Abstract 2161: A transcriptomic signature for measuring YAP1 activity in patient samples and tumor models

Over the past years, the HIPPO tumor suppressor pathway and its downstream effector Yes1-associated transcriptional regulator (YAP1) present increasing interest in cancer research. The YAP1-TEAD complex regulates transcription for cell proliferation, survival, plasticity, and migration. Aberrant activation of YAP1 has been reported for multiple different cancer types. To estimate the proportion of cases where YAP1/TEAD-dependent transcription may be responsible for tumor development or evolution and evaluate the pharmacodynamics of novel TEAD-inhibitors, we have identified a transcriptional signature of YAP1 activity. The signature comprises 500 genes, positive and negative downstream effectors at about equal proportions, selected by differential expression analyses from 10 published datasets reporting, in total, 19 YAP1-activation and 18 YAP1-inhibition experiments. YAP1/TEAD-dependent transcription was scored in single samples as the difference Rp - Rn, where Rp is the mean fractional rank of the positive YAP1-effectors, and Rn, that of the negative effectors. We so scored, and called, YAP1 activation in normal tissues (GTEx collection; N~9000), in primary, recurrent, or metastatic tumors (TCGA; N~10000), and in cell lines (CCLE; N~1000) for the selection of models. We further applied the signature to follow the degree of YAP1 inhibition in cell and tumor models either after genetic knockdown of HIPPO-YAP1 pathway components or by pharmacologic inhibition using small-molecule TEAD-inhibitors. Our data confirm the robustness of the YAP1-transcription signature as a biomarker for both, tumor indication selection and pharmacodynamics of YAP1-TEAD activity. Citation Format: Emmanuel Spanakis, Loreley Calvet, Odette Dos Santos, Colette Dib, Sukhvinder Sidhu, Jurgen Moll, Laurent Debussche, Jack Pollard, Iris Valtingojer. A transcriptomic signature for measuring YAP1 activity in patient samples and tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2161.