Significance of expression of tumor-associated microRNA-21 and -375 for predicting the course of cancer of oral cavity.

Aim: To investigate the features of expression of miRNA-21 and miRNA-375 in tumor cells of patients with cancer of oral cavity (COC) and to determine the possibility of their use to predict the aggressiveness of COC course.

Materials And Methods: The work is based on the results of examination and treatment of 50 patients with stage II-IV COC. miRNA expression in tumor cells was analyzed by real time reverse transcription polymerase chain reaction.

Results: High levels of miRNA-21 expression (> 0.26 a.u.) and miRNA-375 (> 0.36 a.u.) were determined in 72.0% and 63.0% of cases. We revealed a tendency to decreased miRNA-21 expression and increased miRNA-375 expression in tumors of patients with recurrence-free survival less than 12 months and the presence of metastatic lesions in regional lymph nodes. In patients with COC of low differentiation grade, the level of miRNA-21 was 2.0 times lower compared with tumors of moderate differentiation grade (p < 0.05), while the expression of miRNA-375, on the contrary, was higher in tumors of low differentiation grade. A decreased expression of miRNA-21 (< 0.26 a.u.) against the background of decreased levels of miRNA-375 (< 0.36 a.u.) in tumor cells was associated with worse recurrence-free survival.

Conclusions: The obtained results indicate the relation between the main clinical and pathological characteristics of patients with COC and the levels of miRNA-21 and -375 expression in tumor tissue, which indicates the involvement of these miRNAs in the formation of COC malignancy evidencing on their potential usefulness as additional prognostic markers.