Mac-1 (CD11b/CD18)-is an integrin expressed on bone marrow-derived immune cells that binds ICAM-1 to regulate leukocyte adhesion and migration across the endothelium or epithelium. The role of CD11b in tumorigenesis and colitis is controversial. It has been reported that deficiency of CD11b exacerbates dextran sodium sulfate (DSS)-induced colitis. The opposite scenario, in which CD11b deficiency suppresses intestinal tumor growth in CD11b -/- APC min/+ animals by reducing myeloid cell recruitment has also been reported.