For instance, Markstein et al. performed an antitumor chemical screening using an intestinal tumor model in Drosophila. By overexpressing Raf (RafOE), which is an activator of the epidermal growth factor receptor pathway, specifically in intestinal stem cells (ISCs), these investigators generated a colon cancer model for large-scale compound screening. Here, EGFR is linked to malignant colon neoplasm.