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The tumour-associated stroma, consisting of fibroblasts, inflammatory cells, vasculature and extracellular matrix proteins, plays a critical role in tumour growth, but how it regulates cancer cell migration and metastasis is poorly understood. The Wnt-planar cell polarity (PCP) pathway regulates convergent extension movements in vertebrate development. However, it is unclear whether this pathway also functions in cancer cell migration. In addition, the factors that mobilize long-range signalling of Wnt morphogens, which are tightly associated with the plasma membrane, have yet to be completely characterized. Here, I show that fibroblasts secrete membrane microvesicles of endocytic origin, termed exosomes, which promote tumour cell protrusive activity, motility and metastasis via the exosome component Cd81. In addition, I demonstrate that fibroblast exosomes activate autocrine Wnt-PCP signalling in breast cancer cells as detected by the association of Wnt with Fzd receptors and the asymmetric distribution of Fzd-Dvl and Vangl-Pk complexes in exosome-stimulated cancer cell protrusive structures. Moreover, I show that Pk expression in breast cancer cells is essential for fibroblast-stimulated cancer cell metastasis. Lastly, I reveal that trafficking in cancer cells promotes tethering of autocrine Wnt11 to fibroblast exosomes. These studies further our understanding of the role of the tumour-associated stroma in cancer metastasis and bring us closer to a more targeted approach for the treatment of cancer spread.

The tumour-associated stroma, consisting of fibroblasts, inflammatory cells, vasculature and extracellular matrix proteins, plays a critical role in tumour growth, but how it regulates cancer cell migration and metastasis is poorly understood. The Wnt-planar cell polarity (PCP) pathway regulates convergent extension movements in vertebrate development. However, it is unclear whether this pathway also functions in cancer cell migration. In addition, the factors that mobilize long-range signalling of Wnt morphogens, which are tightly associated with the plasma membrane, have yet to be completely characterized. Here, I show that fibroblasts secrete membrane microvesicles of endocytic origin, termed exosomes, which promote tumour cell protrusive activity, motility and metastasis via the exosome component Cd81. In addition, I demonstrate that fibroblast exosomes activate autocrine Wnt-PCP signalling in breast cancer cells as detected by the association of Wnt with Fzd receptors and the asymmetric distribution of Fzd-Dvl and Vangl-Pk complexes in exosome-stimulated cancer cell protrusive structures. Moreover, I show that Pk expression in breast cancer cells is essential for fibroblast-stimulated cancer cell metastasis. Lastly, I reveal that trafficking in cancer cells promotes tethering of autocrine Wnt11 to fibroblast exosomes. These studies further our understanding of the role of the tumour-associated stroma in cancer metastasis and bring us closer to a more targeted approach for the treatment of cancer spread.

Therapeutic resistance of tumours represents an important clinical issue. We can classify the therapeutic tumour resistance in two ways. According to the clinical course, tumours can behave either as primary resistant, i.e. from the very beginning not responsive, or they can display a secondary (also called acquired) resistance, whereby an initial clinical response is lost and the tumour develops into chemo-, radio- or immunoresistant disease. An alternative classification distinguishes cell autonomous resistance mechanisms from resistance that relies on complex interactions within the context of tumour microenvironment. From the research perspective, modelling therapeutic resistance frequently involves experimental treatment of sensitive cancer cells and selection of daughter resistant cell lines. The Ph.D. thesis includes derivation of two unique models of urothelial bladder carcinoma therapeutic resistance. The first model involves newly established urothelial carcinoma cell lines BC44 and BC44DoxoR, which resulted from a prolonged doxorubicin exposure of the mother cell line. The daughter chemoresistant cell line exhibits multidrug resistant phenotype, which extends beyond the selecting drug - doxorubicin - to four additional chemotherapeutic drugs (cisplatin, methotrexate, vinblastine, and...

The tumor microenvironment is a key modulator in cancer progression and has become a novel target in cancer therapy. An increase in hyaluronan (HA) accumulation and metabolism can be found in advancing tumor progression and are often associated with aggressive malignancy, drug resistance and poor prognosis. Wound-healing related myofibroblasts or activated cancer-associated fibroblasts (CAF) are assumed to be the major sources of HA. Both cell types are capable to synthesize new matrix components as well as reorganize the extracellular matrix. However, to which extent myofibroblasts and CAF perform these actions are still unclear. In this work, we investigated the matrix remodeling and HA production potential in normal human dermal fibroblasts (NHFB) and CAF in the absence and presence of transforming growth factor beta -1 (TGF-β1), with TGF-β1 being a major factor of regulating fibroblast differentiation. Three-dimensional (3D) collagen matrix was utilized to mimic the extracellular matrix of the tumor microenvironment. We found that CAF appeared to response insensitively towards TGF-β1 in terms of cell proliferation and matrix remodeling when compared to NHFB. In regards of HA production, we found that both cell types were capable to produce matrix bound HA, rather than a soluble counterpart, in response to TGF-β1. However, activated CAF demonstrated higher HA production when compared to myofibroblasts. The average molecular weight of produced HA was found in the range of 480 kDa for both cells. By analyzing gene expression of HA metabolizing enzymes, namely hyaluronan synthase (HAS1-3) and hyaluronidase (HYAL1-3) isoforms, we found expression of specific isoforms in dependence of TGF-β1 present in both cells. In addition, HAS2 and HYAL1 are highly expressed in CAF, which might contribute to a higher production and degradation of HA in CAF matrix. Overall, our results suggested a distinct behavior of NHFB and CAF in 3D collagen matrices in the presence of TGF-β1 in terms of matrix remodeling and HA production pointing to a specific impact on tumor modulation.