During zebrafish gastrulation, highly coordinated cellular rearrangements lead to the formation of the three germ layers, ectoderm, mesoderm and endoderm. Recent studies have identified silberblick (slb/wnt11) as a key molecule that regulates gastrulation movement through a conserved pathway, which shares significant similarity with a signalling pathway that establishes epithelial planar cell polarity (PCP) in Drosophila (Heisenberg et al., 2000; Veeman et al., 2003), suggesting a role for cell polarity in regulating gastrulation movements. However, the cellular and molecular mechanisms by which slb/wnt11 functions during zebrafish gastrulation are still not fully understood. In the first part of the thesis, the three-dimensional movement and morphology of individual cells in living embryos during the course of gastrulation were recorded and analysed using high resolution confocal microscopy. It was shown that in slb/wnt11 mutant embryos, hypoblast cells within the forming germ ring display slower, less directed migratory movements at the onset of gastrulation, which are accompanied by defects in the orientation of cellular processes along the individual movement directions of these cells. The net movement direction of the cells is not changed, suggesting that slb/wnt11-mediated orientation of cellular processes serves to facilitate and stabilize cell movements during gastrulation. By using an in vitro reaggregation assay on mesendodermal cells, combined with an analysis of the endogenous expression levels and distribution of E-cadherin in zebrafish embryos at the onset of gastrulation, E-cadherin mediated adhesion was found to be a downstream mechanism regulating slb/wnt11 function during gastrulation. Interestingly, the effects of slb/wnt11 on cell adhesion appear to be dependent on Rab5-mediated endocytosis, suggesting endocytic turnover of cell-cell contacts as one possible mechanism through which slb/wnt11 mediates its effects on gastrulation movements. - Die Druckexemplare enthalten jeweils eine CD-ROM als Anlagenteil: QuickTimeMovies (ca. 23 MB)- Übersicht über Inhalte siehe Dissertation S. 92 - 93"

Topographical and mechanical properties of adhesive substrates provide important biological cues that affect cell spreading, migration, growth, and differentiation. The phenomenon has led to the increased use of topographically patterned and flexible substrates in studying cultured cells. However, these studies may be complicated by various limitations. For example, the effects of ligand distribution and porosity are affected by topographical features of 3D biological constructs. Similarly, many studies of mechanical cues are compounded with cellular deformation from external forces, or limited by comparative studies of separate cells on different substrates. Furthermore, understanding cell responses to mechanical input is dependent upon reliable measurements of mechanical properties. This work addresses each of these issues. To determine how substrate topography and focal adhesion kinase (FAK) affect cell shape and movement, I studied FAK-null (FAK -/-) and wild type mouse 3T3 fibroblasts on chemically identical polystyrene substrates with either flat surfaces or micron-sized pillars, I found that, compared to cells on flat surfaces, those on pillar substrates showed a more branched shape, an increased linear speed, and a decreased directional stability, which were dependent on both myosin-II and FAK. To study the dynamic responses to changes in substrate stiffness without other confounding effects, I developed a UV-modulatable substrate that softens upon UV irradiation. As atomic force microscopy (AFM) proved inadequate to detect microscale changes in stiffness, I first developed and validated a microsphere indentation method that is compatible with fluorescence microscopy. The results obtained with this method were comparable to those obtained with AFM. The UV-modulatable substrates softened by ~20-30% with an intensity of irradiation that has no detectable effect on 3T3 cells on control surfaces. Cells responded to global softening of the substrate with an initial retraction followed by a gradual reduction in spread area. Precise spatial control of softening is also possible - while there was little response to posterior softening, anterior softening elicited a pronounced retraction and either a reversal of cell polarity or a significant decrease in spread area if the cells move into the softened region. In conclusion, these techniques provide advances in gaining mechanistic insight into cellular responses to topographical and mechanical cues. Additionally, there are various other potential applications of the novel UV-softening substrate, particularly in regenerative medicine and tissue engineering.

<p>UVOD: Karcinom kolona (KK) je velik javnozdravstveni problem usled visoke incidence i stope mortaliteta. Kod KK je stadijum bolesti najvažniji pojedinačni nezavisni faktor prognoze. U prisustvu nepovoljnih prognostičkih parametara, u koje spadaju visok histolo&scaron;ki gradus, ileus, limfo-vaskularna i perineuralna invazija, nakon potencijalno kurativne operacije se kod pacijenata u stadijumu II indikuje primena adjuvantne hemioterapije koja ima pozitivan uticaj na ukupno preživljavanje i na produženje perioda bez bolesti. Međutim, relapsi bolesti nastaju kod nekih bolesnika bez negativnih prognostičkih faktora, &scaron;to ukazuje na moguće postojanje drugih tkivnih faktora lo&scaron;e prognoze. U novije vreme se sve veća pažnja posvećuje fenomenu tumorskog pupljenja koje predstavlja pojavu tumorskih pupoljaka (TP), odnosno oligocelularnih grupa tumorskih ćelija koje se na invazivnom frontu tumora odvajaju od glavne tumorske mase. Ove tumorske ćelije poprimaju fenotip mezenhimnih ćelija i stiču sposobnost ameboidnog kretanja kroz ekstracelularni matriks, uz pomoć citoplazmatskih podija koje se na dvodimenzionalnim histolo&scaron;kim rezovima vizualizuju kao citoplazmatski pseudofragmenti (CPF). Značaj gustine TP i CPF je jo&scaron; uvek nedovoljno ispitan, ali postoje indicije da se radi o moćnom prediktoru biolo&scaron;kog pona&scaron;anja tumora. CILJ: Cilj je bio da se ispita zavisnost dužine perioda bez relapsa, veličine primarnog tumora, gustine peritumorske limfocitne infiltracije i konfiguracije tumorske margine od gustine TP i CPF kod bolesnika sa KK u stadijumu II. METODOLOGIJA: Istraživanjem je obuhvaćeno 114 bolesnika operisanih od KK u stadijumu II na Institutu za onkologiju Vojvodine, bez nepovoljnih prognostičkih faktora i bez indikacija za primenu adjuvantne hemioterapije. Mikroskopskom analizom rutinskih histolo&scaron;kih i imunohistohemijskih preparata utvrđivana je gustina TP i CPF, koja je zatim korelirana sa vremenom pojave relapsa, veličinom primarnog tumora, gustinom peritumorske limfocitne infiltracije i konfiguracijom tumorske margine. REZULTATI: Velika gustina TP i/ili CPF nađena je kod 45 tumora (39,5%). U ovoj grupi se relaps dogodio kod 26 bolesnika (57,8%). U grupi bolesnika sa malom gustinom TP/CPF relaps je registrovan u 4 slučaja (5,8%). Poređenje krivih preživljavanja pokazalo je da je verovatnoća relapsa značajno veća ako se u tumoru nalazi velika gustina TP/CPF (p&lt;0,0001). Tumori sa velikom gustinom TP/CPF su imali najveći prečnik koji je varirao u rasponu od 25 do 100 mm, dok su tumori sa malom gustinom TP/CPF bili najvećeg prečnika od 20 do 110 mm (p=0,6744). Intenzitet peritumorskog limfoidnog odgovora je bio velik kod 13 tumora sa velikom gustinom TP/CPF (28,9%) i kod 17 tumora sa malom gustinom TP/CPF (24,6%), p=0,7747. Konfiguracija tumorske margine je bila infiltrativna u svim tumorima sa velikom gustinom TP/CPF, kao i kod 42 tumora sa malom gustinom TP/CPF (60,9%). ZAKLJUČAK: Velika gustina TP/CPF je nezavisan tkivni indikator lo&scaron;e prognoze kod bolesnika sa KK u stadijumu II, koji je ne korelira ni sa veličinom primarnog tumora ni sa intenzitetom peritumorskog limfoidnog odgovora. Velika gustina TP/CPF nije kompatibilna sa ekspanzivnom konfiguracijom tumorske margine, ali infiltrativna konfiguracija tumorske margine nije prediktor velike gustine TP/CPF.</p> / <p>INTRODUCTION: Colonic carcinoma (CC) is a serious public health problem due to its high incidence and mortality rate. Stage is the single most important independent prognosticator in patients with CC. In the presence of indicators of poor prognosis, including high histologic grade, ileus, lympho-vascular invasion and perineural invasion, there is a need for adjuvant chemotherapy after a potentially curative operation in patients with stage II CC, because the therapy improves both overall survival and disease-free survival. However, some patients with no documented poor prognostic factors suffer recurrences, which indicates that there may be some other tissue features that confer poor prognosis. In the recent publications there is an increasing interest in the phenomenon of tumor budding, a term assigned to the presence of small groups of discohesive tumor cells at the invasive front of the tumor &ndash; tumor buds (TB&#39;s). These cells acquire mesenchymal phenotype and gain the ability to migrate through the extracellular matrix by means of cytoplasmic extrusions which are visible on the two-dimensional immunohistologic sections and are called cytoplasmic pseudofragments (CPF&#39;s). Significance of density of TB&#39;s and CPF&#39;s is still to be evaluated, but the pool of evidence suggests that this is a powerful predictor of biologic behaviour of CC. AIM: The aim of this study was to determine the influence of density of TB&#39;s and CPF&#39;s on the risk of recurrence in patients with stage II CC. This research also attempted to establish whether there is a correlation between the density of TB&#39;s and CPF&#39;s and several other morphologic features such as tumor diameter, peritumoral lymphocytic response and the configuration of the tumor margin. METHODS: 114 patients with stage II CC were enrolled in the study. All the patients received surgery at the Institute of Oncology in Sremska Kamenica and no patient had indication for adjuvant chemotherapy. Microscopic analysis of routine histologic and immunohistochemical slides was performed to establish the density of TB&#39;s and CPF&#39;s, to estimate the intensity of the peritumoral lymphocytic response and to determine the configuration of the tumor margin. RESULTS: High density of TB&#39;s and/or CPF&#39;s was found in 45 tumors (39.5%). In this group recurrence occured in 26 patients (57.8%). In the group of patients with low density of TB/CPF in the tumor tissue 4 patients relapsed (5.8%). Comparison of survival curves showed that the probability of recurrence was significantly greater if the density of TB/CPF&#39;s was high (p&lt;0.0001). Tumors with high density of TB/CPF&#39;s ranged from 25 to 100 mm in greatest diameter, while those with low density measured from 20 to 110 mm (p=0.6744). Intensity of peritumoral lymphocytic response was high in 13 tumors with high density of TB/CPF&#39;s (28.9%) and in 17 tumors with low density of TB/CPF&#39;s (24.6%), p=0.7747. All tumors with high density of TB/CPF&#39;s and 42 tumors with low density of TB/CPF&#39;s (60.9%) had infiltrative configuration of tumor margin. CONCLUSION: High density of TB/CPF&#39;s is an independent indicator of poor prognosis in patients with stage II CC and it correlates neither with tumor diameter nor with intensity of peritumoral lymphocytic response. High density of TB/CPF&#39;s is not compatible with the expansive configuration of tumor margin, but the infiltrative configuration of tumor margin is not a predictor of high density of TB/CPF&#39;s.</p>

Infiltration of myeloid cells in the tumor microenvironment is often associated with enhanced angiogenesis and tumor progression, resulting in poor prognosis in many types of cancer. The polypeptide chemokine PK2 (Bv8, PROK2) has been shown to regulate myeloid cell mobilization from the bone marrow, leading to activation of the angiogenic process, as well as accumulation of macrophages and neutrophils in the tumor site. Neutralizing antibodies against PK2 were shown to display potent anti-tumor efficacy, illustrating the potential of PK2-antagonists as therapeutic agents for the treatment of cancer. In this study we demonstrate the anti-tumor activity of a small molecule PK2 antagonist, PKRA7, in the context of glioblastoma and pancreatic cancer xenograft tumor models. For the highly vascularized glioblastoma, PKRA7 was associated with decreased blood vessel density and increased necrotic areas in the tumor mass. Consistent with the anti-angiogenic activity of PKRA7 in vivo, this compound effectively reduced PK2-induced microvascular endothelial cell branching in vitro. For the poorly vascularized pancreatic cancer, the primary anti-tumor effect of PKRA7 appears to be mediated by the blockage of myeloid cell migration/infiltration. At the molecular level, PKRA7 inhibits PK2-induced expression of certain pro-migratory chemokines and chemokine receptors in macrophages. Combining PKRA7 treatment with standard chemotherapeutic agents resulted in enhanced effects in xenograft models for both types of tumor. Taken together, our results indicate that the anti-tumor activity of PKRA7 can be mediated by two distinct mechanisms that are relevant to the pathological features of the specific type of cancer. This small molecule PK2 antagonist holds the promise to be further developed as an effective agent for combinational cancer therapy. / Dissertation