Epigenetic repression of miR‐375 is the dominant mechanism for constitutive activation of the PDPK1/RPS6KA3 signalling axis in multiple myeloma

Abstract

Cytogenetic/molecular heterogeneity is the hallmark of multiple myeloma (MM). However, we recently showed that the serine/threonine kinase PDPK1 and its substrate RPS6KA3 (also termed RSK2) are universally active in MM, and play pivotal roles in myeloma pathophysiology. In this study, we assessed involvement of aberrant miR-375 repression in PDPK1 overexpression in MM. An analysis of plasma cells from 30 pre-malignant monoclonal gammopathies of undetermined significance and 73 MM patients showed a significant decrease in miR-375 expression in patient-derived plasma cells regardless of the clinical stage, compared to normal plasma cells. Introduction of miR-375 reduced PDPK1 expression in human myeloma cell lines (HMCLs), indicating that miR-375 is the dominant regulator of PDPK1 expression. In addition, miR-375 introduction also downregulated IGF1R and JAK2 in HMCLs. CpG islands in the MIR375 promoter were pathologically hypermethylated in all 8 HMCLs examined and in most of 58 patient-derived myeloma cells. Treatment with SGI-110, a hypomethylating agent, and/or trichostatin A, a histone deacetylase inhibitor, increased miR-375 expression, but repressed PDPK1, IGF1R and JAK2 in HMCLs. Collectively, these results show the universal involvement of overlapping epigenetic dysregulation for abnormal miR-375 repression in MM, which is likely to contribute to myelomagenesis and to subsequent myeloma progression by activating oncogenic signalling pathways.

hsa_circ_0000729, a potential prognostic biomarker in lung adenocarcinoma

“…Researchers have found that microRNA 375 can regulate proliferation and migration in colon cancer by suppressing the CTGF‐EGFR signaling pathway . Meanwhile, a recent study reported that epigenetic repression of miR‐375 may be the dominant mechanism for sustaining activation of the PDPK1/RPS6KA3 signaling axis in multiple myeloma . Accordingly, we present the theory that the mRNA‐microRNA‐circRNA axis may be the potential molecular regulatory mechanism of LUAD.…”

MicroRNA181c inhibits prostate cancer cell growth and invasion by targeting multiple ERK signaling pathway components

“…The microRNAs miR198, miR329‐3p, and miR634 also target ERK2, suppressing tumor cell proliferation, migration, and invasion, or restoring drug sensitivity in prostate, uterine cervical, and ovarian cancers. RSK2 is a target of miR375 and miR634 . SRF has been shown to be regulated by various miRNAs, such as miR22, miR101‐3p, miR483‐30, and miR181a/b .…”

Aberrant BUB1 Overexpression Promotes Mitotic Segregation Errors and Chromosomal Instability in Multiple Myeloma

“…Bone marrow mononuclear cells were labeled with anti-CD138 MicroBeads, and CD138-positive plasma cells were isolated using a MACS separator (Miltenyi Biotec, San Diego, CA, USA). The purity of primary plasma cells after separation was 94.8 ± 2.4% (mean ± SD), as assessed by morphology [27]. The plasma cells of three healthy donors were used as control samples.…”

“…Total RNA extraction and quantitative RT-PCR (qRT-PCR) were performed, as described elsewhere [27,32,52,53]. Primer sequences for qRT-PCR were as follows: BUB1 FW: 5 -ACC ATT CCA CAA GCT TCC AGT G-3 , BUB1 RV: 5 -TGA AGG CAC CAC CAT GTT TTC C-3 , β-Actin (ACTB) FW: 5 -TTC TAC AAT GAG CTG CGT GTG G-3 , and ACTB RV: 5 -TGG GGT GTT GAA GGT CTC AAA C-3 .…”

“…Western blotting was performed, as described previously [27,32,52,53], using rabbit anti-BUB1 (Abcam Cat#ab9000, Cambridge, UK) and mouse anti-ACTB (Sigma-Aldrich Cat# A2228, St. Louis, MO, USA) primary antibodies.…”