mda-9/Syntenin promotes metastasis in human melanoma cells by activating c-Src

The scaffold PDZ-domain containing protein mda-9/syntenin functions as a positive regulator of cancer cell progression in human melanoma and other tumors. mda-9/Syntenin regulates cell motility and invasion by altering defined biochemical and signaling pathways, including focal adhesion kinase (FAK), p38 mitogen-activated protein kinase (MAPK) and NF-κB, but precisely how mda-9/syntenin organizes these multiprotein signaling complexes is not well understood. Using a clinically relevant human melanoma model, we demonstrate that mda-9/syntenin physically interacts with c-Src and this communication correlates with an increase in FAK/c-Src complex formation and c-Src activation. Inhibiting mda-9/syntenin, using an adenovirus expressing antisense mda-9/syntenin or addition of c-Src siRNA, suppresses melanoma cell migration, anchorage-independent growth, and spontaneous tumor cell dissemination in vivo in a human melanoma animal metastasis model. These data are compatible with a model wherein interaction of MDA-9/syntenin with c-Src promotes the formation of an active FAK/c-Src signaling complex, leading to enhanced tumor cell invasion and metastatic spread. These provocative findings highlight mda-9/syntenin and its interacting partners as promising therapeutic targets for intervention of metastasis.     

c-Src激酶对脂多糖致炎过程中occludin蛋白表达的影响

目的 探讨在脂多糖(lipopolysaccharide,LPS)处理小鼠肺泡上皮细胞(mouse lung epithelial-12,MLE-12)过程中,c-Src激酶对occhdin蛋白表达的影响. 方法 将培养的MLE-12细胞按随机数字表法分3组(每组3孔细胞):对照组(C组)、LPS实验组(L组)、LPS+c-Src激酶抑制剂PP2组(L+P组).C组不做任何处理;L组用LPS(浓度为10 mg/L)处理,处理时间为1、3、6 h;L+P组用PP2(浓度为100 μmol/L)预处理60 min,然后LPS(浓度为10 mg/L)处理6h.Western blot法和免疫荧光染色法分别检测各组不同时间点occludin蛋白的表达. 结果 Western blot发现,与C组比较:L组中6h时点occludin蛋白表达下调明显、c-Src表达明显升高,差异均有统计学意义(P＜0.05);与L组6h比较,L+P组occludin蛋白表达上调(P＜0.05).免疫荧光染色显示,occludin蛋白主要表达于细胞膜上,LPS影响occludin蛋白在膜上分布,PP2可以减轻LPS的影响. 结论 LPS导致MLE-12细胞紧密连接蛋白occludin表达下调,c-Src激酶参与其调节.     

Modification of insulin-like growth factor 1 receptor, c-Src, and Bcl-XL protein expression during the progression of Barrett's neoplasia

Oncogenes, growth factors, cell surface receptors, and cell-cycle and apoptotic regulatory proteins have been implicated in the growth regulation and progression of Barrett's-associated neoplasia. Among these, insulin-like growth factor 1 receptor (IGF1-R) and c-Src are reported to be key regulators of mitogenesis and tumorigenesis. In addition, c-Src may exert its transforming capability by inducing increased expression of IGF1-R on the neoplastic cells. Bcl-X(L), a member of the Bcl-2 family, blocks apoptosis and has been reported to increase in Barrett's-associated neoplasia. To study the modifications in IGF1-R, c-Src, and Bcl-X(L) protein expression during the progression of Barrett's-associated neoplasia, we analyzed 34 resected gastroesophagectomy specimens by immunohistochemistry using antibodies to human IGF1-R, c-Src, and Bcl-X(L). In these cases, we found 22 intestinal (Barrett's) metaplasias (IMs), 25 low-grade dysplasias (LGDs), 28 high-grade dysplasias (HGDs), 34 invasive adenocarcinomas (CAs), and 19 lymph node metastases. High IGF1-R cytoplasmic staining was present in 14 of 19 (74%) node metastases, in 28 of 34 (82%) CAs, in 18 of 28 (64%) HGDs, in 13 of 25 (52%) LGDs, and in 5 of 22 (23%) IMs. Strong and diffuse c-Src expression was identified in 17 of 19 (89%) node metastases, in 29 of 34 (85%) Cas, in 26 of 28 (93%) HGDs, in 18 of 25 (72%) LGDs, and in 9 of 22 (41%) IMs. Bcl-X(L) cytoplasmic staining was evident in 12 of 19 (63%) node metastases, in 20 of 34 (59%) Cas, in 20 of 28 (71%) HGDs, in 15 of 25 (60%) LGDs, and in 6 of 22 (27%) IMs. In 11 cases, c-Src activity was measured by kinase assay and reflected the immunohistochemical results. Our data indicate that expression levels of IGF1-R, c-Src, and Bcl-X(L) proteins are coordinately elevated in Barrett's-associated neoplasia. These findings indicate important roles of these growth regulatory proteins in the malignant progression of Barrett's-associated neoplasia.     

Focal complex formation in adult cardiomyocytes is accompanied by the activation of beta3 integrin and c-Src

In pressure-overloaded myocardium, our recent study demonstrated cytoskeletal assembly of c-Src and other signaling proteins which was partially mimicked in vitro using adult feline cardiomyocytes embedded in three-dimensional (3D) collagen matrix and stimulated with an integrin-binding Arg-Gly-Asp (RGD) peptide. In the present study, we improved this model further to activate c-Src and obtain a full assembly of the focal adhesion complex (FAC), and characterized c-Src localization and integrin subtype(s) involved. RGD dose response experiments revealed that c-Src activation occurs subsequent to its cytoskeletal recruitment and is accompanied by p130Cas cytoskeletal binding and focal adhesion kinase (FAK) Tyr925 phosphorylation. When cardiomyocytes expressing hexahistidine-tagged c-Src via adenoviral gene delivery were used for RGD stimulation, the expressed c-Src exhibited relocation: (i) biochemical analysis revealed c-Src movement from the detergent-soluble to the -insoluble cytoskeletal fraction and (ii) confocal microscopic analysis showed c-Src movement from a nuclear/perinuclear to a sarcolemmal region. RGD treatment also caused sarcolemmal co-localization of FAK and vinculin. Characterization of integrin subtypes revealed that beta3, but not beta1, integrin plays a predominant role: (i) expression of cytoplasmic domain of beta1A integrin did not affect the RGD-stimulated FAC formation and (ii) both pressure-overloaded myocardium and RGD-stimulated cardiomyocytes exhibited phosphorylation of beta3 integrin at Tyr773/785 sites but not beta1 integrin at Thr788/789 sites. Together these data indicate that RGD treatment in cardiomyocytes causes beta3 integrin activation and c-Src sarcolemmal localization, that subsequent c-Src activation is accompanied by p130Cas binding and FAK Tyr925 phosphorylation, and that these events might be crucial for growth and remodeling of hypertrophying adult cardiomyocytes.     

25-Methoxyhispidol A, a novel triterpenoid of Poncirus trifoliata, inhibits cell growth via the modulation of EGFR/c-Src signaling pathway in MDA-MB-231 human breast cancer cells

The fruit of Poncirus trifoliata (Rutaceae) has been used a medicinal food and traditional medicine. Recently we reported the isolation of 25-methoxyhispidol A (25-MHA) as a novel triterpenoid from the immature fruit of P. trifoliata with the potential growth inhibition of cancer cells. However, the molecular mechanisms on the anti-proliferative activity in cancer cells remain to be elucidated. In the present study, we investigated the anti-proliferative activity and mechanisms of actions mediated by 25-MHA in estrogen receptor (ER)-negative MDA-MB-231 human breast cancer cells. 25-MHA exhibited the growth inhibitory activity against MDA-MB-231 cells with the cell cycle arrest in the G0/G1 phase. The cell cycle arrest in the G0/G1 by 25-MHA was well correlated with the downregulation of cyclin D1, cyclin dependent kinase (CDK4), CDK2, cyclin A, phosphorylated retinoblastoma protein (pRb), and induction of cdk inhibitor p21^WAF1/Cip1 protein. 25-MHA also suppressed the activation of c-Src/epidermal growth factor receptor (EGFR)/Akt signaling, and consequently led to the inactivation of mTOR and its downstream signal molecules including 4E-binding protein (4E-BP) and p70 S6 kinase. These findings suggest that 25-MHA-mediated inhibitory activity of human breast cancer cell growth might be related with the cell cycle arrest and modulation of signal transduction pathways.     

c-Src参与RANKL诱导的乳腺癌BT-474细胞迁移的机制研究

目的:核因子-κB受体活化因子配体(RANKL)/核因子κB受体活化因子(RANK)通路在肿瘤骨定向性迁移中发挥重要的作用,但具体信号传导机制尚不清楚。本文探讨非受体酪氨酸激酶c-Src在RANKL诱导的乳腺癌BT474细胞迁移中的作用。方法:Western blot检测BT-474细胞表面受体RANK蛋白的表达及RANKL刺激后细胞p-Src及c-Src的表达;Transwell法测定细胞迁移能力。采用SPSS 16.0统计学软件分析实验数据。结果:BT-474细胞表达RANK蛋白,RANKL诱导BT-474细胞迁移能力增强。应用RANKL的圈套受体OPG可阻断RANKL诱导的细胞迁移。RANKL刺激后BT-474细胞p-Src表达升高,应用c-Src激酶抑制剂PP2可显著抑制RANKL诱导的细胞迁移。结论:c-Src信号通路参与RANKL诱导的乳腺癌BT-474细胞迁移。     

PP60c-Src在血管紧张素Ⅱ对大鼠血管平滑肌细胞信息转导中的作用

目的：通过观察c—Src在AngⅡ对大鼠血管平滑肌细胞(VSMC)丝裂原活化的蛋白激酶(MAPK)活性和c—fos蛋白表达的影响，以进一步了解AngⅡ促VSMC增殖的细胞内信息转导机制。方法：原代和传代培养SD大民主动脉VSMC，以脂质体包裹反义c—Src寡脱氧核夺酸(Oligodeoxynucleotides ODNs)转染培养的VSMC以抑制c—Src蛋白表达和激酶活性。以未转染的VSMC为对照，观察10^7mol/L AngⅡ刺激对转染的VSMC的MAPK活性和c—fos蛋白表达的影响。蛋白免疫沉淀和酶自身磷酸化率测定c—Src激酶活性；髓鞘碱性蛋白(MBP)底物磷酸化率测定MAPK放酶活性；Western blot免疫印迹法测定c—Src和c—fos蛋白表达情况。始果：转染不同浓度反义c—Src()DNs的VSMCc—Src蛋白含量至浓度依赖性降低，0.2μmol/L、0.5μmol/L、1．0μmol／L和2．0μmol/L分别为对照的68．2％、34．7％、30。3％和15．8％，经方差分析具有显著性意义(P＜0.01)。c—Src激酶活性也显著抑制；以AngⅡ刺激经转染反义c—Src DNs的VSMC，c—Src激酶活性增幅仅为对照组的8．7％；MAPK活性仅为对照的1．6％；c—fos蛋白表达的增幅为对照组的30．0％。结论：AngⅡ可诱导VSMC c—Src激活和细胞内信息转导，且AngⅡ引起的MAPK和c—fos的激活依赖于c—Src的激活，提示c—Src是AngⅡ促血管平滑细胞增殖的重要信息分于。     

Focal adhesion proteins as markers of malignant transformation and prognostic indicators in breast carcinoma

Focal adhesion kinase (FAK) is one of the central signaling molecules found at focal adhesion sites, which are specific areas on the cell membrane where cells attach to extracellular matrix proteins. Focal adhesion kinase interacts with multiple signaling and adaptor molecules and effects several signaling pathways. Overexpression of FAK and its substrate c-Src has been implicated in malignant transformation and acquisition of an invasive tumor phenotype of different tissues. Overexpression of the multidomain protein paxillin, which is also a FAK ligand and a c-Src substrate, has been associated with less malignant tumor behavior. The purpose of this study was to analyze the involvement of integrin signaling molecules FAK, c-Src, and paxillin in malignant transformation of the breast epithelium. Using phosphospecific antibodies FAK-pY(397) and Src-pY(416), we demonstrated that neither activation of FAK nor activation of c-Src correlates with development of invasive tumor properties. However, activation of both FAK and c-Src correlates with malignant transformation. We further demonstrated that overexpression of paxillin also correlates with malignant transformation and is a marker of a less invasive tumor phenotype. Using tissue microarray, we demonstrated that expression and activation of paxillin inversely correlated with lymph node metastases and lymphovascular invasion, respectively. No correlation between paxillin expression and activation and tumor grade, estrogen, progesterone, and Her2/Neu receptor expression was found. In summary, focal adhesion proteins FAK and c-Src can be used as markers of malignant transformation in epithelial cells but not invasive phenotype, whereas expression and activation of paxillin may represent a good prognosticator in breast carcinoma.     

癌基因c-Src抑制剂对三阴性乳腺癌的疗效评价

目的：探讨癌基因C-Src抑制剂对三阴性乳腺癌的辅助治疗作用。方法体外培养三阴性乳腺癌细胞 MDA-MB-231,并与雌激素受体（ER）、孕激素受体（PR）阳性的乳腺癌细胞 T47D 以及HER2阳性的SK-Br-3细胞做比较。用癌基因 c-Src 抑制剂来治疗三株细胞。采用 MTT 和免疫电泳的方法检测细胞的生长以及细胞信号传导通路的改变。结果c-Src抑制剂可以部分抑制 T47D 细胞生长,对三阴性乳腺癌细胞 MDA-MB-231有很明显的抑制作用。但是,对 SK-Br-3细胞的生长没有阻滞作用。进一步研究发现,是否抑制细胞生长信号传导通路决定 c-Src 抑制剂的治疗效果。HER2抑制剂可以明显抑制 SK-Br-3细胞周期与生长,而对 MDA-MB-231没有效果。结论抑制癌基因c-Src酪氨酸激酶活性对三阴性乳腺癌细胞有很好的治疗效果。