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Microglial SMAD4 regulated by microRNA-146a promotes migration of microglia which support tumor progression in a glioma environment.

ABSTRACT: Glioma tumors constitute a significant portion of microglial cells, which are known to support tumor progression. The present study demonstrates that transforming growth factor-? (TGF?) signaling pathway in microglia in a glioma environment is involved in tumor progression and pathogenesis. It has been shown that the TGF? level is elevated in higher grades of gliomas and its signaling pathway regulates tumor progression through phosphorylation of SMAD2 and SMAD3, which form a complex with SMAD4 to regulate target gene transcription. In an in vitro cell line-based model increased protein levels of pSMAD2/3, total SMAD2/3 and SMAD4 were observed in murine BV2 microglia cultured in glioma conditioned medium (GCM), indicative of the activated TGF? signaling pathway in microglia associated with glioma environment. Immunofluorescence labeling further revealed the expression of SMAD4 in microglial and non-microglial cells of human glioblastomas tissue in vivo. Functional analysis through shRNA-mediated stable knockdown of SMAD4 in microglia revealed the downregulation of the expression of matrix metalloproteinase 9 (MMP9), which has been shown to be involved in tumor progression and cell migration. Further, knockdown of SMAD4 in microglia decreased the migration of microglial cells towards GCM, indicating that SMAD4 promotes microglial migration in glioma environment. In addition, SMAD4 has been shown to be post-transcriptionally regulated by microRNA-146a, which was downregulated in microglia treated with GCM. Overexpression of miR-146a resulted in decreased expression of SMAD4 together with tumor supportive gene MMP9 in microglia, and subsequently suppressed microglial migration towards GCM, possibly through regulation of SMAD4. On the other hand, the cell viability assay revealed decreased viability of glioma cells when they were treated with conditioned medium derived from SMAD4 knockdown microglia or miR-146a overexpressed microglia as compared to glioma cells treated with the medium from control microglial cells. Taken together, the present study suggests that microglial SMAD4 which is epigenetically regulated by miR-146a promotes microglial migration in gliomas and glioma cell viability.

SUBMITTER: Karthikeyan A

PROVIDER: S-EPMC5982777 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Microglial SMAD4 regulated by microRNA-146a promotes migration of microglia which support tumor progression in a glioma environment.

Karthikeyan Aparna A Gupta Neelima N Tang Carol C Mallilankaraman Karthik K Silambarasan Maskomani M Shi Meng M Lu Lei L Ang Beng Ti BT Ling Eng-Ang EA Dheen S Thameem ST

Oncotarget 20180518 38

Glioma tumors constitute a significant portion of microglial cells, which are known to support tumor progression. The present study demonstrates that transforming growth factor-β (TGFβ) signaling pathway in microglia in a glioma environment is involved in tumor progression and pathogenesis. It has been shown that the TGFβ level is elevated in higher grades of gliomas and its signaling pathway regulates tumor progression through phosphorylation of SMAD2 and SMAD3, which form a complex with SMAD4 ...[more]

PMID: 29861845

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Project description:BACKGROUND:microRNAs (miRNAs) are a small, endogenous non-coding RNAs that are involved in post-transcriptional gene regulation of many biological processes, including embryo implantation and placental development. In our previous study, miR-146a-5p was found expressed higher in the serum exosomes of pregnant sows than non-pregnant. The research on miR-146a-5p has been mainly related to human diseases, but there are few studies on its effects on the reproduction of sows in early pregnancy. OBJECTIVE:In this article, our motivation is to study the role of miR-146a-5p in the early pregnancy of sows on the cell proliferetion and apoptosis by targeting SMAD3 and SMAD4. METHODS:Bioinformatics software was used to identify the target genes of miR-146a-5p. The wildtype and mutant-type recombinant plasmids of dual-luciferase reporter with 3'-UTR of Smad3 or 3'- UTR of Smad4 were constructed, and co-transfected in porcine kidney cell (PK-15 cell) with miR- 146a-5p mimic, mimic-NC(M-NC), inhibitor and inhibitor-NC(IN-NC), then dual-luciferase activity analysis, qRT-PCR and Western blot were performed to verify the target genes. After the transfection of BeWo choriocarcinoma cell (BeWo cell) with miR-146a-5p mimic, M-NC, inhibitor and IN-NC, the mRNA expression of Caspase-3, BAX and Bcl-2 was measured using qRT-PCR, and the cell proliferation was measured using CCK-8 kit. RESULTS:The luciferase, mRNA and protein expression of Smad3 in PK-15 cells treated by Smad3- 3'-UTR-W co-transfected with miR-146a-5p mimic were significantly lower than that with miR- 146a-5p M-NC, and the results of Smad4 were similar to Smad3, but the protein expression had a trend to lower in mimic group. The expression level of Bcl-2 in the miR-146a-5p mimic group was significantly lower than that in the miR-146a-5p M-NC group, but the expression pattern of Caspase-3 was just opposite. The mimic of miR-146a-5p reduced the proliferation of BeWo cells, however the inhibitor increased. CONCLUSION:Smad3 and Smad4 are the direct target genes of miR-146a-5p. The expression of Smad3 and Smad4 were affected by the mimic and inhibitor of miR-146a-5p. miR-146a-5p affects cell apoptosis and proliferation by regulating their target genes. This study provided new data to understand the regulation mechanism of early pregnancy in sows.

Dataset Information

Microglial SMAD4 regulated by microRNA-146a promotes migration of microglia which support tumor progression in a glioma environment.

Publications

Microglial SMAD4 regulated by microRNA-146a promotes migration of microglia which support tumor progression in a glioma environment.

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