环氧合酶-2在大肠癌组织中的表达及临床意义的研究

目的探讨COX-2蛋白在大肠癌中的表达与肿瘤发生发展和转移的关系.方法应用免疫组化SP法检测COX-2蛋白在66例大肠癌及22例正常大肠组织的表达情况.结果COX-2蛋白在66例大肠癌组织中高表达(56/66),阳性表达率84.8%,与正常大肠组织相比差异有显著性(P<0.01);COX-2蛋白的表达与肿瘤组织的浸润深度显著相关(P<0.05);与Dukes分期呈正相关(P<0.05);淋巴结有转移组与无转移组差异有显著性(P<0.05).结论COX-2在大肠癌的发生、发展及浸润、转移过程中发挥着重要作用,可望成为预测大肠癌恶性潜能的临床指标之一.     

低氧通过HIF-2α诱导CCNE2表达的初步研究

低氧是肿瘤发生侵袭转移必经的过程之一,它促进了肿瘤致癌基因的表达,从而使肿瘤细胞发生远处转移.低氧环境对于调节肿瘤的EMT过程具有重要作用,刺激肿瘤的恶化和转移,也可促进血管激活因子的表达从而促进肿瘤血管的形成.CCNE2作为调节细胞周期的关键基因,在肿瘤发生和转移过程中的作用已经得到广泛研究,在多种癌细胞中都发现CCNE2蛋白是高表达的.为此在MCF-7细胞中通过一系列的实验证明了CCNE2是一个新的低氧靶基因,并证明了低氧通过刺激HIF-2α促进了CCNE2的表达.     

低氧通过HIF-2α诱导CCNE2表达的初步研究

低氧是肿瘤发生侵袭转移必经的过程之一,它促进了肿瘤致癌基因的表达,从而使肿瘤细胞发生远处转移.低氧环境对于调节肿瘤的EMT过程具有重要作用,刺激肿瘤的恶化和转移,也可促进血管激活因子的表达从而促进肿瘤血管的形成.CCNE2作为调节细胞周期的关键基因,在肿瘤发生和转移过程中的作用已经得到广泛研究,在多种癌细胞中都发现CCNE2蛋白是高表达的.为此在MCF-7细胞中通过一系列的实验证明了CCNE2是一个新的低氧靶基因,并证明了低氧通过刺激HIF-2α促进了CCNE2的表达.     

上海科普大讲坛第二十二讲(上)科学认识肠癌的防护与治疗

据悉上海地区大肠癌发病率已经占所有肿瘤的第二位,肺癌第一位,特别是近50年来随着生活水平不断提高,大肠癌发病也增长了5倍多.它犹如一只隐形的老虎吞噬着人们的健康.谈癌色变依然是很多人对它的第一反应,但是癌症绝对不等同于末日.在全身各个部位的恶性肿瘤,尤其是消化道肿瘤当中大肠癌是治疗效果最好的肿瘤之一,通过规范化的,多学科的综合治疗,可以使相当一部分大肠癌患者完全治愈. 那么我们,尤其是青年人应当如何更好地呵护肠癌,预防大肠癌的发生?我国医学界对于大肠癌肝脏转移的治疗方式又有哪些?     

Ang-2在大肠癌血管生成和肿瘤生长中的作用

目的探讨促血管生成素Ⅱ(Angiopoietin-2，Ang-2)在肠腺瘤和大肠癌组织生长和血管生成中的作用。方法采用免疫组化实验方法检测62例大肠癌和30例肠腺瘤手术标本中Ang-2、CD-34和ki67蛋白表达量，同时以16例正常大肠粘膜组织作对照。结果Ang-2、ki67蛋白和微血管密度(MVD)在大肠癌和肠腺瘤组织中均有高表达，正常大肠粘膜组织表达量少；肠癌组织表达水平明显高于肠腺瘤样组织，且两者均高于正常对照组；肠癌Ang-2与MVD和ki67在相应组织中的表达成正相关。结论肠癌和肠腺瘤组织中过多表达Ang-2与肿瘤血管和肿瘤生长密切相关，Ang-2在大肠癌血管生成及其肿瘤发生、发展过程中起着重要作用。     

血管内皮生长因子-C及其受体Flt-4在大肠癌组织中表达的意义

目的：探讨血管内皮生长因子C(VEGF-C)及其Flt-4受体在大肠癌的表达与淋巴管新生及转移的关系。方法：对58例大肠癌组织及12例正常肠黏膜进行VEGF-C、FLt-4及CD34免疫组织化学染色，并计数微淋巴管密度(LMVD)和血管密度(MVD)。结果：VEGF-C在大肠癌中的表达明显高于正常黏膜(P＜O．01)。大肠癌VEGF-C表达与淋巴结转移及Dukes分期呈显正相关(P＜O．01)。大肠癌微淋巴管密度(LMVD)与淋巴结转移呈正相关(P＜O．01)。结论：VEGF-C在大肠癌中表达升高，可能通过旁分泌方式作用于Flt-4信号通路引发淋巴管新生，有助于发生淋巴结转移；VEGF-C对判断大肠癌预后有辅助作用。     

肿瘤新生血管抑制剂——血管抑素和内皮抑素

血管抑素和内皮抑素是两种内源性肿瘤新生血管抑制剂，主要通过抑制肿瘤内皮细胞的生长达到抑制肿瘤血管生成、诱导肿瘤细胞凋亡、防止肿瘤侵袭和转移的目的。作为两种最有前途的肿瘤新生血管抑制剂克服了肿瘤化疗过程中产生的耐药抗药性。文中对这两种抑制剂的结构与功能及应用研究最新进展作一综述。     

大肠癌中DCC基因表达及其临床意义

目的：探讨大肠癌中DCC蛋白表达及其生物学行为的关系。方法：采用免疫组化法检测45例正常大肠组织、57例大肠癌组织DCC蛋白的表达情况。结果：大肠癌组织DCC蛋白阳性表达率为31．6％,明显低于大肠正常组织（100％）,两组差异显著（P〈0．05）,且DCC的表达与大肠癌分化程度、浸润转移及淋巴结转移显著相关（P〈0．05）,但与患者的性别、年龄、肿瘤部位等无相关性。结论：DCC表达缺失与大肠癌的分化、侵袭、转移有关,可判断大肠癌的预后。     

大肠癌微转移肿瘤标记物检测的研究

大肠癌在我国发病率高且预后较差,根治术后仍有近30%的患者死于肿瘤复发,其原因与微转移的发生密切相关.选用敏感性的检测方法和特异性的标志物检测大肠癌微转移对患者的复发、预后和临床治疗有重要的意义.     

AgNOR和p53在大肠癌中的表达

目的研究AgNOR和p53在大肠癌中的表达及其与大肠癌发生、发展及预后的关系.方法选用大肠癌组织标本80例及相应的癌旁组织标本40例,采用AgNOR染色技术和免疫组织化学法检测大肠癌组织及癌旁组织中AgNOR计数和p53的表达.结果大肠癌中AgNOR计数显著升高,细胞核内AgNOR计数、颗粒分布及形态特点与大肠癌的分化程度、淋巴结转移有相关性(P<0.05);p53在大肠癌组的阳性表达率为66.3%,在癌旁组的阳性表达率为20.8%.两者之间存在显著性差异(P<0.01);大肠癌组织中p53的阳性表达与大肠癌的分化程度、淋巴结转移有相关性(P<0.05),而与大肠癌的发病年龄、性别无关(P>0.05).结论 p53的突变在大肠癌的形成和发展中起了促进作用,AgNOR测定对大肠癌的病理学分级有一定的价值,同时说明AgNOR和p53有可能作为大肠癌发生、发展及预后的肿瘤标志.     

血管内皮生长因子(VEGF)与肝再生

血管内皮生长因子(vascularendothelialgrowthfactor,VEGF)能特异地直接作用于血管内皮细胞,刺激血管内皮细胞的分裂、增殖并诱导血管的形成.它通过与血管内皮细胞的受体结合发挥作用.肝受到各种损伤包括部分肝切除后,肝再生就得以启动.在肝再生过程中,VEGF对内皮细胞的生长增殖起有效促进作用,并且能诱导组织胶原酶、血纤维蛋白酶原的激活,增加血管的通透性,这对血管再生起着极其重要的作用.而血管再生是肝再生的一个重要组成部分,它不仅能给肝细胞提供血液支持,而且能促进肝脏结构的重构.因此VEGF在肝再生过程中具有重要的作用.     

Ultrastructural localization of choline acetyltransferase in vascular endothelial cells in rat brain

Furchgott and Zawadski have shown that acetylcholine (ACh) does not act directly on the smooth muscle of blood vessel walls, but rather via receptors on the endothelial cells lining the lumen, to release an endothelium-derived relaxing factor (EDRF). As it is very unlikely that neurotransmitter released from the periarterial nerves, which are confined to the adventitial-medial border, diffuses all the way through the medial muscle coat before acting on endothelial cells to release EDRF to produce vasodilatation, this discovery has been regarded as an indication of a pathophysiological mechanism, rather than a physiological one (see refs 2, 3). ACh is rapidly degraded in the blood by acetylcholinesterase, so that ACh must be released locally to be effective on endothelial cells. Here we demonstrate the immunocytochemical localization of choline acetyltransferase in endothelial cells of small brain vessels, which is consistent with the view that the ACh originates from endothelial cells that can synthesize and store it. We suggest that release of ACh following damage to endothelial cells during ischaemia contributes to a pathophysiological mechanism of vasodilation which protects that segment of vessel from further damage as well as brain cells from hypoxia.     

A role for VEGF as a negative regulator of pericyte function and vessel maturation

Angiogenesis does not only depend on endothelial cell invasion and proliferation: it also requires pericyte coverage of vascular sprouts for vessel stabilization. These processes are coordinated by vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) through their cognate receptors on endothelial cells and vascular smooth muscle cells (VSMCs), respectively. PDGF induces neovascularization by priming VSMCs/pericytes to release pro-angiogenic mediators. Although VEGF directly stimulates endothelial cell proliferation and migration, its role in pericyte biology is less clear. Here we define a role for VEGF as an inhibitor of neovascularization on the basis of its capacity to disrupt VSMC function. Specifically, under conditions of PDGF-mediated angiogenesis, VEGF ablates pericyte coverage of nascent vascular sprouts, leading to vessel destabilization. At the molecular level, VEGF-mediated activation of VEGF-R2 suppresses PDGF-Rbeta signalling in VSMCs through the assembly of a previously undescribed receptor complex consisting of PDGF-Rbeta and VEGF-R2. Inhibition of VEGF-R2 not only prevents assembly of this receptor complex but also restores angiogenesis in tissues exposed to both VEGF and PDGF. Finally, genetic deletion of tumour cell VEGF disrupts PDGF-Rbeta/VEGF-R2 complex formation and increases tumour vessel maturation. These findings underscore the importance of VSMCs/pericytes in neovascularization and reveal a dichotomous role for VEGF and VEGF-R2 signalling as both a promoter of endothelial cell function and a negative regulator of VSMCs and vessel maturation.     

Macrophage-induced angiogenesis is mediated by tumour necrosis factor-alpha

Macrophages are important in the induction of new blood vessel growth during wound repair, inflammation and tumour growth. We show here that tumour necrosis factor-alpha (TNF-alpha), a secretory product of activated macrophages that is believed to mediate tumour cytotoxicity, is a potent inducer of new blood vessel growth (angiogenesis). In vivo, TNF-alpha induces capillary blood vessel formation in the rat cornea and the developing chick chorioallantoic membrane at very low doses. In vitro, TNF-alpha stimulates chemotaxis of bovine adrenal capillary endothelial cells and induces cultures of these cells grown on type-1 collagen gels to form capillary-tube-like structures. The angiogenic activity produced by activated murine peritoneal macrophages is completely neutralized by a polyclonal antibody to TNF-alpha, suggesting immunological features are common to TNF-alpha and the protein responsible for macrophage-derived angiogenic activity. In inflammation and wound repair, TNF-alpha could augment repair by stimulating new blood vessel growth; in tumours, TNF-alpha might both stimulate tumour development by promoting vessel growth and participate in tumour destruction by direct cytotoxicity.     

Molecular mechanisms and clinical applications of angiogenesis

Blood vessels deliver oxygen and nutrients to every part of the body, but also nourish diseases such as cancer. Over the past decade, our understanding of the molecular mechanisms of angiogenesis (blood vessel growth) has increased at an explosive rate and has led to the approval of anti-angiogenic drugs for cancer and eye diseases. So far, hundreds of thousands of patients have benefited from blockers of the angiogenic protein vascular endothelial growth factor, but limited efficacy and resistance remain outstanding problems. Recent preclinical and clinical studies have shown new molecular targets and principles, which may provide avenues for improving the therapeutic benefit from anti-angiogenic strategies.     

Proliferation and differentiation into endothelial cells of human bone marrow mesenchymal stem cells （MSCs） on poly DL-lactic-co-glycolic acid （PLGA） films

Autologous, allograft and synthetic vessels currently used in clinical vessel replacement have many defi- ciencies, especially in the area of small caliber vessel replacement. The supply of autologous arteries or veins may not be sufficient or suitable fo…     

Regulation of angiogenesis by a non-canonical Wnt-Flt1 pathway in myeloid cells

Myeloid cells are a feature of most tissues. Here we show that during development, retinal myeloid cells (RMCs) produce Wnt ligands to regulate blood vessel branching. In the mouse retina, where angiogenesis occurs postnatally, somatic deletion in RMCs of the Wnt ligand transporter Wntless results in increased angiogenesis in the deeper layers. We also show that mutation of Wnt5a and Wnt11 results in increased angiogenesis and that these ligands elicit RMC responses via a non-canonical Wnt pathway. Using cultured myeloid-like cells and RMC somatic deletion of Flt1, we show that an effector of Wnt-dependent suppression of angiogenesis by RMCs is Flt1, a naturally occurring inhibitor of vascular endothelial growth factor (VEGF). These findings indicate that resident myeloid cells can use a non-canonical, Wnt-Flt1 pathway to suppress angiogenic branching.     

Acetylation-dependent regulation of endothelial Notch signalling by the SIRT1 deacetylase

Notch signalling is a key intercellular communication mechanism that is essential for cell specification and tissue patterning, and which coordinates critical steps of blood vessel growth. Although subtle alterations in Notch activity suffice to elicit profound differences in endothelial behaviour and blood vessel formation, little is known about the regulation and adaptation of endothelial Notch responses. Here we report that the NAD(+)-dependent deacetylase SIRT1 acts as an intrinsic negative modulator of Notch signalling in endothelial cells. We show that acetylation of the Notch1 intracellular domain (NICD) on conserved lysines controls the amplitude and duration of Notch responses by altering NICD protein turnover. SIRT1 associates with NICD and functions as a NICD deacetylase, which opposes the acetylation-induced NICD stabilization. Consequently, endothelial cells lacking SIRT1 activity are sensitized to Notch signalling, resulting in impaired growth, sprout elongation and enhanced Notch target gene expression in response to DLL4 stimulation, thereby promoting a non-sprouting, stalk-cell-like phenotype. In vivo, inactivation of Sirt1 in zebrafish and mice causes reduced vascular branching and density as a consequence of enhanced Notch signalling. Our findings identify reversible acetylation of the NICD as a molecular mechanism to adapt the dynamics of Notch signalling, and indicate that SIRT1 acts as rheostat to fine-tune endothelial Notch responses.     

Controlled growth factor release from synthetic extracellular matrices

Polymeric matrices can be used to grow new tissues and organs, and the delivery of growth factors from these matrices is one method to regenerate tissues. A problem with engineering tissues that exist in a mechanically dynamic environment, such as bone, muscle and blood vessels, is that most drug delivery systems have been designed to operate under static conditions. We thought that polymeric matrices, which release growth factors in response to mechanical signals, might provide a new approach to guide tissue formation in mechanically stressed environments. Critical design features for this type of system include the ability to undergo repeated deformation, and a reversible binding of the protein growth factors to polymeric matrices to allow for responses to repeated stimuli. Here we report a model delivery system that can respond to mechanical signalling and upregulate the release of a growth factor to promote blood vessel formation. This approach may find a number of applications, including regeneration and engineering of new tissues and more general drug-delivery applications.     

Dll4 signalling through Notch1 regulates formation of tip cells during angiogenesis

In sprouting angiogenesis, specialized endothelial tip cells lead the outgrowth of blood-vessel sprouts towards gradients of vascular endothelial growth factor (VEGF)-A. VEGF-A is also essential for the induction of endothelial tip cells, but it is not known how single tip cells are selected to lead each vessel sprout, and how tip-cell numbers are determined. Here we present evidence that delta-like 4 (Dll4)-Notch1 signalling regulates the formation of appropriate numbers of tip cells to control vessel sprouting and branching in the mouse retina. We show that inhibition of Notch signalling using gamma-secretase inhibitors, genetic inactivation of one allele of the endothelial Notch ligand Dll4, or endothelial-specific genetic deletion of Notch1, all promote increased numbers of tip cells. Conversely, activation of Notch by a soluble jagged1 peptide leads to fewer tip cells and vessel branches. Dll4 and reporters of Notch signalling are distributed in a mosaic pattern among endothelial cells of actively sprouting retinal vessels. At this location, Notch1-deleted endothelial cells preferentially assume tip-cell characteristics. Together, our results suggest that Dll4-Notch1 signalling between the endothelial cells within the angiogenic sprout serves to restrict tip-cell formation in response to VEGF, thereby establishing the adequate ratio between tip and stalk cells required for correct sprouting and branching patterns. This model offers an explanation for the dose-dependency and haploinsufficiency of the Dll4 gene, and indicates that modulators of Dll4 or Notch signalling, such as gamma-secretase inhibitors developed for Alzheimer's disease, might find usage as pharmacological regulators of angiogenesis.