Abstract
MicroRNA-155 (miR-155) is overexpressed in many human cancers; however, the function of miR-155 is largely unknown in esophageal squamous cell carcinoma (ESCC). In the present study, we found that miR-155 is dramatically increased in ESCC tissues compared with the paired adjacent normal tissues, which suggested that miR-155 acts as an oncogene in ESCC. We predicted that tumor protein p53-induced nuclear protein 1 (TP53INP1) is a candidate target gene of miR-155 given that miR-155 expression decreased mRNA and protein levels of TP53INP1 as determined by RT-PCR and Western blot analysis. In addition, miR-155 and TP53INP1 showed a negative relation in ESCC tissues. Dual luciferase-based reporter assay indicated direct regulation of TP53INP1 by miR-155. Furthermore, we demonstrated that RNA interference of TP53INP1 increased the proliferation and colonies formation of EC-1 cells. Up-regulation of TP53INP1 abrogated miR-155 induced growth in EC-1 cells and mutation of TP53INP1 in 3'-UTR restored the effects when co-transfected with miR-155. We also indicated that overexpression of miR-155 significantly promoted the proliferation of EC-1 cells in vitro and the development of tumors in nude mice. Taken together, our study reveals that miR-155 acts as an oncogene by targeting TP53INP1 in ESCC.