CEACAM6 cross-linking induces caveolin-1-dependent, Src-mediated focal adhesion kinase phosphorylation in BxPC3 pancreatic adenocarcinoma cells

Despite lacking transmembrane or intracellular domains, glycosylphosphatidylinositol-anchored proteins can modulate intracellular signaling events, in many cases through aggregation within membrane "lipid raft" microdomains. CEACAM6 is a glycosylphosphatidylinositol-linked cell surface protein of importance in the anchorage-independent survival and metastasis of pancreatic adenocarcinoma cells. We examined the effects of antibody-mediated cross-linking of CEACAM6 on intracellular signaling events and anchorage-independent survival of the CEACAM6-overexpressing pancreatic ductal adenocarcinoma cell line, BxPC3. CEACAM6 cross-linking increased c-Src activation and induced tyrosine phosphorylation of p125(FAK) focal adhesion kinase. Focal adhesion kinase phosphorylation was dependent on c-Src kinase activation, for which caveolin-1 was required. CEACAM6 cross-linking induced a significant increase in cellular resistance to anoikis. These observations represent the first characterization of the mechanism through which this important cell surface oncoprotein influences intracellular signaling events and hence malignant cellular behavior.     

High levels of ezrin expressed by human pancreatic adenocarcinoma cell lines with high metastatic potential.

Ezrin is a membrane cytoskeleton crosslinker protein that is a member of the ERM (ezrin/radixin/moesin) family. Ezrin binds adhesion molecules such as CD43, CD44, ICAM-1, and ICAM-2, which are implicated in cell migration and metastasis. Ezrin is expressed by many tumor cell lines; however, little is known about the function of ezrin in tumorigenesis and metastasis. Here, we investigated expression of ezrin in pancreatic adenocarcinoma cell lines of different metastatic potential. Among 16 pancreatic adenocarcinoma cell lines, several cell lines showed strong expression of ezrin. Two cell lines with high metastatic potential, S2-CP9 and S2-VP10, showed very high levels of ezrin mRNA and protein, whereas other sublines showed lower levels. There was no relationship between the expression levels of ezrin and the differentiation grades of the cell lines. These results suggest that there is a relationship between high expression of ezrin and metastatic potential of pancreatic carcinomas.     

Adult Stromal Cells Derived from Human Adipose Tissue Provoke Pancreatic Cancer Cell Death both In Vitro and In Vivo

Background

Normal tissue homeostasis is maintained by dynamic interactions between epithelial cells and their microenvironment. Disrupting this homeostasis can induce aberrant cell proliferation, adhesion, function and migration that might promote malignant behavior. Indeed, aberrant stromal-epithelial interactions contribute to pancreatic ductal adenocarcinoma (PDAC) spread and metastasis, and this raises the possibility that novel stroma-targeted therapies represent additional approaches for combating this malignant disease. The aim of the present study was to determine the effect of human stromal cells derived from adipose tissue (ADSC) on pancreatic tumor cell proliferation.

Principal Findings

Co-culturing pancreatic tumor cells with ADSC and ADSC-conditioned medium sampled from different donors inhibited cancer cell viability and proliferation. ADSC-mediated inhibitory effect was further extended to other epithelial cancer-derived cell lines (liver, colon, prostate). ADSC conditioned medium induced cancer cell necrosis following G1-phase arrest, without evidence of apoptosis. In vivo, a single intra-tumoral injection of ADSC in a model of pancreatic adenocarcinoma induced a strong and long-lasting inhibition of tumor growth.

Conclusion

These data indicate that ADSC strongly inhibit PDAC proliferation, both in vitro and in vivo and induce tumor cell death by altering cell cycle progression. Therefore, ADSC may constitute a potential cell-based therapeutic alternative for the treatment of PDAC for which no effective cure is available.     

Epithelial Mesenchymal Transition and Pancreatic Tumor Initiating CD44+/EpCAM+ Cells Are Inhibited by γ-Secretase Inhibitor IX

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with a high rate of metastasis. Recent studies have indicated that the Notch signalling pathway is important in PDAC initiation and maintenance, although the specific cell biological roles of the pathway remain to be established. Here we sought to examine this question in established pancreatic cancer cell lines using the γ-secretase inhibitor IX (GSI IX) to inactivate Notch. Based on the known roles of Notch in development and stem cell biology, we focused on effects on epithelial mesenchymal transition (EMT) and on pancreatic tumor initiating CD44+/EpCAM+ cells. We analyzed the effect of the GSI IX on growth and epithelial plasticity of human pancreatic cancer cell lines, and on the tumorigenicity of pancreatic tumor initiating CD44+/EpCAM+ cells. Notably, apoptosis was induced after GSI IX treatment and EMT markers were selectively targeted. Furthermore, under GSI IX treatment, decline in the growth of pancreatic tumor initiating CD44+/EpCAM+ cells was observed in vitro and in a xenograft mouse model. This study demonstrates a central role of Notch signalling pathway in pancreatic cancer pathogenesis and identifies an effective approach to inhibit selectively EMT and suppress tumorigenesis by eliminating pancreatic tumor initiating CD44+/EpCAM+ cells.     

Ezrin gone rogue in cancer progression and metastasis: An enticing therapeutic target

Cancer metastasis is the primary cause of morbidity and mortality in cancer as it remains the most complicated, devastating, and enigmatic aspect of cancer. Several decades of extensive research have identified several key players closely associated with metastasis. Among these players, cytoskeletal linker Ezrin (the founding member of the ERM (Ezrin-Radixin-Moesin) family) was identified as a critical promoter of metastasis in pediatric cancers in the early 21st century. Ezrin was discovered 40 years ago as a aminor component of intestinal epithelial microvillus core protein, which is enriched in actin-containing cell surface structures. It controls gastric acid secretion and plays diverse physiological roles including maintaining cell polarity, regulating cell adhesion, cell motility and morphogenesis. Extensive research for more than two decades evinces that Ezrin is frequently dysregulated in several human cancers. Overexpression, altered subcellular localization and/or aberrant activation of Ezrin are closely associated with higher metastatic incidence and patient mortality, thereby justifying Ezrin as a valuable prognostic biomarker in cancer. Ezrin plays multifaceted role in multiple aspects of cancer, with its significant contribution in the complex metastatic cascade, through reorganizing the cytoskeleton and deregulating various cellular signaling pathways. Current preclinical studies using genetic and/or pharmacological approaches reveal that inactivation of Ezrin results in significant inhibition of Ezrin-mediated tumor growth and metastasis as well as increase in the sensitivity of cancer cells to various chemotherapeutic drugs. In this review, we discuss the recent advances illuminating the molecular mechanisms responsible for Ezrin dysregulation in cancer and its pleiotropic role in cancer progression and metastasis. We also highlight its potential as a prognostic biomarker and therapeutic target in various cancers. More importantly, we put forward some potential questions, which we strongly believe, will stimulate both basic and translational research to better understand Ezrin-mediated malignancy, ultimately leading to the development of Ezrin-targeted cancer therapy for the betterment of human life.     

The Loss of miR-26a-Mediated Post-Transcriptional Regulation of Cyclin E2 in Pancreatic Cancer Cell Proliferation and Decreased Patient Survival

Background

miR-26a plays a critical role in tumorigenesis, either as a tumor suppressor or as an oncogenic miRNA, depending on different tumor types. However, the function of miR-26a in pancreatic cancer has not been clearly elucidated. The present study was designed to determine the roles of miR-26a in pancreatic cancer and its association with the survival of patients with pancreatic cancer.

Methods

The expression of miR-26a was examined in 15 pairs of pancreatic duct adenocarcinoma (PDAC) and their adjacent benign pancreatic tissues (ABPT), by qRT-PCR. The results were confirmed by in situ hybridization using two panels of 106 PDACs and their ABPT microarray. The association of miR-26a expression with overall survival was determined. The proliferation and cell cycle distribution of Capan-2, SW-1990, and Panc-1 cells, transfected with miR-26a mimics or a miR-26a inhibitor, were assessed using the Cell Counting Kit-8 assay and flow cytometry, respectively. The cell tumorigenicity was evaluated via murine xenograft experiments. Cyclin D2, E2, EZH2, and PCNA levels were analyzed by Western blot and immunohistochemistry.

Results

miR-26a was expressed in the cytoplasm of pancreatic ductal epithelial cells, whereas its expression was significantly downregulated in PDAC tissues compared with that of ABPT. Patients with low miR-26a expression had a significantly shorter survival than those with high miR-26a expression. The in vitro and in vivo assays showed that overexpression of miR-26a resulted in cell cycle arrest, inhibited cell proliferation, and decreased tumor growth, which was associated with cyclin E2 downregulation.

Conclusions

miR-26a is an important suppressor of pancreatic ductal carcinoma, and can prove to be a novel prognostic factor and therapeutic target for pancreatic cancer treatment.     

Tyrosine nitration of c-SRC tyrosine kinase in human pancreatic ductal adenocarcinoma

During pancreatic tumorigenesis, the equilibrium between cell survival and cell death is altered, allowing aggressive neoplasia and resistance to radiation and chemotherapy. Local oxidative stress is one mechanism regulating programmed cell death and growth and may contribute to both tumor progression and suppression. Our recent in situ immunohistochemical studies demonstrated that levels of total nitrotyrosine, a footprint of the reactive nitrogen species peroxynitrite, are elevated in human pancreatic ductal adenocarcinomas. In this study, quantitative HPLC-EC techniques demonstrated a 21- to 97-fold increase in the overall levels of nitrotyrosine of human pancreatic tumor extracts compared to normal pancreatic extracts. Western blot analysis of human pancreatic tumor extracts showed that tyrosine nitration was restricted to a few specific proteins. Immunoprecipitation coupled with Western analysis identified c-Src tyrosine kinase as a target of both tyrosine nitration and tyrosine phosphorylation. Peroxynitrite treatment of human pancreatic carcinoma cells in vitro resulted in increased tyrosine nitration and tyrosine phosphorylation of c-Src kinase, increased (>2-fold) c-Src kinase activity, and increased association between c-Src kinase and its downstream substrate cortactin. Collectively, these observations suggest that peroxynitrite-mediated tyrosine nitration and tyrosine phosphorylation of c-Src kinase may lead to enhanced tyrosine kinase signaling observed during pancreatic ductal adenocarcinoma growth and metastasis.     

埃兹蛋白的表达与非小细胞肺癌转移的关系研究

目的:探究埃兹蛋白(Ezrin)的表达与非小细胞肺癌转移的关系。方法:通过免疫组化检测Ezrin在有无转移的非小细胞肺癌组织中的表达差异,通过细胞免疫组化、western-blot、RT-PCR检测Ezrin在不同转移潜能肺癌细胞系中的表达差异,通过transwell考察Ezrin对不同转移潜能癌细胞侵袭和迁移能力的影响。结果:Ezrin蛋白在有转移的非小细胞肺癌组织中的表达水平明显高于无转移的肺癌组织,在高转移潜能肺癌细胞系中的表达高于低转移潜能细胞系,受抑制时会削弱高转移潜能肺癌细胞的迁移和侵袭能力,过表达时会增强低转移潜能肺癌细胞的侵袭和迁移能力。结论:Ezrin可能在非小细胞肺癌及其转移中发挥重要作用。     

Identification of a Novel Subpopulation of Tumor-Initiating Cells from Gemcitabine-Resistant Pancreatic Ductal Adenocarcinoma Patients

Pancreatic ductal adenocarcinoma is highly resistant to systemic chemotherapy. Although there are many reports using pancreatic cancer cells derived from patients who did not receive chemotherapy, characteristics of pancreatic cancer cells from chemotherapy-resistant patients remain unclear. In this study, we set out to establish a cancer cell line in disseminated cancer cells derived from gemcitabine-resistant pancreatic ductal adenocarcinoma patients. By use of in vitro co-culture system with stromal cells, we established a novel pancreatic tumor-initiating cell line. The cell line required its direct interaction with stromal cells for its in vitro clonogenic growth and passaging. Their direct interaction induced basal lamina-like extracellular matrix formation that maintained colony formation. The cell line expressed CD133 protein, which expression level changed autonomously and by culture conditions. These results demonstrated that there were novel pancreatic tumor-initiating cells that required direct interactions with stromal cells for their in vitro cultivation in gemcitabine-resistant pancreatic ductal adenocarcinoma. This cell line would help to develop novel therapies that enhance effects of gemcitabine or novel anti-cancer drugs.     

RhoC Interacts with Integrin α5β1 and Enhances Its Trafficking in Migrating Pancreatic Carcinoma Cells

Human pancreatic ductal adenocarcinoma (PDAC) is characterized by early systemic dissemination. Although RhoC has been implicated in cancer cell migration, the relevant underlying molecular mechanisms remain unknown. RhoC has been implicated in the enhancement of cancer cell migration and invasion, with actions which are distinct from RhoA (84% homology), and are possibly attributed to the divergent C-terminus domain. Here, we confirm that RhoC significantly enhances the migratory and invasive properties of pancreatic carcinoma cells. In addition, we show that RhoC over-expression decreases cancer cell adhesion and, in turn, accelerates cellular body movement and focal adhesion turnover, especially, on fibronectin-coated surfaces. Whilst RhoC over-expression did not alter integrin expression patterns, we show that it enhanced integrin α5β1 internalization and re-cycling (trafficking), an effect that was dependent specifically on the C-terminus (180-193 amino acids) of RhoC protein. We also report that RhoC and integrin α5β1 co-localize within the peri-nuclear region of pancreatic tumor cells, and by masking the CAAX motif at the C-terminal of RhoC protein, we were able to abolish this interaction in vitro and in vivo. Co-localization of integrin α5β1 and RhoC was demonstrable in invading cancer cells in 3D-organotypic cultures, and further mimicked in vivo analyses of, spontaneous human, (two distinct sources: operated patients and rapid autopsy programme) and transgenic murine (LSL-KrasG12D/+;LSL-Trp53R172H/+;Pdx-1-Cre), pancreatic cancers. In both cases, co-localization of integrin α5β1 and RhoC correlated with poor differentiation status and metastatic potential. We propose that RhoC facilitates tumor cell invasion and promotes subsequent metastasis, in part, by enhancing integrin α5β1 trafficking. Thus, RhoC may serve as a biomarker and a therapeutic target.     

c-Src-dependent cross-talk between CEACAM6 and alphavbeta3 integrin enhances pancreatic adenocarcinoma cell adhesion to extracellular matrix components

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is an immunoglobulin superfamily member with a diversity of extracellular ligands that is implicated in the initiation and progression of a variety of malignancies. We sought to characterize the effects of CEACAM6 crosslinking on pancreatic adenocarcinoma cellular interaction with the extracellular matrix (ECM) components fibronectin and vitronectin. Antibody-mediated CEACAM6 crosslinking was performed and the ability of BxPC3 cells, which inherently overexpress CEACAM6, to adhere to fibronectin and vitronectin was quantified. The roles of the archetypal fibronectin (alpha5beta1 integrin) and vitronectin (alphavbeta3 integrin) receptors were determined. The effects of c-Src inhibition were investigated using the Src family kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) and c-Src specific RNA interference. CEACAM6 crosslinking initiates c-Src-dependent cross-talk between CEACAM6 and alphavbeta3 integrin, leading to increased ECM component adhesion. CEACAM6-mediated signaling events may contribute to the invasive and metastatic potential of pancreatic adenocarcinoma cells by promoting their interaction with ECM components.     

Tenascin-C enhances pancreatic cancer cell growth and motility and affects cell adhesion through activation of the integrin pathway

Background

Pancreatic cancer (PDAC) is characterized by an abundant fibrous tissue rich in Tenascin-C (TNC), a large ECM glycoprotein mainly synthesized by pancreatic stellate cells (PSCs). In human pancreatic tissues, TNC expression increases in the progression from low-grade precursor lesions to invasive cancer. Aim of this study was the functional characterization of the effects of TNC on biologic relevant properties of pancreatic cancer cells.

Methods

Proliferation, migration and adhesion assays were performed on pancreatic cancer cell lines treated with TNC or grown on a TNC-rich matrix. Stable transfectants expressing the large TNC splice variant were generated to test the effects of endogenous TNC. TNC-dependent integrin signaling was investigated by immunoblotting, immunofluorescence and pharmacological inhibition.

Results

Endogenous TNC promoted pancreatic cancer cell growth and migration. A TNC-rich matrix also enhanced migration as well as the adhesion to the uncoated growth surface of poorly differentiated cell lines. In contrast, adhesion to fibronectin was significantly decreased in the presence of TNC. The effects of TNC on cell adhesion were paralleled by changes in the activation state of paxillin and Akt.

Conclusion

TNC affects proliferation, migration and adhesion of poorly differentiated pancreatic cancer cell lines and might therefore play a role in PDAC spreading and metastasis in vivo.     

The Rescue of miR-148a Expression in Pancreatic Cancer: An Inappropriate Therapeutic Tool

MicroRNAs are small non-coding RNAs that physiologically modulate proteins expression, and regulate numerous cellular mechanisms. Alteration of microRNA expression has been described in cancer and is associated to tumor initiation and progression. The microRNA 148a (miR-148a) is frequently down-regulated in cancer. We previously demonstrated that its down-regulation by DNA hypermethylation is an early event in pancreatic ductal adenocarcinoma (PDAC) carcinogenesis, suggesting a tumor suppressive function. Here, we investigate the potential role of miR-148a over-expression in PDAC as a therapeutic tool. We first report the consequences of miR-148a over-expression in PDAC cell lines. We demonstrate that miR-148a over-expression has no dramatic effect on cell proliferation and cell chemo-sensitivity in four well described PDAC cell lines. We also investigate the modulation of protein expression by a global proteomic approach (2D-DIGE). We show that despite its massive over-expression, miR-148a weakly modulates protein expression, thus preventing the identification of protein targets in PDAC cell lines. More importantly, in vivo data demonstrate that modulating miR-148a expression either in the epithelia tumor cells and/or in the tumor microenvironment does not impede tumor growth. Taken together, we demonstrate herein that miR-148a does not impact PDAC proliferation both in vitro and in vivo thus suggesting a weak potential as a therapeutic tool.     

Lipocalin2 Promotes Invasion,Tumorigenicity and Gemcitabine Resistance in Pancreatic Ductal Adenocarcinoma

Lipocalin 2 (LCN2) is a small secreted protein and its elevated expression has been observed in pancreatic as well as other cancer types. LCN2 has been reported to promote resistance to drug-induced apoptosis, enhance invasion through its physical association with matrix metalloproteinase-9, and promote in vivo tumor growth. LCN2 was found to be commonly expressed in patient PDAC samples and its pattern of immunohistochemical staining intensified with increasing severity in high-grade precursor lesions. Downregulation of LCN2 in two pancreatic ductal adenocarcinoma cell lines (BxPC3 and HPAF-II) with high LCN2 expression significantly reduced attachment, invasion, and tumour growth in vivo, but not proliferation or motility. Downregulation of LCN2 in two pancreatic ductal adenocarcinoma cell lines (BxPC3 and HPAF-II) with high expression significantly reduced attachment, invasion, and tumour growth in vivo. In contrast, LCN2 overexpression in PANC1, with low endogenous expression, significantly increased invasion, attachment, and enhanced tumor growth. Suppression of LCN2 in BxPC3 and HPAF-II cells increased their sensitivity to gemcitabine in vitro, and in vivo when BxPC3 was tested. Furthermore, LCN2 promotes expression of VEGF and HIF1A which contribute to enhanced vascularity. These overall results demonstrate that LCN2 plays an important role in the malignant progression of pancreatic ductal carcinoma and is a potential therapeutic target for this disease.     

神经导向因子在肿瘤中的作用及其机制

神经导向因子Netrins作为分泌蛋白与膜结合蛋白,在神经细胞迁移、分化及凋亡等生物学过程中发挥重要的作用。自发现以来,Netrins被认为负责指导中枢神经系统组织形态的发育,随后发现它也广泛参与一些非神经组织的黏附、迁移和分化等生理过程,如血管生成、淋巴管形成和炎症等。最近的研究表明,Netrins也参与调控肿瘤的发生与发展,在结直肠癌、胰腺导管腺癌等多种肿瘤组织中发挥重要的调控作用。由于Netrins的功能多样性且通过结合不同受体在肿瘤组织中发挥不同的生物学效应,其在肿瘤中的具体作用机制尚不清楚。文中结合课题组目前的实验研究进展,阐述了近年来关于Netrins的研究,特别是在肿瘤领域取得的最新研究结果,总结了其作用机制,并对其研究及应用前景进行了展望。     

Ezrin蛋白的生物学作用及其与肿瘤转移的关系

Ezrin蛋白是ERM蛋白家族中的一员,最早被发现。人体几乎所有的组织细胞中都有Ezrin蛋白的存在。Ezrin蛋白分子通过磷酸化等方式来激活,暴露其分子上的功能位点,形成具有功能分子结构。亚细胞定位在胞浆中,细胞膜与骨架蛋白之间,通过链接细胞内骨架蛋白与膜蛋白来实现其多项复杂而又重要的功能。近年来发现Ezrin蛋白存在多种功能,包括参与细胞形态学、参与免疫突触的形成,与黏附分子作用进而来调节细胞与细胞或细胞与基质间的黏附、调节细胞运动性等。最重要的是它在多种肿瘤中高表达并促进肿瘤细胞的增殖及转移等活动,参与肿瘤的发生与发展。干扰肿瘤细胞内的Ezrin蛋白表达或抑制其磷酸化后,可以明显抑制肿瘤的转移。所以,Ezrin可能成为将来抑制肿瘤转移研究的潜在靶点。