MicroRNA-31: a pivotal oncogenic factor in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) continuously constitutes a major challenge for treatment and prognosis due to approximately half of treated OSCC patients dying from locoregional recurrences and distant metastases. MicroRNA-31 (miR-31), an early mammalian miRNA identified, has been gaining importance in the field of OSCC research in recent years. This comprehensive review was conducted for the first time to summarize the current evidence on the association between miR-31 and OSCC. The vast majority of relevant studies (20/21, 95%) demonstrated that miR-31 was an oncogenic factor in the tumorigenesis and progression of OSCC. miR-31 expression is significantly upregulated in plasma, saliva, and tumor tissue of OSCC. miR-31 played an essential role in OSCC development by constituting a complex network with its targeted genes (e.g. RhoA, FIH, ACOX1, VEGF, SIRT3, LATS2, KANK1, and NUMB) and the signaling cascades (e.g. EGF-AKT signaling axis, ERK-MMP9 cascade, Hippo pathway, Wnt signaling, and MCT1/MCT4 regulatory cascade). This review highlights that miR-31 might function as a potential diagnostic, prognostic, and predictive biomarker for OSCC. Further studies are still warranted to better illuminate the clinicopathological features and the molecular mechanisms of miR-31-mediated OSCC development.