HES1-mediated down-regulation of miR-138 sustains NOTCH1 activation and promotes proliferation and invasion in renal cell carcinoma.

ABSTRACT

BACKGROUND: Although the aberrant activation of NOTCH1 pathway causes a malignant progression of renal cell carcinoma (RCC), the precise molecular mechanisms behind the potential action of pro-oncogenic NOTCH1/HES1 axis remain elusive. Here, we examined the role of tumor suppressive miR-138-2 in the regulation of NOTCH1-HES1-mediated promotion of RCC. METHODS: This study employed bioinformatics, xenotransplant mouse models, ChIP assay, luciferase reporter assay, functional experiments, real-time PCR and Western blot analysis to explore the mechanisms of miR-138-2 in the regulation of NOTCH1-HES1-mediated promotion of RCC, and further explored miR-138-2-containing combination treatment strategies. RESULTS: There existed a positive correlation between down-regulation of miR-138 and the aberrant augmentation of NOTCH1/HES1 regulatory axis. Mechanistically, HES1 directly bound to miR-138-2 promoter region and thereby attenuated the transcription of miR-138-5p as well as miR-138-2-3p. Further analysis revealed that miR-138-5p as well as miR-138-2-3p synergistically impairs pro-oncogenic NOTCH1 pathway through the direct targeting of APH1A, MAML1 and NOTCH1. CONCLUSIONS: Collectively, our current study strongly suggests that miR-138-2 acts as a novel epigenetic regulator of pro-oncogenic NOTCH1 pathway, and that the potential feedback regulatory loop composed of HES1, miR-138-2 and NOTCH1 contributes to the malignant development of RCC. From the clinical point of view, this feedback regulatory loop might be a promising therapeutic target to treat the patients with RCC.