YAP1 and nonpapillary renal cell carcinoma: We have previously shown that activation of YAP, either by treatment with XMU-MP-1, a small molecule inhibitor of Hpo/MST1/2 kinase (33), or by overexpression of a constitutively active YAP (YAP-5SA) (9), inhibited ccRCC cell growth in both 3D cultures and xenografts (25).