Tumorigenesis is induced (a) spontaneously at an old age or (b) upon feeding on the Notch pathway inhibitor DAPT at a young age. For example, male wild type Oregon-R and w1118 flies ~40 days old feeding on standard cornmeal-yeast-sucrose media develop tumors of more than 80 cells big at a low rate (2-15% of flies) [Siudeja, 2015]. Similarly, female wild type Oregon-R and w1118 flies raised for 3-7 days on standard cornmeal-yeast-sucrose media and for 5 more days on yeast-sucrose media containing 3 x 108/ml of the human bacterial pathogen Pseudomonas aeruginosa along with 50μg/ml of the gamma-secretase inhibitor DAPT (Sigma) develop stem cell tumors of more than 8 cells in >50% of flies [Apidianakis, 2009]. Tumor size and incidence for both assays will be measured via fluorescence microscopy from at least 200 male and 30 female Drosophila midguts respectively, using the ImageJ software (https://imagej.net/ImageJ). Midguts will be double-stained with anti-Delta (for stem cells) and anti-prospero (for enteroentocrine cells) both obtained from Developmental Studies Hybridoma Bank and diluted 1:100.