miR766-3p and miR124-3p Dictate Drug Resistance and Clinical Outcome in HNSCC

SIMPLE SUMMARY: Despite improvements in therapeutics, head and neck squamous cell carcinomas (HNSCC) relapse in more than 50% of cases due to the development of chemo-radiotherapy resistance during sequential treatments. Our findings provide a strong rationale which can improve potential therapeutic strategies for overcoming drug resistance in HNSCC. We demonstrated that expression of miR124-3p and miR766-3p is associated with drug resistance in HNSCC, and their blockade greatly enhances the efficacy of standard anti-HNSCC therapeutics including 5-fluorouracil and cisplatin (FP chemotherapy), as well as radiotherapy. We discovered miR124-3p and miR766-3p-mediated mechanisms of resistance involve transcriptional factors CREBRF and NR3C2 in HNSCC. These results warrant testing miR766-3p and miR124-3p as predictors of response to chemo-radiotherapy in clinical settings and as markers for selecting patients for alternative treatment approach. ABSTRACT: Head and neck squamous cell carcinoma (HNSCC) is a highly aggressive disease with poor prognosis, which is mainly due to drug resistance. The biology determining the response to chemo-radiotherapy in HNSCC is poorly understood. Using clinical samples, we found that miR124-3p and miR766-3p are overexpressed in chemo-radiotherapy-resistant (non-responder) HNSCC, as compared to responder tumors. Our study shows that inhibition of miR124-3p and miR766-3p enhances the sensitivity of HNSCC cell lines, CAL27 and FaDu, to 5-fluorouracil and cisplatin (FP) chemotherapy and radiotherapy. In contrast, overexpression of miR766-3p and miR124-3p confers a resistance phenotype in HNSCC cells. The upregulation of miR124-3p and miR766-3p is associated with increased HNSCC cell invasion and migration. In a xenograft mouse model, inhibition of miR124-3p and miR766-3p enhanced the efficacy of chemo-radiotherapy with reduced growth of resistant HNSCC. For the first time, we identified that miR124-3p and miR766-3p attenuate expression of CREBRF and NR3C2, respectively, in HNSCC, which promotes aggressive tumor behavior by inducing the signaling axes CREB3/ATG5 and β-catenin/c-Myc. Since miR124-3p and miR766-3p affect complementary pathways, combined inhibition of these two miRNAs shows an additive effect on sensitizing cancer cells to chemo-radiotherapy. In conclusion, our study demonstrated a novel miR124-3p- and miR766-3p-based biological mechanism governing treatment-resistant HNSCC, which can be targeted to improve clinical outcomes in HNSCC.