MicroRNA in adenoid cystic carcinoma (Review)

Abstract

Adenoid cystic carcinoma (ACC) usually arises in the salivary glands, and is a rare tumor, accounting for 1% of all head and neck cancer cases. According to estimates, there are 3‑4.5 cases of ACC for every one million individuals. Numerous studies have reported the association between ACC and microRNAs (miRNAs/miRs). miRNAs are endogenous, non‑coding small RNAs, 19‑25 nt in length, that can regulate target gene expression at the post‑transcriptional level. The aberrant expression of miRNAs may be associated with the prognosis and treatment of patients, as well as with tumorigenesis and tumor development. miRNAs are becoming reliable biomarkers for disease detection due to their varied characteristics, and miRNA target‑based therapies are increasingly being used in clinical practice. The present review provides a brief introduction to ACC and the biogenesis of miRNAs. A summary of the miRNAs that have been validated by in vitro or in vivo studies is then presented, describing their role in ACC.

Keywords: adenoid cystic carcinoma; biomarker; miRNA; pathogenesis; therapy.

Figure 1

Biogenesis of miRNA. Step A: miRNAs are initially produced by RNA polymerase II or III in the nucleus, and transcribed into pri-miRNA. Step B: Drosha and Dicer are bound by the pri-miRNAs; this microprocessor complex is formed by drosha with DGCR8, and then pre-miRNA is liberated. Step C: Exportin-5 exports pre-miRNA to the cytoplasm. Step D: The mature miRNA/miRNA duplex are produced by dicer. Step E: Inactive strands are degraded. Step F: The incorporation of the mature strand into RISC. The gene expression is suppressed by RISC with Step G: mRNA degradation or Step H: translational repression, then regulates cellular function. Step I: In addition, exosomes can package miRNAs. Step J: Exosomes are then compartmentalized into an MVB. Step K: The plasma membrane is fused by the MVB, and then miRNA-containing exosomes are transferred to recipient cells and influence gene regulation. miRNA, microRNA; pri-, primary; pre-, precursor; RISC, RNA-induced silencing complex; mRNA, messenger RNA; MVB, multivesicular body; 3′UTR, 3′-untranslated region; ORF, open reading frame; DGCR8, DGCR8 microprocessor complex subunit.