The elucidation of cell-intrinsic factors promoting tumor growth has been the focus of intense research in the past several decades and has revealed important details on the molecular bases of tumor development. However, it is now clear that in addition to these factors, tumor heterogeneity and cell-cell interactions within the tumor microenvironment significantly influence tumor progression in ways we don’t fully understand. One of our laboratory interests is to understand how cell-cell signaling events are initiated, interpreted, and integrated in tumor cells to modulate tumor cells behavior. We use a Drosophila tumor model and investigate how epithelial tumor cells communicate with each other and with host cells, including immune cells, to promote tumor overgrowth and metastasis. Indeed, tumor-immune cells interactions represent one of the most important and exciting aspects of cancer biology. In addition, cellular crowding causes tumors to have distinct mechanical properties in the host tissue. We are investigating a role for mechanical cues in tumor overgrowth and metastasis.