Knockdown of Nedd8­conjugating enzyme UBE2M suppresses the proliferation and induces the apoptosis of intrahepatic cholangiocarcinoma cells.

As an important regulator of neddylation, neural precursor cell expressed developmentally downregulated 8 (Nedd8)­conjugating enzyme E2M (UBE2M) mediates cullin neddylation. Upregulation of the neddylation pathway is associated with tumor progression in intrahepatic cholangiocarcinoma (ICC). The present study was designed to assess the effects of Nedd8­conjugating enzyme UBE2M knockdown on intrahepatic cholangiocarcinoma cells, and to determine the potential underlying mechanisms. UBE2M and associated protein expression levels were determined via immunohistochemistry and western blotting. ICC cells were transfected with short hairpin RNA to knockdown UBE2M expression. Cell Counting Kit­8 and colony formation assays, and xenograft experiments were used to examine cell viability and colony survival in vitro, and tumor formation in vivo. Survival was evaluated using Kaplan­Meier analysis and log­rank tests. Patients with ICC presenting high expression of UBE2M exhibited worse accumulative recurrence and overall survival compared with patients with low expression. Knockdown of UBE2M expression led to a decrease in the viability and clonogenic survival of QBC939 and HUCCT1 cells, and suppressed tumor formation in vivo. UBE2M silencing caused accumulation of cullin­RING ligase substrates (chromatin­licensing and DNA replication factor 1 and origin recognition complex subunit 1), inducing DNA damage responses and apoptosis. The present findings suggested that UBE2M serves an important role in ICC progression and may present as a novel target for the treatment of ICC.