microRNA-29 negatively regulates EMT regulator N-myc interactor in breast cancer

Abstract

BackgroundN-Myc Interactor is an inducible protein whose expression is compromised in advanced stage breast cancer. Downregulation of NMI, a gatekeeper of epithelial phenotype, in breast tumors promotes mesenchymal, invasive and metastatic phenotype of the cancer cells. Thus the mechanisms that regulate expression of NMI are of potential interest for understanding the etiology of breast tumor progression and metastasis.MethodWeb based prediction algorithms were used to identify miRNAs that potentially target the NMI transcript. Luciferase reporter assays and western blot analysis were used to confirm the ability of miR-29 to target NMI. Quantitive-RT-PCRs were used to examine levels of miR29 and NMI from cell line and patient specimen derived RNA. The functional impact of miR-29 on EMT phenotype was evaluated using transwell migration as well as monitoring 3D matrigel growth morphology. Anti-miRs were used to examine effects of reducing miR-29 levels from cells. Western blots were used to examine changes in GSK3β phosphorylation status. The impact on molecular attributes of EMT was evaluated using immunocytochemistry, qRT-PCRs as well as Western blot analyses.ResultsInvasive, mesenchymal-like breast cancer cell lines showed increased levels of miR-29. Introduction of miR-29 into breast cancer cells (with robust level of NMI) resulted in decreased NMI expression and increased invasion, whereas treatment of cells with high miR-29 and low NMI levels with miR-29 antagonists increased NMI expression and decreased invasion. Assessment of 2D and 3D growth morphologies revealed an EMT promoting effect of miR-29. Analysis of mRNA of NMI and miR-29 from patient derived breast cancer tumors showed a strong, inverse relationship between the expression of NMI and the miR-29. Our studies also revealed that in the absence of NMI, miR-29 expression is upregulated due to unrestricted Wnt/β-catenin signaling resulting from inactivation of GSK3β.ConclusionAberrant miR-29 expression may account for reduced NMI expression in breast tumors and mesenchymal phenotype of cancer cells that promotes invasive growth. Reduction in NMI levels has a feed-forward impact on miR-29 levels.

Production of Homogeneous Cultured Human Corneal Endothelial Cells Indispensable for Innovative Cell Therapy

“…35 Interestingly, miR29 reportedly has an EMT-promoting effect. 36 Reportedly, TGF-b can initiate and maintain the EMT in various biological and pathologic systems. 26,37 Moreover, the findings in those two studies showed that suppression of TGFb signaling promoted CST under an inflammatory microenvironment, and that MMP2 was activated in the benign tissues with intact TGF-b signaling.…”

Tamoxifen differentially regulates miR-29b-1 and miR-29a expression depending on endocrine-sensitivity in breast cancer cells

“…Forced overexpression of miR-29b and miR-29a promoted an epithelial-to-mesenchymal transition (EMT) in MCF-7 and T47D cells while miR-29a repression reduced invasiveness of MDA-MB-231 triple negative breast cancer (TNBC) cells [25]. However, other studies indicate that miR-29a and miR-29b act as oncosuppressors in breast cancer cells by repressing cell proliferation, differentiation, and metastasis [21, 26, 27].…”

High expression of N-myc (and STAT) interactor predicts poor prognosis and promotes tumor growth in human glioblastoma

“…Previous studies showed that NMI was highly expressed in myeloid leukemias and pancreatic ductal adenocarcinomas [25, 38]. By contrast, it was reported recently that NMI retarded breast cancer growth [39] while loss of NMI promoted epithelial-mesenchymal transition of breast cancer [40, 41]. However, the function and prognostic significance of NMI in glioma have never been studied.…”