|The subject of this dissertation was the establishment of models of glioblastoma, an aggressive brain tumor. Cell lines established from glioblastoma tissue or xenografts enable the representation of different aspects of the tumor. Among those is the amplification of the EGFR-gene that is often found in glioblastoma. Adaptation of cell culture conditions allows enrichment of tumor cell subpopulations that show increased resistance towards chemotherapeutic drugs. This highlights the need for the use of different glioblastoma models to gain a better understanding of the complex tumor biology.