MicroRNA (miRNA) is a form of small noncoding RNA that regulates the expression of genes either by inhibiting
mRNA translation or by inducing its degradation. Small microRNA play important roles in regulating a large number
of cellular processes, including development, proliferation and apoptosis. This study examined the biological
functions of miR-205 as a tumor suppressor in KB oral cancer cells. The results showed that miR-205 expression
was significantly lower in KB oral cancer cells than in human normal oral keratinocytes. Furthermore, the miR-205
over-expressed in KB oral cancer cells increased the cell cytotoxicity and induced apoptosis through the activation
of caspase-3/-7. The transfection of miR-205 into KB oral cancer cells strongly induced IL-24, a well known cytokine
that acts as a tumor suppressor in a range of tumor tissues. In addition, miR-205 targeted the IL-24 promoter directly
to induce gene expression. Overall, miR-205 has significant therapeutic potential to turn on silenced tumor
suppressor genes by targeting them with miRNA.

Keywords: apoptosis, human oral cancer, interleukin-24, microRNA-205