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Wege H.,University of Hamburg | Heim D.,University of Hamburg | Lutgehetmann M.,University of Hamburg | Dierlamm J.,University of Hamburg | And 2 more authors.
Molecular Cancer Research | Year: 2011

Hepatocarcinogenesis is a multistep process driving the progressive transformation of normal liver cells into highly malignant derivatives. Unlimited proliferation and telomere maintenance have been recognized as prerequisites for the development of liver cancer. Moreover, recent studies identified illegitimate β-catenin signaling as relevant hit in a considerable subset of patients. To further investigate the currently not well-understood malignant evolution driven by telomerase and β-catenin, we monitored cytogenetic and phenotypic alterations in untransformed telomerase-immortalized human fetal hepatocytes following forced activation of β-catenin signaling. As expected, constitutive activation of β-catenin signaling significantly enhanced proliferation with decreasing serum dependence. Previously intact contact inhibition was almost completely eliminated. Interestingly, after several passages in cell culture, immortalized clones with dominant-positive β-catenin signaling acquired additional chromosomal aberrations, in particular translocations, anchorage-independent growth capabilities, and formed tumors in athymic nude mice. In further support for the driving role of β-catenin during hepatocarcinogenesis, improved colony growth in soft agar and accelerated tumor formation was also confirmed in Huh7 cells following stable expression of the constitutively active S33Y β-catenin mutant. Telomerase inhibition showed that short-term expansion of transformed clones was not telomerase dependent. Finally, cancer pathway profiling in derived tumors revealed upregulation of characteristic genes associated with invasion and angiogenesis. In conclusion, illegitimate activation of β-catenin signaling enhances the transformation from immortalization to malignant growth in human fetal hepatocytes. Our data functionally confirm a permissive role for β-catenin signaling in the initial phase of hepatocarcinogenesis. ©2011 AACR. Source


Herget G.W.,Albert Ludwigs University of Freiburg | Strohm P.,Albert Ludwigs University of Freiburg | Rottenburger C.,University Hospitaol Basle | Kontny U.,Albert Ludwigs University of Freiburg | And 4 more authors.
Neoplasma | Year: 2014

The Enchondroma is a common, benign, cartilage forming tumour. They usually occur as a single, asymptomatic lesion. Occasionally patients present with multiple enchondromas which is generally defined as enchondromatosis. This entity encompasses several different subtypes including Ollier disease and Maffucci syndrome (enchondromatosis associated with soft tissue haemangiomas) as the most commons. Some of them have a complicated clinical course when malignant transformation occurs. This malignant progression is a well known fact especially in enchondromatosis, but up to now there is still a lack of recommendations concerning the follow up. The aim of this article is to review the clinical and imaging features of patients with solitary enchondroma and enchondromatosis focusing on the development of secondary chondrosarcoma and the follow up. Source


Brassat U.,University of Hamburg | Balabanov S.,University of Hamburg | Bali D.,University of Hamburg | Dierlamm J.,University of Hamburg | And 11 more authors.
Experimental Hematology | Year: 2011

Objective: In chronic myeloid leukemia (CML), increased cellular turnover of hematopoietic cells driven by the oncogene BCR-ABL leads to accelerated telomere shortening despite increased telomerase activity. It has been postulated that shortened telomeres, particularly in the context of increased telomerase activity, might facilitate accumulation of genetic aberrations and, consequently, disease progression from chronic phase to accelerated phase and blast crisis. Therefore, inhibition of telomerase might be a promising approach in CML therapy. Material and Methods: To investigate the therapeutic potential of telomerase inhibition in this model disorder, we used a small molecule telomerase inhibitor, BIBR1532 as well as expression of a dominant-negative mutant of hTERT (DNhTERT-IRES-GFP) in the p53-negative CML blast crisis cell line K562 and characterized the effects in long-term culture. Furthermore, we expressed an inducible p53 construct (vector pBabe-p53ERtam) via retroviral transduction in cells with critically short telomeres and in cells with a normal telomere length to explain the role of the tumor suppressor in response to critical telomere shortening in BCR-ABL-positive cells. Results: BIBR1532-treated bulk cultures did not show altered growth kinetics despite significant telomere shortening to a critical length of approximately 5 kb. In comparison, DNhTERT-expressing clones either lost telomere length, leading to a significant but transient slow down in proliferation but eventually all escaped senescence/crisis (group I) or, alternatively, remained virtually unaffected despite measurable telomerase inhibition (group II). Further analyses of group I clones revealed impaired DNA damage response and an accumulation of dicentric chromosomes. However, upon restoration of p53 in telomerase-negative K562 clones with critically short telomeres, immediate reinduction of apoptosis and complete eradication of cells was observed, whereas vector control cells continued to escape from crisis. Conclusions: These results suggest that the success of strategies aimed at telomerase inhibition in CML is highly dependent on the presence of functional p53 and should be explored preferentially in chronic phase CML. © 2011 ISEH - Society for Hematology and Stem Cells. Source


Pflanz R.,Max Planck Institute for Chemistry | Voigt A.,Max Planck Institute for Chemistry | Voigt A.,University Medical Center Aachen | Yakulov T.,Max Planck Institute for Chemistry | And 2 more authors.
Open Biology | Year: 2015

Tao-1, the single representative of the Sterile 20 kinase subfamily in Drosophila, is best known for destabilizing microtubules at the actin-rich cortex, regulating the cytoskeletal architecture of cells. More recently, Tao-1 was shown to act in the Salvador-Warts-Hippo pathway by phosphorylating Hippo, regulating cell growth as well as cell polarity. Here, we show that tao-1 encodes two proteins, one with the Sterile 20 kinase domain (Tao-L) and one without it (Tao-S), and that they act in an antagonistic manner. Tao-L expression causes lamellipodialike cell protrusions, whereas Tao-S expression results in filopodia-like structures that make cells stick to the surface they attach to. Ectopic Tao-1 expression in the anterior region of Drosophila embryos results in pole cell formation as normally observed at the posterior end. Tao-S expression causes primordial germ cells (PGCs) to adhere to the innerwall of the gut primordia and prevents proper transepithelial migration to the gonads. Conversely, RNAi knockdowns of Tao-1 cause disordered migration of PGCs out of the gut epithelium, their dispersal within the embryo and cell death. The results reveal a novel function of Tao-1 in cell migration, which is based on antagonistic activities of two proteins encoded by a single gene. © 2015 The Authors. Published. Source


Lissat A.,Charite - Medical University of Berlin | Joerschke M.,Albert Ludwigs University of Freiburg | Shinde D.A.,Institute of Oncology Research | Braunschweig T.,RWTH Aachen | And 8 more authors.
BMC Cancer | Year: 2015

Background: The prognosis of patients with Ewing sarcoma (ES) has improved over the course of the last decades. However, those patients suffering from metastatic and recurrent ES still have only poor chances of survival and require new therapeutic approaches. Interleukin-6 (IL6) is a pleiotropic cytokine expressed by immune cells and a great variety of cancer cells. It induces inflammatory responses, enhances proliferation and inhibits apoptosis in cancer cells, thereby promoting chemoresistance. Methods: We investigated expression of IL6, its receptors and the IL6 signal transduction pathway in ES tumor samples and cell lines applying reverse transcriptase PCR, immunoblot and immunohistochemistry. The impact of IL6 on cell viability and apoptosis in ES cell lines was analyzed by MTT and propidium iodide staining, migration assessed by chorioallantoic membrane (CAM) assay. Results: Immunohistochemistry proved IL6 expression in the stroma of ES tumor samples. IL6 receptor subunits IL6R and IL6ST were expressed on the surface of ES cells. Treatment of ES cells with rhIL6 resulted in phosphorylation of STAT3. rhIL6 protected ES cells from serum starvation-induced apoptosis and promoted migration. IL6 blood serum levels were elevated in a subgroup of ES patients with poor prognosis. Conclusions: These data suggest that IL6 contributes to ES tumor progression by increasing resistance to apoptosis in conditions of cellular stress, such as serum starvation, and by promotion of metastasis. © 2015 Lissat et al. Source

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