AIRE is induced in oral squamous cell carcinoma and promotes cancer gene expression

Autoimmune regulator (AIRE) is a transcriptional regulator that is primarily expressed in medullary epithelial cells, where it induces tissue-specific antigen expression. Under pathological conditions, AIRE expression is induced in epidermal cells and promotes skin tumor development in association with stress-responsive keratin KRT17. This study aimed to clarify the role of AIRE in the pathogenesis of oral squamous cell carcinoma (OSCC). AIRE expression was evaluated in seven OSCC cell lines and in OSCC tissue specimens. Transient or constitutive expression of AIRE in 293A cells induced KRT17 expression. cDNA microarray analysis of 293A cells stably expressing AIRE revealed that STAT1 and ICAM1 were significantly upregulated by AIRE. Expression of KRT17, STAT1, ICAM1, MMP9, CXCL10, and CXCL11 was elevated in 293A cells stably expressing AIRE, and conversely, was decreased in AIRE-knockout HSC3 OSCC cells when compared to the respective controls. Upregulation of KRT17, STAT1, and ICAM in OSCC cells was confirmed in tissue specimens by immunohistochemistry. We provide evidence that AIRE exerts transcriptional control in cooperation with ETS1. Expression of STAT1, ICAM1, CXCL10, and MMP9 was increased in 293A cells upon Ets1 transfection, and coexpression of AIRE resulted in enhanced expression of STAT1. AIRE coprecipitated with ETS1 in a modified immunoprecipitation assay using formaldehyde crosslinking. Chromatin immunoprecipitation and quantitative PCR analysis revealed that promoter fragments of STAT1, ICAM1, CXCL10, and MMP9 were enriched in the AIRE precipitates. In oral cancer cells, ETS1 was diffusely located in the nucleus and partially overlapped with dot-like AIRE accumulation sites. Nuclear translocation of AIRE was promoted by cotransfection with Ets1 . These results indicate that AIRE is induced in OSCC and supports cancer-related gene expression in cooperation with ETS1. This is a novel function of AIRE in extrathymic tissues under the pathological condition.