Abstract 2434: Transcriptional crosstalk between YAP, TEAD and TP63 is associated with early lung carcinogenesis
Authors: Ning Boting , Tilston-Lunel Andrew , Hicks-Berthet Julia , Mazzilli Sarah A. , Beane Jennifer E. , Varelas Xaralabos , Lenburg Marc E. 
Published: July 2021

Introduction: The Hippo pathway effector YAP contributes to carcinogenesis by directing stem cell activity, cell proliferation and cell survival signals. In the lung, aberrant nuclear YAP activity promotes bronchial epithelial growth, which in animal models can drive pathology that resembles lung premalignant lesions (PMLs). However, the molecular mechanisms by which YAP contributes to aberrant lung epithelial pathology are poorly understood. In this project, we investigated the DNA binding pattern and gene expression program regulated by YAP and associated TEAD and TP63 transcriptional factors in primary normal human bronchial epithelial cells (HBECs) and lung cancer cell lines.

Methods: RNA-seq experiments were conducted using HBEC, H2170 and SW900 cells transfected with siRNA targeting YAP, TEADs or TP63, and expression profiles were compared to corresponded controls to derive gene signatures. In parallel, ChIP-seq experiments were carried out using antibodies specific for the respective proteins to identify genome binding peaks. Direct target genes were inferred with Binding and Expression Target Analysis (BETA) using gene signature and peak profile of each factor in each cell line respectively. The metagene score for target genes in longitudinally collected endobronchial biopsies from patients with PMLs was calculated using GSVA and the association with PML phenotypes was tested with a mixed-effects model adjusting for batch and patient as random effect (GSE109743).

Results: Chromatin binding analyses revealed that YAP co-occupies genomic regions with TEAD and TP63 in normal bronchial epithelial cells aligning with H3K27ac chromatin modifications. Integrating genomic binding and gene expression profiling, we identified large overlaps in target genes directly regulated by YAP, TEAD and TP63 in HBECs, demonstrating cooperation between these factors in the control of bronchial epithelial transcription. YAP-TEAD-TP63 induced targets in HBECs are enriched for genes involved in cell proliferation and extracellular matrix alteration, while repressed targets are enriched for genes involved in cell fate specification. Notably, cooperatively regulated genes are strongly associated with gene expression profile identified in progressive PML, and in particular with genes linked to early immune responses that are observed with PML pathology progression. Similar analyses of YAP, TEAD and TP63 in lung cancer cells revealed an altered transcriptional program for YAP with a divergence of YAP-TEAD away from TP63, suggesting contextual changes in YAP activity with cancer progression.

Conclusion: We found that YAP, TP63 and TEADs co-regulate lung epithelial gene expression related to PML pathology progression. These findings provide insight into potential YAP function in the early stages of lung carcinogenesis and offer potential new avenues to develop lung cancer interception strategies.

Citation Format: Boting Ning, Andrew Tilston-Lunel, Julia Hicks-Berthet, Sarah A. Mazzilli, Jennifer E. Beane, Xaralabos Varelas, Marc E. Lenburg. Transcriptional crosstalk between YAP, TEAD and TP63 is associated with early lung carcinogenesis [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 2434.