Downregulation of miR-503 Promotes ESCC Cell Proliferation, Migration, and Invasion by Targeting Cyclin D1

Esophageal squamous cell carcinoma （ESCC） is one of the most aggressive cancers in China, but the underlying molecular mechanism of ESCC is still unclear. Involvement of micro- RNAs has been demonstrated in cancer initiation and progression. Despite the reported function of miR-503 in several human cancers, its detailed anti-oncogenic role and clinical significance in ESCC remain undefined. In this study, we examined miR-503 expression by qPCR and found the downregulation of miR-503 expression in ESCC tissue relative to adjacent normal tissues. Fur- ther investigation in the effect of miR-503 on ESCC cell proliferation, migration, and invasion showed that enhanced expression of miR-503 inhibited ESCC aggressive phenotype and overexpres- sion of CCND1 reversed the effect of miR-503-mediated ESCC cell aggressive phenotype. Our study further identified CCND1 as the target gene of miR-503. Thus, miR-503 functions as a tumor suppressor and has an important role in ESCC by targeting CCND1.