of DNA alkylation, in contrast to temozolomide which strongly alkylated DNA preferentially at guanine residues. At high concentrations, PYRZ inhibited the synthesis of DNA, RNA and protein 3 h after treatment, in contrast to temozolomide which, in previous work, was found to preferentially inhibit DNA synthesis in OVCAR-3 cells. In cells exposed to PYRZ, alkaline sucrose density-gradient centrifugation showed a dose-dependent increase in DNA fragmentation only 12 and 24 h after treatment. PYRZ induced increasing accumulation of cells in late S and G2+M 6-24 h after treatment. This also contrasts with previous work that showed delayed cell cycle arrest induced by temozolomide in OVCAR-3 cells and in the murine leukaemia Li 210 cells. Cell-killing kinetics by PYRZ showed a series of sigmoidal dose-response curves with 50-90% cell killing attained as early as 24 h after treatment in the 25-100 gM dose range. (IC50 clonogenic assay 18 FM). The results suggest that the mechanism of cell killing by PYRZ may be different from that of its parent drug temozolomide, and other alkyl-triazene-containing molecules of the same class.

Synthesis and antiproliferative activity of 3-(2-chloroethyl)-5-methyl-6-phenyl-8-(trifluoromethyl)-5,6-dihydropyrazolo[3,4-f][1,2,3,5]tetrazepin-4-(3H)-one

“…Due to the significant activity of 1,2,3,5-tetrazepin-4-(3H)-ones on Mer þ cell lines, expressing elevated levels of MGMT, and the low number of example in the literature of tetrazepinones fused with an heterocyclic ring [11,14], we reported in earliest papers [16,17] the synthesis of the two pyrazolo [3,4-f] [1,2,3,5]tetrazepinones 6 and 7 (Fig. 2), as well as the antiproliferative activity and the antiapoptotic effects against K562, K562R (imatinib mesilate resistant), HL60 and multidrug resistant (MDR) HL60 cell lines of 7.…”

A novel organobismuth compound, 1-[(2-di-p-tolylbismuthanophenyl)diazenyl]pyrrolidine, induces apoptosis in the human acute promyelocytic leukemia cell line NB4 via reactive oxygen species

“…Triazenes possessing cytotoxic alkylating effects have been known to show anticancer activity [1][2][3][4][5][6][7][8]. Clinical studies show that triazenes exhibit anti-neoplastic activity in patients with acute leukemia [9][10][11].…”