LncRNA ANRIL promotes multiple myeloma progression and bortezomib resistance by EZH2-mediated epigenetically silencing of PTEN.

Abstract

Multiple myeloma (MM) is a plasma cell malignancy of bone marrow. In the present study, we aimed to study the function and potential mechanism of the antisense non-coding RNA in the INK4 Locus (ANRIL) in MM. The expression levels of ANRIL in MM patients and healthy donors were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). The effects and mechanisms of ANRIL in MM were evaluated by cell viability assay, BrdU incorporation assay, tumor xenograft model, flow cytometry, western blot, RNA immunoprecipitation (RIP), transcriptome RNA sequencing, and chromatin immunoprecipitation (ChIP). We found that ANRIL was upregulated in MM patients and cell lines, and associated with advanced international staging system (ISS) stage and poor overall survival. Enforced ANRIL expression promoted proliferation and tumor xenograft growth of MM cells, while knockdown of ANRIL exhibited opposite effects. Moreover, ANRIL overexpression increased the half-maximal inhibitory concentration (IC50) of bortezomib and reduced bortezomib-induced apoptosis in MM cells. ANRIL was found to accumulate in the nuclei of MM cells, and interact with EZH2 by RIP assay. Transcriptome RNA sequencing identified PTEN as a target of ANRIL in MM cells. In the ChIP assay, knockdown of ANRIL reduced EZH2 occupancy and H3K27me3 binding to the promoter region of PTEN. Furthermore, EZH2 knockout or PTEN restoration abrogated the effects caused by ANRIL overexpression in MM cells. Our results indicated that ANRIL exerted oncogenic functions and conferred chemoresistance of MM cells by EZH2-mediated epigenetically silencing of PTEN.