PBOX-15, a novel microtubule targeting agent, induces apoptosis, upregulates death receptors, and potentiates TRAIL-mediated apoptosis in multiple myeloma cells

• Published in: British journal of cancer 2011-01, Vol.104 (2), p.281-289
• Main Authors: Maginn, E N, Browne, P V, Hayden, P, Vandenberghe, E, MacDonagh, B, Evans, P, Goodyer, M, Tewari, P, Campiani, G, Butini, S, Williams, D C, Zisterer, D M, Lawler, M P, McElligott, A M
• Format: Article
• Language: English
• Subjects: 631/208/200; 631/80/82/23; 631/92/609; 692/699/67/1990/804; Apoptosis; Apoptosis - drug effects; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Cancer Research; Cancer therapies; Cell culture; Cell cycle; Cell death; Cell Line, Tumor; Down-Regulation - drug effects; Drug Resistance; Epidemiology; Humans; Immunodeficiencies. Immunoglobulinopathies; Immunoglobulinopathies; Immunopathology; Leukemia; Ligands; Medical research; Medical sciences; Microscopy, Fluorescence; Microtubules - drug effects; Molecular Medicine; Multiple myeloma; Multiple Myeloma - pathology; Oncology; Oxazepines - pharmacology; Pyrroles - pharmacology; Receptors, Death Domain - metabolism; TNF-Related Apoptosis-Inducing Ligand - physiology; Translational Therapeutics; Tumor necrosis factor-TNF; Tumors; Up-Regulation - drug effects
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/sj.bjc.6606035

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.