Wnt信号通路与干细胞定向分化

Wnt信号通路在胚胎发育过程中参与背腹轴的形成、细胞极性的建立以及决定细胞命运.利用干细胞定向分化模型可在体外培养条件下探索Wnt信号通路在哺乳动物早期胚胎发育过程中的分子机理,了解其信号网络对干细胞定向分化中各个事件的调控机制.本文通过综合近期Wnt信号通路的研究,阐述经典Wnt信号通路(Canonical Wnt signaling pathway)在干细胞定向分化中的作用.     

Wnt信号通路与心脏发育和心肌诱导分化

Wnt信号通路是调控心肌细胞分化和心脏发育的重要信号通路.在哺乳动物中,迄今已发现19个分泌性Wnt蛋白,10个Frizzled受体和多个拮抗分子,显示Wnt信号家族效应广泛复杂.Wnt通路大致分为β-catenin依赖的经典通路和β-catenin非依赖的非经典通路,二者均在心脏发育中发挥重要的作用,广泛调控心肌细胞的增殖、分化、黏附、迁移和极化等.研究发现,Wnt信号通路在心肌细胞分化进程中存在明显的阶段特异性效应,呈现典型的双相性作用.通过小分子或转基因等调制Wnt信号通路,可有效提高体外多能干细胞向心肌的诱导分化效率.     

Wnt信号通路在哺乳动物卵泡发育中的作用

Wnt是一类癌基因。Wnt信号分子家族调控着多个组织脏器的胚胎发育,在动物发育过程中具有广泛的作用。Wnt信号通路作为一种在进化中高度保守的信号通路,在动物生长、发育、代谢和干细胞维持等多种生物学过程中发挥重要作用。     

Wnt信号通路在肝纤维化中的作用

肝纤维化是多种慢性肝病进展至肝硬化的中间过程，特征为以胶原蛋白为主的细胞外基质合成与降解失衡，是多条细胞信号转导通路和一系列细胞信号分子网络共同控制的结果。Wnt信号通路包括经典通路和非经典通路，参与调控细胞的分化，癌变，凋亡，机体免疫及应激等生理病理过程。最近有研究表明Wnt信号通路与肝星状细胞的活化及肝纤维化的发生相关。本文就Wnt通路的组成分子，信号转导路径，在肝纤维化发展中的作用做简要综述。     

Wnt/β-catenin信号通路对舌味觉乳头发育及舌癌的调控作用

Wnt经典信号通路(Wnt/β-catenin信号通路)在小鼠舌味觉乳头的早期发育以及味蕾再生过程中具有重要的调控作用,该信号通路的关键因子的缺失或者过表达可导致舌味觉乳头发育缺陷以及味蕾功能异常.此外,Wnt/β-catenin信号通路在成体舌的异常还与舌癌的发生有关.     

信号转导通路与异常黑胆质证NEI网络功能紊乱的关系

 为探讨信号转导通路与异常黑胆质证神经-内分泌-免疫(NEI)网络功能紊乱的关系,采用基因芯片技术检测异常黑胆质证与非异常黑胆质(异常血液质、异常黏液质、异常胆液质)证白细胞结构基因表达水平,筛选差异表达基因,利用生物信息学技术分析差异表达基因参与的相关信号转导通路。芯片结果提示,与非异常黑胆质证相比,异常黑胆质证白细胞中有75个结构基因表达上调,生物信息学分析显示差异表达基因中富集到信号转导生物学过程的基因有12个,这些基因主要涉及MAPK、Toll样受体和Wnt信号转导通路等。由此可见,MAPK、Toll样受体、Wnt信号转导通路在异常黑胆质证患者体内存在异常激活现象,这可能与异常黑胆质证神经-内分泌-免疫网络功能紊乱密切相关。     

氨甲环酸与Wnt信号通路中含kringle结构域蛋白的结合对新生小鼠骨密度的影响

最近研究发现Wnt信号通路在骨形成过程中发挥重要作用Wnt受体如脂蛋白相关蛋白5（lrp5）和孤独受体（Ror2）的缺失或突变导致骨的不正常发育．Dkk是一个分泌型规范Wnt信号系统的抑制剂，通过与脂蛋白相关蛋白5和最近新发现的一种含kringle结构域的蛋白kremen形成三聚体复合物．这种复合物随即被细胞内吞，从而导致细胞表面Wnt受体脂蛋白相关蛋白5水平迅速下降，从而达到抑制Wnt信号通路的日地．通过对kremen和Ror2蛋白序列分析发现kremen和Ror2的胞外部分均含有一个结构上能与赖氨酸结合的kringle结构域．通过给怀孕母鼠注射一种赖氨酸类似物——氨甲环酸来研究kremen和Ror2的kringle结构域上的赖氨酸结合位点被占据对小鼠骨发育的作用．但是，研究结果表明AMCA组和对照组之间的骨密度并没有显著差异，揭示赖氨酸结合位点不参与骨的发育调控．     

β-Catenin和Wnt5a蛋白在人牙齿早期发育过程中的表达

以人牙胚为材料,运用免疫组织化学染色技术分别检测经典Wnt信号通路的β-Catenin和非经典Wnt信号通路的Wnt5a的表达模式．结果表明：从12w人牙胚帽状期到15w钟状期。β-Catenin蛋白在牙上皮细胞的表达强于牙问充质细胞,且其在磨牙细胞的表达强于门牙;随着发育的成熟,β-Catenin蛋白在内釉上皮细胞的表达增强,而在外釉上皮层和星网状层的表达降低．WntSa蛋白在人牙胚中的牙间充质细胞的表达强于牙上皮：从帽状期到钟状期．Wnt5a蛋白在内釉上皮层和星网状层的表达降低,β-Catenin蛋白的表达整体明显高于WntSa．因此,经典Wnt信号通路在人牙齿早期发育过程中发挥重要的作用．     

经典Wnt信号通路与弥漫大B细胞淋巴瘤

弥漫性大B细胞淋巴瘤(DLBCL)的发病机制虽未完全阐明,但研究显示与信号通路表达异常有关,如经典Wnt通路。在DLBCL发病机制的研究中观察到经典Wnt通路的重要下游因子β-catenin的表达和核内定位。同时证据显示经典Wnt通路不仅与DLBCL发病机制有关,还和DLBCL临床分期密切相关,经典Wnt通路通路有可能成为治疗DLBCL潜在的有用靶点。     

Napabucasin对结直肠癌细胞增殖及迁移的影响

为了探究新型小分子抑制剂Napabucasin对结直肠癌细胞增殖以及迁移的影响. 首先通过分子模拟对接分析了Napabucasin与STAT3蛋白的互作机制. 然后利用克隆形成实验、细胞划痕实验等方法在多种结直肠癌细胞系中证明了Napabucasin能够显著抑制结直肠癌细胞的集落形成能力以及迁移能力. 进而使用Napabucasin与Wnt信号通路激活剂Wnt agonist 1共处理结直肠癌细胞HCT116,结合蛋白质印迹实验发现,Wnt信号通路介导了Napabucasin对结直肠癌细胞的迁移以及增殖的抑制过程. 研究结果显示,Napabucasin能够在体外抑制结直肠癌细胞的增殖能力以及迁移能力,并且Wnt信号通路参与介导了这一抑制过程.     

RANK ligand mediates progestin-induced mammary epithelial proliferation and carcinogenesis

RANK ligand (RANKL), a TNF-related molecule, is essential for osteoclast formation, function and survival through interaction with its receptor RANK. Mammary glands of RANK- and RANKL-deficient mice develop normally during sexual maturation, but fail to form lobuloalveolar structures during pregnancy because of defective proliferation and increased apoptosis of mammary epithelium. It has been shown that RANKL is responsible for the major proliferative response of mouse mammary epithelium to progesterone during mammary lactational morphogenesis, and in mouse models, manipulated to induce activation of the RANK/RANKL pathway in the absence of strict hormonal control, inappropriate mammary proliferation is observed. However, there is no evidence so far of a functional contribution of RANKL to tumorigenesis. Here we show that RANK and RANKL are expressed within normal, pre-malignant and neoplastic mammary epithelium, and using complementary gain-of-function (mouse mammary tumour virus (MMTV)-RANK transgenic mice) and loss-of function (pharmacological inhibition of RANKL) approaches, define a direct contribution of this pathway in mammary tumorigenesis. Accelerated pre-neoplasias and increased mammary tumour formation were observed in MMTV-RANK transgenic mice after multiparity or treatment with carcinogen and hormone (progesterone). Reciprocally, selective pharmacological inhibition of RANKL attenuated mammary tumour development not only in hormone- and carcinogen-treated MMTV-RANK and wild-type mice, but also in the MMTV-neu transgenic spontaneous tumour model. The reduction in tumorigenesis upon RANKL inhibition was preceded by a reduction in pre-neoplasias as well as rapid and sustained reductions in hormone- and carcinogen-induced mammary epithelial proliferation and cyclin D1 levels. Collectively, our results indicate that RANKL inhibition is acting directly on hormone-induced mammary epithelium at early stages in tumorigenesis, and the permissive contribution of progesterone to increased mammary cancer incidence is due to RANKL-dependent proliferative changes in the mammary epithelium. The current study highlights a potential role for RANKL inhibition in the management of proliferative breast disease.     

Specific protection against breast cancers by cyclin D1 ablation.

Breast cancer is the most common malignancy among women. Most of these cancers overexpress cyclin D1, a component of the core cell-cycle machinery. We previously generated mice lacking cyclin D1 using gene targeting. Here we report that these cyclin D1-deficient mice are resistant to breast cancers induced by the neu and ras oncogenes. However, animals lacking cyclin D1 remain fully sensitive to other oncogenic pathways of the mammary epithelium, such as those driven by c-myc or Wnt-1. Our analyses revealed that, in mammary epithelial cells, the Neu-Ras pathway is connected to the cell-cycle machinery by cyclin D1, explaining the absolute dependency on cyclin D1 for malignant transformation in this tissue. Our results suggest that an anti-cyclin D1 therapy might be highly specific in treating human breast cancers with activated Neu-Ras pathways.     

Generation of a functional mammary gland from a single stem cell

The existence of mammary stem cells (MaSCs) has been postulated from evidence that the mammary gland can be regenerated by transplantation of epithelial fragments in mice. Interest in MaSCs has been further stimulated by their potential role in breast tumorigenesis. However, the identity and purification of MaSCs has proved elusive owing to the lack of defined markers. We isolated discrete populations of mouse mammary cells on the basis of cell-surface markers and identified a subpopulation (Lin-CD29hiCD24+) that is highly enriched for MaSCs by transplantation. Here we show that a single cell, marked with a LacZ transgene, can reconstitute a complete mammary gland in vivo. The transplanted cell contributed to both the luminal and myoepithelial lineages and generated functional lobuloalveolar units during pregnancy. The self-renewing capacity of these cells was demonstrated by serial transplantation of clonal outgrowths. In support of a potential role for MaSCs in breast cancer, the stem-cell-enriched subpopulation was expanded in premalignant mammary tissue from MMTV-wnt-1 mice and contained a higher number of MaSCs. Our data establish that single cells within the Lin-CD29hiCD24+ population are multipotent and self-renewing, properties that define them as MaSCs.     

Distinct stem cells contribute to mammary gland development and maintenance

The mammary epithelium is composed of several cell lineages including luminal, alveolar and myoepithelial cells. Transplantation studies have suggested that the mammary epithelium is maintained by the presence of multipotent mammary stem cells. To define the cellular hierarchy of the mammary gland during physiological conditions, we performed genetic lineage-tracing experiments and clonal analysis of the mouse mammary gland during development, adulthood and pregnancy. We found that in postnatal unperturbed mammary gland, both luminal and myoepithelial lineages contain long-lived unipotent stem cells that display extensive renewing capacities, as demonstrated by their ability to clonally expand during morphogenesis and adult life as well as undergo massive expansion during several cycles of pregnancy. The demonstration that the mammary gland contains different types of long-lived stem cells has profound implications for our understanding of mammary gland physiology and will be instrumental in unravelling the cells at the origin of breast cancers.     

Purification and unique properties of mammary epithelial stem cells

Elucidation of the cellular and molecular mechanisms that maintain mammary epithelial tissue integrity is of broad interest and paramount to the design of more effective treatments for breast cancer. Evidence from both in vitro and in vivo experiments suggests that mammary cell differentiation is a hierarchical process originating in an uncommitted stem cell with self-renewal potential. However, analysis of the properties and regulation of mammary stem cells has been limited by a lack of methods for their prospective isolation. Here we report the use of multi-parameter cell sorting and limiting dilution transplant analysis to demonstrate the purification of a rare subset of adult mouse mammary cells that are able individually to regenerate an entire mammary gland within 6 weeks in vivo while simultaneously executing up to ten symmetrical self-renewal divisions. These mammary stem cells are phenotypically distinct from and give rise to mammary epithelial progenitor cells that produce adherent colonies in vitro. The mammary stem cells are also a rapidly cycling population in the normal adult and have molecular features indicative of a basal position in the mammary epithelium.     

乳房再造成形在乳腺疾病治疗中的应用：（研究技术报告）

乳腺疾病为常见多发病,现代治疗的基本任务是选择既能切除乳腺病变组织,减少致残因素,又能保持体态平衡,提高生活质量的手术方法。作者自80年代初开始研究设计,应用临床至1991年10月止,共施行带蒂皮瓣法乳房成形和乳房再造手术127例233只乳房。通过手术重建乳房,乳房缺陷得到纠正,祛病与形体两全其美,给女性及家庭带来幸福和愉快。     

190例乳腺癌的二维及高频彩色多普勒超声分析

目的:探讨二维及高频彩色超声在乳腺癌诊断中的应用价值.方法:搜集经手术病理证实的190例(193个)乳腺癌,回顾分析二维及彩色多普勒检查结果,着重分析乳腺肿块内部回声的特点、肿块的大小、形态、边界、后方回声、纵横比、微钙化、有无包膜和肿块彩色血流丰富程度、频谱多普勒中的多项测量指标的变化以及腋窝淋巴结转移情况.结果:193个乳腺癌中,肿块形态不规则169个(87.5%),边界不清晰154个(79.7%),内部回声不均匀162个(83.9%),无包膜179个(92.7%),后方回声衰减135个(69.9%),纵横比>1有111个(57.5%),肿块中有微钙化灶86个(44.5%),腋窝淋巴结转移83个(43.0%),179个(92.7%)彩色多普勒血流显像(CDH)检出肿块内及周边血流信号,147个(76.1%)RI≥0.7.结论:乳腺癌的超声表现具有一定的特征性,综合分析二维声像图及CDFI表现,有利于提高乳腺癌超声诊断的正确率.     

Osteoclast differentiation factor RANKL controls development of progestin-driven mammary cancer

Breast cancer is one of the most common cancers in humans and will on average affect up to one in eight women in their lifetime in the United States and Europe. The Women's Health Initiative and the Million Women Study have shown that hormone replacement therapy is associated with an increased risk of incident and fatal breast cancer. In particular, synthetic progesterone derivatives (progestins) such as medroxyprogesterone acetate (MPA), used in millions of women for hormone replacement therapy and contraceptives, markedly increase the risk of developing breast cancer. Here we show that the in vivo administration of MPA triggers massive induction of the key osteoclast differentiation factor RANKL (receptor activator of NF-κB ligand) in mammary-gland epithelial cells. Genetic inactivation of the RANKL receptor RANK in mammary-gland epithelial cells prevents MPA-induced epithelial proliferation, impairs expansion of the CD49f(hi) stem-cell-enriched population, and sensitizes these cells to DNA-damage-induced cell death. Deletion of RANK from the mammary epithelium results in a markedly decreased incidence and delayed onset of MPA-driven mammary cancer. These data show that the RANKL/RANK system controls the incidence and onset of progestin-driven breast cancer.