The role of endothelial cells in tumor invasion and metastasis

Summary Metastasis is one of the most devastating aspects of cancer. It is a complex multistep processes that results in spread of tumorigenic cells to secondary sites in various organs. The actual events that are involved in metastasis are the subject of several recent reviews [1–3].Upon growth of neoplastic cells beyond a certain mass (2 mm in diameter) an extensive vascularization through angiogenesis occurs. The new capillary network provides a supply of nutrients and gas exchange that allows further growth and development of the tumor mass. The network of the blood vessels also provides an entry site into the circulation for the neoplastic cells that detach from the tumor mass. Only a small percentage of circulating tumor cells (< 0.01%) survive travel in the circulation and arrest in the capillary beds of distant organs, extravasate and proliferate within the organ parenchyma producing a successful metastasis [1].Vasculature plays an important role in several steps of the metastatic process; 1) at the site of metastasis, vessels capture the cancer cell and provide the entry route into the secondary organ, and 2) through angiogenesis, vascular endothelial cells provide the supply of nutrients for the growth of the primary tumor mass and the route of intravasation. The lining of all blood vessels are covered with endothelial cells which play an active role in both processes. The metastatic properties of cancer cells have been extensively studied. Here, we will discuss the role of endothelial cells in the metastatic process with focus on their interaction with cancer cells at the site of extravasation.     

Fibroblast growth factor-2 but not Mel-CAM and/or beta3 integrin promotes progression of melanocytes to melanoma

A variety of melanoma-associated antigens have been identified that mediate adhesion, growth, proteolysis, and modulation of immune response. However, the mechanisms by which human normal melanocytes become malignant are not clearly understood. Among the most consistent observations is the up-regulation of fibroblast growth factor-2 (FGF-2) and of the adhesion molecules beta3 integrin and Mel-CAM during melanoma progression. To evaluate the potential role of FGF-2, beta3 integrin and Mel-CAM in melanoma development we overexpressed FGF-2, beta3 integrin and Mel-CAM in normal human melanocytes using replication-deficient adenoviruses as a gene delivery vehicle. Fibroblast growth factor-2 overexpressing melanocytes in monolayer culture displayed cytological atypia. Furthermore, in human skin reconstructs where the physiological milieu is recreated in vitro, FGF-2-overexpressing melanocytes exhibited marked proliferation, upwards migration, cluster formation and type IV collagen expression within the epidermal compartment, simulating early radial growth phase melanoma. In contrast, overexpression of beta3 integrin and/or Mel-CAM in melanocytes did not affect their biological behaviour in human skin reconstructs. The described results of the current and previous studies emphasise the key role of FGF-2 in melanoma development and progression, underscoring the promise of FGF-2 as a target for therapy.     

整合素α5β1与恶性肿瘤侵袭转移关系的研究进展

目的：综述整合素α5β1与恶性肿瘤侵袭转移的关系。方法：查阅国内外相关文献进行分析和归纳。结果：α5β1是整合素家族的一员，参与肿瘤的发生、发展与转移。而这种作用可能是通过影响肿瘤细胞与细胞外基质的黏附、细胞外基质的水解、诱导肿瘤血管的生成、调节肿瘤细胞的凋亡等作用而实现的。结论：深入研究α5β1在恶性肿瘤中的表达与功能，有助于进一步认识恶性肿瘤侵袭转移的分子机制，且有可能为恶性肿瘤的诊断和预后判断提供新的指标。     

围排卵期应用左炔诺孕酮对着床期子宫内膜整合素表达的影响

目的:研究合成孕激素左炔诺孕酮对子宫内膜着床期整合素亚单位表达的影响。方法:20名妇女,随机分为两组,在LH-2日(LH-2组)或LH+2日(LH+2组)服用左炔诺孕酮0.75 mg/次,bid。每组妇女在服药周期前一个周期于LH-2日或LH+2日服用安慰剂,作为对照周期。两组均以超声波和尿LH峰检测确定服药日。每一周期均于LH+7日取子宫内膜标本。用整合素亚单位a1、a4、avb3抗体,以免疫组化和计算机图象分析方法检测和评价这些亚单位的表达。结果:两组在服用左炔诺酮后亚单位a1染色强度降低,但avb3无变化。亚单位a4在LH-2组明显降低,在LH+2组则差别不明显,而两组集合也是明显降低的。结论:妇女紧急避孕应用左炔诺酮后,其子宫内膜整合素亚单位a1和a4的表达与甾体激素的调控密切相关,有关机理尚需进一步研究。     

整合素和粘着斑激酶在JWA基因抑制诱导的人肺动脉平滑肌细胞迁移调控中的作用

目的探讨整合素和粘着斑激酶是否在JWA基因抑制诱导的人肺动脉平滑肌细胞（PASMCs）迁移调控中起作用。方法前期实验将JWA核酶基因构建到逆转录病毒载体pLXSN上，转染人体外培养的人PASMCs内，并证实转染的JWA特异性核酶基因能抑制PASMCs内JWA基因的表达。该研究应用改良Boyden小室法测定细胞迁移情况．半定量RT-PCR（sqRT-PCR）法测定细胞内整合素αv、整合素β3。粘着斑激酶的mRNA表达量．Western blot法检测细胞内整合素αv、整合素β3、粘着斑激酶的蛋白表达量。结果与空载体转染细胞（P-pLXSN组）及未转染细胞（PASMCs组）比较．转染JWA核酶基因的细胞（P-JWARZ组）迁移率显著增加，细胞内整合素αv、整合素β3、粘着斑激酶的mRNA及蛋白表达量均显著增加。结论整合素、粘着斑激酶信号通路可能在JWA基因抑制诱导的人肺动脉平滑肌细胞迁移中起调控作用。     

Activated human platelets express β2 integrin

Abstract: The expression of molecules of the β2 integrin family (CD11a, CD11b, CD11c and CD18) was explored on 2 human megakaryocytic cell lines and on platelets from different donors by immunofluorescence and flow cytometry using a large panel of mAb. CD11a, CD11b, CD11c and CD18 were detected on the megakaryocytic cell lines DAMI and HEL. A low and variable expression of CD11a, CD11b and CD18 determinants was also detected on resting platelets: this expression was markedly increased when platelets were activated by thrombin. Expression of CD18 was closely correlated to that of CD11a or CD11b when comparing the fluorescence intensity observed in different experiments. In presence of Ca⁺⁺, platelets did bind to a RAJI cell line which exhibits a high expression level of CD54. This binding was increased when platelets were activated by thrombin and was decreased by an anti CD11a, CD18 and anti CD54 mAb. This study indicates that human platelets express molecules of the β2 integrin family, when activated, which allows them to bind to CD54 bearing cells.     

Molecular mechanisms of sperm–egg interactions and egg activation

Summary.  The binding of acrosome reacted mammalian sperm to the egg plasma membrane initiates a series of signaling events in the egg, termed "egg activation", which lead to the completion of meiosis II and the initiation of a mitotic cell cycle. Many of these signaling events have characteristics of classical signal transduction events in somatic cells. Currently, there are two hypotheses for how sperm-induced egg activation is initiated. In the "receptor" hypothesis, the fertilizing sperm interacts with a specific egg surface receptor, and this interaction leads to signal transduction and effector activation. In the "fusion" hypothesis it is postulated that following fusion of the sperm and egg plasma membranes a soluble sperm-derived factor enters the egg's cytoplasm and activates pathways leading to egg activation. This chapter will provide an overview of the processes of cell–cell interaction and signal transduction leading to mammalian egg activation. It will concentrate on specific molecules proposed to be involved in sperm-egg interaction, signal transduction and effector mechanisms involved in egg activation, and a discussion of sperm-associated factors that have been implicated in egg activation.     

Reelin, integrin and DAB1 interactions during embryonic cerebral cortical development

Extracellular matrix-like molecule reelin and cell surface adhesion receptors such as alpha3beta1 integrin can regulate neuronal migration and position in the developing cerebral cortex. Here we show that alpha3beta1 integrin binds to the N-terminal region of reelin, a site distinct from the region of reelin shown to associate with other reelin receptors such as VLDLR/ApoER2. Furthermore, Dab1, a member of the reelin signaling pathway, can complex with the cytoplasmic region of beta1 integrin in a reelin-dependent manner. Thus, alpha3beta1 integrin-reelin interactions may contribute to appropriate neuronal placement in the developing cerebral cortex.     

CrkII regulates focal adhesion kinase activation by making a complex with Crk-associated substrate, p130Cas

CrkII is an adaptor protein possessing oncogenic potential despite the lack of an enzymatic domain. We investigated here the physiological functions of CrkII by studying its ability to induce anchorage-independent cell growth. We found that inhibition or null mutation of focal adhesion kinase (FAK) blocked the anchorage-independent growth induced by CrkII overexpression, indicating that FAK is a critical determinant of the transforming activity of CrkII. CrkII overexpression enhanced the autophosphorylation of FAK at Tyr-397 and tyrosine phosphorylation of p130(Cas) (Crk-associated substrate, Cas) upon stimulation of integrin by fibronectin. Moreover, the constitutive phosphorylation of FAK and Cas was observed in CrkII-overexpressing cells, even when they were in the suspended condition, consistent with the ability of CrkII to induce anchorage-independent growth. Using Cas-deficient cells, we showed Cas function to be essential for both the CrkII-induced phosphorylation of FAK (Tyr-397) and anchorage-independent cell growth. The CrkII-induced FAK autophosphorylation depended upon CrkII-Cas complex formation. Furthermore, we showed that CrkII knockdown resulted in defects in integrin-mediated events, such as cell spreading, haptotactic migration, and FAK autophosphorylation. The integrin-mediated FAK autophosphorylation was also reduced in Cas-deficient cells. These results suggest that the CrkII-Cas complex functions in integrin-mediated FAK activation signaling. Our findings show the importance of CrkII in integrin-mediated events, acting upstream of FAK to affect the activation of this kinase, which appears to have a central role in this pathway.