DC-81, an antitumor antibiotic produced by Streptomyces species, belongs to the pyrrolo[2,1-c] [ 1,4]benzodiazepine (PBD) family, which are potent inhibitors of nucleic acid synthesis. We previously reported an efficient synthesis of PBD hybrids linked with indole carboxylates. Recently, we have also shown that a PBD hybrid (IN6CPBD) agent can activate the apoptotic pathway mediated by mitochondria. In this study, we will examine the transcription factors nuclear factor-kappa B (NF-kappa B) and activator protein- 1 (AP-1) that functionally regulate cell proliferation, transformation, and apoptosis. To investigate the IN6CPBD-induced alterations in NF-kappa B and AP-1 activity that involve cell cycle regulation, we exposed human melanoma A375 cells to different concentrations of IN6CPBD. Our data revealed that treatment of A375 cells with IN6CPBD resulted in a marked loss of cells from the G2/M phase of the cell cycle and an increase in Ca2+ and cAMP and promoted phosphorylation of Jun N-terminal kinase (JNK) expression. By using the luciferase reporter assay, the NF-kappa B activities were decreased; however, AP-1 activity was further enhanced after A375 cells were treated with graded concentrations of IN6CPBD. Blockade of NF-kappa B or JNK activity further enhanced caspase-3 substrate PARP cleavage and subsequent apoptotic cell death.
