Esophageal cancerrelated gene 4 (ECRG4) is down-regulated in esophageal squamous-cell carcinoma (ESCC) and inhibits the tumorigenicity of ESCC cells. Ubiquitin conjugating enzyme E2 (UBE2C), an E2 ubiquitin-conjugating enzyme, is upregulated in numerous human cancers, including ESCC.

mRNA and protein expression was determined by real-time PCR and western blotting analysis, respectively. Cell apoptosis was assessed by Annexin V-fluorescein isothiocyanate staining and flow cytometry analysis.

By analyzing previous quantitative proteomics data on EC9706 cells, we found that UBE2C was significantly down-regulated in ECRG4 overexpressed cells. Western blotting analysis validated the proteomics results in both EC9706 and EC-18 cells. In addition, Pearson’s correlation analysis demonstrated a negative correlation between the mRNA levels of ECRG4 and UBE2C in ESCC tissues. Then, we found that Nuclear Factor-κB (NF-κB) inhibitor, pyrriolidine-dithiocarbamate (PDTC), could inhibit NF-κB p65 nuclear translocation and UBE2C expression, which was partially reversed by ECRG4 silence. More importantly, UBE2C knockdown in TE-1 cells significantly inhibited cell proliferation and induced cell apoptosis, which was partially reversed by ECRG4 knockdown.

ECRG4 down-regulated UBE2C expression in ESCC cells via NF-κB signaling. UBE2C was involved in the anti-proliferative and pro-apoptotic functions of ECRG4 in ESCC cells.