MiR-1207 overexpression promotes cancer stem cell–like traits in ovarian cancer by activating the Wnt/β-catenin signaling pathway

Wnt/β-catenin signaling pathway is strictly controlled by multiple negative regulators. However, how tumor cells override the negative regulatory effects to maintain constitutive activation of Wnt/β-catenin signaling, which is commonly observed in various cancers, remains puzzling. In current study, we reported that overexpression of miR-1207 in ovarian cancer activated Wnt/β-catenin signaling by directly targeting and suppressing secreted Frizzled-related protein 1 (SFRP1), AXIN2 and inhibitor of β-catenin and TCF-4 (ICAT), which are vital negative regulators of the Wnt/β-catenin pathway. We found that the expression of miR-1207 was ubiquitously upregulated in both ovarian cancer tissues and cells, which inversely correlated with patient overall survival. Furthermore, overexpression of miR-1207 enhanced, while silencing miR-1207 reduced, stem cell-like traits of ovarian cancer cells in vitro and in vivo, including tumor sphere formation capability and proportion of SP+ and CD133+ cells. Importantly, upregulating miR-1207 promoted, while silencing miR-1207 inhibited, the tumorigenicity of ovarian cancer cells. Hence, our results suggest that miR-1207 plays a vital role in promoting the cancer stem cell-like phenotype in ovarian cancer and might represent a potential target for anti-ovarian cancer therapy.     

miR-942 promotes cancer stem cell-like traits in esophageal squamous cell carcinoma through activation of Wnt/β-catenin signalling pathway

The Wnt/β-catenin signalling pathway is known to play a vital role in the maintenance of cancer stem cells (CSCs), which are reported to be the origine of malignant cancers, and result in poor prognosis of multiple kinds of cancer. Therefore, it is of great importance to illuminate the mechanism by which the Wnt/β-catenin pathway regulates the cancer stem cell-like traits in cancers. Here, we report that miR-942 is significantly upregulated in esophageal squamous cell carcinoma (ESCC), and miR-942 levels are associated with poor prognosis in ESCC patients. Overexpression of miR-942 promotes, whereas inhibition of miR-942 decreases, the tumor sphere formation, the CD90⁺ subpopulation cells and the expression of pluripotency associated markers. Moreover, in vivo assay shows that miR-942 overexpressing cells form larger tumors and display higher tumourigenesis. Furthermore, we demonstrate that miR-942 upregulates the Wnt/β-catenin signaling activity via directly targeting sFRP4, GSK3β and TLE1, which are multiple level negative regulators of the Wnt/β-catenin signaling cascade. In addition, our results indicate that c-myc directly binds to the miR-942 promoter and promotes its expression. Taken together, our findings establish an oncogenic role of miR-942 in ESCC and indicate that miR-942 might be an effective therapeutic target for ESCC.     

FSTL1调控乳腺癌细胞干细胞样特性并增强耐药性的机制研究

目的:探讨卵泡抑素样蛋白1（follistatin like 1,FSTL1）在乳腺癌中的表达对肿瘤干细胞样特性及化疗耐药性的影响。方法:应用RT-PCR和免疫组化（IHC)等多种生物学实验方法,从临床标本实验的角度探究FSTL1促进乳腺癌细胞干细胞和化疗耐药性的作用及可能与miR-137/FSTL1/整合素β3/Wnt/β-联蛋白信号通路的相关性。结果:FSTL1在三阴性乳腺癌（triple negative breast cancer,TNBC）组织及细胞系中的表达显著高于非TNBC组织及细胞系。耐药TNBC细胞系中FSTL1 的表达亦显著高于其在母细胞系中的表达。研究证实FSTL1可促进乳腺癌干细胞表面标志物的表达上调,并促进肿瘤细胞集落形成和球体形成。FSTL1通过调控整合素β3表达进而活化Wnt/β-联蛋白信号通路发挥其生物学作用,而miR-137则可负性调控FSTL1的表达。结论:FSTL1能促进乳腺癌细胞干细胞样特性和化疗耐药性,乳腺癌细胞中存在miR-137/FSTL1/整合素β3/Wnt/β-联蛋白信号轴调节干细胞的功能和化疗耐药性。     

干细胞标志物在卵巢癌SKOV3细胞侧群细胞中的表达

目的：检测干细胞相关标志物在卵巢癌SKOV3细胞系侧群（side population,SP）细胞和非侧群（Non-SP）细胞中的表达差异,确定卵巢癌干细胞特异性标志物。 方法： Hoechst 33342染色检测SKOV3细胞中SP细胞的比例,流式细胞术检测SKOV3细胞的SP和Non-SP细胞中干细胞标志物CD133、CD117、CD44、ABCG2、ALDH1 的表达情况,荧光定量PCR检测SP和Non-SP细胞中 ABCG2、ALDH2、NANOG、OCT4、SOX2、CD133、CD117 mRNA的表达水平。 结果： SKOV3细胞中SP细胞比例为(1.56±0.35)%。 ALDH1、ABCG2在SP细胞中表达率分别为（87.3±5.76）%、（29.48±4.43）%,在Non-SP的表达率分别为（5.32±0.47）%、（3.01±1.69）%,差异有统计学意义（ P <0.01）;CD44在这两种细胞亚群中的表达率均高于99%（ P >005）;CD133、CD117在这两种细胞亚群中均不表达。 ALDH1、ABCG2、 NANOG、OCT4和SOX2 mRNA在SP细胞中的表达分别是Non-SP细胞的21.03倍（ P =0.001）、3.14倍（ P =0.001）、23.94倍（ P =0.001）、10.73倍（ P =0.009）和21.46倍( P =0001), CD133、CD117 mRNA在两种细胞亚群中均不表达。 结论： 人卵巢癌细胞株SKOV3中存在SP细胞亚群, ALDH1、ABCG2和NANOG、OCT4、SOX2 mRNA可能是卵巢癌干细胞标志物,为诊断及治疗卵巢癌提供了潜在的靶点。     

SOX8 regulates cancer stem‐like properties and cisplatin‐induced EMT in tongue squamous cell carcinoma by acting on the Wnt/β‐catenin pathway

A sub‐population of chemoresistant cells exhibits biological properties similar to cancer stem cells (CSCs), and these cells are believed to be a main cause for tumor relapse and metastasis. In our study, we explored the role of SOX8 and its molecular mechanism in the regulation of the stemness properties and the epithelial mesenchymal transition (EMT) of cisplatin‐resistant tongue squamous cell carcinoma (TSCC) cells. We found that SOX8 was upregulated in cisplatin‐resistant TSCC cells, which displayed CSC‐like properties and exhibited EMT. SOX8 was also overexpressed in chemoresistant patients with TSCC and was associated with higher lymph node metastasis, advanced tumor stage and shorter overall survival. Stable knockdown of SOX8 in cisplatin‐resistant TSCC cells inhibited chemoresistance, tumorsphere formation, and EMT. The Wnt/β‐catenin pathway mediated the cancer stem‐like properties in cisplatin‐resistant TSCC cells. Further studies showed that the transfection of active β‐catenin in SOX8 stable‐knockdown cells partly rescued the SOX8 silencing‐induced repression of stem‐like features and chemoresistance. Through chromatin immunoprecipitation and luciferase assays, we observed that SOX8 bound to the promoter region of Frizzled‐7 (FZD7) and induced the FZD7‐mediated activation of the Wnt/β‐catenin pathway. In summary, SOX8 confers chemoresistance and stemness properties and mediates EMT processes in chemoresistant TSCC via the FZD7‐mediated Wnt/β‐catenin pathway.     

Wnt3a expression is associated with epithelial-mesenchymal transition and promotes colon cancer progression

Introduction

Epithelial–mesenchymal transition (EMT) contributes to the progression and metastasis of cancer cells and is associated with a more invasive phenotype of cancer. The Wnt/β-catenin signaling pathway is one of the major pathways involved in EMT regulation. Many studies provide evidence that β-catenin, the key regulator of the canonical Wnt signaling pathway, is important in regulating EMT in cancer. However, the roles of Wnt3a, the representative canonical Wnt ligand, in EMT and colon cancer progression have not yet been fully explored.

Methods

The expression levels of Wnt3a and EMT-associated proteins (E-cadherin, vimentin, and β-catenin) were assessed by immunohistochemistry in human colon cancer tissues to evaluate the clinicopathological significance of Wnt3a, as well as the correlation between Wnt3a and EMT. We then upregulated Wnt3a expression in HCT116 colon cancer cells, established a nude mouse xenograft model, detected the expression of EMT and Wnt/β-catenin signaling-associated proteins, and observed invasion and clone-initiating abilities.

Results

In 203 human colon cancer tissue samples, Wnt3a protein overexpression was related to colon cancer histological differentiation (P = 0.004), clinical stage (P = 0.008), presence of metastasis and recurrence (P = 0.036), and survival time (P = 0.007) of colon cancer patients. Wnt3a expression was notably concomitant with EMT immunohistochemical features, such as reduced expression of the epithelial marker E-cadherin (P = 0.012), increased expression of the mesenchymal marker vimentin (P = 0.002), and cytoplasmic distribution of β-catenin (P = 0.021). Results of in vitro and in vivo experiments showed that Wnt3a overexpression could alter cell morphology, regulate EMT-associated protein expression, and enhance clone-initiation and invasion. Dkk1 (antagonist of Wnt/β-catenin signaling) could also partially reverse the expression of EMT-associated proteins in Wnt3a-overexpressing cells.

Conclusions

Wnt3a expression was associated with EMT and promoted colon cancer progression. The EMT-inducing effect was partially due to the stimulative effect of Wnt3a on the Wnt/β-catenin pathway.     

MicroRNA-200a suppresses the Wnt/β-catenin signaling pathway by interacting with β-catenin

The Wnt/β-catenin signaling pathway is crucial for human organ development and is involved in tumor progression of many cancers. Accumulating evidence suggests that the expression of β-catenin is, in part, regulated by specific microRNAs (miRNAs). The purpose of this study was to determine the expression of a recently identified epithelial to mesenchymal transition (EMT)-associated tumor suppressor microRNA (miR)-200a, in cancer cells. We also aimed to identify specific miR-200a target genes and to investigate the antitumor effects of miR-200a on the Wnt/β-catenin signaling pathway. We employed TOP/FOP flash luciferase assays to identify the effect of miR-200a on the Wnt/β-catenin pathway and we confirmed our observations using fluorescence microscopy. To determine target genes of miR-200a, a 3' untranslated region (3' UTR) luciferase assay was performed. Cell viability, invasion and wound healing assays were carried out for functional analysis after miRNA transfection. We further investigated the role of miR-200a in EMT by Western blot analysis. We found fluctuation in the expression of miR-200a that was accompanied by changes in the expression of members of the Wnt/β-catenin signaling pathway. We also determined that miR-200a can directly interact with the 3' UTR of CTNNB1 (the gene that encodes β-catenin) to suppress Wnt/β-catenin signaling. MiR-200a could also influence the biological activities of SGC790 and U251 cells. Our results demonstrate that miR-200a is a new tumor suppressor that can regulate the activity of the Wnt/β-catenin signaling pathway via two mechanisms. MiR-200a is a candidate target for tumor treatment via its regulation of the Wnt/β-catenin signaling pathway.     

miRNA-101通过靶向CDK8调控结肠癌细胞侵袭和Wnt/β-catenin通路活化

目的 探讨miRNA-101（miR-101）通过靶向CDK8对结肠癌细胞侵袭和Wnt/β-catenin通路激活的影响。方法 采用qRT-PCR和Western blot测定结肠癌组织、癌旁正常组织及五种结肠癌细胞株中miR-101和CDK8的表达。双荧光素酶报告实验测定其相互作用关系。通过miR-101 mimic、pBabe-CDK8转染调控CDK8表达并测定其对肿瘤细胞侵袭和Wnt/β-catenin激活的影响。结果 与癌旁正常组织相比,miR-101在结肠癌组织中表达水平显著降低,而CDK8的表达显著增加。双荧光素酶报告实验证实miR-101可直接与CDK8 3'UTR的结合位点作用调节荧光素酶的活性。转染miR-101 mimic组细胞的侵袭能力比阴性对照组和CDK8组明显下降。转染miR-101 mimic后TOP/FOP荧光素酶活性显著降低,β-catenin的蛋白表达也出现下降。CDK8过表达载体转染能显著减弱miR-101 mimic对荧光素酶活性和β-catenin蛋白表达的作用。结论 miRNA-101可通过靶向CDK8调控结肠癌细胞侵袭和Wnt/β-catenin通路活化。     

Downregulation of MicroRNA-147 Inhibits Cell Proliferation and Increases the Chemosensitivity of Gastric Cancer Cells to 5-Fluorouracil by Directly Targeting PTEN

Gastric cancer is the fourth most common malignancy and the third leading cause of cancer-related deaths worldwide. This study aimed to investigate the expression patterns, biological roles, and underlying mechanisms of microRNA-147 (miR-147) in gastric cancer. The present study demonstrated that miR-147 was significantly upregulated in gastric cancer tissues and cell lines. Downregulation of miR-147 decreased cell proliferation and enhanced the chemosensitivity of gastric cancer cells to 5-fluorouracil (5-FU) through the cell apoptosis pathway. In addition, phosphatase and tensin homolog (PTEN) was mechanically identified as the direct target of miR-147 in gastric cancer. PTEN knockdown reversed the effects of miR-147 downregulation on the proliferation, chemosensitivity, and 5-FU-induced apoptosis of gastric cancer cells. Moreover, miR-147 regulated the PI3K/AKT signaling pathway in gastric cancer by targeting PTEN. In conclusion, miR-147 suppressed the proliferation and enhanced the chemosensitivity of gastric cancer cells to 5-FU by promoting cell apoptosis through directly targeting PTEN and regulating the PI3K/AKT signaling pathway. This study provides important insight into the molecular mechanism that underlies the chemoresistance of gastric cancer cells. The results of this study could aid the development of a novel therapeutic strategy for gastric cancer.     

微小RNA-223-3p靶向调控TGFBR3影响肺癌细胞上皮间质转化及Wnt/β-catenin通路

目的:探讨微小RNA-223-3p（miR-223-3p）对转化生长因子Ⅲ型受体（TGFBR3）的靶向调控及对肺癌上皮间质转化（EMT）及Wnt/β-catenin通路相关指标的影响。方法:采用实时荧光定量PCR（qPCR）检测肺癌细胞（95D、LTEP-α-2、A549及NCI-H460）以及人肺上皮细胞BEAS-2B的miR-223-3p和TGFBR3水平,经双荧光素酶报告基因实验验证miR-223-3p和TGFBR3的靶向关系。将A549细胞分成3组:对照组、miR-223-3p NC组（转染miR-223-3p NC）、miR-223-3p mimic组（转染miR-223-3p mimic）,MTT法、划痕实验及Transwell小室实验分别检测3组细胞的增殖及迁移能力。接着收集3组转染后的细胞,分别制备裸鼠移植瘤,处死裸鼠并剥离肿瘤组织,测量肿瘤体积及重量,免疫组化法对比各组镜下TGFBR3蛋白的表达情况,Western blotting实验检测EMT相关指标上皮钙黏蛋白（E-Cadherin）、神经型钙黏蛋白（N-Cadherin）、波形蛋白（Vimentin）及Wnt/β-catenin通路相关因子（Wnt1和β-catenin）的表达。结果:与BEAS-2B细胞对比,肺癌细胞miR-223-3p及TGFBR3的表达水平均降低,差异有统计学意义（P＜0.05）;miR-223-3p能靶向调控TGFBR3的表达。miR-223-3p mimic组A549细胞的增殖活力、划痕愈合率及穿膜细胞数均较miR-223-3p NC组明显降低（P＜0.05）;此外,miR-223-3p mimic组裸鼠瘤体体积及重量均明显低于miR-223-3p NC组。免疫组化结果显示,miR-223-3p mimic组TGFBR3阳性表达率上升,与miR-223-3p NC组相比,差异具有统计学意义（P＜0.05）;Western blotting结果提示,与miR-223-3p NC组相比,miR-223-3p mimic组肿瘤组织中TGFBR3、E-Cadherin表达水平升高,而N-Cadherin、Vimentin、Wnt1和β-catenin表达水平均下降（P＜0.05）。对照组与miR-223-3p NC组的增殖活力、划痕愈合能力以及EMT和Wnt/β-catenin通路相关因子水平的差异无统计学意义（P＞0.05）。结论:miR-223-3p在肺癌中异常低表达,miR-223-3p通过靶向调控TGFBR3来抑制肺癌A549细胞的增殖、迁移侵袭、EMT过程并阻断Wnt/β-catenin通路,在肺癌进展中发挥抑癌作用。     

Pluripotency transcription factors and cancer stem cells:small genes make a big difference

Cancer stem cells (CSCs) are thought to drive uncontrol ed tumor growth, and the existence of CSCs has recently been proven by direct experimental evidence, including tracing cel lineages within a grow...     

BRACHYURY confers cancer stem cell characteristics on colorectal cancer cells

Cancer stem cells (CSCs) are initiating cells in colorectal cancer (CRC). Colorectal tumours undergo epithelial to mesenchymal transition (EMT)-like processes at the invasive front, enabling invasion and metastasis, and recent studies have linked this process to the acquisition of stem cell-like properties. It is of fundamental importance to understand the molecular events leading to the establishment of cancer initiating cells and how these mechanisms relate to cellular transitions during tumourigenesis. We use an in vitro system to recapitulate changes in CRC cells at the invasive front (mesenchymal-like cells) and central mass (epithelial-like cells) of tumours. We show that the mesoderm inducer BRACHYURY is expressed in a subpopulation of CRC cells that resemble invasive front mesenchymal-like cells, where it acts to impose characteristics of CSCs in a fully reversible manner, suggesting reversible formation and modulation of such cells. BRACHYURY, itself regulated by the oncogene β-catenin, influences NANOG and other 'stemness' markers including a panel of markers defining CRC-CSC whose presence has been linked to poor patient prognosis. Similar regulation of NANOG through BRACHYURY was observed in other cells lines, suggesting this might be a pathway common to cancer cells undergoing mesenchymal transition. We suggest that BRACHYURY may regulate NANOG in mesenchymal-like CRC cells to impose a 'plastic-state', allowing competence of cells to respond to signals prompting invasion or metastasis.     

The SOX17/miR-371-5p/SOX2 axis inhibits EMT,stem cell properties and metastasis in colorectal cancer

Cancer stem cells (CSCs) and EMT-type cells, which share molecular characteristics with CSCs, have been believed to play critical roles in tumor metastasis. Although much progress has been garnered in elucidating the molecular pathways that trigger EMT, stemness and metastasis, a number of key mechanistic gaps remain elusive. In the study, miR-371-5p was obviously down-regulated in primary CRC tissues compared with matched adjacent normal mucosa and correlated significantly with differentiation, tumor size, lymphatic and liver metastases. MiR-371-5p could attenuate proliferation, invasion in vitro and metastasis in vivo in CRC cells. It also suppressed EMT by regulating Wnt/β-catenin signaling and strongly decreased the CRC stemness phenotypes. Moreover, demethylation of SOX17 induced miR-371-5p expression and consequently suppressed its direct target SOX2 in CRC cells. MiR-371-5p was necessary for SOX17 mediated cancer-related traits and SOX2 was a functional target of miR-371-5p. A positive relationship between SOX17 and miR-371-5p expression and a negative one between miR-371-5p and SOX2 expression were observed in CRC cell lines and tissues. In conclusion, we identified miR-371-5p as an important “oncosuppressor” in CRC progression and elucidated a novel mechanism of the SOX17/miR-371-5p/SOX2 axis in the regulation of EMT, stemness and metastasis, which may be a potential therapeutic target.     

Programmed death ligand 1 regulates epithelial–mesenchymal transition and cancer stem cell phenotypes in hepatocellular carcinoma through the serum and glucocorticoid kinase 2/β-catenin signaling pathway

Programmed death ligand 1 (PD-L1) plays an important role in the occurrence of hepatocellular carcinoma (HCC). The present study indicated that epithelial–mesenchymal transition (EMT) and induction of cancer stem cell (CSC)-like properties contribute to metastasis of cancers. However, the molecular mechanisms underlying PD-L1 and EMT and CSC phenotypes in HCC remain to be elucidated. Here, we report that PD-L1 regulates not only EMT but also the stem-like transition in liver cancer cells. We observed high PD-L1 expression in CD133⁺ liver CSCs and CSC-enriched tumor spheres. Altering PD-L1 expression promoted liver CSC phenotypes by increasing the expression of stemness genes, the CD133⁺ cell population sizes, and the ability to form tumor spheres. Programmed death ligand 1 enhanced HCC cell tumorigenicity and invasion in nude mice. Additionally, PD-L1 overexpression in cells significantly increased cell motility and invasion, as well as the EMT process. Conversely, suppression of PD-L1 in cells had an opposite effect. Prolonged treatment of HCC cells with Akt inhibitor prefosine leads to activation of serum and glucocorticoid kinase 2 (SGK2) and rescued downregulation of PD-L1. Mechanistically, PD-L1 directly interacted with SGK2. Programmed death ligand 1 upregulated SGK2 and activated the SGK2/β-catenin signaling pathway, and promoted EMT and CSC expansion in liver cancer cells, highlighting the role of SGK2 in PD-L1-mediated EMT and CSC phenotypes in liver cancer cells. In conclusion, our findings suggest that PD-L1 activated the SGK2/β-catenin signaling pathway, to induce EMT and acquisition of a stem cell phenotype.     

MicroRNA-182 promotes epithelial-mesenchymal transition by targeting FOXN3 in gallbladder cancer

Increasing evidence has suggested an association between the expression profiles of microRNAs (miRs) and gallbladder cancer (GBC). Recently, miR-182 has been demonstrated to exert tumor-promoting effects. However, the biological activity and molecular mechanisms of miR-182 in GBC remain unclear. The results of the present study demonstrated that miR-182 expression was significantly upregulated in GBC tissues and cell lines (GBC-SD and SGC-996). In addition, miR-182-knockdown attenuated epithelial-mesenchymal transition (EMT) in GBC cells, as indicated by decreased cell migratory and invasive abilities, decreased vimentin expression, and increased E-cadherin expression. The activities of β-catenin and its downstream factors, Cyclin D1 and c-Myc, were also demonstrated to decrease following miR-182-knockdown. Forkhead box N3 (FOXN3) was identified as the direct target of miR-182. Overexpression of FOXN3 ameliorated EMT and the β-catenin pathway. Taken together, the results of the present study suggested that miR-182 promotes EMT in GBC cells by targeting FOXN3, which suppresses the Wnt/β-catenin pathway.     

β-Catenin/LEF1 transactivates the microRNA-371-373 cluster that modulates the Wnt/β-catenin-signaling pathway

The microRNA-371-373 (miR-371-373) cluster is specifically expressed in human embryonic stem cells (ESCs) and is thought to be involved in stem cell maintenance. Recently, microRNAs (miRNAs) of this cluster were shown to be frequently upregulated in several human tumors. However, the regulatory mechanism for the involvement of the miR-371-373 cluster in human ESCs or cancer cells remains unclear. In this study, we explored the relationship between this miRNA cluster and the Wnt/β-catenin-signaling pathway, which has been shown to be involved in both stem cell maintenance and tumorigenesis. We show that miR-371-373 expression is induced by lithium chloride and is positively correlated with Wnt/β-catenin-signaling activity in several human cancer cell lines. Mechanistically, three TCF/LEF1-binding elements (TBEs) were identified in the promoter region and shown to be required for Wnt-dependent activation of miR-371-373. Interestingly, we also found that miR-372&373, in turn, activate Wnt/β-catenin signaling. In addition, four protein genes related to the Wnt/β-catenin-signaling pathway were identified as direct targets of miR-372&373, including Dickkopf-1 (DKK1), a well-known inhibitor of Wnt/β-catenin signaling. Using a lentiviral system, we showed that overexpression of miR-372 or miR-373 promotes cell growth and the invasive activity of tumor cells as knockdown of DKK1. Taken together, our study demonstrates a novel β-catenin/LEF1-miR-372&373-DKK1 regulatory feedback loop, which may have a critical role in regulating the activity of Wnt/β-catenin signaling in human cancer cells.