1. PBOX-15, a novel microtubule targeting agent, induces apoptosis, upregulates death receptors, and potentiates TRAIL-mediated apoptosis in multiple myeloma cells.
- Author
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Maginn EN, Browne PV, Hayden P, Vandenberghe E, MacDonagh B, Evans P, Goodyer M, Tewari P, Campiani G, Butini S, Williams DC, Zisterer DM, Lawler MP, and McElligott AM
- Subjects
- Cell Line, Tumor, Down-Regulation drug effects, Humans, Microscopy, Fluorescence, Apoptosis drug effects, Microtubules drug effects, Multiple Myeloma pathology, Oxazepines pharmacology, Pyrroles pharmacology, Receptors, Death Domain metabolism, TNF-Related Apoptosis-Inducing Ligand physiology, Up-Regulation drug effects
- Abstract
Background: In recent years, much progress has been made in the treatment of multiple myeloma. However, a major limitation of existing chemotherapeutic drugs is the eventual emergence of resistance; hence, the development of novel agents with new mechanisms of action is pertinent. Here, we describe the activity and mechanism of action of pyrrolo-1,5-benzoxazepine-15 (PBOX-15), a novel microtubule-targeting agent, in multiple myeloma cells., Methods: The anti-myeloma activity of PBOX-15 was assessed using NCI-H929, KMS11, RPMI8226, and U266 cell lines, and primary myeloma cells. Cell cycle distribution, apoptosis, cytochrome c release, and mitochondrial inner membrane depolarisation were analysed by flow cytometry; gene expression analysis was carried out using TaqMan Low Density Arrays; and expression of caspase-8 and Bcl-2 family of proteins was assessed by western blot analysis., Results: Pyrrolo-1,5-benzoxazepine-15 induced apoptosis in ex vivo myeloma cells and in myeloma cell lines. Death receptor genes were upregulated in both NCI-H929 and U266 cell lines, which displayed the highest and lowest apoptotic responses, respectively, following treatment with PBOX-15. The largest increase was detected for the death receptor 5 (DR5) gene, and cotreatment of both cell lines with tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), the DR5 ligand, potentiated the apoptotic response. In NCI-H929 cells, PBOX-15-induced apoptosis was shown to be caspase-8 dependent, with independent activation of extrinsic and intrinsic apoptotic pathways. A caspase-8-dependent decrease in expression of Bim(EL) preceded downregulation of other Bcl-2 proteins (Bid, Bcl-2, Mcl-1) in PBOX-15-treated NCI-H929 cells., Conclusion: PBOX-15 induces apoptosis and potentiates TRAIL-induced cell death in multiple myeloma cells. Thus, PBOX-15 represents a promising agent, with a distinct mechanism of action, for the treatment of this malignancy.
- Published
- 2011
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