MiR-21 is a Predictor for Chemoradioresistance and a Novel Therapeutic Target in Head and Neck Squamous Cell Carcinoma

ObjectiveThis study aimed to clarify whether circulating miR-21 represents a predictive biomarker in patients with head and neck squamous cell carcinoma (HNSCC) undergoing chemoradiotherapy, and to investigate the effect of miR-21 inhibitor for chemoradiation in human SCC cells.MethodsPlasma samples were obtained from 22 patients with HNSCC and 25 non-cancer volunteers. Plasma miR-21 expression was measured using real-time quantitative reverse transcription polymerase chain reaction. The effects of miR-21 inhibitor in human SCC cells were investigated by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and Western blot analysis.ResultsPlasma miR-21 expression was higher in HNSCC patients than in control patients (p< 0.001). Seven patients with recurrence showed significantly higher plasma miR-21 than the 15 patients without recurrence. Moreover, miR-21 inhibition significantly enhanced cisplatin- or radiation-induced apoptosis. Western blot analysis suggested the programmed cell death 4 (PDCD4) protein as a potential target of miR-21 in relation to apoptosis. Adding miR-21 inhibition to radiation or cisplatin treatment provided clear and potent suppression of tumor cell proliferation.ConclusionThis study provides new insights into the role of miR-21 as a predictive biomarker for HNSCC treated with chemoradiotherapy, and suggests a potential target to improve the effects of chemoradiotherapy against HNSCC.