degrasyn and Lymphoma--Mantle-Cell

Usp9x was recently shown to be highly expressed in myeloma patients with short progression-free survival and is proposed to enhance stability of the survival protein Mcl-1. In this study, we found that the partially selective Usp9x deubiquitinase inhibitor WP1130 induced apoptosis and reduced Mcl-1 protein levels. However, short hairpin RNA-mediated knockdown (KD) of Usp9x in myeloma cells resulted in transient induction of apoptosis, followed by a sustained reduction in cell growth. A compensatory upregulation of Usp24, a deubiquitinase closely related to Usp9x, in Usp9x KD cells was noted. Direct Usp24 KD resulted in marked induction of myeloma cell death that was associated with a reduction of Mcl-1. Usp24 was found to sustain myeloma cell survival and Mcl-1 regulation in the absence of Usp9x. Both Usp9x and Usp24 were expressed and activated in primary myeloma cells whereas Usp24 protein overexpression was noted in some patients with drug-refractory myeloma and other B-cell malignancies. Furthermore, we improved the drug-like properties of WP1130 and demonstrated that the novel compound EOAI3402143 dose-dependently inhibited Usp9x and Usp24 activity, increased tumor cell apoptosis, and fully blocked or regressed myeloma tumors in mice. We conclude that small-molecule Usp9x/Usp24 inhibitors may have therapeutic activity in myeloma.

Topics: Animals; Apoptosis; Cell Line, Tumor; Cyanoacrylates; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Humans; Lymphoma, Mantle-Cell; Male; Mice; Multiple Myeloma; Myeloid Cell Leukemia Sequence 1 Protein; Pyridines; Ubiquitin Thiolesterase

Mantle cell lymphoma (MCL) is an aggressive histotype of B-cell non-Hodgkin lymphoma that has increased in incidence over the past few decades and is incurable, usually poorly responsive to standard chemotherapy combinations, and associated with poor prognoses. Discovering new therapeutic agents with low toxicity that produce better outcomes in patients with MCL is an ongoing challenge. Recent studies showed that degrasyn, a novel small-molecule inhibitor of the Janus kinase/signal transducer and activation of transcription (JAK/STAT) pathway, exerts antitumor activity in lymphoid tumors by inhibiting key growth and survival signaling (JAK/STAT) pathways. In the present study, we found that treatment of both typical and blastoid-variant MCL cells with degrasyn in combination with bortezomib resulted in synergistic growth inhibition and apoptosis induction in vitro. The apoptosis in these cells was correlated with the downregulation of constitutive NF-kappaB and phosphorylated STAT3 activation, leading to the inhibition of c-Myc, cyclin D1, and bcl-2 protein expression and the upregulation of bax protein expression. In vivo, degrasyn and bortezomib interacted to synergistically prevent tumor development and prolong survival durations in a xenotransplant severe combined immunodeficient mouse model of MCL. These findings suggest that agents such as degrasyn that can pharmacologically target constitutively expressed NF-kappaB and STAT3 in MCL cells may be useful therapeutic agents for MCL when administered together with bortezomib.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Blotting, Western; Boronic Acids; Bortezomib; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cells, Cultured; Cyanoacrylates; Cyclin D1; Dose-Response Relationship, Drug; Drug Synergism; Female; Gene Expression Regulation, Leukemic; Humans; Lymphoma, Mantle-Cell; Mice; Mice, SCID; NF-kappa B; Nitriles; Phosphorylation; Proto-Oncogene Proteins c-myc; Pyrazines; Pyridines; Reverse Transcriptase Polymerase Chain Reaction; STAT3 Transcription Factor; Survival Analysis; Xenograft Model Antitumor Assays