Increase of microRNA miR-31 level in plasma could be a potential marker of oral cancer.

Oral squamous cell carcinoma (OSCC) is a worldwide disease. MicroRNAs are endogenously expressed non-coding RNAs that have important biological and pathological functions. miR-31 was found markedly up-regulated in OSCC and several other malignancies. However, miR-31 expression was also down-regulated in the metastasis process of breast carcinoma. Using quantitative RT-PCR analysis, we identified plasma miR-31 in OSCC patients (n = 43) and case controlled individuals (n = 21). Nine OSCC patients saliva were also analyzed. The Mann-Whitney test and Wilcoxon matched pairs test were used to compare the differences among the various clinical variants. miR-31 in plasma was significantly elevated in OSCC patients relative to age and sex-matched control individuals. This marker yielded a receiver operating characteristic curve area of 0.82 and an accuracy of 0.72 defined by leave-one-out cross-validation. In addition, the plasma miR-31 in patients was remarkably reduced after tumor resection suggesting that this marker is tumor associated. Our preliminary analysis also demonstrated the feasibility of detecting the increase of miR-31 in patient's saliva. This study concluded that plasma miR-31 could be validated a marker of OSCC for diagnostic uses.