Immune checkpoint inhibitors for hepatocellular carcinoma - A game changer in treatment landscape.

Rapidly expanding armamentarium of systemic therapy for advanced hepatocellular carcinoma (HCC) occurred in the recent few years. Multikinase inhibitors (MKI) or targeted therapy with antiangiogenic properties have been the focus of clinical studies in advanced HCC in the past decade. The remarkable efficacy of single agent immune checkpoint inhibitors (ICI), including nivolumab and pembrolizumab, in early phase studies led to accelerated approvals as second-line treatment for advanced HCC. The excellent toxicity profile of single agent ICI also lends support to be developed as combination therapy with other targeted therapies. The success of combining atezolizumab and bevacizumab over sorafenib as the first-line treatment in advanced HCC marked the newest paradigm shift in advanced HCC. The combination exhibited unprecedented objective response rate of 30% and a median survival of 19.2 months. Many other similar ICI-based combinations are expected to be approved in the foreseeable future. In this narrative review, the development of ICI alone and in combination in advanced HCC were described and the potential impact in all stages of HCC, safety issues of ICI-based combinations, and future perspectives were discussed.

Sorafenib overcomes TRAIL resistance of hepatocellular carcinoma cells through the inhibition of STAT3.

PURPOSE: Recombinant tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising antitumor agent. However, many hepatocellular carcinoma (HCC) cells show resistance to TRAIL-induced apoptosis. Here, we report that sorafenib improves the antitumor effect of TRAIL-related agents in resistant HCC. EXPERIMENTAL DESIGN: HCC cell lines (PLC5, Huh-7, Hep3B, and Sk-Hep1) were treated with sorafenib and/or TRAIL-related agents (TRAIL or LBY135) and analyzed in terms of apoptosis and signal transduction. In vivo efficacy was determined in nude mice with PLC5 xenografts. RESULTS: Sorafenib, the only approved drug for HCC, sensitizes resistant HCC cells to an agonistic DR5 antibody (LBY135) and TRAIL-induced apoptosis in TRAIL-resistant HCC cells. We found that STAT3 played a significant role in mediating TRAIL sensitization. Our data showed that sorafenib downregulated phospho-STAT3 (pSTAT3) and subsequently reduced the expression levels of STAT3-related proteins (Mcl-1, survivin, and cyclin D1) in a dose- and time-dependent manner in TRAIL-treated HCC cells. Knockdown of STAT3 by RNA interference overcame apoptotic resistance to TRAIL in HCC cells, and ectopic expression of STAT3 in HCC cells abolished the TRAIL-sensitizing effect of sorafenib. Moreover, SHP-1 inhibitor reversed downregulation of pSTAT3 and apoptosis induced by sorafenib, and silencing of SHP-1 by RNA interference abolished the effects of sorafenib on pSTAT3. Notably, sorafenib increased SHP-1 activity in PLC5 cells. Finally, sorafenib plus LBY135 significantly suppressed PLC5 xenograft tumor growth. CONCLUSIONS: Sorafenib sensitizes resistant HCC cells to TRAIL-induced apoptosis at clinical achievable concentrations, and this effect is mediated via the inhibition of STAT3.

Synergistic interactions between sorafenib and bortezomib in hepatocellular carcinoma involve PP2A-dependent Akt inactivation.

BACKGROUND & AIMS: Previously we reported that Akt inactivation determines the sensitivity of hepatocellular carcinoma (HCC) cells to bortezomib. Here we report that combined treatment with sorafenib and bortezomib shows synergistic effects in HCC. METHODS: HCC cell lines (PLC/PRF/5, Huh-7, and Hep3B) were treated with sorafenib and/or bortezomib and analyzed in terms of apoptosis signal transduction. In vivo efficacy was determined in nude mice with PLC/PRF/5 xenografts. RESULTS: Pretreatment with sorafenib enhanced bortezomib-induced apoptotic cell death by restoring bortezomib's ability to inactivate Akt in PLC/PRF/5 cells. Knocking down Akt1 by RNA-interference overcame apoptotic resistance to bortezomib in PLC/PRF/5 cells and ectopic expression of active Akt in HCC cells abolished the bortezomib sensitizing effect of sorafenib, indicating Akt inactivation plays a key role in mediating the combinational effects. Moreover, okadaic acid, a protein phosphatase 2A (PP2A) inhibitor, reversed down-regulation of phospho-Akt (P-Akt) expression induced by co-treatment with sorafenib and bortezomib, and 1, 9 di-deoxy-forskolin, a PP2A agonist, restored bortezomib's effect on P-Akt and apoptosis. Importantly, silencing of PP2A by RNA-interference reduced the apoptotic effect induced by sorafenib-bortezomib co-treatment, indicating that PP2A is indispensable for mediating the effects of these drugs. Notably, sorafenib with bortezomib increased PP2A activity in PLC/PRF/5 cells without altering protein levels of PP2A complex or the interaction between PP2A and Akt proteins. Finally, sorafenib plus bortezomib significantly suppressed PLC/PRF/5 xenograft tumor growth, down-regulated P-Akt expression, and up-regulated PP2A activity. CONCLUSIONS: The combination of sorafenib and bortezomib shows synergy in HCC through PP2A-dependent Akt inactivation.