Molecular targeting of CSN5 in human hepatocellular carcinoma: a mechanism of therapeutic response

Abstract

Development of targeted therapy for hepatocellular carcinoma (HCC) remains a major challenge. We have recently identified an elevated expression of the fifth subunit of COP9 signalosome (CSN5) in early HCC as compared to dysplastic stage. In the present study, we explored the possibility of CSN5 being a potential therapeutic target for HCC. Our results show that CSN5 knockdown by small interfering (si) RNA caused a strong induction of apoptosis and inhibition of cell cycle progression in HCC cells in vitro. The downregulation of CSN5 was sufficient to interfere with CSN function as evidenced by the accumulation of neddylated Cullin1 and changes in the protein levels of CSN controlled substrates SKP2, p53, p27 and NF-kB, albeit to a different degree depending on the HCC cell line, which could account for the CSN5 knockdown phenotype. The transcriptomic analysis of CSN5 knockdown signature showed that the anti-proliferative effect was driven by a common subset of molecular alterations including downregulation of CDK6 and ITGB1, which were functionally interconnected with key oncogenic regulators MYC and TGFβ1 involved in the control of proliferation, apoptotic cell death and HCC progression. Consistent with microarray analysis, western blotting revealed that CSN5 depletion increased phosphorylation of Smad 2/3, key mediators of TGFβ1 signaling, decreased the protein levels of ITGB1, CDK6, and cyclin D1 and caused reduced expression of anti-apoptotic Bcl-2 while elevating the levels of pro-apoptotic Bak. A chemically modified variant of CSN5 siRNA was then selected for in vivo application based on the growth inhibitory effect and minimal induction of unwanted immune response. Systemic delivery of the CSN5 3/8 variant by stable-nucleic-acid-lipid-particles (SNALP) significantly suppressed the tumor growth in Huh7-luc+ orthotopic xenograft model. Taken together, these results indicate that CSN5 plays a pivotal role in HCC pathogenesis and maybe an attractive molecular target for systemic HCC therapy.

Acetylcholinesterase is associated with a decrease in cell proliferation of hepatocellular carcinoma cells

“…As a model to study the effects of AChE activity changes on the cell growth of malignant liver we used the hepatocellular carcinoma Huh-7 cell line, whose malignant phenotype and high survival rate make them the model of choice for testing the benefit of promising therapeutic targets [37,38]. Monolayer cell culture below confluence is not necessarily a good model to explore protein expression changes in cancer studies owing to the fact that, contrary to cells in monolayer cultures, cells in tumor pieces display tight cell-cell contacts, a circumstance which probably alters the expression of many proteins.…”

Suppression of CSN5 promotes the apoptosis of gastric cancer cells through regulating p53-related apoptotic pathways

“…In fact, CSN5 is not only represents a prognostic marker for malignant transformation but also contributes to cancer cell biological behaviors, and those results had been found in some types of cancer cells, such as the human colorectal cancer cell lines 20 and the human hepatocellular carcinoma cell lines. 27 In the present study, we demonstrated that the expression of CSN5 was higher in gastric cancer tissues and gastric cancer cells, meanwhile, knockdown of CSN5 inhibited proliferation and induced apoptosis in human gastric cancer cell lines. The results suggested that CSN5 may play an important role in gastric cancer cells progressing.…”

Dynamic Regulation of the COP9 Signalosome in Response to DNA Damage

“…Indeed, accumulating evidence indicates a correlation between aberrant functioning of the CSN and multiple cancers, making it an attractive target for therapeutic intervention (19,20). Frequent overexpression of CSN subunits, especially the MPN proteins CSN5 and CSN6, in a variety of human cancers is correlated with cancer progression and poor survival (21)(22)(23)(24), while inhibition or knockdown of CSN5 was shown to suppress tumor growth in mice (21,25). Targeting CSN for cancer intervention, however, requires an in-depth understanding of the processes that regulate its mode of action.…”