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Introduction. Neuroblastoma is a tumor arising from primordial neural crest cells and is the most common extracranial solid tumor in children. Amplification of the MYCN oncogene is a genetic abnormality linked to neuroblastoma and is strongly associated with the presence of metastatic disease and poor prognosis in spite of aggressive multimodal therapy. Some antimicrobial peptides are known to induce death in cancer cell. We therefore investigated the cytotoxic activity of the antimicrobial peptide, LfcinB, against several neuroblastoma cell lines. Methods and Results. LfcinB induced cell death both in MYCN-amplified (Kelly, SKN-D-Z, IMR-32, SKN-BE2) and non MYCN-amplified (SHEP-1, SH-SY-5Y) cell lines. Normal fibroblasts were eleven fold less sensitive to LfcinB exposure than the most susceptible neuroblastoma cell line tested. A destabilizing effect on the cytoplasmic membrane and formation of membrane blebs were evident in Kelly cells after a few min of LfcinB exposure. LfcinB was internalized and both immuno- and fluorescent-labelled LfcinB indicated a co-localization with mitochondria in the cells. A depolarization of the mitochondria inner membrane and irreversible changes in the mitochondria morphology was evident after LfcinB exposure. Even though caspases were shown to become activated, specific and broad-spectrum caspase inhibitors did not inhibit LfcinB-induced cell death. Conclusion. LfcinB is cytotoxic to neuroblastoma cells in vitro and seems to display a direct destabilizing effect on both the cytoplasmic membrane and the mitochondria membrane in MYCN-amplified Kelly cells. Our results may have important implications for the potential use of LfcinB in the treatment of neuroblastoma. Key words: Antimicrobial peptide, LfcinB, neuroblastoma, mitochondria, apoptosis, necrosis

[Proc Amer Assoc Cancer Res, Volume 46, 2005]