Expression of S100A8 is induced by interleukin­1α in TR146 epithelial cells through a mechanism involving CCAAT/enhancer binding protein ß.

Calprotectin in mucosal epidermal keratinocytes has an important role in fighting microbial infections. S100A8 belongs to the S100 protein family and is a subunit of calprotectin (heterodimer complex of S100A8/A9). Interleukin­1α (IL­1α) is one of the cytokines produced by oral keratinocytes. The primary aims of the present study were to investigate the effect of IL­1α on the expression of S100A8 and its underlying molecular mechanism in oral epithelial cells. Determining the molecular mechanism of the induced expression of S100A8 by IL­1α aims to improve current understanding of the roles of calprotectin during the infection of mucosal epithelial cells. The expression analysis indicated that IL­1α significantly induced the expression of S100A8 in human TR146 epithelial cells at the mRNA and protein levels, respectively. The reporter assay demonstrated that the upregulatory effect of S100A8 induced by IL­1α was dependent on the S100A8 promoter specific region (­165/­111). The results of electrophoresis mobility shift assay and chromatin immunoprecipitation assay also demonstrated that the CCAAT/enhancer binding protein ß (C/EBPß) binding site (­113/­109) in the S100A8 promoter region was involved into the upregulatory effect on the expression of S100A8 induced by IL­1α. Taken together, these results suggested that the activation of the expression of S100A8 induced by IL­1α in TR146 epithelial cells involves a mechanism by which the binding activity of C/EBPß to the specific site (­113/­109) of the S100A8 promoter is increased.

DNA methylation directly downregulates human cathelicidin antimicrobial peptide gene (CAMP) promoter activity.

LL-37, the active product of human cathelicidin antimicrobial peptide (CAMP) has a broad spectrum of antibacterial activity. LL-37 also has important physiological functions in immune regulation, angiogenesis and in modulating apoptosis. The roles of LL-37 in oral squamous cell carcinoma (OSCC) are still not clear. The correlation between DNA methylation and human CAMP expression is also unknown. Here human CAMP/LL-37 expression was assessed by immunohistochemistry in normal and OSCC tissues. The results indicated that low expression of CAMP/LL-37 correlated with histological differentiation and lymph node metastasis and also promoted tumor progression. A cell-specific methylation pattern in the promoter region of human CAMP was detected. Treatment with 5-aza-2'-deoxycytidine, a DNA demethylation reagent can increase human CAMP expression in epithelial cancer cells. The reporter assay showed that unmethylated human CAMP promoter activity was significantly higher than methylated promoter activity. Taken together, these results suggested that human CAMP/LL-37 might act as a tumor-suppressor in OSCC and DNA methylation might play roles during carcinogenesis via directly downregulating human CAMP promoter activity.