Targeting of the C-Jun/BCL-XL/P21 Axis Accelerates the Switch from Senescence to Apoptosis Upon ROC1 Knockdown in Gastric Cancer Cells.

Background/aims: Regulator of cullins-1 (ROC1) is a pivotal component of cullin-RING E3 ubiquitin ligases, which help to regulate distinct cellular processes by governing the degradation of various substrates. Because the role of ROC1 in gastric cancer is largely uncharacterized, we investigated the relationship between ROC1 expression and the prognosis of gastric cancer patients and explored the biological function of ROC1 and its underlying mechanisms in gastric cancer.

Methods: Kaplan-Meier and multivariate Cox regression analyses were used to evaluate the correlation between the carcinogenesis of gastric cancer and ROC1. SA-β-gal staining and the senescence-associated secretory phenotype (SASP) were used to assess ROC1 silencing-induced cellular senescence. A xenograft zebrafish model was used to evaluate the effects of BCL-XL and ROC1 co-silencing on tumor formation in vivo.

Results: High ROC1 expression was correlated with poor prognosis and a low 5-year survival rate of gastric cancer patients. ROC1 depletion significantly inhibited the growth of gastric cancer cells by sequentially inducing p21-mediated cellular senescence and mitochondrial-dependent apoptosis. Functional studies revealed successive upregulation of c-Jun, BCL-XL, and p21 upon ROC1 knockdown. BCL-XL suppression via RNA interference or a BH3 mimetic (ABT-737 or ABT-263) efficiently enhanced the anti-tumor effects of ROC1 knockdown. Equally as important, BCL-XL silencing strengthened ROC1 knockdown-induced apoptosis by blocking p21-mediated senescence.

Conclusions: The c-Jun/BCL-XL/p21 axis promotes senescence to resist ROC1 knockdown-induced apoptosis in gastric cancer cells. Targeted inactivation of BCL-XL could sensitize gastric cancer cells to ROC1 knockdown in clinical practice.