Many oncogenes and tumor suppressor genes have been identified and mapped to signaling pathways that regulate cell growth and death. Dysregulation allows oncogenes and tumor suppressor genes to transform mammalian cells and cancers arise in conditions where multiple such events occur in the same cell. Many proto-oncogenes and tumor suppressors have been mapped to canonical signaling pathways, providing a more holistic view of growth control mechanisms and paving the way for systems level analysis of cancer mechanisms.It has also been found that a subset of the cells present in a tumor, called cancer stem cells, retain the ability to self-renew and to give rise to all cell types in a particular cancer. An emerging concept is that tumors also strongly depend on external signals for maintenance and expansion. To fully understand tumor development and progression, a deeper knowledge of the cross-talk between tumor cells and their microenvironment and the interactions between cancer cells and cancer stem cells is needed. Aims of event This symposium brings together researchers from complementing fields to enhance our understanding of the communication between cancer cells and their microenvironment. Important open questions are: Which signals do cancer cells transmit to and receive from the stroma and how do these signals promote malignant growth? What roles does the extracellular matrix play during neoplastic transformation? What is the contribution of immune cells to tumor progression? How is the inflammatory response of the tumor microenvironment regulated by the microbiota?