YAP1 Expression in Lichen Planus and Squamous Cell Carcinoma: Role in Disease Pathogenesis and Potential Therapeutic Target

Background: Lichen planus (LP), especially oral type, reported a potential risk of malignant transformation to squamous cell carcinoma (SCC). Yes-Associated Protein (YAP1), a key component of the Hippo pathway, acts as a transcription cofactor regulating expression of genes involved in cell proliferation, apoptosis, and migration. Therefore, it has been implicated in carcinogenesis of a wide variety of human cancers. Objectives: To study YAP1 expression in LP and SCC in comparison to normal control (NC) specimens. Patients and methods: This study was conducted on 50 NC specimens, 50 LP specimens, and 50 SCC specimens. They were categorized into 2 main groups; cutaneous (25 NC, 25 LP, 25 SCC), and oral (25 NC, 25 LP, 25 SCC). All specimens were examined for YAP1 antibody expression by immunohistochemistry and YAP1 mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR). Results: In both cutaneous and oral groups; significant upregulation of YAP1 expressions was observed in SCC specimens followed by LP and then NC specimens in the same sequence. Its expression in SCC was found to be significantly higher in poorly and moderately differentiated types than well differentiated types. Conclusion: YAP1 may have a potential role in the pathogenesis of LP and oncogenesis and progression of SCC. Moreover, it could be considered as a novel therapeutic target for such cases.