Interferon Alpha And Sola Fini Joint Treatment Of Liver Cancer And Rack1 Study Of Interferon Alpha Signaling Pathways Regulating

Hepatocellular carcinoma (HCC) is among the most common and lethal cancers, accounting for more than748,300new cases and695,000cancer deaths worldwide in2008. Curative therapies such as surgical resection, liver transplantation and ablative therapies have led to improvement in the survival of patients with HCC. Unfortunately, most patients are still diagnosed at advanced stage and could only receive palliative treatments. Thus, novel therapeutic strategies are urgently required for patients with advanced HCC. Interferon-α (IFN-α) and sorafenib are extensively used against a viriety of malignancies. Combinationation therapies based on IFN-α and/or sorafenib are also widely studied. To our knowledge, no previous research addressed combined anti-tumor effect of IFN-α and sorafenib on HCC treatment.We first determined the combined inhibitory effect on cell viability of IFN-α and sorafenib in HCC cell lines using WST assay. Further study demonstrated that IFN-α and sorafenib synergistically induced cell cycle arrest and apoptosis in HCC cells. To explore the underlying mechanism, we next examined the expression levels of cell cycle-and apoptosis-related proteins. Results showed that the combined treatment worked in synergy to down-regulate Cyclin A, Cyclin B, Cdk2and pro-survival Bcl-2family proteins. We also found that sorafenib inhibited IFN-α induced STAT3, AKT and ERK phosphorylation but not STAT1activation. Xenograft nude mice experiment also confirmed the cooperation effect of IFN-α and sorafenib on tumor proliferation inhibition and apoptosis induction in vivo. In conclusion, these results provide a rationale for the combined treatment of HCC with IFN-α and sorafenib. Interferon-a (IFN-a) belongs to type I interferon family of cytokines originally identified for their antiviral properties. IFN-a exerts its biological functions mainly through activation of the JAK/STAT signaling pathway, the MAPKs and the PI3K-AKT pathways are also induced by IFN-a. In addition to STATl which functions as a tumor suppressor activated by IFN-a, STAT3, a well-known oncogene is also activated by IFN-a, but the mechanism is still unknown. IFN-a is now widely used against malignancies including hepatocellular carcinoma (HCC); however, several studies reported IFN-a resistant cases and underlying mechanism remains unclear. RACKl, the receptor for activated C-kinase1, interacts with various signal molecules and membrane receptors including IFN-a receptor, STAT3and ERK, thus mediate various biological activities. Several reports have indicated RACKl mediates apoptosis resistance in various tumor cells.In our study, we first demonstrated that IFN-a induced both tyrosine and serine phosphorylation of STAT3, and overexpression of RACKl further enhanced the two sites activation. It is reported that ERK mediates STAT3serine phosphorylation. We found that ERK inhibitor specifically inhibited its activation. Co-IP assay showed that overexpression of RACKl enhanced the interaction between ERK and STAT3upon IFN-a treatment. Moreover, overexpression of RACKl reduced IFN-a-mediated apoptosis in HCC cells. Taken together, our results provide evidence for IFN-a-induced STAT3activation and suggest that RACKl might be a target of IFN-resistance in HCC treatment.