Wnt/β-catenin信号通路与干细胞衰老

Wnt/β-catenin信号通路作为一条进化保守的信号通路,有着广泛的生物学作用。研究发现,Wnt/β-catenin信号通路与干细胞衰老之间存在联系。激活Wnt/β-catenin信号通路可导致干细胞发生衰老变化,而抑制Wnt/β-catenin信号通路可延缓干细胞的衰老。本文对Wnt/β-catenin信号通路与干细胞衰老之间的关系及其作用机制作一综述。     

Kindlin家族调控Wnt/β-catenin信号通路的研究进展

Kindlin家族属于新型的局灶性黏附蛋白家族,是由三个进化上具有高度保守性和同源性的蛋白质(Kindlin-1、2和3)组成,在整合素调节、细胞基质黏附和信号转导中发挥重要作用。尽管由三个不同的基因编码,Kindlin家族成员有相似的结构和序列,在C端均含有1个FERM结构域。Wnt/β-catenin信号通路是生物体中普遍存在的调节细胞增殖和细胞分化的重要信号通路之一,在生长发育等生理过程和肿瘤等病理过程中发挥着重要作用。越来越多研究显示,Kindlin家族成员通过调控Wnt/β-catenin信号通路参与包括肿瘤在内的许多疾病的发生和发展过程。因此,该文围绕Kindlin家族的结构、主要功能以及调控Wnt/β-catenin信号通路等方面的研究进展进行综述。     

Wnt/β-catenin信号通路与肝癌

肝细胞癌是常见的恶性肿瘤,其发病机制尚未完全明确。Wnt信号通路与人体内多种病理生理过程相关,其中肝癌的发生、发展可能与经典的Wnt/β-catenin信号通路密切相关。Wnt/β-catein信号通路通过表达癌症相关基因、激活肝星状细胞、调控肝干细胞行为、促进肝癌细胞侵袭转移等方式调控肝癌的发生、发展。Wnt/β-catein信号通路在肝癌发生、发展中的作用有望为肝癌研究提供新的思路。     

抗肿瘤干细胞药物盐霉素对Wnt/β-catenin信号通路的抑制

肿瘤干细胞(cancer stem cells, CSCs)是一小群具有自我更新和分化潜力,并能产生异质性细胞的肿瘤细胞亚群,该群细胞在肿瘤的发生发展、复发、转移和耐药中起着十分重要的作用,因此通过研发针对CSCs的靶向药物,将为抗肿瘤药物的研究提供新的方向,并为未来根治肿瘤带来新的希望.近年来,大量实验研究证实了盐霉素对多种类型的肿瘤干细胞具有明显的杀伤作用,这些肿瘤包括肝癌、乳腺癌、胃癌、结直肠癌、前列腺癌和骨肉瘤等.盐霉素可以抑制肿瘤干细胞的增殖、分化及转移,并诱导其凋亡. Wnt/β-catenin信号通路是一种在生物进化过程中高度保守的信号系统,与组织的发育和器官形成等生物学过程密切相关,该通路的异常活化在肿瘤及肿瘤干细胞的发生发展中起关键作用.通过靶向阻断异常活化的Wnt信号通路,可以抑制肿瘤细胞和肿瘤干细胞的增殖并诱导其凋亡,因此该通路已经成为抗肿瘤药物领域的研究热点. Wnt/β-catenin信号通路在盐霉素抗肿瘤干细胞过程中起重要作用,本文综述了盐霉素通过调节Wnt/β-catenin信号通路抑制肿瘤干细胞的研究进展.     

miR-26a通过调控Wnt/β-catenin信号通路抑制食管癌发生发展

目的 探讨miR-26a在裸鼠体内对食管癌发生发展以及调控Wnt/β-catenin信号通路的影响.方法 在45对手术切除并经病理检查证实食管鳞癌组织和正常癌旁组织配对样本中,用RT-PCR检测miR-26a的表达,通过慢病毒干扰技术在食管癌细胞株中干扰miR-26a和过表达miR-26a,并将在裸鼠荷瘤实验中观察肿瘤...     

miRNA-26a靶向调控GSK-3β参与Wnt/β-catenin信号通路调节IgA肾病肾纤维化

目的:通过检测IgA肾病不同程度肾间质纤维化患者肾组织miRNA-26a、β-catenin、GSK-3β、α-SMA的表达,探究miRNA-26a通过靶向调控GSK-3β参与Wnt/β-catenin信号通路所致肾间质纤维化。方法:根据肾间质纤维化程度将46例IgA患者分为实验组(轻度组、中度组、重度组),对照组为7例肾脏肿瘤远离肿瘤组织的正常肾组织。采用RT-qPCR方法检测各实验组及正常对照组共53例IgA肾病患者肾组织miRNA-26a的表达水平,分析miRNA-26a与IgA肾病肾纤维化的关系。分别采用RT-qPCR技术及免疫组化技术检测各组肾组织β-catenin、GSK-3β、α-SMAmRNA及蛋白的表达水平,各组之间进行比较,并与miRNA-26a进行相关性分析。结果:(1)与正常对照组相比,IgA肾病患者肾活检组织miRNA-26a呈低表达,且随着肾间质病变程度加重,miRNA-26a表达水平显著降低,各组间差异具有统计学意义(P0.05);(2)与正常对照组比较,IgA肾病患者肾组织GSK-3β、β-catenin、α-SMAmRNA和蛋白的表达升高,且表达程度随着肾间质病变程度加重逐渐增强,各组间比较差异具有统计学意义(P0.05);(3)相关性分析:肾组织miRNA-26a与肾间质纤维化程度呈负相关(r=-0.943,P0.05),肾间质及肾小管GSK-3β、β-catenin、α-SMA的表达强度与肾间质纤维化程度正相关(r=0.917,P0.05;r=0.943,P0.05;r=0.926,P0.05),肾间质GSK-3β与β-catenin蛋白表达正相关(r=0.834,P0.05)。结论:miRNA-26a可通过靶向调控GSK-3β参与Wnt/β-catenin信号通路肾间质纤维化。     

Wnt/β-catenin信号通路在宫颈癌形成中的作用机制

<正>宫颈癌是常见妇科恶性肿瘤之一,发病率居妇科恶性肿瘤前列,严重威胁女性的健康与生命安全。在全球女性中,宫颈癌为第三大常见肿瘤,是导致肿瘤相关死亡的第四大病因。据最新统计显示,宫颈癌每年新发生病例约52万,死亡病例约28万,其中86%发生在发展中国家[1]。我国每年新发生病例约14万,并逐渐呈年轻化及上升趋势[2]。随着分子生物学方法在肿瘤发生发展研究中的应用,越来越多的基因和信号通路被证明与肿瘤的形成相关,其中Wnt/β-catenin     

Wnt3a诱导小鼠胚胎干细胞向心肌细胞分化的研究

目的：研究Wnt3a在诱导小鼠胚胎干细胞心肌细胞分化中的作用和原理。方法：设计不同浓度,不同成分的Wnt3a条件培养基对小鼠胚胎干细胞诱导分化,对分化细胞进行形态学鉴定,通过免疫细胞化学检测心肌肌钙蛋白-T（cTnT）的表达,通过RT．PCR检测肌球蛋白重链（ot．MHC）和肌球蛋白轻链（MLC．2v）的表达。结果：Wnt3a诱导小鼠胚胎干细胞分化为心肌样细胞,分化细胞具有自动收缩性,免疫细胞化学检测心肌肌钙蛋白．T（cTllT）表达阳性,RT．PCR检测肌球蛋白重链（d—MHC）和肌球蛋白轻链（MLC-2v）表达阳性。经典Wnt信号途径的抑制剂Frizzled一8／Fc,能够抑制Wnt3a的诱导分化作用。结论：Wnt3a通过经典Wnt信号途径诱导小鼠胚胎干细胞向心肌细胞分化。     

WNT/beta-catenin pathway up-regulates Stat3 and converges on LIF to prevent differentiation of mouse embryonic stem cells

Embryonic stem (ES) cells rely on growth factors provided by feeder cells or exogenously to maintain their pluripotency. In order to identify such factors, we have established sub-lines of STO feeder cells which exhibit variable ability in supporting ES cell self-renewal. Functional screening identifies WNT5A and WNT6 as STO cell-produced factors that potently inhibit ES cell differentiation in a serum-dependent manner. Furthermore, direct activation of beta-catenin without disturbing the upstream components of the WNT/beta-catenin pathway fully recapitulates the effect of WNTs on ES cells. Importantly, the WNT/beta-catenin pathway up-regulates the mRNA for Stat3, a known regulator of ES cell self-renewal in the mouse. Finally, LIF is able to mimic the serum effect to act synergistically with WNT proteins to inhibit ES cell differentiation. Therefore, our study reveals part of the molecular mechanisms by which the WNT/beta-catenin pathway acts to prevent ES cell differentiation through convergence on the LIF/JAK-STAT pathway at the level of STAT3.     

Lithium chloride promotes proliferation of neural stem cells in vitro,possibly by triggering the Wnt signaling pathway

The objective of this study was to clarify the relationship between the effect and associated mechanisms of lithium chloride on neural stem cells (NSCs) and the Wnt signaling pathway. The expression of key molecules proteins related to the Wnt signaling pathway in the proliferation and differentiation of control NSCs and lithium chloride-treated NSCs was detected by Western blot analysis. Flow cytometry analysis was applied to study the cell cycle dynamics of control NSCs and NSCs treated with lithium chloride. The therapeutic concentrations of lithium chloride stimulated NSC proliferation. β-catenin expression gradually decreased, while Gsk-3β expression gradually increased (P?P?in vitro and preventing the cells from differentiating, which is potentially mediated by activation of the Wnt signaling pathway.     

Activation of non-canonical Wnt/JNK pathway by Wnt3a is associated with differentiation fate determination of human bone marrow stromal (mesenchymal) stem cells

The canonical Wnt signaling pathway can determine human bone marrow stromal (mesenchymal) stem cell (hMSC) differentiation fate into osteoblast or adipocyte lineages. However, its downstream targets in MSC are not well characterized. Thus, using DNA microarrays, we compared global gene expression patterns induced by Wnt3a treatment in two hMSC lines: hMSC-LRP5^T253 and hMSC-LRP5^T244 cells carrying known mutations of Wnt co-receptor LRP5 (T253I or T244M) that either enhances or represses canonical Wnt signaling, respectively. Wnt3a treatment of hMSC activated not only canonical Wnt signaling, but also the non-canonical Wnt/JNK pathway through upregulation of several non-canonical Wnt components e.g. naked cuticle 1 homolog (NKD1) and WNT11. Activation of the non-canonical Wnt/JNK pathway by anisomycin enhanced osteoblast differentiation whereas its inhibition by SP600125 enhanced adipocyte differentiation of hMSC. In conclusion, canonical and non-canonical Wnt signaling cooperate in determining MSC differentiation fate.     

Wnt signaling associated small molecules improve the viability of pPSCs in a PI3K/Akt pathway dependent way

Although we have obtained porcine pluripotent stem cell lines (pPSCs) from blastocysts, the cells exhibit flat clonal morphology and do not support single-cell passage. There is massive cell death after cell dissociation, and the efficiency of single-cell colony is generally ≤10%. In a recent study, we got a new pPSCs using two Wnt signaling pathway regulators CHIR99021 and XAV939. This cell had strong biological viability, small-domed morphology, and its cloning efficiency after dissociation was 80–90%. The CH/XAV-treated cells expressed elevated levels of pluripotent genes, and possessed differentiation abilities both in vitro and in vivo, proven by the formation of embryonic bodies and teratomas with three germ layers. Furthermore, we found that the combinative use of CHIR99021 and XAV939 resulted in β-catenin-maintained expression in the cytoplasm but not translocation to the nuclei for WNT/TCF activation. In the meanwhile, E-cadherin located on the cell membrane, thereby activated the PI3K/Akt signaling pathway to enhance the pluripotency of the cells. Our study obtained new pPSCs, which were even closer to the naïve state with only two small molecule inhibitors, and the improved pluripotency of pPSCs could facilitate transgenic manipulation and regenerative medicine research. Besides, our study casted a light on the understanding of pPSCs and the derivation of authentic porcine embryonic stem cells.     

Role of Lef1 in sustaining self-renewal in mouse embryonic stem cells

Embryonic stem cells (ESCs) can self-renew indefinitely while maintaining the ability to generate all three germ-layer derivatives.Despite the importance of ESCs in developmental biology and their potential impact on regenerative medicine,the molecular mechanisms controlling ESC behavior are incompletely understood.Previously,activation of the canonical Wnt signaling pathway has been shown to contribute to mouse ESC self-renewal.Here we report that ectopic expression of Lef1,a component of the Wnt signaling pathway,has a positive effect on the self-renewal of mouse ESCs.Lef1 up-regulates Oct4 promoter activity and physically interacts with Nanog,two key components of the ESC pluripotency machinery.Moreover,siRNA for Lef1 induced mouse ESC differentiation.Our results thus suggest that in response to Wnt signaling Lef1 binds to stabilized β-catenin and helps maintain the undifferentiated status of ESCs through modulation of Oct4 and Nanog.     

Retinoic acid maintains self-renewal of murine embryonic stem cells via a feedback mechanism

Embryonic stem cells (ESCs) are pluripotent cells derived from the inner cell mass (ICM) that are able to self-renew or undergo differentiation depending on a complex interplay of extracellular signals and intracellular factors. However, the feedback regulation of differentiation-dependent ESC self-renewal is poorly understood. Retinoic acid (RA), a derivative of vitamin A, plays a critical role in ESC differentiation and embryogenesis. In the present study, we demonstrate that short-term treatment of murine (m) ESCs with RA during the early differentiation stage prevented spontaneous differentiation of mESCs. The RA-treated cells maintained self-renewal capacity and could differentiate into neuronal cells, cardiomyocytes, and visceral endoderm cells derived from three germ layers. The differentiation-inhibitory effect of RA was mimicked by conditioned medium from RA-treated ESCs and was accompanied with up-regulated expression of leukemia inhibitory factor (LIF), Wnt3a, Wnt5a, and Wnt6. Such RA-induced prevention of ESC differentiation was attenuated by a neutralizing antibody against LIF or by a specific Wnt antagonist Fz8-Fc and was totally reversed in the presence of both of them. Furthermore, knock-down of beta-catenin, a component of the Wnt signaling pathway, by small interfering RNA counteracted the effect of RA. In addition, RA treatment enhanced expression of endodermal markers GATA4 and AFP but inhibited expression of primitive ectodermal marker Fgf-5 and mesodermal marker Brachyury. These findings reveal a novel role of RA in ESC self-renewal and provide new insight into the regulatory mechanism of differentiation-dependent self-renewal of ESCs, in which Wnt proteins and LIF induced by RA have the synergistic action. The short-term treatment of ESCs with RA also offers a unique model system for study of the regulatory mechanism that controls self-renewal and specific germ-layer differentiation of ESCs.     

Novel Daple-like protein positively regulates both the Wnt/beta-catenin pathway and the Wnt/JNK pathway in Xenopus

Wnt signaling pathways are essential in various developmental processes including differentiation, proliferation, cell migration, and cell polarity. Wnt proteins execute their multiple functions by activating distinct intracellular signaling cascades, although the mechanisms underlying this activation are not fully understood. We identified a novel Daple-like protein in Xenopus and named it xDal (Xenopus Daple-like). As with Daple, xDal contains several leucine zipper-like regions (LZLs) and a putative PDZ domain-binding motif, and can interact directly with the dishevelled protein. In contrast to mDaple, injection of xDal mRNA into the dorso-vegetal blastomere does not induce ventralization and acted synergistically with xdsh in secondary axis induction. XDal also induced expression of siamois and xnr-3, suggesting that XDal functions as a positive regulator of the Wnt/beta-catenin pathway. Injection of xDal mRNA into the dorso-animal blastomere, however, induced gastrulation-defective phenotypes in a dose-dependent manner. In addition, xDal inhibited activin-induced elongation of animal caps and enhanced c-jun phosphorylation. Based on these findings, xDal is also thought to function in the Wnt/JNK pathway. Moreover, functional domain analysis with several deletion mutants indicated that xDal requires both a putative PDZ domain-binding motif and at least one LZL for its activity. These findings with xDal will provide new information on the Wnt signaling pathways.