Malignant gliomas are characterized by their high level of resistance to chemo- and radiotherapy and new treatment options are urgently required. We previously demonstrated that brefelamide, an aromatic amide isolated from methanol extracts of cellular slime molds Dictyostelium brefeldianum and D. giganteum, had antiproliferative effects on 1321N1 human astrocytoma cells, a model of glioma. In this study, we investigated the mechanisms by which brefelamide inhibited 1321N1 and PC12 rat pheochromocytoma cell proliferation. When cells were cultured in serum-free medium, hepatocyte growth factor (HGF) increased survival of 1321N1 cells but not PC12 cells. HGF receptor, c-MET, was strongly expressed in 1321N1 cells, but not in PC12 cells. Pretreatment of 1321N1 cells with brefelamide inhibited both HGF-induced cell survival and expression of c-MET. Phosphorylation of extracellular signal-regulated kinase (ERK) and AKT was increased by HGF, but these changes were inhibited by brefelamide pretreatment. Moreover, HGF mRNA levels and secretion were reduced by brefelamide. These results suggest that brefelamide reduces survival of 1321N1 cells via multiple effects including suppression of HGF receptor expression and HGF secretion and inhibition of ERK and AKT phosphorylation.
Keywords: Astrocytoma; Brefelamide; Cell survival; Hepatocyte growth factor; c-MET.