YAP1 and breast carcinoma: Interestingly, in breast cancer, the activity of the upstream negative regulators MST1/2 was not different between NFs and CAFs, while the activity of LATS kinases and phosphorylated YAP was augmented in CAFs,269 suggesting that YAP was not activated by the attenuated activity of the canonical MST/LATS signaling pathway in CAFs.