Search

Alterations of the Hippo--YAP pathway are potential targets for oral squamous cell carcinoma (OSCC) therapy, but heterogeneity in this pathway could be responsible for therapeutic resistance. We analysed the Hippo--YAP signatures in a cohort of characterised keratinocyte cell lines derived from the mouth floor and buccal mucosa from different stages of OSCC tumour progression and focused on the specific role of YAP on invasive and metastatic potential. We confirmed heterogeneity in the Hippo--YAP pathway in OSCC lines, including overexpression of YAP1, WWTR1 (often referred to as TAZ) and the major Hippo signalling components, as well as the variations in the genes encoding the intercellular anchoring junctional proteins, which could potentially regulate the Hippo pathway. Specifically, desmoglein-3 (DSG3) exhibited a unique and mutually exclusive regulation of YAP via YAP phosphorylation during the collective migration of OSCC cells. Mechanistically, such regulation was associated with inhibition of phosphorylation of epidermal growth factor receptor (EGFR) (S695/Y1086) and its downstream effectors heat shock protein beta-1 (Hsp27) (S78/S82) and transcription factor AP-1 (c-Jun) (S63), leading to YAP phosphorylation coupled with its cytoplasmic translocation and inactivation. Additionally, OSCC lines displayed distinct phenotypes of YAP dependency or a mixed YAP and TAZ dependency for cell migration and present distinct patterns in YAP abundance and activity, with the latter being associated with YAP nuclear localisation. In conclusion, this study provides evidence for a newly identified paradigm in the Hippo--YAP pathway and suggests a new regulation mechanism involved in the control of collective migration in OSCC cells. [ABSTRACT FROM AUTHOR]

The Yes-associated protein (YAP) is a downstream effector of the Hippo pathway and acts as a key transcription co-factor to regulate cell migration, proliferation, and survival. The Hippo pathway is evolutionarily conserved and controls tissue growth and organ size. Dysregulation and heterogeneity of this pathway are found in cancers, including oral squamous cell carcinoma (OSCC), leading to overexpression of YAP and its regulated proliferation machinery. The activity of YAP is associated with its nuclear expression and is negatively regulated by the Hippo kinase-mediated phosphorylation resulting in an induction of its cytoplasmic translocation. This review focuses on the role of YAP in OSCC in the context of cancer metastatic potential and highlights the latest findings about the heterogeneity of YAP expression and its nuclear transcription activity in oral cancer cell lines. The review also discusses the potential target of YAP in oral cancer therapy and the recent finding of the unprecedented role of the desmosomal cadherin desmoglein-3 (DSG3) in regulating Hippo-YAP signaling. [ABSTRACT FROM AUTHOR]

The Yes-associated protein (YAP) is a downstream effector of the Hippo pathway and acts as a key transcription co-factor to regulate cell migration, proliferation, and survival. The Hippo pathway is evolutionarily conserved and controls tissue growth and organ size. Dysregulation and heterogeneity of this pathway are found in cancers, including oral squamous cell carcinoma (OSCC), leading to overexpression of YAP and its regulated proliferation machinery. The activity of YAP is associated with its nuclear expression and is negatively regulated by the Hippo kinase-mediated phosphorylation resulting in an induction of its cytoplasmic translocation. This review focuses on the role of YAP in OSCC in the context of cancer metastatic potential and highlights the latest findings about the heterogeneity of YAP expression and its nuclear transcription activity in oral cancer cell lines. The review also discusses the potential target of YAP in oral cancer therapy and the recent finding of the unprecedented role of the desmosomal cadherin desmoglein-3 (DSG3) in regulating Hippo-YAP signaling., Competing Interests: The authors declare that they have no conflicts of interest to report regarding the present study., (© 2022 Ahmad, Saravanan and Wan.)