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MicroRNA-184 antagonizes microRNA-205 to maintain SHIP2 levels in epithelia.

ABSTRACT: Despite their potential to regulate approximately one-third of the whole genome, relatively few microRNA (miRNA) targets have been experimentally validated, particularly in stratified squamous epithelia. Here we demonstrate not only that the lipid phosphatase SHIP2 is a target of miRNA-205 (miR-205) in epithelial cells, but, more importantly, that the corneal epithelial-specific miR-184 can interfere with the ability of miR-205 to suppress SHIP2 levels. This is the first example of a miRNA negatively regulating another to maintain levels of a target protein. Interfering with miR-205 function by using a synthetic antagomir, or by the ectopic expression of miR-184, leads to a coordinated damping of the Akt signaling pathway via SHIP2 induction. This was associated with a marked increase in keratinocyte apoptosis and cell death. Aggressive squamous cell carcinoma (SCC) cells exhibited elevated levels of miR-205. This was associated with a concomitant reduction in SHIP2 levels. Partial knockdown of endogenous miR-205 in SCCs markedly decreased phosphorylated Akt and phosphorylated BAD levels and increased apoptosis. We were able to increase SHIP2 levels in SCC cells after inhibition of miR-205. Therefore, miR-205 might have diagnostic value in determining the aggressivity of SCCs. Blockage of miR-205 activity with an antagomir or via ectopic expression of miR-184 could be novel therapeutic approaches for treating aggressive SCCs.

SUBMITTER: Yu J

PROVIDER: S-EPMC2587229 | biostudies-literature |

REPOSITORIES: biostudies-literature

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MicroRNA-205 promotes keratinocyte migration via the lipid phosphatase SHIP2.

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microRNA-184 Induces a Commitment Switch to Epidermal Differentiation.

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Keratin 20 helps maintain intermediate filament organization in intestinal epithelia.

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BCL6 Antagonizes NOTCH2 to Maintain Survival of Human Follicular Lymphoma Cells.

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Project description:The repressive Hippo pathway has a profound tumour suppressive role in cancer by restraining the growth-promoting function of the transcriptional coactivator, YAP. We previously showed that the stem cell transcription factor Sox2 maintains cancer stem cells (CSCs) in osteosarcomas. We now report that in these tumours, Sox2 antagonizes the Hippo pathway by direct repression of two Hippo activators, Nf2 (Merlin) and WWC1 (Kibra), leading to exaggerated YAP function. Repression of Nf2, WWC1 and high YAP expression marks the CSC fraction of the tumor population, while the more differentiated fraction has high Nf2, high WWC1 and reduced YAP expression. YAP depletion sharply reduces CSCs and tumorigenicity of osteosarcomas. Thus, Sox2 interferes with the tumour-suppressive Hippo pathway to maintain CSCs in osteosarcomas. This Sox2-Hippo axis is conserved in other Sox2-dependent cancers such as glioblastomas. Disruption of YAP transcriptional activity could be a therapeutic strategy for Sox2-dependent tumours.

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MicroRNA-184 inhibits cell proliferation and invasion, and specifically targets TNFAIP2 in Glioma.

Project description:miRNA-184 is an oncogene in human hepatocellular carcinoma but acts as a tumor suppressor in tongue squamous cell carcinoma. Studies have shown that miR-184 was down-regulated in glioma and TNFα-induced protein 2 (TNFAIP2) was closely related to tumorigenesis. This study aimed to determine the functions of miR-184 in glioma and the mechanisms of miRNA-184-TNFAIP2 mediated glioma progression.Real-time reverse-transcription PCR detected expression of miR-184 and TNFAIP2. U87 and U251 cells were transfected with miR-184 mimic, inhibitor, or negative control miRNA, and their invasion abilities were assayed. Cellular proliferation was measured by the cell counting kit-8 assay. miR-184 effects on glioma cell apoptosis and cell cycle were assessed by flow cytometer. Biological information software have predicted that miR-184 could target TNFα-induced protein 2 (TNFAIP2), Which was further validated by Western blot and qRT-PCR in glioma cells. In vivo, U87 cells transduced with either lentiviral over-expressed miR-184 or control lentivirus were injected into nude mice subcutaneously and intracranial respectively.Expression of miR-184 was significantly lower in glioma tissues and cell-lines compared to normal brain tissues. Protein and mRNA expression of TNFAIP2 were inversely correlated with miR-184 in glioma. In vitro, proliferation and invasion abilities were also decreased in U87 and U251 cells after transfection with miR-184 mimic. In vivo, the xenografted tumor size in the miR-184 overexpressing group were smaller than the miR-NC group. Concordantly, U87 and U251 cells transfected with miR-184 mimic had a higher apoptosis rate, triggering an accumulation of cells at the G0/G1 phase and decreased cells in S-phase.miR-184 could regulate TNFAIP2 expression and affected its translation in glioma. miR-184 could also inhibit glioma progression and might serve as a novel therapeutic target in glioma.

| S-EPMC4387599 | biostudies-other

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| S-EPMC4855227 | biostudies-literature

Crowding induces live cell extrusion to maintain homeostatic cell numbers in epithelia.

Project description:For an epithelium to provide a protective barrier, it must maintain homeostatic cell numbers by matching the number of dividing cells with the number of dying cells. Although compensatory cell division can be triggered by dying cells, it is unknown how cell death might relieve overcrowding due to proliferation. When we trigger apoptosis in epithelia, dying cells are extruded to preserve a functional barrier. Extrusion occurs by cells destined to die signalling to surrounding epithelial cells to contract an actomyosin ring that squeezes the dying cell out. However, it is not clear what drives cell death during normal homeostasis. Here we show in human, canine and zebrafish cells that overcrowding due to proliferation and migration induces extrusion of live cells to control epithelial cell numbers. Extrusion of live cells occurs at sites where the highest crowding occurs in vivo and can be induced by experimentally overcrowding monolayers in vitro. Like apoptotic cell extrusion, live cell extrusion resulting from overcrowding also requires sphingosine 1-phosphate signalling and Rho-kinase-dependent myosin contraction, but is distinguished by signalling through stretch-activated channels. Moreover, disruption of a stretch-activated channel, Piezo1, in zebrafish prevents extrusion and leads to the formation of epithelial cell masses. Our findings reveal that during homeostatic turnover, growth and division of epithelial cells on a confined substratum cause overcrowding that leads to their extrusion and consequent death owing to the loss of survival factors. These results suggest that live cell extrusion could be a tumour-suppressive mechanism that prevents the accumulation of excess epithelial cells.

| S-EPMC4593481 | biostudies-literature

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