Chaetocochin J exhibits anti-hepatocellular carcinoma effect independent of hypoxia

The most studied epipolythiodioxopiperazine (ETP) alkaloids, such as chetomin, gliotoxin and chaetocin, were reported to exert their antitumor effects through targeting HIF-1 alpha. Chaetocochin J (CJ) is another ETP alkaloid, of which the effect and mechanism on cancer are not fully elucidated. Considering the high incidence and mortality of hepatocellular carcinoma (HCC) in China, in the present study, using HCC cell lines and tumorbearing mice as models, we explored the anti-HCC effect and mechanism of CJ. Particularly, we investigated whether HIF-1a is related to the function of CJ. The results showed that, both under normoxic and CoCl2 induced-hypoxic conditions, CJ in low concentrations (<1 mu M) inhibits the proliferation, induces G2/M phase arrest, leading to the disorder of metabolism, migration, invasion, and caspase-dependent apoptosis in HepG2 and Hep3B cells. CJ also showed anti-tumor effect on a nude xenograft mice model without significant toxicity. Moreover, we demonstrated that the key to CJ's function is mainly associate with its inhibition of PI3K/Akt/ mTOR/p70S6K/4EBP1 pathway independent of hypoxia, and it also could suppress the expression of HIF-1 alpha as well as disrupt the binding of HIF-1 alpha/p300 and subsequently inhibits the expression of its target genes under hypoxic condition. These results demonstrated that CJ possessed a hypoxia-independent anti-HCC effects in vitro and in vivo, which was mainly attributable to its inhibition on the upstream pathways of HIF-1 alpha.