Abstract:

Tongue squamous cell carcinoma (TSCC) is the most common type of oral cancer and is well known for its high rate of proliferation and lymph nodal metastasis. Exploring the underlying pathways regulating TSCC could provide novel ideas for diagnosis and prognosis of TSCC patients, as well as molecular targets for treatment of TSCC. MicroRNAs (miRNAs) are small noncoding RNAs that inhibit gene expression through the 3′ untranslated regions (3′UTRs) of their target messenger RNAs. They play crucial roles in numerous biological processes, including cancer progression. Although great efforts have been made, what role miRNAs may play in the early detection and diagnosis of TSCC is not fully understood. Recently, our team has performed a series of basic and clinical researches in an attempt to investigate the relationships between miRNA expressions and prognosis of patients with TSCC and the mechanisms under regulation of TSCC. The results showed that miR-195, miR-34a, miR-29b, miR-375 and miR-26a could inhibit TSCC cells progression and development via a sophisticated network of genes. Specifically, the anti-tumor effects of miR-195 in TSCC may be partially mediated by its inhibition of CyclinD1 and Bcl-2 expression. The expression of miR-34a could inhibit migration and invasion of TSCC cell lines via targeting MMP9 and MMP14. The function of miR-29b may be through the miR-29b/Sp1/PTEN/AKT axis. Overexpression of miR-375 inhibited Sp1 expression by targeting the 3′ untranslated region of the Sp1 transcript. MEG3 and miR-26a inhibited TSCC cell proliferation, cycle progression and promoted cell apoptosis and miR-26a could increase the MEG3 expression through reduction of the expression of DNMT3B in TSCC. In light of the role of those miRNAs in diagnosis and prognosis of TSCC, we reported that decreased miR-195 and miR-375 expression was associated with poor overall survival rate of the TSCC patients, while miR-34a expression was negatively correlated with cervical lymph node metastases. Furthermore, combined low expression levels of miR-26a and MEG3 emerged as an independent prognostic factor for poor clinical outcomes in TSCC patients, suggesting that combined miR26a and MEG3 expression might prove useful as an independent biomarker of clinical prognosis among TSCC patients.

Key words: Tongue neoplasms, Carcinoma, squamous cell, MicroRNAs, Prognosis, Biological beha-vior of tumor