Functional genomic screens uncover FERMT2 as a critical regulator of YAP/TAZ-driven tumorigenicity.

Abstract

YAP and TAZ are transcriptional regulators essential for mechanotransduction, development, and tissue homeostasis, whose dysregulation is implicated in multiple diseases, including cancer. To identify key regulators of YAP/TAZ signaling required for breast cancer cell fitness, we performed CRISPR/Cas9-based loss-of-function genetic screens both in vitro and in vivo. A custom sgRNA library targeting 216 candidate YAP/TAZ modulators was screened across three breast cancer cell lines. Among these, FERMT2, a component of the integrin signaling pathway, consistently emerged as a strong drop-out hit, highlighting its essential role in sustaining YAP/TAZ-dependent fitness. Bioinformatic analysis of large-scale cancer datasets further revealed genetic co-dependency between FERMT2, YAP, and TAZ, particularly in tumors with high YAP/TAZ expression. Functional validation through FERMT2 knockout and silencing demonstrated its requirement for proliferation, anchorage-independent growth, and tumorigenicity in triple-negative breast cancer cells. FERMT2 loss impaired YAP/TAZ nuclear accumulation, reduced the expression of YAP/TAZ target genes, and decreased phosphorylation at key tyrosine residues. Mechanistically, FERMT2 regulates YAP/TAZ independently of the canonical Hippo pathway through integrin-mediated activation of FAK. Consistent with this, glucocorticoid-driven FAK activation restored YAP/TAZ signaling in FERMT2-depleted cells. Partial epistasis analyses also indicate that FERMT2 modulates actin-dependent regulation of YAP/TAZ. Together, these findings identify FERMT2 as a pivotal upstream regulator of YAP/TAZ via FAK signaling, demonstrate that YAP/TAZ are principal effectors of integrin activity, and suggest that FERMT2 may represent a selective vulnerability in cancers with elevated YAP/TAZ signaling.