H3K27me3 Aggregate Promoter Of MEG3 LncRNA And Induce Apoptosis Escape Of RPMI8226 Cell Through MDM2/p53 Pathway

Objective Multiple myeloma(MM)is a cancer of plasma cells,that develops in B lymphocytes with characteristics,such as,proliferation of monoclonalplasma cells.The underlying mechanism involves abnormal plasma cells producing ineffective immunoglobulin(Ig)which can suppress the secretion of normal Ig,andcause damage to kidney,bone and other relevant organs or soft tissues additionally.The prevalence of MM represent 1% of all types of cancers and 10% hematologic cancers.It usually occurs to elderly people,and 2/3 of newly diagnosed patients areolder than 65 years old.With an aging population in China,the number of elderly with age older than 65 years rises and consequently the incident rate of MM has been increasing.The common symptoms of MM includes pathological fracture,bone pain,renal failure.anemia and immune deficiency.Studies show that the occurrence of MM is closely related with abnormal epigenesis,which induces abnormal gene or protein expression.A number of patients are accompanied withsilencing oftumorsuppressor genes,which regulate gene expression in theepigenetic manner includinghistone modification,DNAmethylation,and long non-coding RNA(Inc RNA).Abnormal DNA methylation is supposed to play an important role in occurrenceof several types of tumor.The present study investigated the interaction of lnc RNA and aberrant histone modification in MM cells escaping from apoptosis,aiming to reveal the interaction between Inc RNA and other epigenesis and provide further evidence for gene diagnosis and therapy of MM.Methods Cell proliferation activity was tested by MTT.Annexin V-FITC/PI dual staining was used to test apoptotic cells.RT-PCR was used to test the m RNA expression of EZH2,MEG3 lnc RNA,MDM2 and p53.The bonding site of promoter of MEG3 by H3K27me3 was confirmed by Ch IP-Real-time PCR.sh RNA interference was used to downregulate H3K27me3 through inhibiting the expression of EZH2.Results The expression of H3K27me3 could be significantly inhibited by EZH2 interference,which meant downregulation of H3K27me3 and induced apoptosis of RPMI8226 cells.H3K27me3 protein can bind to MEG3 lnc RNA promoter directly.H3K27me3 inhibition can increase the expression of MEG3 lnc RNA.Furthermore,MEG3 lnc RNA could be downregulated by MEG3 lnc RNA-si RNA in RPMI8226 cells.Meanwhile,both protein and m RNA of MDM2 increased in cells.Ubiquitination of p53 was founded upregulation and p53 degradation when RPMI8226 cells incubated with MDM2 inhibitor.Conclusion H3K27me3 highly expresses in RPMI8226 MM cells,which cause loss of MEG3 lnc RNA.The lost expression of MEG3 lnc RNAcouldparalyze the inhibition of MDM2,and promote the degradation or inaction of p53 protein.This could be one of the mechanisms of MM cells escape from apoptosis.