Colorectal cancer (CRC) is a devastating and deadly disease, with increasing incidence in Western society. CRC development involves complex interactions between intestinal microbes, the intestinal epithelium and the host immune system. For the first time, we are able to study these interaction using a new mouse model of microbiota-dependent CRC. My project aims to investigate the molecular interactions in this microbiota-tumor-immune network, using state-of-the-art germfree and gnotobiotic mouse technology. These studies will generate new knowledge on the mechanisms behind CRC which may lead to the development of new therapies to treat CRC.