MicroRNA-21 as a Regulator of Cancer Stem Cell Properties in Oral Cancer

Oral squamous cell carcinoma (OSCC) is a highly aggressive malignancy with poor prognosis, mainly due to the presence of cancer stem cells (CSCs), a small subpopulation of cells that contribute to therapy resistance and tumor progression. The principal objective of this study was to investigate the role of miRNA-21 in the maintenance of cancer cell stemness and the possibility of altering it. The CD44 antigen was used as a marker for CSC isolation from oral cancer cell cultures. CD44+ and CD44- populations were sorted via magnetic separation. miRNA-21 inhibition was performed in CD44+ cells via transfection. CD44+ cells possessed a significantly higher migration and invasion potential compared to CD44- cells, higher levels of miRNA-21 (<i>p</i> = 0.004) and β-catenin (<i>p</i> = 0.005), and lower levels of BAX (<i>p</i> = 0.015). miRNA-21 inhibition in CD44+ cells reduced migration, invasion, and colony formation while increasing apoptosis. Stemness markers were significantly downregulated following miRNA-21 inhibition: <i>OCT4</i> (<i>p</i> = 0.013), <i>SOX2</i> (<i>p</i> = 0.008), and <i>NANOG</i> (<i>p</i> = 0.0001), as well as β-catenin gene (<i>CTNNB1)</i> (<i>p</i> < 0.05), an important member of WNT signaling pathway. Apoptotic activity was enhanced, with a significant downregulation of the antiapoptotic Bcl-2 (<i>p</i> = 0.008) gene. In conclusion, miRNA-21 plays a critical role in the regulation of oral cancer CD44+ cells properties. Targeting and inhibiting miRNA-21 in CD44+ cells could represent a promising novel strategy in OSCC treatment.