FIS1 and colon carcinoma: However, the role of Fis1 in mitochondrial dynamics of mammals has become controversial with the discovery that loss of Fis1 fails to alleviate Drp1 recruitment and prevent mitochondrial fission, given by the conditional knockout of Fis1 in human colon carcinoma cells34, although the overexpression of Fis1 promotes mitochondrial fission35,36.