The Mechanisms And Effects Of Long Noncoding RNA Maternally Expressed 3 In Multiple Myeloma

ObjectiveMultiple myeloma(MM)is a plasma cell malignant disease which is associated with complex molecular cytogenetic abnormalities and notable difference of clinical prognosis.Although in recent years,some progress has been achieved in MM molecular genetics,MM still cannot be cured so far.Maternally expressed gene3(MEG3)is the first discovered lnc RNA with anti-tumor effect,which is down-regulated or absent in a variety of tumor tissues.Previous studies found that abnormal methylation of MEG3 gene promoter is one of the reasons leading to the lack of MEG3 expression in various tumor tissues.Our research aims to prove the correlation between MEG3 expression in MM and its clinical characters and prognosis,and discuss the role of MEG3 in MM cells and its possible mechanism.MethodsWe detected expression of MEG3 in CD138~+ bone marrow plasma cells of 39 primary MM patients by qRT-PCR.We transfected MM cells ARP-1 by MEG3 over-expression plasmids successfully.Utilizing transfected cells,we detected cell proliferation rates by CCK8 assay,cell cycle and apoptosis by flow cytometry detection and expression of p53 by Western blot.We detected methylation of MEG3 gene promoters in cells of 39 MM patients by methylation specific PCR(MSP)and expression of MEG3,cell proliferation inhibition rate,cell cycle and expression level of p53 with application of demethylation drug 5-Aza-deoxycytidine(5-Aza-CdR)to ARP-1 cells.ResultsMEG3 was low-expressed in bone marrow CD138~+ plasma cells in 39 early-stage MM patients,while MEG3 was not detected in 3 cases(7.7%).Furthermore,MEG3 expression quantity and ISS staging was negative correlation(p= 0.016).Overexpression of MEG3 inhibited proliferation of ARP-1 cells,promoted the cell apoptosis and arrested most cells in G0-G1.Overexpression of MEG3 in ARP-1 cells also increased p53 protein levels.Abnormal methylation of promoters was detected in 8 cases(20.5%)of 39 early-stage MM patients.After application of demethylation drug(5-Aza-CdR)to ARP-1 cells,expression of MEG3 gradually has been increased with higher drug concentrations,meanwhile,cell proliferation inhibition rate and apoptosis rate have been increased with G1 / S phase arrest,but no significant difference was found in the p53 protein levels between the control and demethylated cells.ConclusionsLow expression or loss of expression of MEG3 was showed in primary MM patients because of high level of methylation in its promoter regions.Demethylation drugs could improve expression of MEG3 and inhibit growth of myeloma cells,which might be a potential therapeutic target for MM.