YAP1 and cancer: As FAT1 mutations may ultimately render cancer cells dependent on YAP1 function, we next knocked down YAP1 expression using tetracycline-inducible YAP1 shRNA lentiviruses in CAL27 and CAL33 cells, and in tumorigenic HN12 that display normal FAT1 levels (Fig. 4a) but harbor YAP1 gene copy gain25.