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The diagnosis of pancreatic cancer has generally a poor prognosis, due to the lack of specific symptoms in the early stages of the disease, which leads to an unobserved growth and early metastasis. Even if the disease is discovered at an early stage, there is no specific therapy to treat the cancer effectively. The discovery of exosomes and micro-RNAs could contribute to improving the applied therapies in the future.
This thesis focuses on the interaction of macrophages with pancreatic cancer cells. It is known that there are multiple reciprocal interactions between these cells, which have an impact on invasiveness, metastasis and prognosis. It is supposed that these interactions are, among others, based on the transition of molecules, which are incorporated in small vesicles, e.g. exosomes. The main topic of this thesis was the analysis of the possible transfer of micro-RNAs in exosomes from one cell type to another and its potential influence on the polarisation and functionality of macrophages.
Accordingly, we developed and improved a protocol to culture primary monocytes and macrophages. With these cultured cells, we demonstrated that different subtypes of macrophages can be produced, which can be differentiated by analyzing the expression of specific markers on m-RNA-level. Furthermore, we showed that the polarisation of macrophages can be changed towards the M2-phenotype by adding concentrated supernatants to the cells, which were extracted from pancreatic cancer cells. Staining the cell membranes of Panc-1 cells revealed that a transfer of membrane-containing particles secreted from Panc-1 cells to macrophages is possible. We also showed that the polarisation of macrophages is not a constant state and that it can be changed in vitro. We found evidence that a pre-existing M2-polarisation can be kept by a co-culture with pancreatic cancer cells and pre-existing M1-polarisation can be reversed with this treatment. Finally, we transfected pancreatic cancer cells with two different types of micro-RNAs and demonstrated that a co-culture with these transfected cells and macrophages can modify the polarisation of the macrophages towards a kind of hybrid, which expresses both M1- and M2-specific markers. These cells cannot be classified in the "classic" polarisation system of macrophages and by now it is not known if they act more like M1 or more like M2 macrophages. Therefore, further studies are needed to reveal their functions