The significance of these unique findings using primary human cells is underscored by our confirmation of the opposite ability of YAP activation alone to promote the display of more transformed features by MCF10A cells in vitro, and an increased metastatic activity in vivo by MDA-MB-231 cells, a highly tumorigenic established human breast cancer cell line with a similar KRAS mutation. Here, YAP1 is linked to breast carcinoma.