Alexander König

Sp1 is required for transforming growth factor-beta-induced mesenchymal transition and migration in pancreatic cancer cells.

Transition from a sessile epithelial phenotype to a migrating mesenchymal phenotype is a crucial step in transforming growth factor-beta (TGF-beta)-induced pancreatic cancer cell migration and invasion. These profound morphologic and functional alterations are associated with characteristic changes in TGF-beta-regulated gene expression, defined by rapid repression of epithelial markers and a strong and sustained transcriptional induction of mesenchymal markers such as the intermediate filament vimentin. In this study, we have analyzed the role of the transcription factor Sp1 in TGF-beta-induced and Smad-mediated gene regulation during epithelial to mesenchymal transition (EMT) and migration of pancreatic cancer cells. Here, we show that Sp1 is required for TGF-beta-induced EMT, and that this function is especially mediated through transcriptional induction of vimentin. Our results emphasize the functional relevance of vimentin in TGF-beta-induced EMT because prevention of its induction strongly reduces cell migration. Altogether, this study helps to better understand the role of Sp1 in TGF-beta-induced progression of pancreatic cancer. It suggests that Sp1, via transcriptional induction of vimentin, cooperates with activated Smad complexes in mesenchymal transition and migration of pancreatic cancer cells upon TGF-beta stimulation.

Selective Internal Radiotherapy with Yttrium-90 Microspheres for Hepatic Metastatic Neuroendocrine Tumors: A Prospective Single Center Study

Background: To assess prospectively the safety and efficacy of Yttrium-90 microspheres in patients with unresectable liver metastases from neuroendocrine tumors. Materials and Methods: Microspheres were administered via a temporarily placed hepatic catheter. Patients were monitored prospectively. All patients were followed with laboratory and imaging studies at regular intervals to determine response rates. Toxicity and quality of life scores were measured. Results: Nine patients (7 female) with a mean age of 58.8 years were enrolled in this prospective trial. The mean tumor load was 58.8%. The estimated percentage shunting to the lungs on MAA scans was 5.04 ± 2.4%. Visceral artery embolization of extrahepatic arteries before treatment was performed in 6 patients. The median dose of microspheres was 2.1 ± 0.4 GBq. A total of 12 therapy sessions was performed. The mean follow-up was 21.7 months. Technical success was 100%. No major complications occurred. Survival rates were 100, 57 and 57% for 1, 2 and 3 years, respectively. Three months after SIRT therapy partial response (PR) was seen in 6 patients (66%). Calculated reduction of liver metastasis volume was 49%. In 3 patients (33%) stable disease was seen with a calculated tumor reduction of 13%. The estimated time to progression was 11.1 months. Conclusion: Radioembolization with 90Y microspheres is safe and produces high response rates even with extensive tumor replacement for up to 1 year. Acute and late toxicity was very low. Further investigations compared with other local ablative techniques is warranted.

Collagen type I-induced Smad-interacting protein 1 expression downregulates E-cadherin in pancreatic cancer.

Pancreatic cancer is a devastating disease with poor prognosis. Production of large quantities of extracellular matrix and early metastasis are characteristics of this disease. One important step in the development of various cancers is the loss of E-cadherin gene expression or inactivation of E-cadherin mediated cell–cell adhesion. It has been shown that collagen type I promotes downregulation of E-cadherin expression, which correlates with enhanced cell migration and invasiveness. In this context, we elucidated the role of Smad-interacting protein 1 (SIP1), which has been discussed as a negative regulator of E-cadherin gene expression. We demonstrate that SIP1 upregulation shows an inverse relationship with E-cadherin in advanced pancreatic tumour stages. In Panc-1 cells, SIP1 expression can be induced by exposure to collagen type I in a src-dependent manner. In addition, overexpression of SIP1 reduces E-cadherin mRNA and protein levels. Taken together, these results suggest that SIP1 is involved in the progression of pancreatic cancer and plays a role in mediating signal transduction from collagen type I to downregulate E-cadherin expression.

Sequential Activation of NFAT and c-Myc Transcription Factors Mediates the TGF-β Switch from a Suppressor to a Promoter of Cancer Cell Proliferation

Transforming growth factor β (TGF-β) has a dual role in carcinogenesis, acting as a growth inhibitor in early tumor stages and a promoter of cell proliferation in advanced diseases. Although this cellular phenomenon is well established, the underlying molecular mechanisms remain elusive. Here, we report that sequential induction of NFAT and c-Myc transcription factors is sufficient and required for the TGF-β switch from a cell cycle inhibitor to a growth promoter pathway in cancer cells. Mechanistically, TGF-β induces in a calcineurin-dependent manner the expression and activation of NFAT factors, which then translocate into the nucleus to promote c-Myc expression. In response to TGF-β, activated NFAT factors bind to and displace Smad3 repressor complexes from the previously identified TGF-β inhibitory element (TIE) to transactivate the c-Myc promoter. c-Myc in turn stimulates cell cycle progression and growth through up-regulation of D-type cyclins. Most importantly, NFAT knockdown not only prevents c-Myc activation and cell proliferation, but also partially restores TGF-β-induced cell cycle arrest and growth suppression. Taken together, this study provides the first evidence for a Smad-independent master regulatory pathway in TGF-β-promoted cell growth that is defined by sequential transcriptional activation of NFAT and c-Myc factors.

Inflammation-Induced NFATc1–STAT3 Transcription Complex Promotes Pancreatic Cancer Initiation by KrasG12D

UNLABELLED Cancer-associated inflammation is a molecular key feature in pancreatic ductal adenocarcinoma. Oncogenic KRAS in conjunction with persistent inflammation is known to accelerate carcinogenesis, although the underlying mechanisms remain poorly understood. Here, we outline a novel pathway whereby the transcription factors NFATc1 and STAT3 cooperate in pancreatic epithelial cells to promote Kras(G12D)-driven carcinogenesis. NFATc1 activation is induced by inflammation and itself accelerates inflammation-induced carcinogenesis in Kras(G12D) mice, whereas genetic or pharmacologic ablation of NFATc1 attenuates this effect. Mechanistically, NFATc1 complexes with STAT3 for enhancer-promoter communications at jointly regulated genes involved in oncogenesis, for example, Cyclin, EGFR and WNT family members. The NFATc1-STAT3 cooperativity is operative in pancreatitis-mediated carcinogenesis as well as in established human pancreatic cancer. Together, these studies unravel new mechanisms of inflammatory-driven pancreatic carcinogenesis and suggest beneficial effects of chemopreventive strategies using drugs that are currently available for targeting these factors in clinical trials. SIGNIFICANCE Our study points to the existence of an oncogenic NFATc1-STAT3 cooperativity that mechanistically links inflammation with pancreatic cancer initiation and progression. Because NFATc1-STAT3 nucleoprotein complexes control the expression of gene networks at the intersection of inflammation and cancer, our study has significant relevance for potentially managing pancreatic cancer and other inflammatory-driven malignancies.

Unique expression pattern of the EMT markers Snail, Twist and E-cadherin in benign and malignant parathyroid neoplasia

BACKGROUND Epithelial and mesenchymal transitions (EMT) are essential for embryonic development and progression of non-invasive tumor cells into malignant, metastatic carcinomas. During embryogenesis, the parathyroid glands develop from pharyngeal pouches and migrate to their final destinations, densely enclosed by mesenchymal neural crest cells. In this study, we examined the expression of the EMT markers Snail, Twist and E-cadherin in normal parathyroid glands and benign and malignant parathyroid diseases. METHODS Using immunohistochemistry, we compared expression of E-cadherin, Snail and Twist in 25 patients with parathyroid adenoma, 25 patients with parathyroid hyperplasia, and nine patients with parathyroid cancer with normal parathyroid glands. RESULTS Normal parathyroid glands, parathyroid adenomas, and parathyroid hyperplasias showed a typical membranous E-cadherin staining pattern. Expression of Snail was found in 22/25 parathyroid adenomas and in all parathyroid hyperplasias. Twist was expressed in 22/25 of parathyroid adenomas and in 20/25 parathyroid hyperplasias. Snail and Twist positive cells were homogeneously distributed throughout the gland. However, in all nine parathyroid carcinomas, membranous E-cadherin staining was lost. In addition, the expression pattern of Snail and Twist was changed and mostly limited to the invasive front of cancer tissue samples. CONCLUSION Expression of Snail and Twist at the invasive front and consecutive loss of E-cadherin in parathyroid carcinomas suggests a key role of EMT in the tumorigenesis of this cancer. The unique expression pattern could help to distinguish between an adenoma and a non-metastatic carcinoma. Loss of E-cadherin and change of the expression pattern of Snail and Twist together should result in an en bloc resection or a close follow-up.

Primers on molecular pathways--the NFAT transcription pathway in pancreatic cancer.

The calcineurin-responsive nuclear factor of activated T cells (NFAT) family of transcription factors was originally identified as a group of inducible nuclear proteins, which regulate transcription during T lymphocyte activation. However, following their initial discovery, a multitude of studies quickly established that NFAT proteins are also expressed in cells outside the immune system, where they participate in the regulation of the expression of genes influencing cell growth and differentiation. Ectopic activation of individual NFAT members is now recognized as an important aspect for oncogenic transformation in several human malignancies, most notably in pancreatic cancer. Sustained activation of the Ca2+/calcineurin/NFAT signaling pathway has emerged as a powerful regulatory principle governing pancreatic cancer cell growth. Activated NFAT proteins form complexes with key oncogenic proteins to regulate the transcription of master cell cycle regulators and proteins with functions in cell survival, migration and angiogenesis. This review pays particular attention to recent advances in our understanding of how the NFAT transcription pathway controls gene expression during development and progression of pancreatic cancer.

Disruption of a Nuclear NFATc2 Protein Stabilization Loop Confers Breast and Pancreatic Cancer Growth Suppression by Zoledronic Acid

The aminobisphosphonate zoledronic acid has elicited significant attention due to its remarkable anti-tumoral activity, although its detailed mechanism of action remains unclear. Here, we demonstrate the existence of a nuclear GSK-3β-NFATc2 stabilization pathway that promotes breast and pancreatic cancer growth in vitro and in vivo and serves as a bona fide target of zoledronic acid. Specifically, the serine/threonine kinase GSK-3β stabilizes nuclear NFATc2 through phosphorylation of the serine-rich SP2 domain, thus protecting the transcription factor from E3-ubiquitin ligase HDM2-mediated proteolysis. Zoledronic acid disrupts this NFATc2 stabilization pathway through two mechanisms, namely GSK-3β inhibition and induction of HDM2 activity. Upon nuclear accumulation, HDM2 targets unphosphorylated NFATc2 for ubiquitination at acceptor lysine residues Lys-684/Lys-897 and hence labels the factor for subsequent proteasomal degradation. Conversely, mutagenesis-induced constitutive serine phosphorylation (Ser-215, Ser-219, and Ser-223) of the SP2 domain prevents NFATc2 from HDM2-mediated ubiquitination and degradation and consequently rescues cancer cells from growth suppression by zoledronic acid. In conclusion, this study demonstrates a critical role of the GSK-3β-HDM2 signaling loop in the regulation of NFATc2 protein stability and growth promotion and suggests that double targeting of this pathway is responsible, at least to a significant part, for the potent and reliable anti-tumoral effects of zoledronic acid.

Epithelial-mesenchymal transition is a critical step in tumorgenesis of pancreatic neuroendocrine tumors.

The transcription factors Snail, Slug and Twist repress E-cadherin and induce epithelial-mesenchymal transition (EMT), a process exploited by invasive cancer cells. In this study, we evaluated the role of EMT in the tumorgenesis of neuroendocrine tumors of the pancreas (PNETs) in vitro, in vivo and human tumor specimen. Expression of EMT markers was analyzed using immunohistochemistry and real-time PCR. For in vitro studies, BON-1 cells were analyzed regarding expression of EMT markers before and after transfection with siRNA against Slug or Snail, and cell aggregation assays were performed. To asses in vivo effects, Rip1Tag2 mice were treated with vehicle or the snail-inhibitor polythlylenglykol from week 5-10 of age. The resected pancreata were evaluated by weight, tumor cell proliferation and apoptosis. Snail and Twist was expressed in 61 % and 64% of PNETs. This was associated with loss of E-cadherin. RT-PCR revealed conservation of the EMT markers Slug and Snail in BON-1 cells. Transfection with siRNA against Slug was associated with upregulation of E-cadherin, enhanced cell-cell adhesion and inhibition of cell proliferation. Snail-inhibition in vivo by PEG was associated with increased apoptosis, decreased tumor cell proliferation and dramatic reduced tumor volume in Rip1Tag2 mice. The presented data show that EMT plays a key role in tumorgenesis of PNETs. The activation of Snail in a considerable subset of human PNETs and the successful effect of Snail inhibition by PEG in islet cell tumors of transgenic mice provides first evidence of Snail as a drug target in PNETs.

Diagnostik und Therapie der chronischen Pankreatitis

ZusammenfassungDie chronische Pankreatitis (CP) ist eine schubweise verlaufende, chronische Entzündung des Pankreas, die mit einem sukzessiven Verlust der exokrinen und endokrinen Organfunktion sowie einem chronischen Schmerzsyndrom einhergeht. Am häufigsten wird die CP durch chronischen Alkoholabusus verursacht. Am zweithäufigsten wird bei Fehlen von bekannten verursachenden Faktoren eine idiopathische CP diagnostiziert. Diese Diagnose wird jedoch durch die zunehmende Entdeckung genetischer und autoimmuner Ursachen seltener. Leitsymptome der CP sind gürtelförmig ausstrahlende Oberbauchschmerzen, Diarrhö, Steatorrhö sowie die Entwicklung eines Diabetes mellitus. Die Diagnose wird klinisch, morphologisch anhand von typischen Veränderungen des Pankreasgangsystems und Kalzifikationen in bildgebenden Verfahren sowie mittels Pankreasfunktionstests gestellt. Die Behandlung der CP erfolgt in einem multimodalen Therapieansatz. Die Therapie umfasst die Überwachung symptomfreier Patienten, die Korrektur der exokrinen und endokrinen Organinsuffizienz, eine adäquate Schmerztherapie, die Behandlung akuter Schübe der Pankreatitis sowie die endoskopische oder chirurgische Behandlung lokaler Komplikationen wie Pseudozysten, Pankreasgangsteine oder Stenosen des Pankreasgangs und der Gallenwege.AbstractChronic pancreatitis (CP) is characterized by progressive, chronic inflammation of the pancreas, resulting in loss of exocrine and endocrine function and chronic abdominal pain. In most cases, CP is induced by long-term alcoholism. The second most frequent diagnosis is idiopathic CP, in the absence of known causes of CP. However, the identification of genetic and immunological causes continuously reduces the number of cases classified as idiopathic pancreatitis. Common symptoms of CP comprise abdominal pain radiating to the back, diarrhea, steatorrhea and the development of diabetes. The diagnosis is mainly based on clinical features, typical morphological findings such as pancreatic calcifications, duct stenoses and dilatations, as well as pathologic pancreatic function tests. Treatment of CP includes watch and wait strategies in asymptomatic patients, symptomatic treatment of the clinical features such as pain, exocrine and endocrine insufficiency, as well as interventional or surgical therapy of complications such as pseudocysts, pancreatic duct stenosis, stones or biliary obstruction.