microRNA profiling in mantle cell lymphoma cell lines before and after 5-azadC treatment

Mantle cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin’s lymphoma (NHL). In cancers, tumour suppressive microRNAs may be silenced by DNA hypermethylation. By microRNA profiling, miR-155-3p was significantly upregulated upon demethylation treatment of MCL cell lines with 5-aza-2’-deoxycytidine (5-azadC). Methylation-specific PCR, verified by pyrosequencing, showed complete methylation of miR-155-3p in one MCL cell line (REC-1). 5-azadC treatment of REC-1 led to demethylation and re-expression of miR-155-3p. Over-expression of miR-155-3p led to increased sub-G1 apoptotic cells and reduced cellular viability, demonstrating its tumour suppressive properties. By luciferase assay, lymphotoxin-beta (LT-β) was validated as a miR-155-3p target. In 31 primary MCL, miR-155-3p was found hypermethylated in 6(19%) cases. To test if methylation of miR-155-3p was MCL-specific, miR-155-3p methylation was tested in an additional 191 B-cell, T-cell and NK-cell NHLs, yielding miR-155-3p methylation in 66(34.6%) including 36(27%) non-MCL B-cell, 24(53%) T-cell and 6(46%) of NK-cell lymphoma. Moreover, in 72 primary NHL samples with RNA, miR-155-3p methylation correlated with miR-155-3p downregulation (p=0.030), and LT-β upregulation (p=0.004). Collectively, miR-155-3p is tumour suppressive microRNA hypermethylated in MCL and other NHL subtypes. As miR-155-3p targets LT-β, which is an upstream activator of the non-canonical NF-kB signalling, miR-155-3p methylation is potentially important in lymphomagenesis Total RNA isolated from MINO and JEKO-1 before and after 5-azadC treatment were converted into cDNA by MegaplexTM RT Primers and TaqMan® MicroRNA Reverse Transcription Kit. cDNA was pre-amplified using MegaplexTM PreAmp Primer and loaded onto 384-well format Taqman® human microRNA array A V2.0 & B V3.0. Real-time PCR was performed on 7900HT Real-Time PCR system and raw data were analyzed normalizing to mean of three endogenous controls (U6snRNA, RNU44 and RNU48). Relative microRNA levels were determined by ΔΔCt using endogenous controls and untreated controls using SDS 2.4 and RQ manager 1.2. All experimental procedures and analyses were performed according to manufacturer’s instruction, using reagents, system and softwares acquired from Applied Biosystems (Foster City, USA).