Additionally, two upstream regulators of this pathway are frequently altered in HNSCC, namely FAT1 and PIK3CA. Inactivation of FAT1 (deletion, truncating mutations) or activation of PIK3CA (overexpression) are associated with YAP-dependent transcriptional activation in HNSCC [24,27]. The gene discussed is YAP1; the disease is head and neck squamous cell carcinoma.