The Research On The Mechanisms Of Long Noncoding RNA DARS-AS1 And Montelukast In Multiple Myeloma

Multiple myeloma(MM)is located in the hypoxic bone marrow microenvironment and characterized by the malignant proliferation of plasma cells.It has a highly heterogeneous genetic background and clinical manifestations,and the prognosis is poor.Long non-coding RNAs(lncRNAs)are a class of RNA molecules that are longer than 200 nt and do not encode proteins.LncRNA can be involved in many physiological processes such as chromatin modification,transcriptional activation,and intranuclear transport.Previous studies have reported that hypoxia-associated lncRNA can be involved in hypoxia/HIF-1 related cancer progression.Hypoxic microenvironment is essential for the occurrence,development,drug resistance and recurrence of MM,so we used RNA high-throughput sequencing to analyze the differentially expressed lncRNA molecules in myeloma cell line U266under hypoxic and normoxic culture conditions.We found that HIF-1αpromotes transcription of lncRNA DARS-AS1 in myeloma cell lines.We have demonstrated that overexpression of DARS-AS1 promotes myeloma cell proliferation and inhibits apoptosis both in vivo and in vitro.Knockdown of DARS-AS1 inhibited myeloma cell proliferation and promoted apoptosis.By RNA-Pulldown combined with protein mass spectrometry,we detected that RBM39 is a target protein of DARS-AS1.Overexpression of RBM39 partially rescued the cellular phenotype after knockdown of DARS-AS1.We conclude that DARS-AS1 may exert its biological functions by affecting the expression level of RBM39.Further studies have shown that DARS-AS1 could attenuate the interaction between RBM39 and E3 ubiquitin ligase RNF147,thereby reducing the ubiquitination degradation of RBM39.Down-regulation of DARS-AS1 or RBM39 levels in myeloma cell lines inhibits mTOR signaling pathways.Activation of the mTOR pathway promotes translation of HIF-1α,so there may be exist a positive feedback between DARS-AS1 and HIF-1α,which promotes disease progression of MM.In conclusion,we found that DARS-AS1promotes myeloma cell proliferation and inhibits apoptosis.This study is helpful to understand the pathogenesis of myeloma,DARS-AS1/RBM39 may be a new target for myeloma treatment.Montelukast is an anti-asthmatic medication,and has recently showed its inhibitory effects on the proliferation of cancers.The purpose of this study was to identify the cytotoxic effects of montelukast on multiple myeloma(MM)cells and the combination effects of montelukast and carfilzomib in the treatment of MM.Results revealed that montelukast induced a dose-and time-dependent cytotoxicity in MM cells lines and significantly suppressed the colony formation of myeloma cells.Furthermore,montelukast enhanced the cytotoxicity of carfilzomib in MM cell lines.This anti-tumor effect was associated with decreased c-Myc via the inhibition of mTOR signaling pathway.Moreover,the combination of montelukast and carfilzomib induced apoptosis of myeloma cells effectively,even in the presence of bone marrow stromal cells(BMSCs).It is more important to note that the co-treatment exhibited similar cytocidal effects in carfilzomib-resistant cell lines(U266R and 8226R).In addition,the combined effects were noted in two MM xenograft mice models and 7 cases of human CD138~+myeloma cells(4 newly diagnosed cases and 3 relapsed cases)with no cytotoxicity on peripheral blood mononuclear cells(PBMCs)from 5 healthy donors.Our data suggested that montelukast enhanced the cytotoxicity of carfilzomib in both carfilzomib-sensitive and carfilzomib-resistant MM cell lines.These findings may facilitate the development of therapeutic strategies and provide a promising therapeutic combination regimen for the treatment of refractory myeloma.