APC and colorectal carcinoma: The similarities between mammalian and Drosophila intestines prompted us to investigate whether the generation of compound Apc-Ras clones in the adult midgut epithelia, mutant for both forms of the Drosophila APC gene, Apc and Apc2, and over-expressing the oncogenic form of Ras, UAS-RasV12 (refs [28], [29]), would reproduce the first steps of CRC.