Pramanicin (PMC) is a novel anti-fungal agent. In this study, among eight analogues screened by MTT cell proliferation assay for their potential cytotoxic effect on HCT116 colon cancer cells, Pramanicin-A and Pramanicin-F were found to be the most effective candidates at the concentration of 25uM and 75uM respectively. Flow-cytometric analyses with Annexin-V staining and M30 apoptosense eliza assay confirmed that PMC-A is a more effective apoptotic agent compared to PMC-F, thus PMC-A was selected for further studies. Moreover, no difference in cytotoxicity was observerved in puma and bax defficient cell lines, therefore further studies were conducted with HCT116 wild type cells. In order to get insight into the mechanism of apoptotic response by PMC-A, we followed MAP kinase pathways with using specific MAPK antibodies and inhibitors. Our immunoblotting data reveals that PMC-A induced the activation/phosphorilation of c-jun terminal kinase (JNK), p38 and extracellular signal-regulated kinases (ERK1/2) in different time kinetics. Inhibition of caspase-3, and caspase-9 with their specific inhibitors prevent apoptosis. Interestingly inhibition of JNK and p38 activations/phosphorilations potentiated the apoptotic response. These data indicate that PMC-A induced apoptosis is mediated by caspase dependent pathways, activation of JNK and p38 but not ERK 1/2 may have a pro-survival role.Finally our data from flow-cytometric and flourometric analyses with D2CDF-DA staining revealed induction of reactive oxygen species (ROS) acting as second messengers which may activate MAPK signaling pathways as well as other signaling pathways in apoptotic response of cells to PMC-A at early (1h, 2h) and late (24h) time points
