miR-377 was formulated with in vivo-jetPEI and injected weekly intravenously into mice. - ESCC cells were subcutaneously injected into mice to establish tumor xenograft. Two weeks later when tumor reached ~0.5 cm diameter, the mice were randomized into three different treatment groups to receive weekly intravenous injections of 40 μg miR-377 oligonucleotide, miR-CON oligonucleotide and vehicle, respectively. - KYSE150-luc cells were injected into nude mice via the tail vein and randomized into four groups. Three groups (n=6/group) were treated once every two weeks with intravenous injections of 20 μg miR-377 oligonucleotide, miR-CON oligonucleotide and vehicle, respectively, commencing one week after injection of cancer cells.

Esophageal cancer is one of the most lethal cancers worldwide with poor survival and limited therapeutic options. The discovery of microRNAs created a new milestone in cancer research. miR-377 is located in chromosome region 14q32, which is frequently deleted in esophageal squamous cell carcinoma (ESCC), but the biological functions, clinical significance and therapeutic implication of miR-377 in ESCC are largely unknown. In this study, we found that miR-377 expression was significantly downregulated in tumor tissue and serum of patients with ESCC. Both tumor tissue and serum miR-377 expression levels were positively correlated with patient survival. Higher serum miR-377 expression was inversely associated with pathologic tumor stage, distant metastasis, residual tumor status and chemoradiotherapy resistance. The roles of miR-377 in suppressing tumor initiation and progression, and the underlying molecular mechanisms were investigated. Results of in vitro and in vivo experiments showed that miR-377 overexpression inhibited the initiation, growth and angiogenesis of ESCC tumors as well as metastatic colonization of ESCC cells, whereas silencing of miR-377 had opposite effects. Mechanistically, miR-377 regulated CD133 and VEGF by directly binding to their 3' untranslated region. Moreover, systemic delivery of formulated miR-377 mimic not only suppressed tumor growth in nude mice but also blocked tumor angiogenesis and metastasis of ESCC cells to the lungs without overt toxicity to mice. Collectively, our study established that miR-377 plays a functional and significant role in suppressing tumor initiation and progression, and may represent a promising non-invasive diagnostic and prognostic biomarker and therapeutic strategy for patients with ESCC.