YAP1 and breast cancer: Moreover, it has been shown in U20S, MCF-7 breast cancer, and BWT skin squamous cell carcinoma cells that JNK1/2 are able to directly phosphorylate YAP on five distinct sites; THR-119, SER-138, THR-153, SER-31, and THR362, the latter two being the most phosphorylated in vivo.