O6 Dissecting the shift in YAP/TAZ signalling modalities with disease progression in cancer-associated fibroblasts of cutaneous squamous cell carcinoma
Maria Moran, Tjaša Bensa, Gernot Walko, Emanuel RognoniAbstract
Introduction and aims
Cancer-associated fibroblasts (CAFs) can promote or supress tumour growth. Yes-associated protein/transcriptional coactivator with PDZ-binding motif (YAP/TAZ) signalling is often dysregulated in cancers, including cutaneous squamous cell carcinoma (cSCC), and YAP-transcriptional enhanced associated domain (TEAD) inhibitors are in clinical trials for cancers. Little is known about YAP/TAZ signalling in CAFs during cancer progression and how inhibition affects CAF phenotype. Using isogenic fibroblast lines isolated in our lab from normal skin tissue, primary tumour, and recurrent tumour, we aim to dissect the distinct YAP/TAZ signalling modalities in CAFs. We hypothesize that YAP/TAZ signals through different cofactors in cancer cells and CAFs and that targeted inhibition will affect these cell types differently during cSCC progression.
Methods
Changes in YAP/TAZ signalling with disease progression were assessed using assay for transposase-accessible chromatin (ATAC)/RNA sequencing (RNAseq) datasets, two-dimensional and three-dimensional skin coculture models, YAP/TAZ transient knockdowns, and YAP-TEAD inhibitor treatment as a discovery tool.
Results
Immunofluorescent staining of cSCC tissue shows increased stromal YAP/TAZ expression, and RNAseq and reverse transcriptase quantitative polymerase chain reaction data confirmed YAP/TAZ signalling in CAFs increases with disease progression. While YAP/TAZ signal through TEADs in cSCC keratinocytes, analysis of ATAC/RNAseq data indicates a shift in association of YAP/TAZ between TEAD and activator protein (AP)-1 in our CAF progression series. Accessibility of AP-1 binding motifs peaks in primary CAFs, and TEAD motif accessibility peaks in recurrent CAFs. While normal fibroblasts respond strongly to TEAD-specific inhibition, impacting proliferation, contraction and extracellular matrix remodelling, CAFs become less responsive with disease progression, providing further evidence of a signalling switch. We are currently investigating how this switch influences CAF–cancer cell crosstalk by modulating YAP-TEAD and AP-1 signalling in three-dimensional organotypic cocultures.
Conclusions
These results suggest YAP/TAZ signalling is altered in CAFs and evolves with disease progression. A switch in association of YAP/TAZ with downstream transcription factors could affect efficacy of TEAD inhibitors in clinical development at different stages of cSCC.