The Yes-associated protein (YAP), a well-known downstream effector molecule of the Hippo pathway, has been the center of continuous discussion during the last decade. There is plenty of evidence showing its role as a tumor suppressor molecule, but there are also some publications showing that it is essential for tumor progression playing a key role in cancer cell proliferation, apoptosis, metastasis and maintenance of stemness. Thus, scientists were speculating about its role in different types of cancers.

Surprisingly, it has just been published in Cancer Cell that all cancers can be classified into two well distinct types: YAP-on or YAP-off tumors. In fact, depending on this classification, YAP/TAZ can act as tumor suppressor, or it can be found regulating adhesion, tumor metabolism, genetics and most importantly, tumor drug profiles. Importantly, these researchers have observed that YAP silencing is intrinsic to the cell of origin, but it can also be acquired with lineage switching and drug resistance. Thus, YAP is the pivotal switch in all tumor types and obviously this drives important therapeutic implications.