CEACAM1 and neoplasm: Strikingly, we could detect variant-specific changes in the capacity to grow in vitro under anchorage-independent conditions by analyzing the CEACAM1 isoform transfectants, whereas expression of exogenous CEACAM1-3S leads to initial tumor cell assembling in semisolid media but diminished the formation of proliferative colonies, indicated by the reduced colony size (Figures 1A,B).