Figure 1.

RAF^gof expression in intestinal stem cells and progenitor cells leads to tumor formation. (A) Overview of the posterior midgut (top panels) and cross-section of the abdomen (lower panels) of control (ctrl, EGT;Luc2 > w¹¹¹⁸) and tumor-bearing flies (EGT;Luc2 > RAF^gof) after 3 days of oncogene induction (29°C). The white arrowhead indicates normal-sized progenitor cells in controls and the yellow arrow indicates progenitor cell accumulations in RAF^gof expressing flies. Note the cell clusters protruding into the lumen. Actin was stained with phalloidin (red) with additional staining of nuclei with DAPI (blue). Scale bar: 50 µm. (B) RAF^gof co-expressed luciferase signal in control flies and tumor-bearing flies (mean ± SEM, n=5-6). The level of luminescence measured after 24h of oncogene induction in the tumor-bearing flies is taken as 100%. (C) The gut integrity of healthy controls and tumor-bearing flies was not significantly affected after 3 days of oncogene induction (n=100). (D) Resting metabolic rate of control and tumor-bearing flies over time (mean ± SEM, n=5-10). (E) Lifespan of control and tumor-bearing flies at 29°C (n=450 flies per treatment). In all experiments, flies were fed a normal control diet. Here and in all figures, significance is indicated as * p < 0.05; ** p < 0.01; *** p < 0.001; ns: not significant, with colors representing the partner for comparison.