COPS5 and hepatocellular carcinoma: We found that curcumin conferred a rapid down-regulating effect on CSN5 protein expression at 6 h post-treatment in human hepatic carcinoma HepG2 cells in the dose-dependent manner, but CSN5 down-regulation was not observed for other anticancer drugs including etoposide, fluorouracil (5-FU) and cisplatin in the same cells even for long time exposure (18 h) (Figure 1A).