黏着斑激酶与肿瘤

黏着斑激酶是一种非受体酪氨酸激酶,通过多种信号途径在细胞周期调控、生长调节、黏附、细胞骨架组装、运动、生存等方面发挥重要作用。研究发现,黏着斑激酶在多种肿瘤中高表达,参与肿瘤的发生、发展、侵袭、转移等。黏着斑激酶已成为当前肿瘤研究热点,有可能成为肿瘤治疗的新靶点。     

黏着斑激酶与肿瘤

黏着斑激酶(focal adhesion kinase,FAK)是近几年新发现的一种受体型酪氨酸激酶,它可以调节细胞的增殖、转移和生存等能力,它的异常表达与肿瘤的发生、发展及转移有密切的关系.研究FAK的作用机制、针对FAK靶点进行肿瘤的综合治疗,是肿瘤治疗的一个非常有前途的方向.本文对FAK在肿瘤中的表达、作用机制及其在肿瘤治疗中的应用前景作一综述.

Abstract：

Focal adhesion kinase ( FAK ) is a kind of newly found receptor tyrosine kinase, which can modulate the abilities of cell growth, metastasis and survival. The abnormal expression of FAK can affect the development and metastasis of cancer intimately. A promoting direction of oncotherapy can be applied by the study on FAK mechanism and FAK target. Herein, we will review the the expression of FAK, the action mechanism and the application of FAK target in cancer.     

黏着斑激酶与肿瘤

黏着斑激酶(FAK)最初是在1992年被发现的,因其定位于整合素簇集的部位即黏着斑,故命名为之[1].FAK属非受体酪氨酸激酶家族中的FAK/PTK2亚家族,该亚家族仅有两个成员:FAK(PTK2)和PYK2(PTK2B).FAK在哺乳动物以及低等真核生物如果蝇、斑马鱼等的大多数组织及细胞类型中都有表达,且其序列在进化上具有保守性性[2],而PYK2表达具有一定的组织特异性.     

黏着斑激酶与纤维化

黏着斑激酶（FAK）是一种非受体胞质酪氨酸蛋白激酶,处于细胞内多条信号传导通路的交汇点,活化后可调节多种细胞生物学行为。研究发现,FAK在多种纤维化疾病的发生发展中发挥重要作用,有可能成为纤维化疾病治疗的新途径。     

Focal adhesion kinase in netrin-1 signaling

Netrins are a family of secreted molecules that are important for axonal outgrowth and guidance in the developing nervous system. However, the signaling mechanisms that lie immediately downstream of netrin receptors remain poorly understood. Here we report that the netrin receptor DCC (deleted in colorectal cancer) interacts with the focal adhesion kinase (FAK), a kinase implicated in regulating cell adhesion and migration. FAK was expressed in developing brains and was localized with DCC in cultured neurons. Netrin-1 induced FAK and DCC tyrosine phosphorylation. Disruption of FAK signaling abolished netrin-1-induced neurite outgrowth and attractive growth cone turning. Taken together, these results indicate a new signaling mechanism for DCC, in which FAK is activated upon netrin-1 stimulation and mediates netrin-1 function; they also identify a critical role for FAK in axon navigation.     

Focal adhesion kinase and tumour angiogenesis

Angiogenesis, the formation of new blood vessels from pre-existing ones, is essential for tumour development. It is initiated and regulated by growth factors via their surface receptors, which activate several intracellular signalling pathways in endothelial cells. Cell adhesion molecules, such as integrins, also regulate angiogenesis. Despite these facts, inhibitors of endothelial cell growth factor receptors or integrins have not been as effective as initially hoped in the long-term inhibition of angiogenesis in cancer patients. Signalling downstream of growth factor receptors and integrins converge on the ubiquitously expressed non-receptor tyrosine kinase focal adhesion kinase (FAK). FAK is involved in endothelial cell proliferation, migration and survival, is up-regulated in many cancers and has recently been shown to control tumour angiogenesis. Indeed, FAK inhibitors are presently being developed for the treatment of cancer. However, recent studies have indicated the complexities of understanding the precise role for FAK in angiogenesis. Here we have summarized some of the key features of FAK, addressed some of the apparently contradictory roles of this molecule in angiogenesis and provided some perspectives for future studies.     

Focal adhesion kinase regulates laminin-induced oligodendroglial process outgrowth

In the central nervous system (CNS), myelination of axons occurs when oligodendrocyte progenitor cells undergo terminal differentiation, and initiate process formation and axonal ensheathment. Although Fyn, a member of the Src-family kinases (SFKs), plays an important role in this differentiation process, the substrates of Fyn in oligodendrocytes are largely unknown. Using mass spectrometric analysis, we identified focal adhesion kinase (FAK) as a tyrosine-phosphorylated protein in the rat-derived CG4 oligodendrocyte cell line. Tyrosine phosphorylation of FAK was enhanced during differentiation of CG4 cells in a Fyn-dependent manner. In addition, phosphorylation of FAK was stimulated by laminin, one of the ligands for integrin. Knockdown of FAK expression in CG4 cells suppressed process outgrowth on laminin. Rac1 and Cdc42 activities, which are required for oligodendrocyte process formation, were down-regulated in FAK-knockdown cells. Expression of wild-type (WT) FAK in FAK-knockdown CG4 cells restored outgrowth of processes, but the Y397F mutant lacking the autophosphorylation site did not. These results suggest that FAK/Fyn-mediated activation of Rac1 and Cdc42 is critical for laminin-induced outgrowth of oligodendrocyte processes.     

Recent advances in endometrial neoplasia.

Electron microscopy, Feulgen nuclear DNA-content analysis and in vitro historadioautography with tritiated thymidine significantly objectivate the presently imprecise light microscopic criteria used for distinguishing between adenomatous hyperplasia and carcinoma in situ of the endometrium. Moreover, the changes observed in hyperplastic endometrium seem to be mediated by chronic estrogenic stimulation in the absence of progesterone. The hyperestrogenic morphologic alterations, such as cilia, surface microvilli, primary lysosomal activity and RNA-synthesis are strikingly decreased in early as well as advanced endometrial neoplasia. Failure to express estrogen-dependent cellular specializations in endometrial malignancy seems to be related to the neoplastic dedifferentiation, rather than to the presence or absence of estrogenic stimulation. The results support the concept that carcinoma in situ rather than adenomatous hyperplasia is the immediate precursor of invasive carcinoma of the endometrium. To date, the available evidence is too meager for a definite establishment of a relationship of adenomatous hyperplasia to the development of preinvasive endometrial carcinoma.     

Focal adhesion kinase regulates metastatic adhesion of carcinoma cells within liver sinusoids

Organ-specific tumor cell adhesion to extracellular matrix (ECM) components and cell migration into host organs often involve integrin-mediated cellular processes that can be modified by environmental conditions acting on metastasizing tumor cells, such as shear forces within the blood circulation. Since the focal adhesion kinase (FAK) appears to be essential for the regulation of the integrin-mediated adhesive and migratory properties of tumor cells, its role in early steps of the metastatic cascade was investigated using in vitro and in vivo approaches. Human colon and hepatocellular carcinoma cells were used to study adhesive properties under static conditions and in a parallel plate laminar flow chamber in vitro. In addition, intravital fluorescence microscopy was used to investigate early interactions between circulating tumor cells and the microvasculature of potential target organs in vivo. Shear forces caused by hydrodynamic fluid flow induced Tyr-hyperphosphorylation of FAK in cell monolayers. Reduced expression of FAK or its endogenous inhibition by FAK-related non-kinase (FRNK) interfered with early adhesion events to extracellular matrix components under flow conditions. In contrast, tumor cell adhesion to endothelial cells under these conditions was not affected. Furthermore, down-regulation of FAK inhibited metastatic cell adhesion in vivo within the liver sinusoids. In summary, FAK appears to be involved in early events of integrin-mediated adhesion of circulating carcinoma cells under fluid flow in vitro and in vivo. This kinase may take part in the establishment of definitive adhesive interactions that enable adherent tumor cells to resist fluid shear forces, resulting in an organ-specific formation of distant metastases.     

Focal adhesion kinase signaling at sites of integrin-mediated adhesion controls axon pathfinding

Extracellular matrix (ECM) components regulate neurite outgrowth in tissue culture and in vivo. Live imaging of phosphotyrosine (PY) signals revealed that Xenopus laevis growth cones extending on permissive ECM substrata assemble adhesive point contacts containing enriched levels of tyrosine-phosphorylated proteins. Whereas focal adhesion kinase (FAK) signaling is dispensable for the assembly of focal adhesions in non-neuronal cells, FAK activity is required for the formation of growth cone point contacts. FAK-dependent point contacts promote rapid neurite outgrowth by stabilizing lamellipodial protrusions on permissive ECM substrata. Moreover, local FAK activity is required for ECM-dependent growth cone turning in vitro, suggesting that FAK may control axon pathfinding in vivo. Consistent with this possibility, proper growth and guidance of Rohon-Beard sensory neurons and spinal commissural interneurons requires FAK activity. These findings identify FAK as a key regulator of axon growth and guidance downstream of growth cone-ECM interactions.     

Focal adhesion kinase is a key mediator of human trophoblast development.

Trophoblast differentiation during the first trimester of pregnancy involves cell proliferation and invasion and extracellular matrix (ECM) remodeling. Reports have indicated that, in a variety of cell types, processes such as proliferation, invasion, and ECM remodeling require the turnover of focal adhesions mediated by a cytoplasmic tyrosine kinase named focal adhesion kinase (FAK). Therefore, in the present study we examined the expression and spatial localization of FAK during early human placental development. Immunocytochemical and immunoblot analysis showed that FAK and a focal adhesion-associated protein named paxillin were highly expressed between the 5th and 8th weeks of gestation, specifically in villous cytotrophoblast and extravillous trophoblast (EVT) cells. Activated FAK, phosphorylated on Tyr-397, colocalized with alpha5 integrin and matrix metalloproteinase-2 (MMP2) expression in EVT cells within a previously characterized intermediate, invasive-restrained region. FAK and paxillin expression dramatically decreased after 10 to 12 weeks of gestation coincident with increasing pO(2) levels. Exposure of human villous explants of 5 to 8 weeks to a 3% O(2) environment resulted in increased trophoblast outgrowth, cell proliferation, and detection of alpha5 integrin and MMP2, as well as increased activation of FAK in EVT cells compared with explants grown in a 20% O(2) environment. To determine whether FAK was a key requisite for trophoblast differentiation, villous explants of 5 weeks gestation were grown in Matrigel in a 3% O(2) environment and incubated with 20-mer antisense FAK oligonucleotides. A dramatic reduction of trophoblast outgrowth was observed in antisense-treated explants compared with missense and control cultures, and, in addition, cell proliferation and MMP2 activity in antisense-treated explants were dramatically reduced. These data suggest that FAK is a key kinase involved in early trophoblast cell differentiation and plays a role in regulating cell proliferation and motility during early placental development.     

黏着斑激酶促进人肺动脉平滑纲细胞增生

目的探讨黏着斑激酶(focal adhesion kinase,FAK)是否参与人肺血管平滑肌细胞增殖。方法将纤黏连蛋白(fibronectin,FN)预处理的培养人肺血管平滑肌细胞进行分组,采用不同浓度的FAK正义寡核苷酸转染,应用免疫沉淀及免疫印迹方法测定FAK的活性及蛋白质表达,并利用MTT比色法及3H-TdR掺入法测定细胞增殖情况。结果FAK正义寡核苷酸转染后,FAK的活性及蛋白质表达量均随着剂量增加而增加,呈浓度和时间依赖性地促进细胞增殖及3H-TdR掺入。结论FAK促进人肺动脉平滑肌细胞增殖。     

Prediction of endometrial carcinoma by subjective endometrial intraepithelial neoplasia diagnosis.

Endometrial intraepithelial neoplasia (also known as 'EIN') is a precursor to endometrioid endometrial adenocarcinoma characterized by monoclonal growth of mutated cells, a distinctive histopathologic appearance, and 45-fold elevated cancer risk. We have applied diagnostic criteria for EIN to 97 successive endometrial biopsies classified as hyperplastic according to World Health Organization criteria and correlated results with computer-assisted morphometry (D-score) and clinical cancer outcomes. Three pathologists separately reviewed all cases for presence or absence of EIN using published criteria (gland area>stromal area, cytologic change in focus of altered architecture, lesion size>1 mm, and exclusion of cancer and mimics). Discordant cases were resolved by a consensus review at a multiheaded scope. Clinical outcomes were obtained in 84 patients from patient visit and pathology records. Diagnoses of presence or absence of EIN were unanimous among all three pathologists in 75% of cases, and intraobserver-reproducibility was very good (kappa 0.73-0.90). Cases rediagnosed as EIN encompassed hyperplasias previously diagnosed as atypical (n=18) or nonatypical (eight complex, two simple). Eight follow-up cancers were scattered between hyperplasia types (5/21 atypical, 3/63 nonatypical), but all classified as EIN (8/25) and D-score 相似文献   

Focal adhesion kinase-related protein tyrosine kinase Pyk2 in T-cell activation and function

Pyk2 is a protein tyrosine kinase expressed primarily in brain and hematopoietic cells. It becomes activated in response to stimulation through numerous receptors, including integrins, chemokine receptors, and antigen receptors, and is found in association with src-family kinases. Although this enzyme associates with many proteins known to be important for activation and has many characteristics of a scaffolding protein, its function remains elusive. A number of studies in non-T-cells suggest that Pyk2 is important for cell spreading, cell migration, and integrin function; however, a defined role in T-cells has not been established. Here, we discuss evidence that implicates Pyk2 in directionality of signaling, which is essential to establishment of the directional killing mediated by cytotoxic lymphocytes.     

Focal adhesion kinase (FAK) expression in normal and neoplastic lymphoid tissues

Focal adhesion kinase (FAK) is a protein tyrosine kinase essential for intracellular regulatory events, such as cell growth, differentiation, migration and tumor metastasis. The aim of this study was to analyze the expression of FAK protein in a series of normal and neoplastic lymphoid tissues.An anti-FAK antibody was used to study the protein expression in paraffin-embedded samples of normal and neoplastic, hematolymphoid and non-hematolymphoid tissues by immunohistochemistry. In normal hematolymphoid tissue, the strongest expression of FAK was detected in germinal center and marginal-zone B cells; positive staining was also found in mantle zone B cells. In human lymphomas, FAK was expressed mostly in B-cell lymphomas and was predominantly negative in T-cell lymphoma. In Hodgkin lymphomas, FAK was found only in the neoplastic cells of lymphocyte predominant type, whereas the tumor cells of the classical form were FAK-negative.We demonstrate for the first time the expression of FAK in paraffin-embedded hematolymphoid tissue samples. Its differential expression in lymphomas may be of relevance for some B-cell neoplasms by using it as an additional marker to distinguish B- from T-lymphoblastic leukemia/lymphoma to further differentiate lymphocyte predominant from classical Hodgkin lymphoma.     

Focal adhesion kinase as a marker of malignant phenotype in breast and cervical carcinomas

Integrins mediate cell adhesion to extracellular matrix and stimulate signals involved in cell proliferation, survival, and migration. Focal adhesion kinase (FAK) is considered the central molecule in integrin-mediated signaling. Previously, FAK has been implicated in invasive tumor behavior based on Northern or Western blot (immunoblot) using total tumor tissue homogenates. We used immunohistochemistry to demonstrate FAK expression in benign cervical epithelium, dysplasia, carcinoma in situ (CIS), and invasive cervical squamous cell carcinomas (SCCs), as well as in benign breast tissue, atypical ductal hyperplasia, and ductal carcinoma in situ (DCIS) and invasive carcinomas of the breast. We also used polymerase chain reaction to analyze whether infection with the high-risk human papillomavirus (HPV) subtypes correlated with FAK overexpression in CIS of the cervix. We found minimal FAK expression in benign cervical and breast epithelium and in low-grade squamous dysplasia (CIN I and CIN I-II) of the cervix, and variable FAK expression in CIS lesions of the cervix (10 of 14 cases). Most of the invasive SCCs of the cervix (13 of 16 cases) and DCIS of the breast (6 of 8 cases) were positive for FAK. Surprisingly, all DCIS of the breast were also strongly positive (7 of 7). Only 3 of 13 cases of atypical ductal hyperplasia were focally positive for FAK. Regardless of the intensity of FAK staining, all CIS of the cervix were positive for either HPV 16 or 18. We conclude that FAK overexpression is not restricted to invasive phenotype, but rather appears to be a marker for malignant transformation.