Novel YAP1 Activator, Identified by Transcription-Based Functional Screen, Limits Multiple Myeloma Growth

Yes-associated protein 1 (YAP1) interacts with numerous transcription factors, including TEA-domain family proteins (TEAD) and p73. YAP1 is negatively regulated by the tumor suppressor Hippo pathway. In human cancers, the deregulation of the Hippo pathway and YAP1 gene amplification lead to the activation of YAP1, which induces epithelial-mesenchymal transition (EMT) and drug resistance. YAP1 inhibitors are expected to be useful in cancer therapy. On the other hand, in certain cancers, YAP1 upregulates p73-dependent gene transcription and behaves as a tumor suppressor. Moreover, as YAP1 regulates self-renewal and differentiation of tissue stem cells and plays an important role in tissue homeostasis, YAP1 activators may contribute to the regenerative medicine. With this in our mind, we screened for YAP1 activators by using human retinal pigment epithelial ARPE-19 cells expressing the TEAD-responsive fluorescence reporter under the coexpression of YAP1. From an extensive chemical compound library (n = 18,606) 47 candidate YAP1 activators were identified. These compounds were characterized to determine whether this assay provides bona fide YAP1 activators. Importantly, one YAP1 activator was effective against the human multiple myeloma IM-9 cells and chronic myeloid leukemia K562 cells.Implications: YAP1 activation limits growth, induces apoptosis, and may be useful at suppressing hematological cancers. Mol Cancer Res; 16(2); 197-211. ©2017 AACR.