Expression Of miR-21 In Cells Research Articles

Schwann cells-derived exosomal miR-21 participates in high glucose regulation of neurite outgrowth

SummaryAs a common complication of diabetes, the pathogenesis of diabetic peripheral neuropathy (DPN) is closely related to high glucose but has not been clarified. Exosomes can mediate crosstalk between Schwann cells (SC) and neurons in the peripheral nerve. Herein, we found that miR-21 in serum exosomes from DPN rats was decreased. SC proliferation was inhibited, cell apoptosis was increased, and the expression of miR-21 in cells and exosomes was downregulated when cultured in high glucose. Increasing miR-21 expression reversed these changes, while knockdown of miR-21 led to the opposite results. When co-cultured with exosomes derived from SC exposed to high glucose, neurite outgrowth was inhibited. On the contrary, neurite outgrowth was accelerated when incubated with exosomes rich in miR-21. We further demonstrated that the SC-derived exosomal miR-21 participates in neurite outgrowth probably through the AKT signaling pathway. Thus, SC-derived exosomal miR-21 contributes to high glucose regulation of neurite outgrowth.

Suppressing miR-21 activity in tumor-associated macrophages promotes an antitumor immune response.

microRNA-21 (miR-21) is the most commonly upregulated miRNA in solid tumors. This cancer-associated microRNA (oncomiR) regulates various downstream effectors associated with tumor pathogenesis during all stages of carcinogenesis. In this study, we analyzed the function of miR-21 in noncancer cells of the tumor microenvironment to further evaluate its contribution to tumor progression. We report that the expression of miR-21 in cells of the tumor immune infiltrate, and in particular in macrophages, was responsible for promoting tumor growth. Absence of miR-21 expression in tumor- associated macrophages (TAMs), caused a global rewiring of their transcriptional regulatory network that was skewed toward a proinflammatory angiostatic phenotype. This promoted an antitumoral immune response characterized by a macrophage-mediated improvement of cytotoxic T-cell responses through the induction of cytokines and chemokines, including IL-12 and C-X-C motif chemokine 10. These effects translated to a reduction in tumor neovascularization and an induction of tumor cell death that led to decreased tumor growth. Additionally, using the carrier peptide pH (low) insertion peptide, we were able to target miR-21 in TAMs, which decreased tumor growth even under conditions where miR-21 expression was deficient in cancer cells. Consequently, miR-21 inhibition in TAMs induced an angiostatic and immunostimulatory activation with potential therapeutic implications.

Targeting miR-21 with Sophocarpine Inhibits Tumor Progression and Reverses Epithelial-Mesenchymal Transition in Head and Neck Cancer

A major challenge for cancer chemotherapy is the development of safe and clinically effective chemotherapeutic agents. With its low toxicity profile, sophocarpine (SC), a naturally occurring tetracyclic quinolizidine alkaloid derived from Sophora alopecuroides L, has shown promising therapeutic properties, including anti-inflammatory, anti-nociceptive, and antivirus activities. However, the antitumor efficacy of SC and its underlying mechanisms have not been completely delineated. In the present study, the inhibitory effect of SC onhead and neck squamous cell carcinoma (HNSCC) progression and possible mechanisms for this effect involving microRNA-21 (miR-21) regulation were investigated. By cell viability, Transwell, and wound healing assays, we show that SC effectively inhibited proliferation, invasion, and migration of HNSCC cells. Moreover, SC exerted its growth-inhibitory effect via the downregulation of miR-21 expression by blocking Dicer-mediated miR-21 maturation. Furthermore, SC treatment led to the increased expression of PTEN and p38MAPK phosphorylation as well as the reversal of epithelial-mesenchymal transition (EMT), which was rescued by ectopic expression of miR-21 in cells. Notably, SC dramatically repressed tumor growth without observable tissue cytotoxicity in a mouse xenograft model of HNSCC. Our findings offer a preclinical proof of concept for SC as a leading natural agent for HNSCC cancer therapy.

MiR-155 Drives Telomere Fragility in Human Breast Cancer by Targeting TRF1

Telomeres consist of DNA tandem repeats that recruit the multiprotein complex shelterin to build a chromatin structure that protects chromosome ends. Although cancer formation is linked to alterations in telomere homeostasis, there is little understanding of how shelterin function is limited in cancer cells. Using a small-scale screening approach, we identified miR-155 as a key regulator in breast cancer cell expression of the shelterin component TERF1 (TRF1). miR-155 targeted a conserved sequence motif in the 3'UTR of TRF1, resulting in its translational repression. miR-155 was upregulated commonly in breast cancer specimens, as associated with reduced TRF1 protein expression, metastasis-free survival, and relapse-free survival in estrogen receptor-positive cases. Modulating miR-155 expression in cells altered TRF1 levels and TRF1 abundance at telomeres. Compromising TRF1 expression by elevating miR-155 increased telomere fragility and altered the structure of metaphase chromosomes. In contrast, reducing miR-155 levels improved telomere function and genomic stability. These results implied that miR-155 upregulation antagonizes telomere integrity in breast cancer cells, increasing genomic instability linked to poor clinical outcome in estrogen receptor-positive disease. Our work argued that miRNA-dependent regulation of shelterin function has a clinically significant impact on telomere function, suggesting the existence of "telo-miRNAs" that have an impact on cancer and aging.

Borna disease virus encoded phosphoprotein inhibits host innate immunity by regulating miR-155

It has been reported that the Borna disease virus (BDV) encoded phosphoprotein (P protein) can inhibit the activity of Traf family member-associated NF-kappaB activator (TANK)-binding kinase 1 (TBK-1), thus preventing the induction of type I interferon (IFN). However, the effects of microRNA on the regulation of BDV infection and the host’s immune response have not been characterized. miR-155 was predicted to be complementary to the BDV P mRNA by RNAhybrid software. Here, we showed that miR-155 was down-regulated in BDV persistently infected human oligodendroglial (OL/BDV) cells and that the BDV P protein, but not the X protein, directly inhibited miR-155 expression in cells. When miR-155 was over-expressed, the inhibition of type I IFNs by BDV in cells was reversed, and the expression of type I IFNs was increased. When miR-155 expression was specifically blocked, cellular IFN expression and the induction of IFN by poly I:C treatment were suppressed. Furthermore, miR-155 promoted type I IFN production by targeting suppressor of cytokine signaling 1 (SOCS1) and SOCS3. Mutations in the nt1138–nt1158 region of SOCS3 abandoned the impact of miR-155 on the expression of SOCS3-enhanced green fluorescent protein (EGFP). The levels of BDV P mRNA and protein were significantly decreased in OL/BDV cells when miR-155 was over-expressed; however, miR-155-mutation did not affect the expression of BDV P-EGFP. Thus, BDV persistent infection inhibited the expression of type I IFNs through the suppression of miR-155, and miR-155 played an important immune regulatory role in BDV persistent infection.

Abstract 5196: CDF inhibits cell migration by inactivating cancer stem cell markers, and expression of VEGF, IL-6 and miR-21 in human pancreatic and prostate cancer cells under hypoxic condition

Abstract Hypoxia has been well recognized to cause therapeutic resistance associated with solid tumors and considered to play critical roles in other of biological events including cell growth and proliferation, cell survival, angiogenesis, immunosurveillance, tumor invasion and metastasis. Hypoxia-inducible factor (HIF) 1α, a master transcription factor that regulates hypoxia responsive genes, plays critical roles in the adaptation of tumor cells to a hypoxic microenvironment. Tumor hypoxia and over-expression of HIF-1α have been reportedly associated with resistance to radiation therapy and chemotherapy, increased risk of invasion and metastasis and poor clinical prognosis, all of which leads to higher mortality of patients diagnosed with solid tumors. Emerging evidence suggest that hypoxia and HIF signaling pathways leads to the acquisition of epithelial-to-mesenchymal transition (EMT), maintenance of cancer stem cell (CSC) functions, and causing inflammatory tumor microenvironment, which contributes to therapeutic resistance; however, the exact mechanisms by which hypoxia/HIF regulates these events are not fully understood. Here, we demonstrates that hypoxia increases the productions of VEGF and IL-6, and increased expression of CSC marker genes such as Nanog, Oct4, EZH2 as well as miR-21, an oncogenic miRNA, in human pancreatic cancer (AsPC-1 and MiaPaCa-2) and prostate cancer (PC-3 and LNCaP) cells. The treatment of these cells with CDF, a novel curcumin analog that was previously shown to be biologically superior than curcumin as an anti-tumor agent both in vitro and in vivo, inhibited the productions of VEGF, IL-6, Nanog, Oct4 and EZH2 mRNAs, as well as down regulated the expression of miR-21 in these cells under hypoxic condition. CDF also decreased cell migration in pancreatic and prostate cancer cells under hypoxic condition as documented by wound healing assay. Taken together, these data suggest for the first time that the anti-tumor effect of CDF could in part be due to inhibition of tumor hypoxic pathways including the inhibition of CSC markers and thereby reconditioning the tumor microenvironment, which would be useful for overcoming therapeutic resistance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5196. doi:1538-7445.AM2012-5196