FIGURE 1.

CEACAM1-S induces lumen formation and migrates to cell-cell contacts. A, expression of wild-type CEACAM1-S induces 97% lumen formation in transfected MCF7 cells grown in three-dimensional culture (300 acini counted; representative acini shown in a), whereas the cytoplasmic domain mutant F454A suppressed lumen formation by >90% (16% lumen formation, 300 acini counted; representative acini shown in b). The data are taken from Chen et al. (5) with permission. B, HeLa cells transfected with a CEACAM1-S-GFP fusion protein (5) showing accumulation of CEACAM1-S (green, a) and F-actin (red, b) at the cell surface of single cells making initial cell-cell contacts with almost complete redistribution of their CEACAM1-S between the cells (c) when cell-cell contact is complete.