Actin dynamics, architecture, and mechanics in cell motility. representative of three independent experiments. Statistical significance of differences was assessed by the Student 0.01. D. CuB and the Adriamycin exerted a synergistic effect on growth inhibition in MM cells. A CCK-8 assay was employed and isobologram analysis was used to determine the mode of the effects of CuB and Adriamycin combinations at equitoxic concentrations in the MM1.S, MM1.R, and U266 cells. CI, combination index, was calculated using Calcusyn software, and CI 1.0 corresponded to a synergistic interaction. One major hurdle to the development of natural product-based anticancer agents is identifying their molecular target(s) and defining their underlying mechanism(s) of action. Although the AZD1390 antitumor activity of CuB has been intensively investigated, its mechanism of action remains controversial. Its anti-proliferative effects have been associated with cell cycle arrest and apoptosis, mediated via inhibition of signaling [14, 15], but some reports argue that its antitumor activity is independent of effects on the pathway [16, 17], and while blocking signaling typically induces G0/G1 arrest [18, 19], CuB and its analogs induce G2/M arrest [9, 20], and direct interaction of CuB and STAT3 has not been demonstrated. Clarifying the role of and other kinases in CuB’s anticancer activity may not only further its development as novel anticancer agent but also elucidate the role of in cancer therapy. Kinases have been one of the hottest classes of molecular targets for cancer drug discovery and development. Advances in high-throughput screening technology, with a range of surface chemistry and activation strategies, have provided a powerful tool for evaluation of chemical-protein interactions and kinase activity inhibition, target identification, and signal pathway elucidation [21]. In this study we employed kinase screening approaches to identify kinase targets of CuB, and sought to identify the molecular mechanisms responsible for CuB-induced apoptosis. CuB treatment was reported to induce de-phosphorylation of Cofilin, a key regulator of actin filament dynamics, causing cell cycle arrest and apoptosis [10, 16]. Dephosphorylated cofilin can be translocated into mitochondria, disturbing mitochondria function or enhancing translocation of pro-apoptotic proteins in the mitochondria. Thus altering mitochondrial membrane potential, triggering release of cytochrome Rabbit polyclonal to TdT c (Cyt c), and apoptosis [22, 23]. Here we attempt to define the role of dephosphorylation of cofilin in the anticancer activity of CuB. One characteristic effect of aurora kinase inhibition is cell cycle arrest in the G2/M phase [24, 25]. In this study we also sought to demonstrate that CuB could act AZD1390 as a novel Aurora A inhibitor in induced MM cells, arresting cells in the G2/M phase. Considering that IL-10 could enhance proliferation of MM cells, and AZD1390 reduce Adriamycin-induced cell death, we hypothesized that CuB-mediated inhibition of the pathway might synergistically enhance the anti-tumor activity of Adriamycin. Additionally, we sought to investigate the relationship between CuB-induced cofilin dephosphorylation and mitochondrial dysfunction. Through these experiments, we aimed to elucidate the mechanism by which CuB reduces proliferation of MM cells, and to provide a basis for the development of this compound as a potential therapeutic agent for the treatment of MM. RESULTS CuB, administered alone or in combination with Adriamycin, inhibits MM AZD1390 proliferation Proliferation of dexamethasone-resistant (MM1.R) and dexamethasone-sensitive (MM1.S), and U266, and RPMI8226 cells incubated with CuB for 24 h was significantly inhibited in a dose-dependent manner. Interestingly, MM1.R cells were more sensitive to CuB than MM1.S cells (Figure ?(Figure1B1B). Furthermore, in order to investigate synergy of CuB and Adriamycin, cells were incubated with both CuB (0, 25, 50, 100 and 200 nM) and Adriamycin (0, 25, 50, 100 and 200 nM) in a checkerboard fashion. Cell viability was assessed after 72 h. Combination treatment inhibited proliferation more effectively than either agent alone (Figure ?(Figure1C).1C). Proliferation AZD1390 of MM1.S, MM1.R and.