Since metastasis is responsible for more than 90% of deaths caused by tumors, it is essential to discover the exact mechanisms of metastasis and its crucial steps like tumor cell invasion. In the case of "solid" tumors, the oxygen supply of tumor cells is lower compared to healthy cells. Fluctuating oxygen supply (hypoxia-reoxygenation) also often occurs in the immediate microenvironment of tumor cells, which has been proven to promote the development of tumor cell resistance and the formation of metastasis. Direct and indirect cell-cell interactions of the tumor cells and stressed cells of the tumor microenvironment also affect the tumor cells' ability to invade. Our goal is to identify molecules and mechanisms that play a central role in this complex communication under hypoxia/reoxygenation induced stress conditions. In our experiments, we use novel in vitro 3D tumor models in addition to classical cell biology methods.