Niederer F, Trenkmann M, Ospelt C, et al. Down-regulation of microRNA-34a* in rheumatoid arthritis synovial fibroblasts promotes apoptosis resistance

University Hospital Zurich, Zurich, Switzerland.
Arthritis & Rheumatology (Impact Factor: 7.76). 06/2012; 64(6):1771-9. DOI: 10.1002/art.34334
Source: PubMed


To investigate the expression and effect of the microRNA-34 (miR-34) family on apoptosis in rheumatoid arthritis synovial fibroblasts (RASFs).
Expression of the miR-34 family in synovial fibroblasts with or without stimulation with Toll-like receptor (TLR) ligands, tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), hypoxia, or 5-azacytidine was analyzed by real-time polymerase chain reaction (PCR). Promoter methylation was studied by combined bisulfite restriction analysis. The effects of overexpression and silencing of miR-34a and miR-34a* on apoptosis were analyzed by annexin V/propidium iodide staining. Production of X-linked inhibitor of apoptosis protein (XIAP) was assessed by real-time PCR and immunohistochemistry analysis. Reporter gene assay was used to study the signaling pathways of miR-34a*.
Basal expression levels of miR-34a* were found to be reduced in synovial fibroblasts from RA patients compared to osteoarthritis patients, whereas levels of miR-34a, miR-34b/b*, and miR-34c/c* did not differ. Neither TNFα, IL-1β, TLR ligands, nor hypoxia altered miR-34a* expression. However, we demonstrated that the promoter of miR-34a/34a* was methylated and showed that transcription of the miR-34a duplex was induced upon treatment with demethylating agents. Enforced expression of miR-34a* led to an increased rate of FasL- and TRAIL-mediated apoptosis in RASFs. Moreover, levels of miR-34a* were highly correlated with expression of XIAP, which was found to be up-regulated in RA synovial cells. Finally, we identified XIAP as a direct target of miR-34a*.
Our data provide evidence of a methylation-specific down-regulation of proapoptotic miR-34a* in RASFs. Decreased expression of miR- 34a* results in up-regulation of its direct target XIAP, thereby contributing to resistance of RASFs to apoptosis.

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    • "). Finally, these broader and evolutionary analyses are accompanied by reporter assays focusing on validating the miRNA * functionality (Okamura et al., 2008; Ogata et al., 2010; Kuchenbauer et al., 2011; Yang et al., 2011; Byrd et al., 2012; Niederer et al., 2012; Chang et al., 2013; Goedeke et al., 2013; Martin et al., 2014). Altogether, these evidences suggest that all miRNA loci are potential dual-function genes, as two distinct miRNAs may originate from the same hairpin and, therefore, target different sets of genes (Okamura et al., 2008; Ogata et al., 2010; Ohanian et al., 2013). "
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    • "The demethylation of the miR-34a * promoter evidently enhanced the expression levels of miR-34a * . miR-34a * promotes apoptosis in both FasL-and TRAIL-stimulated RA synovial fibroblasts (RASFs), whereas the overexpression of the mature strand miR-34a shelters cells from FasL-mediated apoptosis but has no effect on TRAIL-induced cell death [18]. miR-124 is another RArelated miRNA that is involved in cell proliferation. "
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    • "Overexpression of miR-24 significantly abrogated apoptosis resistance through decreasing XIAP expression in cancer cells. A recent report has also found that miR-34a*, the passenger strand, attenuated XIAP expression via targeting the XIAP 3′-UTR in rheumatoid arthritis synovial fibroblast cells, whereas miR-34a, the corresponding mature strand, appeared to be nonfunctional.35 Our study demonstrated that XIAP is a candidate target of miR-519d in ovarian cancer. "
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    ABSTRACT: MicroRNAs (miRNAs) are small, noncoding RNAs that are believed to play fundamental roles in tumorigenesis and tumor development at the posttranscriptional level, as negative regulators of gene expression. This study was designed to evaluate the expression and anticancer effect of miR-519d in ovarian cancer. The expression levels of miR-519d in ovarian cancer cells and tissues were detected by TaqMan quantitative reverse transcriptase-polymerase chain reaction (TaqMan qRT-PCR; Life Technologies, Carlsbad, CA, USA). The effects of miR-519d on ovarian cancer cell proliferation and cisplatin chemosensitivity were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, flow cytometry, and Western blotting assay. A luciferase reporter assay was performed to validate the miR-519d binding sites on the 3' untranslated region of X-linked inhibitor of apoptosis protein (XIAP). The expression levels of XIAP mRNA and protein were examined by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting assay, respectively. miR-519d was significantly downregulated in human ovarian cancer cell lines and tissues. Overexpression of miR-519d in ovarian cancer cells decreased cell proliferation and sensitized ovarian cancer cells to cisplatin-induced cell death accompanied by increased activation of caspase 3 and cleavage of poly(adenosine diphosphate [ADP]-ribose) polymerase 1. Bioinformatics analysis indicated that XIAP was a putative target of miR-519d. Overexpression of miR-519d decreased XIAP expression at both the protein and mRNA levels. In contrast, inhibition of miR-519d increased XIAP expression. Luciferase reporter assay confirmed XIAP as a direct target of miR-519d. XIAP mRNA and protein expression levels were inversely correlated with miR-519d expression in ovarian cancer cell lines and tissues. These findings indicate that miR-519d suppresses cell proliferation and sensitizes ovarian cancer cells to cisplatin-induced cell death by targeting the XIAP transcript, suggesting that miR-519d plays a tumor-suppressive role in human ovarian cancer and highlighting the therapeutic potential of miR-519d in ovarian cancer treatment.
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