miR-125b inhibits osteoblastic differentiation by down-regulation of cell proliferation

Although various microRNAs regulate cell differentiation and proliferation, no miRNA has been reported so far to play an important role in the regulation of osteoblast differentiation. Here we describe the role of miR-125b in osteoblastic differentiation in mouse mesenchymal stem cells, ST2, by regulating cell proliferation. The expression of miR-125b was time-dependently increased in ST2 cells, and the increase in miR-125b expression was attenuated in osteoblastic-differentiated ST2 cells induced by BMP-4. The transfection of exogenous miR-125b inhibited proliferation of ST2 cells and caused inhibition of osteoblastic differentiation. In contrast, when the endogenous miR-125b was blocked by transfection of its antisense RNA molecule, alkaline phosphatase activity after BMP-4 treatment was elevated. These results strongly suggest that miR-125b is involved in osteoblastic differentiation through the regulation of cell proliferation.     

过表达微小RNA miR-125b抑制肝癌细胞上皮-间质转换及促进细胞凋亡

微小RNA-125b（miR-125b）在许多恶性肿瘤的增殖、分化和凋亡等过程中具有很重要的作用,但miR-125b是否涉及肝癌的上皮 间质转换过程（EMT）还有待进一步研究。本研究通过构建过表达miR-125b的肝癌稳转细胞株,初步检测miR-125b对于肝癌的EMT过程和相关的TGF-β信号通路的影响,以及对于肝癌细胞凋亡的影响。以慢病毒载体pHRS-1cla EGFP 构建过表达miR-125b的载体质粒(pHRS-1cla-miR125b-CMV-EGFP),并对上述载体进行NheⅠ、XbaⅠ双酶切和测序鉴定,鉴定正确后,在293T细胞中进行慢病毒包装,浓缩病毒后,对MHCC97-H进行慢病毒感染并采用流式分选GFP阳性的细胞。实时定量PCR检测表明肝癌细胞稳转株MHCC97-H-PHRS-miR-125b-EGFP的miR-125b表达量是空载体转染组的6倍。Western印迹检测发现,与空载体对照组相比,MHCC97-H-PHRS-miR-125b-EGFP细胞中间质细胞标志α-SMA表达显著下调,上皮细胞标志E-cadherin表达显著上调,同样的,用Western印迹检测也发现MHCC97-H-PHRS-miR-125b-EGFP细胞中TGF-β信号通路关键下游分子Smad2和Smad4的表达显著下调,细胞凋亡检测结果表明,与对照组相比,过表达miR-125b的稳转株凋亡率增加到19.66%,加入TGF-β1后,过表达miR-125b的稳转株凋亡率进一步增加到74.7%。同样的,在体内治疗实验中,我们采用商品化的体内核酸转染试剂,在皮下肿瘤组织中过表达miR-125b mimics,结果表明miR-125b的过表达与肿瘤组织的凋亡成正相关性（r=0.83463,P < 0.01）,且免疫组化结果也表明,miR-125b过表达后,E-cadherin表达显著上调,α-SMA及Smad2和Smad4的表达显著下调。上述结果表明,我们成功构建了过表达miR-125b的肝癌细胞稳转株,并成功建立了肿瘤组织中过表达miR-125b mimics的动物模型,在体内外均观察到过表达miR-125b后对肝癌细胞EMT过程的抑制作用和对细胞凋亡的促进作用。相关研究结果加深了我们对miR-125b在肝癌中抑制肝癌发展作用机制的理解,及其作为潜在的治疗肝癌的新靶点的重要性。     

miR-125b靶向MCL1抑制胃癌 MGC-803细胞增殖

探讨mi R-125b对胃癌MGC-803细胞增殖的影响及机制,为阐明胃癌发病的分子机制提供实验依据.采用q RT-PCR和原位杂交,检测mi R-125b在正常胃黏膜(NGM)和胃癌(GAC)组织中的表达.将mi R-125b导入胃癌MGC-803细胞,观察mi R-125b高表达对MGC-803细胞增殖的影响.利用Targetscan 6.2软件及荧光素酶报告基因检测,分析mi R-125b对MCL1基因的靶向性作用.构建MCL1干扰载体,观察干扰MCL1基因表达对MGC-803细胞增殖的影响.结果发现,mi R-125b在胃癌组织中低表达,其表达与胃癌的分化程度及患者预后呈正相关,与TNM分期、淋巴结转移呈负相关(P0.01).mi R-125b高表达后MGC-803细胞的增殖降低、凋亡率增加、裂解caspase-3与裂解PARP表达增加(P0.01);mi R-125b与MCL1基因的3′UTR(2 613~2 620)结合,抑制MCL1的m RNA及蛋白质表达(P0.01);沉默MCL1基因表达后MGC-803细胞的增殖降低、凋亡率增加、裂解caspase-3与裂解PARP表达增加(P0.01).从而得出结论,mi R-125b在胃癌组织中低表达,其表达与胃癌组织分化程度、TNM分期、淋巴结转移及患者预后密切相关;mi R-125b靶向抑制MCL1基因表达,活化caspase-3信号通路,抑制MGC-803细胞增殖.     

Argonaute 2 sustains the gene expression program driving human monocytic differentiation of acute myeloid leukemia cells

MicroRNAs are key regulators of many biological processes, including cell differentiation. These small RNAs exert their function assembled in the RNA-induced silencing complexes (RISCs), where members of Argonaute (Ago) family of proteins provide a unique platform for target recognition and gene silencing. Here, by using myeloid cell lines and primary blasts, we show that Ago2 has a key role in human monocytic cell fate determination and in LPS-induced inflammatory response of 1,25-dihydroxyvitamin D₃ (D3)-treated myeloid cells. The silencing of Ago2 impairs the D3-dependent miR-17-5p/20a/106a, miR-125b and miR-155 downregulation, the accumulation of their translational targets AML1, VDR and C/EBPβ and monocytic cell differentiation. Moreover, we show that Ago2 is recruited on miR-155 host gene promoter and on the upstream region of an overlapping antisense lncRNA, determining their epigenetic silencing, and miR-155 downregulation. These findings highlight Ago2 as a new factor in myeloid cell fate determination in acute myeloid leukemia cells.     

MicroRNA-424通过增加转录因子的表达减轻小鼠缺血性脑损伤

目的研究microRNA-424（miR-424）对小鼠脑缺血后神经细胞凋亡及转录因子表达的影响。方法将制备的慢病毒Lenti-miR-424（10’U／mL,8斗L）通过脑室注射,7d后采用大脑中动脉线栓闭塞（MCAO）的方法建立小鼠脑缺血模型,动物分4组：假手术组,假手术＋miR-424慢病毒,MCAO模型组,MCAO＋miR-424慢病毒处理组（n=6）。缺血8h后取脑组织,石蜡切片进行TUNEL染色,观察神经细胞凋亡的情况;Westernblot检测缺血脑组织中转录因子Pu．1、低氧诱导因子-la（hypoxiainduciblefactor-1a,HIF-1a）、凋亡相关蛋白p53的表达。结果TUNEL免疫荧光观察结果显示,miR-424可以减轻小鼠脑缺血后8h的神经细胞凋亡;Westernblot结果显示,在缺血前和缺血8h后,miR-424对正常小鼠或MCAO模型脑组织中转录因子的调节趋势是相同的,均增加转录因子PU．1蛋白、HIF．1a蛋白、以及凋亡相关蛋白p53的表达。结论miR-424可能通过增加小鼠脑组织转录因子PU．1和HIF-la,以及凋亡相关蛋白p53的表达,从而减轻脑缺血后神经细胞的凋亡。     

MicroRNA-125b Confers the Resistance of Breast Cancer Cells to Paclitaxel through Suppression of Pro-apoptotic Bcl-2 Antagonist Killer 1 (Bak1) Expression

Paclitaxel (Taxol) is an effective chemotherapeutic agent for treatment of cancer patients. Despite impressive initial clinical responses, the majority of patients eventually develop some degree of resistance to Taxol-based therapy. The mechanisms underlying cancer cells resistance to Taxol are not fully understood. MicroRNA (miRNA) has emerged to play important roles in tumorigenesis and drug resistance. However, the interaction between the development of Taxol resistance and miRNA has not been previously explored. In this study we utilized a miRNA array to compare the differentially expressed miRNAs in Taxol-resistant and their Taxol-sensitive parental cells. We verified that miR-125b, miR-221, miR-222, and miR-923 were up-regulated in Taxol-resistant cancer cells by real-time PCR. We further investigated the role and mechanisms of miR-125b in Taxol resistance. We found that miR-125b was up-regulated in Taxol-resistant cells, causing a marked inhibition of Taxol-induced cytotoxicity and apoptosis and a subsequent increase in the resistance to Taxol in cancer cells. Moreover, we demonstrated that the pro-apoptotic Bcl-2 antagonist killer 1 (Bak1) is a direct target of miR-125b. Down-regulation of Bak1 suppressed Taxol-induced apoptosis and led to an increased resistance to Taxol. Restoring Bak1 expression by either miR-125b inhibitor or re-expression of Bak1 in miR-125b-overexpressing cells recovered Taxol sensitivity, overcoming miR-125-mediated Taxol resistance. Taken together, our data strongly support a central role for miR-125b in conferring Taxol resistance through the suppression of Bak1 expression. This finding has important implications in the development of targeted therapeutics for overcoming Taxol resistance in a number of different tumor histologies.     

miR-125b Acts as a Tumor Suppressor in Breast Tumorigenesis via Its Novel Direct Targets ENPEP,CK2-α, CCNJ,and MEGF9

MicroRNAs (miRNAs) play important roles in diverse biological processes and are emerging as key regulators of tumorigenesis and tumor progression. To explore the dysregulation of miRNAs in breast cancer, a genome-wide expression profiling of 939 miRNAs was performed in 50 breast cancer patients. A total of 35 miRNAs were aberrantly expressed between breast cancer tissue and adjacent normal breast tissue and several novel miRNAs were identified as potential oncogenes or tumor suppressor miRNAs in breast tumorigenesis. miR-125b exhibited the largest decrease in expression. Enforced miR-125b expression in mammary cells decreased cell proliferation by inducing G2/M cell cycle arrest and reduced anchorage-independent cell growth of cells of mammary origin. miR-125b was found to perform its tumor suppressor function via the direct targeting of the 3’-UTRs of ENPEP, CK2-α, CCNJ, and MEGF9 mRNAs. Silencing these miR-125b targets mimicked the biological effects of miR-125b overexpression, confirming that they are modulated by miR-125b. Analysis of ENPEP, CK2-α, CCNJ, and MEGF9 protein expression in breast cancer patients revealed that they were overexpressed in 56%, 40–56%, 20%, and 32% of the tumors, respectively. The expression of ENPEP and CK2-α was inversely correlated with miR-125b expression in breast tumors, indicating the relevance of these potential oncogenic proteins in breast cancer patients. Our results support a prognostic role for CK2-α, whose expression may help clinicians predict breast tumor aggressiveness. In particular, our results show that restoration of miR-125b expression or knockdown of ENPEP, CK2-α, CCNJ, or MEGF9 may provide novel approaches for the treatment of breast cancer.     

miR-125b在前列腺癌1E8细胞运动转移中的作用及其分子机制的初步探讨

目的 研究 miR-125b在前列腺癌高低转移潜能细胞中的表达差异及其对高转移细胞株1E8细胞的运动转移中的作用和可能的分子机制.方法 realtime PCR法检测前列腺癌高低转移潜能配对细胞系中 miR-125b的表达差异.通过划痕实验及transwell实验观察1E8细胞及转染 miR-125b 抑制剂及其阴性对照后该细胞运动转移能力的变化.结果 realtime PCR结果显示高转移潜能1E8细胞中miR-125b表达水明显高于低转移潜能2B4细胞;下调miR-125b会减弱1E8细胞的运动转移能力.结论 miR-125b可促进前列腺癌细胞的运动转移能力.