Hyaluronan is a ubiquitous glycosaminoglycan which is an important constituent of the extracellular matrix (ECM). In addition to organizing the extracellular matrix and regulating tissue homeostasis, hyaluronan, by binding to its main cell surface receptor CD44, is involved in intracellular signaling pathways regulating major cellular processes during development, wound healing, inflammation and cancer. Accumulation of hyaluronan in cancer promotes progression of the disease and correlates with poor prognosis. This thesis focuses on the regulation of hyaluronan synthesis and its signaling in normal and cancer cells. Cancer cells in solid tumors are surrounded by stroma, which has an essential role in the growth and metastasis of tumors. Prominent members of the tumor stroma are fibroblasts, which synthesize ECM components, such as hyaluronan, and secrete growth factors, and activate intracellular signaling pathways. We demonstrate a cross-talk between the receptors for platelet-derived growth factor BB (PDGF-BB), transforming growth factor β (TGFβ) and CD44 in dermal fibroblasts. We found that PDGF-BB can activate the Smad signaling pathway downstream of the TGFβ receptor I (TβRI), and that PDGF-BB-induced migration depends on TβRI. CD44 forms a ternary complex with the receptors for PDGF-BB and TGFβ, and negatively regulates their signaling. Furthermore, we demonstrate that TGFβ stimulation of mammary epithelial cells transcriptionally upregulates hyaluronan synthase 2 (HAS2), which is essential for TGFβ-induced epithelial-mesenchymal transition (EMT); in this process, polarized epithelial cells adapt a mesenchymal phenotype which facilitates migration and invasion. HAS2 protein activity and stability is regulated by posttranslational modifications, including ubiquitination. We investigated the ubiquitination of HAS2 in aggressive breast cancer cells, whose metastasizing capability depends on HAS2-synthesized hyaluronan. We identified two deubiquitinating enzymes, USP4 and USP17, which target HAS2 and affect its activity and stability. In summary, these studies increase the knowledge about the regulation of hyaluronan production and its role in cancer progression.

Lysophosphatidic acid (LPA) and transforming growth factor beta (TGFβ) are platelet-derived intercellular mediators of cell proliferation and motility. LPA is a general growth, survival and motility-stimulating factor in mammalian cells. TGFβ prevents proliferation of normal epithelial cells. However, the growth-inhibitory effect of TGFβ is lost or reduced in most malignant cells. Instead, TGFβ promotes migration and invasion of advanced cancer cells. Since LPA and TGFβ are both present in the blood and tumor microenvironments, we were interested in signal integration and functional outcomes in malignant epithelial cells in an LPA and TGFβ co-stimulatory context. In a subset of breast and ovarian cancer cell lines which remain sensitive to the cytostatic effect of TGFβ, we found that LPA up-regulated expression of the cyclin-dependent kinase inhibitor p21Waf1. But this up-regulation was not observed in TGFβ-resistant ones. We examined the possibility that LPA-induced p21 might contribute to the cytostatic response to TGFβ. Indeed, TGFβ alone induced p21 expression weakly in TGFβ-sensitive cells. Serum or serum-borne LPA cooperated with TGFβ to elicit the maximal p21 induction. LPA stimulated p21 via LPA1 and LPA2 receptors and Erk-dependent activation of the CCAAT/enhancer-binding protein beta (C/EBPβ) transcription factor independent of p53. Loss or gain of p21 expression led to a shift between TGFβ sensitive and resistant phenotypes in breast and ovarian cancer cells, indicating that LPA-induced p21 is a key determinant of the growth inhibitory activity of TGFβ. The p21-stimulatory action of LPA is absent from most breast and ovarian cancer cells, leading to their resistance to TGFβ. Therefore we reveal a novel crosstalk between LPA and TGFβ that underlies TGFβ sensitive and resistant phenotypes of breast and ovarian cancer cells. In the next part of our study, we examined the role of interactions between LPA and TGFβ in regulation of tumor cell motility. LPA and, to a much less extent, TGFβ stimulate chemotactic migration and invasion of breast and ovarian cancer cells. However, when combined together with LPA, TGFβ strongly attenuated LPA-driven migration and invasion of breast and ovarian cancer cells. This inhibitory effect was most likely mediated through TGFβ downregulation of expression of LPA1, the major receptor subtype responsible for LPA-regulated cell migration. Knockdown of Smad3 or Smad4 with small hairpin RNA (shRNA) eliminated the inhibitory effects of TGFβ on the LPA1 expression and LPA-dependent cell migration. There are two potential TGFβ inhibitory elements (TIE) (-40 bp and -401 bp) present in the human LPA1 gene promoter. Deletion or point mutation of the distal TIE at around -401 bp abolished the inhibitory effect of TGFβ on the LPA1 promoter activity as revealed by luciferase assays. A DNA pull-down assay showed that the -401-TIE-E2F4/5 sequence was capable of binding Samd3, Smad4, and E2F4/5 in TGFβ-treated cells. The binding of the Smad complex to the native TIE-E2F4/5 sequences of the LPA1 gene promoter was further verified by chromatin immunoprecipitation assay. Our results identify a novel role of TGFβ in the control of LPA1 expression and LPA1-coupled biological activities, adding LPA1 to the list of TGFβ-repressed target genes.

No description available.

The control of growth is a poorly understood aspect of animal development. This thesis focuses on body size regulation in Caenorhabditis elegans, and in particular, how worms grow to a certain size. In C. elegans, a key regulator of size is the TGFβ homologue DBL-1. Mutations that deplete the worm of DBL-1 result in a small body size, whereas overexpression of the gene renders long animals. The small mutants have the same number of cells as wild type suggesting that some or all cells are smaller. DBL-1 activates a TGFβ receptor leading to the nuclear localization of three Smad proteins which then initiate a transcriptional program for size control whose targets are mainly unknown. In order to learn more about how body size in C. elegans is regulated, we set up EMS mutagenesis screens to identify new loci that caused a long phenotype. A subset of the genes we have identified might function in the TGFβ signaling pathway regulating growth while others likely function in parallel pathways. One gene that we found in this screen, lon-3, encodes a cuticle collagen that genetically lies downstream of the DBL-1 TGFβ signaling pathway. Interestingly, loss of function mutations in lon-3 result in a Lon phenotype, whereas increasing the amount of LON-3 protein cause the worms to be dumpy, i.e. shorter, but slightly fatter than wild type. LON-3 is expressed in the hypodermis, the tissue from which the cuticle is synthesized and in which TGFβ signaling, regulating body size, has its focus. This study and previous work have shown that DBL-1 may affect body volume via effects on hypodermal nuclear ploidy, however this is unaffected in lon-3 mutants. Consistent with this finding, the volume of lon-3 mutant worms is not different from wild type. Taken together, our results suggest that another mechanism, by which TGFβ signaling can regulate body length, is by altering the shape of the cuticle via its effect on lon-3 and possibly other cuticle collagens. Studies in worms, flies and mice show that body size and nutrient allocation are closely connected. p70 S6-kinase (S6K) is a known regulator of cell and body size that also plays a role in metabolism. In mice and flies S6K mutants are much smaller than wild type. Our work on the worm homolog, rsks-1, shows that in worms as well, this gene is important for growth regulation and cell size. However, this effect seems to be at least in part independent of DBL-1 TGFβ signaling. Furthermore, rsks-1mutants have a 50 % increase in the amount of stored fat. Fatty acid metabolism has been shown to play an important role in environmental adaptation, especially in regards to temperature changes. Consistent with this idea, rsks-1 mutants appear to have difficulties in adjusting to such changes, reflected in a much-decreased fecundity at 15 and 25 °C compared to their cultivation temperature (20 °C). Within the nervous system the gene is specifically expressed in a subset of the chemosensory neurons that, when nutrients are abundant, secrete signals that promote growth. Intriguingly, this expression seems to be negatively regulated by insulin- like signaling, in contrast to the positive regulation of S6K by insulin in Drosophila and mice. Taken together we show that rsks-1 is an important regulator of growth and fat metabolism in Caenorhabditis elegans.

The vitamin D metabolite 1,25(OH)2D3 has long been known to inhibit growth of prostate cancer cells and this mainly through a VDR-mediated pathway controlling target gene expression, resulting in cell cycle arrest, apoptosis and differentiation. Another major way in which 1,25(OH)2D3 inhibits cell growth in prostate cancer is via membrane-initiated steroid signalling, which triggers activation of signal cascades upon steroid binding to a receptor complex, leading to induction of genes regulating cell growth, proliferation and apoptosis. The main prostate cancer inhibiting membrane-initiated route is the TGFβ signalling pathway, elicited by the protein TGFβ. Two other important proteins downstream in this cascade are Smad2 and Smad3. In this study the early effects of 1,25(OH)2D3 on activated Smad2/3 levelsin PC-3 prostate cancer cells were examined. PC-3 cells were incubated for 3, 5, 10, 30 and 60 minutes as well as 38 hours both together with 1,25(OH)2D3 of the concentrations 10-10 and 10-7 M and without. Western Blots were then performed on supernatants from the cells treated followed by treatment of the membranes with primary antibodies against phosphorylated Smad2/3 C-terminal linker regions, alkaline phosphatase conjugated secondary antibodies and finally visualization with BCIP/ NBT tablets. As the downstream cascade protein JNK is a proposed activator of Smad2/3, this procedure was also repeated with a JNK inhibitor. This is a follow-up to an earlier study which examined the influence of 1,25(OH)2D3 on TGFβ levels using the same doses and time points and which found that 1,25(OH)2D3 initially lowered the level of active TGFβ, then increased it. The results of this study indicated a 1,25(OH)2D3 mediated induction of the same pattern in the levels of active Smad2 and 3, both with and without JNK inhibitor. The results did not indicate that 1,25(OH)2D3 activates the Smad2/3 C-terminal linker region via the JNK pathway.

The vitamin D metabolite 1,25(OH)2D3 has long been known to inhibit growth of prostate cancer cells and this mainly through a VDR-mediated pathway controlling target gene expression, resulting in cell cycle arrest, apoptosis and differentiation. Another major way inwhich 1,25(OH)2D3 inhibits cell growth in prostate cancer is via membrane-initiated steroid signalling, which triggers activation of signal cascades upon steroid binding to a receptor complex, leading to induction of genes regulating cell growth, proliferation and apoptosis. The main prostate cancer inhibiting membrane-initiated route is the TGFβ signalling pathway, elicited by the protein TGFβ. Another important protein downstream in this cascade is Smad2. In this study the early effects of 1,25(OH)2D3 on activated Smad2 levels in PC-3 prostate cancer cells were examined. PC-3 cells were incubated for 5, 10, 30 and 60 minutes as well as 24 and 40 hours both together with 1,25(OH)2D3 of the concentrations 10-10 and 107 M and without. An ELISA assay scanning for activated Smad2 was then performed on supernatants from both treated and untreated cells. This is a follow-up to an earlier study which examined the influence of 1,25(OH)2D3 on TGFβ levels using the same doses and similar time points and which found that 1,25(OH)2D3 initially lowered the level of active TGFβ, then increased it. The results of this study showed a statistically insignificant, time delayed 1,25(OH)2D3 mediated induction of the same pattern in the levels of active Smad2. / Project Work in Biomedicine, Advanced Level, 7.5 ECTS

<p>The vitamin D metabolite 1,25(OH)2D3 has long been known to inhibit growth of prostate cancer cells and this mainly through a VDR-mediated pathway controlling target gene expression, resulting in cell cycle arrest, apoptosis and differentiation. Another major way in which 1,25(OH)2D3 inhibits cell growth in prostate cancer is via membrane-initiated steroid signalling, which triggers activation of signal cascades upon steroid binding to a receptor complex, leading to induction of genes regulating cell growth, proliferation and apoptosis. The main prostate cancer inhibiting membrane-initiated route is the TGFβ signalling pathway, elicited by the protein TGFβ. Two other important proteins downstream in this cascade are Smad2 and Smad3. In this study the early effects of 1,25(OH)2D3 on activated Smad2/3 levelsin PC-3 prostate cancer cells were examined. PC-3 cells were incubated for 3, 5, 10, 30 and 60 minutes as well as 38 hours both together with 1,25(OH)2D3 of the concentrations 10-10 and 10-7 M and without. Western Blots were then performed on supernatants from the cells treated followed by treatment of the membranes with primary antibodies against phosphorylated Smad2/3 C-terminal linker regions, alkaline phosphatase conjugated secondary antibodies and finally visualization with BCIP/ NBT tablets. As the downstream cascade protein JNK is a proposed activator of Smad2/3, this procedure was also repeated with a JNK inhibitor. This is a follow-up to an earlier study which examined the influence of 1,25(OH)2D3 on TGFβ levels using the same doses and time points and which found that 1,25(OH)2D3 initially lowered the level of active TGFβ, then increased it. The results of this study indicated a 1,25(OH)2D3 mediated induction of the same pattern in the levels of active Smad2 and 3, both with and without JNK inhibitor. The results did not indicate that 1,25(OH)2D3 activates the Smad2/3 C-terminal linker region via the JNK pathway.</p>

<p>The vitamin D metabolite 1,25(OH)2D3 has long been known to inhibit growth of prostate cancer cells and this mainly through a VDR-mediated pathway controlling target gene expression, resulting in cell cycle arrest, apoptosis and differentiation. Another major way inwhich 1,25(OH)2D3 inhibits cell growth in prostate cancer is via membrane-initiated steroid signalling, which triggers activation of signal cascades upon steroid binding to a receptor complex, leading to induction of genes regulating cell growth, proliferation and apoptosis. The main prostate cancer inhibiting membrane-initiated route is the TGFβ signalling pathway, elicited by the protein TGFβ. Another important protein downstream in this cascade is Smad2. In this study the early effects of 1,25(OH)2D3 on activated Smad2 levels in PC-3 prostate cancer cells were examined. PC-3 cells were incubated for 5, 10, 30 and 60 minutes as well as 24 and 40 hours both together with 1,25(OH)2D3 of the concentrations 10-10 and 107 M and without. An ELISA assay scanning for activated Smad2 was then performed on supernatants from both treated and untreated cells. This is a follow-up to an earlier study which examined the influence of 1,25(OH)2D3 on TGFβ levels using the same doses and similar time points and which found that 1,25(OH)2D3 initially lowered the level of active TGFβ, then increased it. The results of this study showed a statistically insignificant, time delayed 1,25(OH)2D3 mediated induction of the same pattern in the levels of active Smad2.</p> / Project Work in Biomedicine, Advanced Level, 7.5 ECTS

Prostate cancer is the most common invasive cancer diagnosed in men and a major and growing health problem in Western countries. Deregulation of different pathways has been implicated in progression of prostate cancer, namely nuclear factor kappa enhancer binding protein (NF-κB), transforming growth factor β (TGFβ), phosphoinositide 3ʹ-kinase/AKT (PI3K/AKT) and Src kinase pathways. However, the detailed mechanisms by which TGFβ activates these pathways to contribute in tumorigenesis and invasive behavior of prostate cancer cells have not been elucidated. We have demonstrated (paper I) that the E3 ligase activity of TRAF6 is crucial for recruitment of the regulatory subunit of PI3K, p85α, to TβRI and for TGFβ-induced Lys63-linked polyubiquitination of p85α. TRAF6 is required for the TGFβ-induced recruitment of AKT to the complex of PI3K and TβRI, where the polyubiquitination and activation of AKT occurs. When activated, AKT promotes TGFβ-induced cell migration which is dependent on p85 and PI3K activity, as well as on TRAF6, but not on TβRI kinase activity. Thus, TGFβ-induced activation of PI3K/AKT induces cell motility contributing to the progression of cancer. We have demonstrated (paper II) a pivotal role of TAK1 polyubiquitination in three different pathways, including TNFR, IL-1R, and TLR4 signaling. Lys63-linked polyubiquitination of TAK1 at Lys34 is essential for downstream signaling to NF-κB-mediated target gene expression in both cancer and immune cells. These findings are of importance for the understanding of the mechanism of activation of NF-κB in inflammation and may aid in the development of new therapeutic strategies to treat chronic inflammation and cancer. We have also shown (paper III) that TGFβ activates the tyrosine kinase Src via formation of a complex between TβRI and Src. The E3 ligase TRAF6 promotes the formation of the complex in a manner not dependent on its ubiquitin ligase activity, suggesting that TRAF6 acts as an adaptor. Moreover, the activation of Src is not dependent on the kinase activity of TβRI. On a functional level, Src activity was found to be necessary for TGFβ-induced chemotaxis. In conclusion, we have elucidated molecular mechanisms whereby TGFβ activates non-Smad pathways, i.e. PI3K and Src. Our findings shed light on the pro-tumorigenesis mechanisms of TGFβ. In addition, we have demonstrated how the activation of TAK1, an important component of the TGFβ non-Smad pathway, by TGFβ and other stimuli leads to the activation of NF-κB and thereby induction of inflammation which likely contributes to prostate cancer progression.

The development of the mature cardiovascular system is one of the most captivating stories in embryonic development. The heart is the first organ to form in embryogenesis, and is functional early in development to perfuse the embryo with blood supplying oxygen and the nutrients required for organogenesis. The structural changes in heart development required for formation of the mature four chambered heart are under tight molecular regulation. Severe defects manifest as gross structural malformations of the valves, septa, or vessels that result in physiological consequences that my include hypertension, arrhythmia, or heart failure and may ultimately lead to lethality. According to the American Heart Association, cardiovascular disease is the leading cause of mortality worldwide. A more detailed understanding of the origin of congenital heart defects is necessary for improving prediction, diagnosis, and treatment of cardiovascular disease. Derived from the epicardium, coronary vessel formation relies on growth factor as well as extracellular matrix (ECM) influences on cells of the epicardium that regulate proliferation, motility, invasion and differentiation. The Transforming Growth Factor β (TGFβ) family of receptors have been well described in regulating cardiovascular development. The Type III TGFβ receptor (TGFβR3) has been shown to be required for development of the coronary vessels. Mouse embryos lacking TGFβR3 exhibit inhibited invasion of epicardially derived cells (EPDCs) into the myocardium. This delay of cell invasion of EPDCs and formation of coronary vessels is lethal at E 14.5. Relative to Tgfbr3+/+ cells, epicardial cells lacking TGFβR3 are hypo-proliferative, deficient in cell invasion, and deficient in executing TGFβ ligand and High-Molecular Weight Hyaluronan (HMWHA) stimulated cell invasion. Hyaluronan (HMWHA) is a glycosaminoglycan unmodified sugar extracellular matrix (ECM) molecule synthesized by the Hyaluronan Synthase (Has) family of enzymes. Mouse embryos lacking Hyaluronan Synthase 2 (Has2) are lethal at E 9.5 as a result of severely blocked cardiogenesis due to insufficient endocardial EMT. HA serves structural and bioactive functions in its capacity to stimulate signal transduction pathways required for EMT. Src kinase is a non-receptor tyrosine kinase well characterized to function in growth factor as well as ECM signal transduction, but its role in epicardial cell biology is unclear. Our hypothesis is that Src kinase is a critical regulator of TGFβ and Hyaluronan induced epicardial cell invasion, differentiation and migration during coronary vessel development. Our studies reveal that Src activity is required for TGFβ2-induced synthesis of HA in epicardial cells. We show Src is required for TGFβ2-induced vascular smooth muscle differentiation as well as TGFβ2-induced EMT, cell invasion, and filamentous actin polymerization. Src activity is sufficient to drive epicardial activation of EMT, but not vascular smooth muscle differentiation. These data show that Src is required in the context of TGFβ2-stimulated invasion and differentiation, and sufficient to drive activation of EMT. Next we demonstrate that TGFβR3 and Src are required for HMWHA induced cell invasion and filamentous actin polymerization in epicardial cells. HMWHA induces activation of Src kinase in Tgfbr3+/+ epicardial cells, but not Tgfbr3-/- epicardial cells. siRNA knockdown of TGFβR3 in Tgfbr3+/+ epicardial cells subsequently stimulated with HMWHA phenocopy this deficit in Src activation. Tgfbr3-/- epicardial cells fail to activate Rac1 or RhoA GTPases in the presence of HMWHA. Finally, we demonstrate stimulus independent activation of TGFβR3 is sufficient to activate Src. Taken together, these constitute novel findings establishing TGFβR3 as an HMWHA responsive receptor that is upstream of Src signal transduction. Migration of the epicardium to cover the looped and functioning heart tube is an early step required for development of the coronary vessels. We demonstrate that Tgfbr3-/- epicardial cells are delayed in cell migration relative to Tgfbr3+/+ cells in a wound healing model of cell migration. Tgfbr3-/- cells lack expression of BMP2 mRNA, we found that exogenous BMP2 is sufficient to drive Tgfbr3-/- (but not Tgfbr3+/+) cell migration to levels comparable to unstimulated Tgfbr3+/+ epicardial cells, without enhancing cell proliferation. We demonstrate that Src is required for this BMP2 induced cell migration and filamentous actin polymerization in Tgfbr3-/- cells. These studies demonstrate mechanisms required for TGFβ ligand as well as HMWHA stimulated epicardial cell behavior changes have a common mediator in Src kinase, and provide novel insights into early events in the development of the cardiovascular system. The adult epicardium has been demonstrated to participate in repair of ischemic myocardium in mouse models of myocardial infarction. Expression of molecules required for coronary vessel development are re-expressed in this regeneration (as discussed in chapter 5). Elucidating these pathways will constitute important future targets in aiding in adult cardiovascular regeneration and cardioprotection in adult heart disease.