miR-199b-3p Promotes Radiation-induced Oral Mucositis via DDIT4-mediated mTOR Signal Pathway

Abstract

Background: Radiation-induced oral mucositis (RIOM) is an adverse reaction in patients of head and neck cancer after radiotherapy. However, the key regulatory factors in the pathogenesis of RIOM remain largely unclear. In this article, we discover a novel role of DNA damage-inducible transcript 4 (DDIT4) in regulating RIOM pathogenesis.Methods: We established RIOM in vitro and in vivo models to mimic the biological processes of RIOM. The level of DDIT4 in RIOM was analyzed by real-time PCR and Western blot. Through the bioinformatics analysis and luciferase assay, the relationship between miR-199b-3p and DDIT4 was performed. The level of mTOR signaling were explored by Western blot. Besides, Clone Formation and EDU assay were performed to investigate the effects of miR-199b-3p/DDIT4 on cell proliferation. H&E and immunohistochemistry experiments examined the effects of miR-199b-3p/DDIT4 on RIOM in vivo. Results: We found that the level of DDIT4 was significantly reduced during the RIOM formation, and up-regulated of DDIT4 suppressed the progression of RIOM in vitro and in vivo. Besides, we found DDIT4 was a direct target of miR-199b-3p. Ectopic expression of miR-199b-3p repressed the level of DDIT4 and activated mTOR signal conduction to promote RIOM progress, whereas the silencing of miR-199b-3p promoted the DDIT4-mediated RIOM regulation both in vitro and in vivo. Conclusion: Collectively, our studies not only identified the novel functional role of DDIT4 in modulating pathogenic processes of RIOM but also provided new directions and ideas for the future treatment of radiotherapy oral mucositis.