Identification of key biomarkers and immune infiltration in the co-occurrence of oral lichen planus and Hashimoto's thyroiditis by integrated bioinformatics analysis.

Increasing evidence have suggested the co-occurrence of oral lichen planus (OLP) and Hashimoto thyroiditis (HT), the underlying mechanism remains unclear. The aim of our study was to investigate co-expressed differentially expressed genes (co-DEGs) of OLP and HT, elucidate the mechanisms responsible for co-occurrence of OLP and HT. The expression profiles of GSE52130 and GSE29315 were downloaded from the Gene Expression Omnibus database to obtain DEGs between disease group and healthy control group by GEO2R. Enrichment analysis of co-DEGs were performed by Metascape platform. The protein-protein interaction (PPI) network of co-DEGs were developed utilizing the STRING database. Subsequently, CIBERSORT was utilized to evaluate the infiltration of immune cells in OLP and HT. Finally, enzyme-linked immunosorbent assay and quantitative real-time PCR were conducted to verify the key genes in clinic samples. A total of 76 co-DEGs were recognized. Enrichment analysis demonstrated that these co-DEGs focused primarily on cytokine signaling in immune system. The 10 most firmly related genes among co-DEGs were identified from the PPI network. We found that immune cell infiltration associated with VCAM1 expression was correlated with OLP and HT. The top 3 co-DEGs (CXCL12, CXCL10, and VCAM1) in PPI network were verified in OLP and HT samples. VCAM1 may be closely related pathogenesis of co-occurrence of OLP and HT, and represents a new candidate molecular marker of the occurrence and progression of OLP and HT. Moreover, immune cell infiltration associated with VCAM1 expression plays an important role in the coexistence of OLP and HT.