In vitro and in vivo efficacy of the novel oral proteasome inhibitor NNU546 in multiple myeloma

Abstract

Background Proteasome inhibition demonstrates highly effective impact on multiple myeloma (MM) treatment. Here, we aimed to examine anti-tumor efficiency and underlying mechanisms of a novel well tolerated orally applicable proteasome inhibitor NNU546 and its hydrolyzed pharmacologically active form NNU219. Methods Enzyme activities and inhibition assays was performed to evaluate the effect of NNU219 on proteasome. To explore the anti-MM activity of NNU219 and its related mechanism, multiple in vitro assays such as cell viability, cell cycle and apoptosis assays, Co-immunoprecipitation (Co-IP) and ubiquitination, NF-κB inhibition assay were conducted. Furthermore, in vivo studies were performed to determine the effects of NNU219 on tumors. Results NNU219 showed more selective inhibition to proteasome catalytic subunits and less off-target effect than bortezomib ex vivo. Moreover, intravenous and oral administration of either NNU219 or NNU546 led to more sustained pharmacodynamic inhibitions of proteasome activities compared with bortezomib. Importantly, NNU219 exhibited potential anti-MM activity in both MM cell lines and primary samples in vitro. The anti-MM activity of NNU219 was associated with induction of G2/M-phase arrest, as well as induction of apoptosis via activation of the caspase cascade and endoplasmic reticulum stress response. At well-tolerated doses, significant growth-inhibitory effects of NNU219 and NNU546 were observed in 3 different human MM xenograft mouse models. Furthermore, such observation was even found in the presence of a bone marrow microenvironment. Conclusion Taken together, these findings provided the basis for clinical trial of NNU546 to determine its potential as a candidate for MM treatment.

Splicing factor arginine/serine‐rich 8 promotes multiple myeloma malignancy and bone lesion through alternative splicing of CACYBP and exosome‐based cellular communication

“…The patient‐derived tumor xenograft (PDX_ model was generated by using the biopsy samples collected from an extramedullary tumour subcutaneously under the head skin of a MM patient at the Department of Hematology, the First Affiliated Hospital of Nanjing Medical University. According to the method reported by Zhou et al., 23 the tumour slices were transplanted subcutaneously in 4 to 6‐week old male SCID/NOD mice ( n = 6) under pentobarbital anaesthesia. The tumours were harvested once their sizes reached 500 mm 3 , then the tumour tissues were divided into 2.5 × 2.5 × 2.5 mm 3 pieces and subcutaneously implanted again.…”