RAC1 and colorectal adenocarcinoma: One study found that Rac1 plays a key role in the progression of CRC in vivo: decreased Rac1 expression blocked tumor formation in an orthotopic model of colorectal adenocarcinoma, whereas its overexpression in SW620 cells accelerated colorectal adenocarcinoma progression when the cells were injected into athymic nude mice [49].