miR-494.3p expression in synovial sarcoma: Role of CXCR4 as a potential target gene

Synovial sarcoma (SS) is a rare tumour, with dismal survival when metastasis occurs. SS contains a characteristic translocation (X;18)(p11;q11) and the fusion genes appear to be mutually exclusive and concordant in primary and metastatic tumours. Novel prognostic and predictive factors are required. The C-X-C motif chemokine ligand 12 (CXCL12)/C-X-C chemokine receptor 4 (CXCR4) axis is involved in tumour development and metastatic spread in many types of cancer and previous data have demonstrated a pivotal role of CXCR4 in SS cell migration and invasion. Bioinformatics and biological data indicated CXCR4 is a possible candidate target of miR-494.3p, known to be involved in tumour progression. In this study, we analysed the expression of miR-494.3p and its potential target, CXCR4, in a series of SS specimens. A significantly lower miR-494.3p expression was found in the tumour compared to normal tissue associated with higher levels of CXCR4 both at the gene and protein level. The role of CXCR4 as a potential target of miR-494.3p was assessed in two SS cell lines (SW982 and SYO-I). Transfection with miR-494.3p expression plasmid led to a marked decrease in CXCR4 gene and protein expression, concomitant with a transitory decrease in cell proliferation and migration. The SYO-I cells also responded with an increased apoptotic fraction. The data of this study also demonstrate that the downregulation of miR-494.3p in SS surgical specimens, concomitant with an increased expression of its potential target, CXCR4, was more evident in the metastatic subset. In vitro experiments confirmed that miR-494.3p functioned as a tumour suppressor through the involvement of CXCR4 and ongoing studies are directed to better clarify its role in SS therapeutic strategies.