Jab1 is a coactivator of c-Jun that enhances the transcriptional function of c-Jun. Jab1 is frequently overexpressed in various cancers and is associated with poor prognosis of cancer patients. Thus, Jab1 could be a potential therapeutic target in cancer. However, the role of Jab1 in biliary tract cancer (BTC) has not been studied.
We evaluated the therapeutic potential of Jab1 inhibition in BTC. In vitro studies included western blot, cell growth inhibition assays, cell cycle analysis, wound healing assays, comet assays, real-time PCR, and cycloheximide chase assays. Female Balb/c athymic nude mice were used for in vivo studies.
Among eight BTC cell lines tested (SNU245, SNU308, SNU478, SNU869, SNU1079, SNU1196, HuCCT-1, and TFK-1), many showed higher Jab1 expression levels. In addition, Jab1 silencing by siRNA increased p27 expression levels. Notably, SNU478 and HuCCT-1 cells exhibited profound Jab1 knockdown and increased p27 expression by Jab1-specific siRNA transfection. Jab1 silencing induced anti-proliferative and anti-migratory effects and resulted in G1 cell cycle arrest in SNU478 and HuCCT-1 cells. Jab1 knockdown alone induced spontaneous DNA damage, resulting in anti-proliferative and anti-migratory effects. Moreover, Jab1 knockdown potentiated the anti-proliferative and anti-migratory effects of cisplatin by increasing DNA damage. Interestingly, Jab1 silencing increased PTEN protein half-life without significant increase of PTEN mRNA expression levels, resulting in increased PTEN expression and decreased AKT and Src phosphorylation. In the HuCCT-1 mouse xenograft model, stable knockdown of Jab1 by shRNA also showed anti-proliferative effects in vivo, with decreased Ki-67 expression and AKT phosphorylation and increased TUNEL and p27 expression.
Jab1 knockdown demonstrated anti-proliferative and anti-migratory effects in BTC cells by increasing DNA damage and stabilizing PTEN, resulting in G1 cell cycle arrest and apoptosis. In addition, Jab1 silencing potentiated the anti-proliferative effects of cisplatin by enhancing DNA damage. Our data suggest that Jab1 may be a potential therapeutic target in BTC that is worthy of further investigations.
Clinical trial identification
Legal entity responsible for the study
Ministry of Health & Welfare, Republic of Korea (Grant No. A121508)
All authors have declared no conflicts of interest.