Abstract
Despite the differential expression of S100A14 (a newly identified S100 member) in various human cancers including oral squamous cell carcinomas (OSCCs), its biological role in tumour invasion has not been characterised. The aim of this study was thus to investigate the possible role of S100A14 in OSCC cell invasion. Using immunohistochemistry in normal (n=13), dysplastic (n=10) and OSCC (n=16) archival tissues, S100A14 protein was found to be down-regulated/lost with concomitant membrane to cytoplasmic translocation in OSCCs, especially in the invading tumour islands. These expression data were corroborated by profiling S100A14 mRNA expression using quantitative RT-PCR (qRT-PCR) in an in vitro human OSCC progression model consisting of cell-lines derived from normal (n=3), dysplastic (n=3) and OSCC (n=8) tissues. Employing in vitro Matrigel invasion assay, we demonstrated that retroviral vector mediated over-expression of S100A14 resulted in significant decrease in the invasive potential of OSCC derived CaLH3 and H357 cell-lines whereas siRNA mediated knockdown resulted in significant increase in the invasive potential of CaLH3 cell-line. Pathway focused PCR array and validation using qRT-PCR revealed that S100A14 over-expression was associated with down-regulation of MMP1 and MMP9 mRNAs in both CaLH3 and H357 cell-lines. Further, S100A14 over-expression was found to be associated with suppression of MMP9 gelatinolytic activity in CaLH3 cell-line. Additionally, an inverse correlation between mRNA expression levels of MMP1 and MMP9 with S100A14 was found in 19 cases of OSCCs. Collectively, these data provide the first evidence for a role of S100A14 protein in regulation of OSCC cell invasion by modulating expression of MMP1 and MMP9.