Tesis doctoral de Mª José Docampo García
The extracellular matrix (ecm) is a dynamic network of macromolecules that, besides providing structural support, greatly influences cell behaviour. It is composed of structural proteins such as collagen and elastin, hyaluronan (ha), proteoglycans and glycoproteins. The turnover of the ecm is carried out by several types of proteases, among which the matrix metalloproteinases (mmps) are of great importance. in many types of neoplasms the ecm is altered, by either an aberrant deposition of different matrix components and/or enhanced degradation. The ecm, together with host stromal cells, constitutes the tumour microenvironment, which plays a recognized pivotal role in tumour development. However, little is known about the ecm in neoplastic conditions in the dog. melanocytic tumours are relatively common neoplasms in the dog, with a variable presentation and biological behaviour. They account for 3% of the total of neoplasms and up to 7% of all malignant neoplasms. They constitute the most common neoplasia of the oral cavity, the second digital neoplasia and between 4-20% of all cutaneous neoplasms. Oral and muco-cutaneous melanomas are aggressive tumours that commonly metastasize to the regional lymph nodes and to lungs, whereas cutaneous melanocytic lesions are benign in most dogs. in chapters 1, 2, and 3, the expression of different ecm components and enzymes responsible for its degradation has been characterized in melanocytic tumours of dogs in vivo and in canine melanoma cells in vitro. Moreover, we have explored the contribution of host cells, especially fibroblasts, to these ecm-related molecules production. in chapter 1 we describe the expression of versican, hyaluronan and cd44 in melanocytic tumours of dogs. Our results show that versican and, to a lesser extent, ha were overexpressed in malignant melanoma compared to melanocytoma and propose versican as a potential marker of malignity in these tumours. Both molecules co-localized in tumour tissues, although ha had a more extensive distribution than versican, suggesting that they act in concert to promote tumorigenesis. Neither versican nor ha expression appeared to be correlated to the expression of cd44, the main cell surface receptor for ha. In vitro, the production of ha and the expression of ha-metabolizing enzymes has been investigated in canine dermal fibroblasts and canine melanoma cell lines. Moreover, we have studied the effects of different fixation procedures in the appearance of cell-associated ha. in chapter 2 we show that both dermal fibroblasts and cml-1 and cml-6m canine melanoma cells synthesize tenascin-c in vitro. In melanocytic tumours in vivo, tenascin-c was found to be co-expressed with alpha-sma in some tumour areas, but not in others, suggesting that in this type of tumours not only myofibroblasts are responsible for tenascin-c production. We aimed also to study the expression of decorin, a proteoglycan with antitumorigenic properties, in melanocytic tumours of dogs both in vivo as in vitro. Anyhow, that objective was limited by the lack of reactivity of antibodies with the canine molecule. In human melanocytic lesions, decorin was found completely absent from melanocytic cells and was only detected in the surrounding dermis. In melanoma cell lines, decorin was only detected at the mrna level by rt-pcr, but not translated into protein. in chapter 3 we have analyzed the immunohistochemical expression of the matrix metalloproteinases mmp-9, mmp-2 and mt1-mmp in melanocytic tumours of dogs. Mmp-9 was found to be overexpressed in malignant melanoma compared to melanocytoma, whereas no significant differences in mmp-2 and mt1-mmp immunostaining between the two types of tumours were observed. Not only neoplastic cells, but also stromal cells were often positive for mmps. In vitro, all three melanoma cell lines and dermal fibroblasts produced mmp-2 and mt1-mmp, but only melanoma cells produced mmp-9. Co-culture of cml-1 and cml-10c2 melanoma cells and dermal fibroblasts induced an increase in the active form of mmp-2. Culture of melanoma cells on type i collagen increased the activation state of mt1-mmp. Therefore, the crosstalk between stromal and neoplastic cells, together with matrix components as type i collagen, can regulate mmp production. independently from the characterization of the ecm in melanocytic tumours of dogs, and in the context of a research collaboration project, in chapter 4 we have studied the mechanism underlying the increased deposition of hyaluronan observed in the dermis of shar pei dogs affected by hereditary cutaneous mucinosis. The production and localization of ha in dermal fibroblasts from shar pei dogs, as well as the expression of the enzymes responsible for ha synthesis and degradation, was assessed. Our findings show that dermal fibroblasts from shar pei dogs affected by hereditary mucinosis display enhanced ha production due to the overexpression of the synthesizing enzyme has2.
Datos académicos de la tesis doctoral «Extracellular matrix-related molecules in melanocytic tumours of dogs«
- Título de la tesis: Extracellular matrix-related molecules in melanocytic tumours of dogs
- Autor: Mª José Docampo García
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 29/07/2010
Dirección y tribunal
- Director de la tesis
- Anna María Bassols Teixido
- Tribunal
- Presidente del tribunal: angels Fabra fres
- pedro Alia ramos (vocal)
- (vocal)
- (vocal)