The progression from a locally growing to treatment resistant and metastatic cancer is most often the event responsible for treatment failures. The biology underpinning why some tumor cells are more resistant to the currently available treatments or are prone to become invasive is largely unknown. The theory of cancer initiating cells suggests phenotypic and functional heterogeneity within primary tumor. Cancer initiating cells have been increasingly shown to have an integral role in tumor initiation, disease progression, metastasis and treatment resistance. Therefore our laboratory goal is to understand on the molecular level signaling pathways and molecules that are involved in tumor heterogeneity. We are also interested in the role of microenvironment in the phenotypic and functional diversity of tumor cells. In our experimental approach we use tools of molecular biology, tumor mouse models, functional genomics and in vivo imaging.