Given the facts that Rac1 is a SUMOylation target relevant to cell mobility53 and that ablation of its SUMOylation is associated with reduced cell movement in other cell types, such as tumor cells and synoviocytes54, the impaired migratory capability in the KO macrophages could be caused by the lack of Rac1 SUMOylation. This evidence concerns the gene RAC1 and neoplasm.