Epithelial-to-mesenchymal transdifferentiation (EMT) mediated by transforming growth factor-b (TGF-b) signaling leads to aggressive cancer progression. In this study, we identified zinc-a2-glycoprotein (AZGP1, ZAG) as a tumor suppressor in pancreatic ductal adenocarcinoma whose expression is lost due to histone deacetylation. In vitro, ZAG silencing strikingly increased invasiveness of pancreatic cancer cells accompanied by the induction of a mesenchymal phenotype. Expression analysis of a set of EMT markers showed an increase in the expression of mesenchymal markers (vimentin (VIM) and integrin-a5) and a concomitant reduction in the expression of epithelial markers (cadherin 1 (CDH1), desmoplakin and keratin-19). Blockade of endogenous TGF-b signaling inhibited these morphological changes and the downregulation of CDH1, as elicited by ZAG silencing. In a ZAG-negative cell line, human recombinant ZAG (rZAG) specifically inhibited exogenous TGF-b-mediated tumor cell invasion and VIM expression. Furthermore, rZAG blocked TGF-b-mediated ERK2 phosphorylation. PCR array analysis revealed that ZAG-induced epithelial transdifferentiation was accompanied by a series of concerted cellular events including a shift in the energy metabolism and prosurvival signals. Thus, epigenetically regulated ZAG is a novel tumor suppressor essential for maintaining an epithelial phenotype.
Glutamate has been implicated in tumorigenesis through activation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (AMPAR). However, the function of a glutamate-to-AMPAR signal in pancreatic ductal adenocarcinoma (PDAC) has remained elusive. We now show that glutamate-mediated AMPA receptor activation increases invasion and migration of pancreatic cancer cells via activation of the classical MAPK pathway. Glutamate levels were increased in pancreatic cancer accompanied by downregulation of GluR subunits 1, 2, and 4. In pancreatic cancer precursor lesions, pancreatic intraepithelial neoplasia (PanIN), GluR1 subunit levels were strikingly and step-wise increased but its expression was rare in PDAC. Pharmacological inhibition or RNAi-mediated suppression of GluR1 or GluR2 did not affect cancer cell growth but significantly decreased invasion. In a K-ras wildtype cell line, AMPA receptor activation enhanced K-ras activity and-further downstream-phosphorylation of p38 and of p44/42. Preemptive blockade of AMPA receptors in a mouse model of pancreatic cancer inhibited tumor cell settling. AMPA receptor activation thus not only activates MAPK signalling but also directly increases activity of K-ras. Glutamate might serve as a molecular switch that decreases the threshold of K-ras-induced oncogenic signalling and increases the chance of malignant transformation of pancreatic cancer precursor lesions.Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive human malignancies, with exceptionally low survival rates (5-year survival rate less than 5%). 1 Although the cell of origin of PDAC is controversially discussed, 2 pancreatic intraepithelial neoplasias (PanIN) of different grades (1A, 1B, 2, 3) in which increasing numbers of molecular alterations are found (i.e., mutations in the Kras, Smad4 and p53 genes), are believed to belong to the multistep progression model of pancreatic cancer. 3,4 Neurotransmitters and neuropeptides have been shown to play a role in pancreatic carcinogenesis 5-11 and in pancreas-associated diseases 8,[12][13][14][15][16] however, the role of excitatory neurotransmitters and particularly of glutamate in pancreatic cancer is not well defined. Glutamate activates metabotropic receptors (mGluR; G protein-coupled receptors) and the ionotropic (iGluR) receptors N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate 17,18 receptors. AMPA receptors are heteromeric and are assembled from the four subunits GluR1-4 in different combinations. The presence of GluR2 subunit determines AMPA receptor impermeability to Ca 2þ . 17,19,20 Since AMPA receptor activation regulates differentiation, proliferation and migration of embryonic stem cells, [21][22][23][24] it has been hypothesized that modulation of AMPA receptor-mediated signals might be involved in carcinogenesis, particularly because it has also been shown that AMPA signals via the MAPK pathway. [25][26][27] This hypothesis has subsequently been proven for some ...
Perineural invasion, the growth of tumor cells along nerves, is a key feature of pancreatic cancer. The cardinal symptom of pancreatic cancer, abdominal pain often radiating to the back, as well as the high frequency of local tumor recurrence following resection are both attributed to the unique ability of pancreatic tumor cells to invade the neuronal system. The molecular mechanisms underlying the neuroaffinity of pancreatic tumors are not completely understood. In this study, we developed a novel method to monitor ex vivo perineural invasion into surgically resected rat vagal nerves by different human pancreatic tumor cell lines. Genome-wide transcriptional analyses were employed to identify the consensus set of genes differentially regulated in all highly nerve-invasive (nerve invasion passage 3) versus less invasive (nerve invasion passage 0) pancreatic tumor cells. The critical involvement of kinesin family member 14 (KIF14) and Rho-GDP dissociation inhibitor β (ARHGDIβ) in perineural invasion was confirmed on RNA and protein levels in human pancreatic tumor specimens. We found significant up-regulation of KIF14 and ARHGDIβ mRNA levels in patients with pancreatic cancer, and both proteins were differentially expressed in tumor cells invading the perineural niche of pancreatic cancer patients as detected by immunohistochemistry. Moreover, functional knockdown of KIF14 and ARHGDIβ using small interfering RNA resulted in altered basal and/or perineural invasion of pancreatic tumor cells. Our work provides novel insights into the molecular determinants of perineural invasion in pancreatic cancer. The established nerve invasion model and the consensus signature of perineural invasion could be instrumental in the identification of novel therapeutic targets of pancreatic cancer as exemplified by KIF14 and ARHGDIβ.
EMMPRIN (extracellular matrix metalloproteinase inducer, CD147) participates in the progression of various malignancies by stimulating the synthesis of specific matrix metalloproteinases (MMP) from peritumoral fibroblasts. In the present study, the expression and functional role of EMMPRIN was investigated in pancreatic neoplasm. QRT-PCR, immunohistochemistry, immunoblot, and ELISA analyses were used to analyze the expression, localization, and release of EMMRPIN. Silencing of EMMPRIN was performed using siRNA oligonucleotides, and functional consequences were assessed using growth assays, invasion assays, as well as MMP1/MMP2 and VEGF ELISA. EMMPRIN mRNA levels were 2.2-fold increased in pancreatic cancer (n = 52) and 2.0-3.5-fold increased in other pancreatic neoplasm (n = 105), but unchanged in chronic pancreatitis (n = 10) compared to normal pancreatic tissues (n = 9). Strong and predominantly membranous immunostaining was observed in the cancer cells and surrounding stromal cells. EMMPRIN serum levels were also significantly increased in pancreatic cancer patients (n = 44) (4.13 ± 0.28 ng/ml) with an AUC of 0.97 compared to healthy volunteers (n = 29) (0.95 ± 0.16 ng/ml; p < 0.0001) and with an AUC of 0.74 compared to chronic pancreatitis patients (n = 20) (2.98 ± 0.5 ng/ml; p = 0.0021). EMMPRIN silencing did not significantly affect anchorage-dependent or -independent growth of pancreatic cancer cells. In contrast, EMMPRIN silencing in pancreatic stellate cells slightly repressed VEGF and MMP2 levels but strongly increased pro-MMP1 expression under coculture conditions. In conclusion, Increased EMMPRIN expression is present in different pancreatic neoplasm, likely representing a tumor-specific reaction with the potential to modulate the tumor microenvironment rather than a mere reflection of an activated stroma.
Hsulf-1 is a newly identified enzyme, which has the ability to decrease the growth of hepatocellular, ovarian, and head and neck squamous cell carcinoma cells by interfering with heparin-binding growth factor signaling. Since pancreatic cancers over-express a number of heparin-binding growth factors and their receptors, the expression and function of this enzyme in pancreatic cancer was analyzed.ResultsPancreatic cancer samples expressed significantly (22.5-fold) increased Hsulf-1 mRNA levels compared to normal controls, and Hsulf-1 mRNA was localized in the cancer cells themselves as well as in peritumoral fibroblasts. 4 out of 8 examined pancreatic cancer cell lines expressed Hsulf-1, whereas its expression was below the level of detection in the other cell lines. Stable transfection of the Hsulf-1 negative Panc-1 pancreatic cancer cell line with a full length Hsulf-1 expression vector resulted in increased sulfatase activity and decreased cell-surface heparan-sulfate proteoglycan (HSPG) sulfation. Hsulf-1 expression reduced both anchorage-dependent and -independent cell growth and decreased FGF-2 mediated cell growth and invasion in this cell line.ConclusionHigh expression of Hsulf-1 occurs in the stromal elements as well as in the tumor cells in pancreatic cancer and interferes with heparin-binding growth factor signaling.
Aim: To determine the role of two antiapoptotic proteins of the inhibitor of apoptosis protein family, cellular inhibitor of apoptosis protein 1 (cIAP1) and cellular inhibitor of apoptosis protein 2 (cIAP2), in human pancreatic carcinogenesis. Methods: mRNA levels were measured in pancreatic tissues and pancreatic cancer cell lines by quantitative reverse transcriptase PCR. Protein expression was assessed in pancreatic cancer cell lines by immunoblotting and in pancreatic tissues by immunohistochemistry, and correlated with pathological and survival data. Results: cIAP1 expression was constantly high in non-neoplastic pancreatic tissues, in pancreatic intraepithelial neoplasia (PanIN) lesions, as well as in a subset of primary and metastatic pancreatic ductal adenocarcinomas (PDAC), and a preferential cytoplasmatic localisation was observed in the tumour tissues. cIAP1 expression was rare in a cohort of cystic tumours. cIAP2 mRNA levels were significantly higher (2.4 fold) in PDAC than in normal tissues. cIAP2 protein was overexpressed in PDAC, and was detectable in lowand high-grade PanIN lesions. Moreover, cIAP2 was often expressed in pancreatic cystic tumours. cIAP1 and cIAP2 mRNA and protein were detected in all the examined cell lines. Survival analysis revealed a shorter survival in patients with cIAP1/cIAP2-positive tumours. Conclusions: cIAP1 might contribute to the regulation of the apoptotic process in the normal and in the neoplastic pancreas, depending on its subcellular localisation. Overexpression of cIAP2 is a common and early event in the progression of pancreatic cancer, and could therefore potentially influence the important pathophysiological aspects of PDAC, such as anoikis or chemoresistance. I nhibition of apoptosis prolongs the survival of cancer cells and facilitates their resistance to chemotherapy and radiotherapy. Pancreatic cancer cells have a variety of mechanisms for escaping apoptotic cell death, which explains their extraordinary radioresistance and chemoresistance. Pancreatic cancer cells are resistant to apoptosis mediated by death receptors of the tumour necrosis factor (TNF) death receptor superfamily, owing to downregulation of the Fas receptor and upregulation of the non-receptor protein tyrosine phosphatase FAP-1 (Fasassociated phosphatase), which blocks the function of Fas.
Cell motility is controlled by the dynamic cytoskeleton and its related proteins, such as members of the ezrin/radixin/moesin (ERM) family, which act as signalling molecules inducing cytoskeleton remodelling. Although ERM proteins have been identified as important factors in various malignancies, functional redundancy between these proteins has hindered the dissection of their individual contribution. The aim of the present study was to analyse the functional role of moesin in pancreatic malignancies. Cancer cells of different malignant lesions of human and transgenic mice pancreata were evaluated by immunohistochemistry. For functional analysis, cell growth, adhesion and invasion assays were carried out after transient and stable knock-down of moesin expression in pancreatic cancer cells. In vivo tumourigenicity was determined using orthotopic and metastatic mouse tumour models. We now show that moesin knock-down increases migration, invasion and metastasis and influences extracellular matrix organization of pancreatic cancer. Moesin-regulated migratory activities of pancreatic cancer cells were in part promoted through cellular translocation of β-catenin, and re-distribution and organization of the cytoskeleton. Analysis of human and different transgenic mouse pancreatic cancers demonstrated that moesin is a phenotypic marker for anaplastic carcinoma, suggesting that this ERM protein plays a specific role in pancreatic carcinogenesis.
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