The results were striking in that purified colonocytes from these mice showed CEA/CEACAM6 expression level-dependent molecular changes involving integrin activation similar to those documented in the in vitro systems; tumorigenic cellular changes were observed such as increased proliferation and inhibition of differentiation and anoikis/apoptosis; and, finally, these cellular changes were mirrored by dramatic changes in colonic tissue architecture featuring severe hyperplasia and dysplasia, to the point of rendering the entire colon a massive tumor-like structure. This evidence concerns the gene CEACAM5 and neoplasm.