YAP1 and alveolar rhabdomyosarcoma: However, RASSF4 is significantly upregulated in alveolar rhabdomyosarcoma (aRMS), in which it inhibits the Hippo pathway (by inactivating MST1), leading to sustained activation of YAP1, which drives cell proliferation and escapes from senescence, representing a mechanism underlying the malignant progression in aRMS [19].