Transforming growth factor-beta (TGF beta) has both tumor-suppressive and tumor-promoting effects in breast cancer. These functions are partly mediated through Smads, intracellular transcriptional... Show moreTransforming growth factor-beta (TGF beta) has both tumor-suppressive and tumor-promoting effects in breast cancer. These functions are partly mediated through Smads, intracellular transcriptional effectors of TGF beta. Smads form complexes with other DNA-binding transcription factors to elicit cell-type-dependent responses. Previously, we found that the collagen invasion and migration of pre-malignant breast cancer cells in response to TGF beta and epidermal growth factor (EGF) critically depend on multiple Jun and Fos components of the activator protein (AP)-1 transcription factor complex. Here we report that the same process is negatively regulated by Jun N-terminal kinase (JNK)-dependent cJun phosphorylation. This was demonstrated by analysis of phospho-deficient, phospho-mimicking, and dimer-specific cJun mutants, and experiments employing a mutant version of the phosphatase MKP1 that specifically inhibits JNK. Hyper-phosphorylation of cJun by JNK strongly inhibited its ability to induce several Jun/Fos-regulated genes and to promote migration and invasion. These results show that MEK-AP-1 and JNK-phospho-cJun exhibit distinct pro- and anti-invasive functions, respectively, through differential regulation of Smad- and AP-1-dependent TGF beta target genes. Our findings are of importance for personalized cancer therapy, such as for patients suffering from specific types of breast tumors with activated EGF receptor-Ras or inactivated JNK pathways. Show less
Cao, J.F.; Heijkants, R.C.; Jochemsen, A.G.; Dogrusoz, M.; Lange, M.J. de; Velden, P.A. van der; ... ; Verdijk, R.M. 2017
Cells communicate in multicellular organisms; by secreting and sensing signals, in order to adjust their behavior to the environment. Extracellular signals such as cytokines and growth factors bind... Show moreCells communicate in multicellular organisms; by secreting and sensing signals, in order to adjust their behavior to the environment. Extracellular signals such as cytokines and growth factors bind to cell surface receptors and trigger the activation of multiple protein signal transduction cascades that mediate cellular responses such as proliferation, differentiation, apoptosis and motility. The Mitogen-activated protein kinase (MAPK) family is a group of homologous proteins forming several linear signal transduction pathways. The MAPK family is conserved among eukaryotes and most vertebrates contain at least 14 MAPKs. We are interested in the molecular mechanisms of MAPK signalling that facilitate proper development of the zebrafish embryo. The zebrafish is an excellent model to delineate MAPK associated embryonic processes. The bodyplan is completed within 24hours and within a week most organs are formed. With the current available zebrafish tools molecular mechanisms could be identified and linked to cellular processes and morphological observations. We constructed constitutive active zebrafish Erk2 mutants for identification of new signalling events. We completed expression analysis of all P38 isoforms by expression analysis of the P38_ and P38_ isoforms. We also performed a comparative study between P38_ and Erk2 MAPK in gastrulation. Finally, We addressed the role of P38_ in zebrafish angiogenesis. Show less
Uveal melanoma (UM) is the most common malignancy of the eye in adults and it is the second most common form of melanoma after cutaneous melanoma (CM). The identification of patients who have a... Show moreUveal melanoma (UM) is the most common malignancy of the eye in adults and it is the second most common form of melanoma after cutaneous melanoma (CM). The identification of patients who have a high risk of developing metastases would allow the possibility of providing adjuvant therapies to prevent metastases. The application of FISH on transvitreal fine-needle aspiration biopsies is thought to be a reliable method for assaying genetic parameters such as chromosome 3 loss. However, this is based on the assumption that this chromosomal abnormality is distributed homogeneously throughout the tumor. We show that UM can be heterogeneous for the number of copies of chromosome 3 and investigated whether any evidence can be found for heterogeneity in the regulation of tumor-suppressor genes (TSG). Recently, a segregation study identified a potential locus harboring a TSG. One of the genes in this area, RASEF, was analyzed whether the RASEF gene was affected by mutations or gene silencing due to promoter methylation. The MAPK pathway is involved in the balance between melanocyte proliferation and differentiation. Whereas mutant B-RAF and N-RAS are responsible for the activation of the MAPK pathway in most CM, mutations in these genes are usually absent in UM. Nowadays, an assay with increased potential to identify mutations is available and we set out to reanalyze UM cell lines and primary UM for B-RAF mutations. We set out to explore the MAPK pathway by using MAPK profiling and tyrosine kinase arrays. Finally, conclusions drawn from above mentioned studies are summarized and put into perspective. Show less
Sotos syndrome is a childhood overgrowth disorder which is characterised by an increased statural height and/or head circumference, characteristic facial dysmorphism and a variable level of... Show moreSotos syndrome is a childhood overgrowth disorder which is characterised by an increased statural height and/or head circumference, characteristic facial dysmorphism and a variable level of learning disability. The aim of this study was to perform a comprehensive study of Sotos syndrome and it__s molecular background. Therefore, the following three yet unresolved topics were addressed: 1. The molecular basis and mechanisms of the microdeletions in Sotos syndrome. 2. The causative molecular alterations in patients with features of Sotos syndrome but without NSD1 abnormalities. 3. The signaling pathways and downstream effectors of NSD1. Show less
Multiple processes are influenced by a protein family named the function of Mitogen Activated Protein Kinases (MAPK), where among tissue morphogenesis, cell-proliferation, cell-differentiation,... Show moreMultiple processes are influenced by a protein family named the function of Mitogen Activated Protein Kinases (MAPK), where among tissue morphogenesis, cell-proliferation, cell-differentiation, cell-survival and immune reactions. A consequence of this broad role of these proteins is that disturbed MAPK signaling possibly leads to severe affects, and could even lead to the development of a disease or disturb embryogenesis. The human genome encodes for 14 mapk genes. One of the best characterized MAPK signaling transductions pathways is the Extracellular signal Regulated Kinase 1 and 2 (ERK1/ERK2). The zebrafish is a relatively new, genetic accessible model organism, which is because of their transparency of the embryos, very suitable to study the role of the MAPKs in embryonic development. The study described in this thesis shows that the zebrafish genome encodes for the same mapk genes, which makes it possible to study the functions of these proteins, using the zebrafish. Further investigations to the roles of ERK1 and ERK2 during embryonic development led to the new insight that ERK1 and ERK2 have distinct roles during crucial developmental cell migration processes and the differentiation of tissues and cell types. In addition, it was found that ERK1 and ERK2 affect the expression of common as well as distinct target genes. Show less
