Our research interests lie in breaking new ground in studying mechanism-based functions of AP-1 (Fos/Jun) in vivo with the aim of obtaining a more global perspective on AP-1 in human physiology and disease/cancer. The unresolved issues regarding the AP-1 subunit composition will be tackled biochemically and genetically in various cell types including bone, liver and skin, the primary organs affected by altered AP-1 activity. I plan to utilize the knowledge gained on AP-1 functions in the mouse and transfer it to human disease. The opportunities here lie in exploiting the knowledge of AP-1 target genes and utilizing this information to interfere with pathways involved in normal physiology and disease/cancer. The past investigations revealed that the functions of AP-1 are an essential node at the crossroads between life and death in different cellular systems. I plan to further exploit our findings and concentrate on utilising better mouse models to define these connections. The emphasis will be on identifying molecular signatures and potential treatments in models for cancer, inflammatory and fibrotic diseases. Exploring genetically modified stem cell-based therapies in murine and human cells is an ongoing challenge I would like to meet in the forthcoming years at the CNIO. In addition, the mouse models will be used for mechanism-driven therapeutic strategies and these studies will be undertaken in collaboration with the Experimental Therapeutics Division and the service units such as the tumor bank. The project proposal is divided into 6 Goals (see also Figure 1): Some are a logical continuation based on previous work with completely new aspects (Goal 1-2), some focussing on in depth molecular analyses of disease models with innovative and unconventional concepts, such as for inflammation and cancer, psoriasis and fibrosis (Goal 3-5). A final section is devoted to mouse and human ES cells and their impact for regenerative medicine in bone diseases and cancer.