CD44 regulates cell migration in human colon cancer cells via Lyn kinase and AKT phosphorylation

Colon cancer is among the leading causes of cancer death in North America. CD44, an adhesion and antiapoptotic molecule is overexpressed in colon cancer. Cofilin is involved in the directional motility of cells. In the present study, we looked at how CD44 might modulate cell migration in human colon cancer via cofilin. We used a human colon cancer cell line, HT29, which expresses CD44, HT29 where CD44 expression was knocked down by siRNA, SW620, a human colon cancer cell line which does not express CD44, stably transfected exons of CD44 in SW620 cells and the colon from CD44 knockout and wild-type mouse. Western blot analysis of siRNA CD44 lysates showed increased level of AKT phosphorylation and decreased level of cofilin expression. Similar results were also observed with SW620 cells and CD44 knockout mouse colon lysates. Experiments using the AKT phosphorylation inhibitor LY294002 indicate that AKT phosphorylation downregulates cofilin. Immunoprecipitation studies showed CD44 complex formation with Lyn, providing an essential link between CD44 and AKT phosphorylation. LY294002 also stabilized Lyn from phosphorylated AKT, suggesting an interaction between Lyn and AKT phosphorylation. Immunocytochemistry showed that cofilin and Lyn expression were downregulated in siRNA CD44 cells and CD44 knockout mouse colon. siRNA CD44 cells had significantly less migration compared to HT29 vector. Given the well-defined roles of CD44, phosphorylated AKT in apoptosis and cancer, these results indicate that CD44-induced cell migration is dependent on its complex formation with Lyn and its consequent regulation of AKT phosphorylation and cofilin expression.     

Heterogeneity of CD44 expression among human B-cell subpopulations

Abstract: CD44 is a widely distributed cell surface glycoprotein that participates in a number of cellular adhesion and signal transduction processes. Germinal center B cells express very low levels of CD44, whereas their precursors and differentiation products express much higher levels. In immunofluorescence studies comparing 20 antibodies classified as being against the hematopoietic isoform of CD44, one antibody, AIG3, was unreactive with germinal center B cells, whereas the other antibodies showed low intensity but definite reactivity. Western blotting and sequential immunoprecipitation studies of lysates from density-separated lymphocyte fractions showed two bands that were differentially expressed and reacted differently with AIG3 compared with the other CD44 antibodies. These results suggest that germinal center B cells and non-germinal center B cells express different forms of CD44.Of 21 malignant B-cell populations examined, 5 showed reactivity with a "standard" CD44 reagent and significantly reduced reactivity with AIG3, while one sample showed the opposite pattern and the remainder were positive for both reagents. Of 10 cell lines studied, 5 were differentially stained by AIG3 and a standard CD44 antibody. PCR amplification of reverse transcribed mRNA from sorted human tonsil B-cell subpopulations and Southern blotting showed that B cells express a number of splice isoforms of CD44. These results demonstrate that B cells express multiple forms of CD44; both splice insert isoforms and variants distinguished by AIG3; the form of CD44 expressed depends on B-cell differentiation state.     

Tyrosine kinase-dependent activation of human NK cell functions upon triggering through CD44 receptor

We recently showed evidence of CD44-mediated enhancement of natural killer (NK) cell cytotoxic activity and induction of intracellular Ca²⁺ flux. In this study, we evaluated whether CD44 plays a stimulatory role in NK cell functions, such as cytokine production and activation antigen expression. Our results indicate that ligation of the CD44 receptor results in the induction of expression of the CD69 surface activation antigen as well as in the enhancement of phorbol ester-induced TNF-α secretion. We report also evidence for the coupling of CD44 receptor to a protein tyrosine kinase(s) pathway. CD44 engagement rapidly stimulates the tyrosine phosphorylation of several cellular substrates. Pretreatment of NK cells with the tyrosine kinase inhibitor herbimycin A resulted in marked decrease of CD44-stimulated phosphorylation, indicating that it activates tyrosine kinase(s). Furthermore, the drug also prevents CD44-mediated TNF-α production and CD69 expression. These findings indicate that protein tyrosine phosphorylation is an early and critical event in CD44-mediated activation of NK cell functions.     

人CD44新剪接变异体克隆及分析

目的：应用逆转录多聚酶链式反应（RT-PCR）分析CD44在鼻咽癌组织和鼻咽癌细胞株中表达，来寻找新的人CD44剪接变异体。方法：在CD44基因起始和终止密码子两端及变异剪接外显子v10中和剪接位点处设计特异性引物，以鼻咽癌组织、细胞株5-8F和HNE1 cDNA为模板进行RT-PCR扩增，产物测序。然后，应用生物信息学对克隆序列进行分析。结果：新克隆的CD44剪接变异体有1634bp，包含一个完整的阅读框，起始密码子在序列的12位，终止密码子在序列的1301位，可变剪接区只有变异型剪接外显子10，预测编码429氨基酸。GenBank登陆号：EF581837。结论：一个新的、预测编码429个氨基酸的CD44剪接变异体存在于研究的人鼻咽癌组织和细胞株中，它的功能有待于进一步研究。     

CD44 and its partners in metastasis

The establishment of metastasis requires that tumor cells acquire new adhesion and migration properties to emigrate from primary sites and colonize distant organs. CD44 is a cell membrane protein often overexpressed on tumor cells and, being both a cell–cell and cell–extracellular matrix adhesion protein, is well positioned to contribute to this process. Furthermore the interaction of CD44 with other cellular proteins involved in motogenesis and proteolysis is a determinant factor in cell migration and invasion. This review summarizes current knowledge on the role of CD44 in metastasis, as well as the challenges on understanding how this process operates. This revised version was published online in July 2006 with corrections to the Cover Date.     

他莫昔芬抑制胶质瘤细胞系SHG-44增殖及钠通道电流

目的 研究他莫昔芬对SHG-44胶质瘤细胞的增殖及其细胞膜上钠通道电流的作用.方法 用四唑盐比色试验分析细胞活性,通过流式细胞仪检测细胞增殖和凋亡.以全细胞膜片钳法记录SHG-44细胞的钠通道电流.结果 加入他莫昔芬后,SHG-44细胞变老、脱落,细胞总数减少.他莫昔芬组G2/M期细胞较对照组增多,凋亡细胞比例增加.钠通道电流特性为内向电流、快速激活失活.他莫昔芬可剂量依赖性及电压依赖性阻断该电流.在0 mV时,8 μmol/L他莫昔芬对钠通道电流抑制率为69%.半数抑制浓度(IC50)为5.54 μmol/L.结论 他莫昔芬可明显阻断SHG-44胶质瘤细胞上的钠通道,这可能是其抑制胶质瘤细胞增殖的机制之一.     

血管细胞黏附分子-1增强人脑胶质瘤细胞系迁移和侵袭能力

目的探讨血管细胞黏附分子-1(VCAM-1)在脑胶质瘤细胞迁移侵袭能力中作用。方法用慢病毒p SGU6/GFP/Neo介导VCAM-1的shRNA、慢病毒EF1a-GFP/puro介导VCAM-1过表达载体、划痕迁移、Transwell侵袭、蛋白免疫印迹(Western blot)和细胞染色等实验技术和方法,观察了VCAM-1蛋白表达水平对人脑胶质瘤T98G和U251细胞系细胞迁移和侵袭能力的影响。其中,T98G细胞分为空白对照组、空载体对照组、乱序对照组和实验组(抑制VCAM-1蛋白表达水平组),U251细胞分为空白对照组、空载体对照组和实验组(过表达VCAM-1组),每组6个复孔。结果首先利用慢病毒介导VCAM-1的shRNA和过表达载体建立了稳定低表达VCAM-1的T98G细胞和稳定过表达VCAM-1的U251细胞。稳定低表达VCAM-1的T98G细胞划痕恢复能力(迁移能力)明显减弱(P0.01);而稳定过表达VCAM-1的U251细胞迁移能力明显提高(P0.05)。同样,稳定低表达VCAM-1的T98G细胞侵袭能力显著减弱(P0.05);而稳定过表达VCAM-1的U251细胞侵袭能力明显增强(P0.01)。结论VCAM-1可显著增强人脑胶质瘤细胞系细胞的迁移和侵袭能力。     

Palmitoylation of CD44 interferes with CD3-mediated signaling in human T lymphocytes

We studied the interactions between CD44 and four differentmonoclonal antl-CD44 antibodies. All four monoclonal anti-CD44antibodies studied (P3H9, Bu52, IM.7, and GKW.A3) act in synergywith human anti-CD2 antibodies in stimulating normal human peripheralblood lymphocytes to proliferate. GKW.A3 and IM.7 but not P3H9or Bu52 Inhibited the proliferation of normal human peripheralblood lymphocytes stimulated by antl-CD3. Interestingly, onlyGKW.A3 and IM.7 stimulated the incorporation of [3H]palmltlcacid and palmitoylation of CD44 molecules by normal human peripheralblood lymphocytes. The two monoclonal antl-CD44 antibodies (P3H9and Bu52) that failed to inhibit antl-CD3 induced proliferationalso failed to induce the incorporation of [³H]palmltlc acid.More Importantly, the inhibitory effects of GKW.A3 were reversedin the presence of cerulenln, an inhibitor of protein palmitoylation.Therefore, palmitoylation of CD44 may interfere with antl-CD3mediated signaling pathways. These data support the hypothesisthat palmitoylation of cell surface receptors may play an activerole in receptor and receptor interactions and signal transductlonin normal human T lymphocytes.     

ADAM-17 associated with CD44 cleavage and metastasis in oral squamous cell carcinoma

ADAM-17 (a disintegrin and metalloproteinase 17) is a membrane-anchored protein, which can cleave the ectodomain in a variety of transmembrane proteins. In the in vitro experiments with tumor cells, ADAM-17 is reported to cleave CD44, an adhesion molecule that interacts with hyaluronic acid, to promote tumor cell migration. In the present study, we examined ADAM-17 expression and CD44 cleavage in specimens from 50 patients diagnosed to have oral squamous cell carcinoma (SCC). Each specimen was divided into two pieces, one was studied by immunohistochemistry and the other was subjected to a Western blot. By coordinating the results of both analyses, ADAM-17 expression was evaluated to be high in 23 cases (46%). When CD44 cleavage was also studied by immunohistochemical staining as well as with Western blotting, CD44 cleavage was judged to be positive in 29 cases (58%). When the ADAM-17 expression level was compared with the CD44 cleavage state, most of the cases expressing high levels of ADAM-17 (87%) showed positive CD44 cleavage. The level of ADAM-17 expression was significantly correlated to the nodal metastasis and local recurrence in oral SCC. Our findings suggest that ADAM-17 is involved in CD44 cleavage and contributes to tumor progression in oral SCC.     

CD44和CD44v6基因在胃腺癌组织中的表达及其意义

目的： 研究胃腺癌组织中ＣＤ４４ 的表达及其与淋巴结转移和预后的关系。方法： 应用免疫组化方法, 对１０５ 例胃腺癌组织中ＣＤ４４ 的表达进行了观察, 并对其中６２ 例患者做了随访。结果： ＣＤ４４ 和ＣＤ４４ｖ６ 基因的表达率分别为５４－３ ％ 和４８－６ ％ 。ＣＤ４４ｖ６ 在胃腺癌组织中的表达与癌细胞的分化、浸润深度, 以及临床分期和预后有关（Ｐ＜ ０－０５）, 而ＣＤ４４ 的表达则与上述临床病理指标无关。另外, 抗ＣＤ４４ 和抗ＣＤ４４ｖ６ 抗体的阳性反应, 与癌细胞的淋巴结转移有关（ＣＤ４４ｖ６, Ｐ＜ ０－０１ ; ＣＤ４４ , Ｐ＜ ０－０５） 。结论： ＣＤ４４ 的表达可用于胃癌患者的病情监测, 其中ＣＤ４４ｖ６ 有望作为判断预后的一个指标。     

Role of fibronectin-stimulated tumor cell migration in glioma invasion in vivo: clinical significance of fibronectin and fibronectin receptor expressed in human glioma tissues

In order to clarify the role of fibronectin in glioma invasion in vivo, we analyzed the relationship between fibronectin-stimulated cell migration and adhesion in 14 primary glioma cells and the expression of fibronectin and the fibronectin receptor in the corresponding tumor tissues. The tumors comprised nine glioblastomas (GB) and five anaplastic gliomas (AG) consisting of two astrocytomas, two oligoastrocytomas and one ependymoma. All glioma cells tested in the primary cell culture were found to migrate to fibronectin in a dose-dependent manner. The extent of cell migration to fibronectin was not significantly different for the GB and AG groups. On the other hand, cell adhesion to fibronectin in the AG was much stronger than that in the GB group. Immunohistochemistry demonstrated that fibronectin positively stained in the extra-cellular matrix (ECM) in eight cases and that the fibronectin receptor was positive in tumor cell membranes in 10 cases. In addition, cellular fibronectin isoforms containing ED-A and ED-B sequences were found to be immunolocalized in the tumor cells and the ECM of GB. These isoforms were also specifically expressed in tumor vessels within tumor tissues, but not in those within normal brain tissues. Cell migration tended to be expressed more strongly by glioma cells derived from tumor tissues in which fibronectin was posi-tively immunolocalized in the ECM than from tissues with negative fibronectin in the ECM. Four glioma cells derived from GB whose tumor cells did not positively stain for fibronectin receptors migrated much less extensively to fibronectin than other glioma cells whose tissues showed positive staining for the fibronectin receptor. Of these four GB, two had loss of heterozygosity in the locus of fibronectin receptor b1 gene. These results suggest that fibronectin deposited in the extracellular matrix of tumors, which can be derived from both plasma and the tumor cell itself, strongly promotes the migration of glioma cells, and that expression of the fibronectin receptor may play a critical role in the biological behavior of the tumor cells, particularly in fibronectin-stimulated cell migration in vivo.© Kluwer Academic Publishers 1998     

CD44与乳腺癌的研究进展

CD44基因蛋白是一种细胞表面跨膜糖蛋白,属于黏附分子家族。CD44基因外显子根据表达方式可分为标准型CD44(CD44s)和变异型CD44(CD44v)两种类型。大量研究发现,CD44蛋白参与细胞-细胞、细胞-胞外基质之间的特异性粘附,CD44及其亚型在乳腺癌的异常表达可能与癌症的发生、发展和转移密切相关。此外,乳腺癌干细胞表面高度表达CD44分子,针对CD44分子与乳腺癌干细胞关系的研究,将会为临床上对乳腺癌的诊断、治疗选择以及预后预测提供更充分的理论依据。     

Chimeric CD4/CD44 molecules associate with CD44 via the transmembrane region and reduce hyaluronan binding in T cell lines

Cells of the immune system tightly regulate the binding ability of cell adhesion molecules. The binding of the extracellular matrix component hyaluronan to CD44 is no exception, yet the mechanisms that regulate its binding are poorly understood. In this study a chimeric CD4/CD44 molecule, containing the extracellular domain of CD4 and the transmembrane and cytoplasmic domains of CD44, was expressed in two CD44⁺ mouse T lymphoma cell lines, BW5147 and T28. This resulted in the reduced ability of endogenous CD44 to constitutively bind hyaluronan. Immunoprecipitation of the chimeric protein in 1 % Brij-96 indicated an association between the chimera and endogenous CD44. Using various chimeric CD4/CD44 molecules, the transmembrane region of CD44 was found to mediate this association. In addition, the association of chimeric CD4/CD44 molecules with endogenous CD44 correlated with reduced hyaluronan binding. Thus, the transmembrane region of CD44 is required for the association with CD44 molecules in the cell membrane and we propose that the self-association of CD44 molecules occurs on the T cell surface to promote hyaluronan binding. Cellular events altering the interactions of the transmembrane region of CD44 thus have the potential to regulate the hyaluronan binding ability of CD44.     

丙戊酸钠对人脑胶质瘤细胞系SHG-44增殖分化的影响

目的 研究丙戊酸钠对培养人脑胶质瘤细胞系SHG-44细胞的增殖抑制和分化诱导作用。方法 以0.25、0.5、1.0、2.0、4.0mmol/L丙戊酸钠处理SHG-44细胞,用MTT比色、流式细胞术、光镜观察、免疫组化染色等方法检测处理细胞。结果 SHG-44细胞经丙戊酸钠处理后：（1）细胞增殖受到明显抑制,并具有时间,剂量依赖性;（2）细胞周期受阻,S期细胞比例减少,G1期细胞比例增多;（3）胶质纤维酸性蛋白（glialfibrillaryacidicprotein,GFAP）表达增强。结论 丙戊酸钠能抑制人脑胶质瘤细胞系SHG-44细胞的增殖,1.0mmol/L丙戊酸钠能诱导SHG-44细胞发生明显分化。     

Localization of CD44 at the Invasive Margin of Glioblastomas by Immunoelectron Microscopy

Glioblastoma multiforme is a highly invasive primary brain tumor, which is known to strongly express the CD44 cell adhesion receptor. A number of experimental studies suggest that the interaction of this receptor with extracellular matrix (ECM) proteins such as hyaluronic acid may in part mediate human glioma cell adhesion and invasion of brain tissue. Although the expression of CD44 and its spliced variants in brain tumors have been extensively studied, there have been no reports localizing its expression to the invasive margin of the tumor. The authors used immunoelectron microscopy to investigate the expression patterns of CD44 in an in vitro organotypic invasion assay. Tumor spheroids initiated from the U373 MG human glioblastoma line were confronted with fetal rat brain aggregates in a spheroid coculture system. The CD44 expression appeared at the interface between glioblastoma tumor spheroids and brain tissue, as well as in the spheroid itself. CD44 immunoreactivity was not detectable in mature 21-day fetal brain aggregates. The findings provide direct evidence that CD44 is expressed at the confrontational invasive border between glioblastomas and brain tissue, further supporting its role in glioma cell-ECM recognition and attachment.     

Expression of CD44 splice variants in human skin and epidermal tumours

Splice variants of the adhesion molecule CD44 (CD44v) are important in the lymphatic spread of rat carcinoma cells. In several human tumours expression of CD44v correlates with tumour progression. However, little is known about the physiological functions of distinct variant exons. Here we report on the immunohistological evaluation of CD44 expression in normal human skin and epidermal tumours which do not metastasise, or do so vary rarely. Frozen tissues were stained with a panel of monoclonal antibodies, recognizing epitopes of the CD44 standard isoform, as well as of variant exons v5, v6, v7, v7–v8 and v10. Stratum basale and spinosum as well as the root shaft of hairs reacted strongly with the whole panel of anti-CD44 antibodies. Stratum corneum, acinar cells of sebaceous and eccrine sweat glands stained with anti-CD44v5, anti-CD44v6 and anti-CD44v7, but not with anti-CD44v10, the latter recognizing the epithelial isoform (CD44v8–v10) of CD44. Ductal cells of glands and apocrine glands did not express CD44v. Compared with its expression in normal human skin, CD44v expression was reduced in basal cell carcinoma and squamous cell carcinoma of the skin. This was particularly true of CD44v10. The expression of CD44v in normal skin and dermal appendages indicates that not all combinations of variant exons are involved in tumour progression. Since the epithelial isoform is particularly downregulated in basal cell carcinoma and squamous cell carcinoma of the skin, it is unlikely that exons v8–v10 play a role in tumour progression. Rather, they may be of functional importance in maintenance of the epidermal structure.     

CD44s和CD44v6在宫颈鳞癌中表达及其临床意义

目的：探讨宫颈鳞癌中CD44s和CD44v6的表达及其与临床病理资料的关系。方法：应用免疫组化EnVision两步法对31例宫颈鳞标本中CD44s和CD44v6蛋白表达并进行分析。结果：肿瘤原发灶中CD44s阳性表达率为61．3％（19／31）。CD44v6阳性表达率为93．5％（29／31）,CD44v6阳性率高于CD44s,CD44s阳性表达与临床分期,病理分级和分类无关（P＞0．05）,CD44v6阳性表达与肿瘤细胞分化程度无关,但与浸润程度及分期有关（P＜0．05）,结论：CD44v6基因蛋白与宫颈鳞癌的侵袭,转移相关,可作为预测肿瘤进展和预后的一种有用指标。