Sorafenib sensitizes hepatocellular carcinoma cells to physiological apoptotic stimuli

A mesenchymal-like phenotype and expression of CD44 predict lack of apoptotic response to sorafenib in liver tumor cells

The multikinase inhibitor sorafenib is the only effective drug in advanced cases of hepatocellular carcinoma (HCC). However, response differs among patients and effectiveness only implies a delay. We have recently described that sorafenib sensitizes HCC cells to apoptosis. In this work, we have explored the response to this drug of six different liver tumor cell lines to define a phenotypic signature that may predict lack of response in HCC patients. Results have indicated that liver tumor cells that show a mesenchymal-like phenotype, resistance to the suppressor effects of transforming growth factor beta (TGF-β) and high expression of the stem cell marker CD44 were refractory to sorafenib-induced cell death in in vitro studies, which correlated with lack of response to sorafenib in nude mice xenograft models of human HCC. In contrast, epithelial-like cells expressing the stem-related proteins EpCAM or CD133 were sensitive to sorafenib-induced apoptosis both in vitro and in vivo. A cross-talk between the TGF-β pathway and the acquisition of a mesenchymal-like phenotype with up-regulation of CD44 expression was found in the HCC cell lines. Targeted CD44 knock-down in the mesenchymal-like cells indicated that CD44 plays an active role in protecting HCC cells from sorafenib-induced apoptosis. However, CD44 effect requires a TGF-β-induced mesenchymal background, since the only overexpression of CD44 in epithelial-like HCC cells is not sufficient to impair sorafenib-induced cell death. In conclusion, a mesenchymal profile and expression of CD44, linked to activation of the TGF-β pathway, may predict lack of response to sorafenib in HCC patients.

Valproic acid overcomes transforming growth factor-β-mediated sorafenib resistance in hepatocellular carcinoma

Sorafenib is a multi-kinase inhibitor approved for hepatocellular carcinoma, but rarely causes tumor regression in patients with chronic liver diseases. To investigate whether growth factor-mediated signaling is involved in sorafenib resistance, HepG2 and PLC/PRF/5 hepatoma cells were exposed to epidermal growth factor (EGF), hepatocyte growth factor (HGF) or transforming growth factor-β (TGF-β) prior to treatment with sorafenib. Furthermore, to identify an effective combination treatment with sorafenib, growth factor-sensitized cells were treated with sorafenib alone or in combination with celecoxib, lovastatin or valproic acid (VPA). Trypan blue staining and Annexin V assays showed that the cytotoxic effect of sorafenib was inhibited by 15-54% in cells sensitized to TGF-β (P<0.05). Western blotting analysis showed that TGF-β significantly activated extracellular signal-regulated kinase (ERK)-mediated AKT signaling, and sorafenib failed to suppress both ERK and AKT in TGF-β-sensitized cells. The decreased anti-tumor effect of sorafenib was rescued by chemical inhibition of ERK and AKT. When TGF-β-sensitized cells were treated with sorafenib plus VPA, the levels of phosphorylated ERK and AKT were considerably suppressed and the numbers of dead cells were increased by 3.7-5.7-fold compared with those exposed to sorafenib alone (P<0.05). Moreover, low dose sorafenib-induced cell migration was effectively suppressed by combination treatment with sorafenib and VPA. Collectively, TGF-β/ERK/AKT signaling might play a critical role in sorafenib resistance in hepatoma cells, and combination treatment with VPA may be effective against this drug resistance.

Simultaneous inhibition of tumor growth and angiogenesis for resistant hepatocellular carcinoma by co-delivery of sorafenib and survivin small hairpin RNA

The development of multidrug resistance (MDR) in human hepatocellular carcinoma (HCC) is one of the major obstacles for successful chemotherapy of HCC. Co-delivery of sorafenib (SF) and survivin shRNA (shSur) was postulated to achieve synergistic effects in reversing MDR, suppressing tumor growth and angiogenesis. For this purpose, in this work, SF and shSur co-loaded pluronic P85-polyethyleneimine/d-α-tocopheryl polyethylene glycol 1000 succinate nanocomplexes (SSNs) were first designed and developed for the treatment of drug resistant HCC. The experimental results showed that SSNs could achieve effective cellular internalization and shSur transfection efficiency, induce significant downregulation of the survivin protein, and cause remarkable cell arrest and cell apoptosis. The tube formulation assay demonstrated that SSNs completely disrupted the enclosed capillary networks formed by human microvascular endothelial cells. The in vivo antitumor efficacy showed that SSNs were superior to that of other treatments on drug resistant hepatocellular tumor models. Therefore, it could be an efficient strategy to co-deliver SF and shSur for therapy of drug resistant HCC.

Dovitinib induces mitotic defects and activates the G2 DNA damage checkpoint

Dovitinib (TKI258; formerly CHIR-258) is an orally bioavailable inhibitor of multiple receptor tyrosine kinases. Interestingly, Dovitinib triggered a G₂/M arrest in cancer cell lines from diverse origins including HeLa, nasopharyngeal carcinoma, and hepatocellular carcinoma. Single-cell analysis revealed that Dovitinib promoted a delay in mitotic exit in a subset of cells, causing the cells to undergo mitotic slippage. Higher concentrations of Dovitinib induced a G₂ arrest similar to the G₂ DNA damage checkpoint. In support of this, DNA damage was triggered by Dovitinib as revealed by γ-H2AX and comet assays. The mitotic kinase CDK1 was found to be inactivated by phosphorylation in the presence of Dovitinib. Furthermore, the G₂ arrest could be overcome by abrogation of the G₂ DNA damage checkpoint using small molecule inhibitors of CHK1 and WEE1. Finally, Dovitinib-mediated G₂ cell cycle arrest and subsequent cell death could be promoted after DNA damage repair was disrupted by inhibitors of poly(ADP-ribose) polymerases. These results are consistent with the recent finding that Dovitinib can also target topoisomerases. Collectively, these results suggest additional directions for use of Dovitinib, in particular with agents that target the DNA damage checkpoint.

Changes of cytokines in patients with liver cirrhosis and advanced hepatocellular carcinoma treated by sorafenib

PURPOSE

Recently, the oral multikinase inhibitor sorafenib has been used to treat advanced hepatocellular carcinoma (aHCC). Tumor necrosis factor (TNF) induces apoptosis of tumor cells by binding to TNF-related apoptosis-inducing ligand, while binding of the Fas ligand on cytotoxic T lymphocytes to the Fas receptor on hepatocytes also causes apoptosis. The aim of this study was to retrospectively evaluate changes of cytokines in patients with liver cirrhosis (LC) and aHCC receiving sorafenib therapy.

METHODS

Fifty-seven adult Japanese LC patients received sorafenib for aHCC (200-800 mg/day for 4 weeks) between 2009 and 2012 at our hospital. Blood samples were collected in the early morning before and after treatment, and the serum levels of soluble TNF-alpha (sTNF-alpha), soluble TNF receptor (sTNF-R), soluble Fas ligand (sFas L), and soluble Fas (sFas) were evaluated.

RESULTS

Ten patients were treated with sorafenib at 200 mg/day (200 mg group), 37 patients were given 400 mg/day (400 mg group), and 10 patients received 800 mg/day (800 mg group). The serum level of sTNF-alpha was significantly increased after treatment compared with before treatment in the 400 and 800 mg groups. The serum level of sTNF-R also showed a significant increase after treatment in the 400 mg group, although there was no significant difference of sTNF-R between before and after treatment in the 200 and 800 mg groups. sFas showed a significant decrease after treatment compared with before treatment in the 400 and 800 mg groups, although the serum level of sFas L never exceeded 0.15 ng/ml.

CONCLUSIONS

These findings suggest that treatment with sorafenib at doses ≥400 mg/day might promote TNF-related or Fas-related apoptosis by increasing the circulating level of TNF-alpha or decreasing that of sFas.

Epigenetic upregulation of Bak by ZBP-89 inhibits the growth of hepatocellular carcinoma

Zinc-binding protein-89 regulates Bak to facilitate apoptosis in cancer cells. This study examined if zinc-binding protein-89 regulates Bak through an epigenetic mechanism in hepatocellular carcinoma. We first demonstrated that the expression of Bak was reduced but the levels of deoxyribonucleic acid methyltransferase 1 and histone deacetylase 3 were increased in hepatocellular carcinoma cancer tissues compared to the corresponding non-cancer tissues. Moreover, there was a negative correlation between Bak expression and deoxyribonucleic acid methyltransferase 1 levels in hepatocellular carcinoma. Administration of zinc-binding protein-89 downregulated histone deacetylase 3 expression and suppressed the activities of histone deacetylase and deoxyribonucleic acid methyltransferase, which led to maintenance of histone acetylation status, inhibited the binding of methyl-CpG-binding protein 2 to genomic deoxyribonucleic acid and demethylated CpG islands in the Bak promoter in hepatocellular carcinoma cells. Using the xenograft mouse tumor model, we demonstrated that zinc-binding protein-89 or inhibitors of either epigenetic enzymes could stimulate Bak expression, induce apoptosis, and arrest tumor growth and that the maximal effort was achieved when zinc-binding protein-89 and the enzyme inhibitors were used in combination. Conclusively, zinc-binding protein-89 upregulates the expression of Bak by targeting multiple components of the epigenetic pathway in hepatocellular carcinoma.

Iron-dependent cell death of hepatocellular carcinoma cells exposed to sorafenib

The multikinase inhibitor sorafenib is currently the treatment of reference for advanced hepatocellular carcinoma (HCC). In our report, we examined the cytotoxic effects of sorafenib on HCC cells. We report that the depletion of the intracellular iron stores achieved by using the iron chelator deferoxamine (DFX) strikingly protects HCC cells from the cytotoxic effects of sorafenib. The protective effect of the depletion of intracellular iron stores could not be explained by an interference with conventional forms of programmed cell death, such as apoptosis or autophagic cell death. We also found that DFX did not prevent sorafenib from reaching its intracellular target kinases. Instead, the depletion of intracellular iron stores prevented sorafenib from inducing oxidative stress in HCC cells. We examined the possibility that sorafenib might exert a cytotoxic effect that resembles ferroptosis, a form of cell death in which iron-dependent oxidative mechanisms play a pivotal role. In agreement with this possibility, we found that pharmacological inhibitors (ferrostatin-1) and genetic procedures (RNA interference against IREB-2) previously reported to modulate ferroptosis, readily block the cytotoxic effects of sorafenib in HCC cells. Collectively, our findings identify ferroptosis as an effective mechanism for the induction of cell death in HCC. Ferroptosis could potentially become a goal for the medical treatment of HCC, thus opening new avenues for the optimization of the use of sorafenib in these tumors.

Selective internal radiation therapy of hepatocellular carcinoma: potential hepatopulmonary shunt reduction after sorafenib administration

Sorafenib, a protein kinase inhibitor, is a systemic drug that has been licensed for the treatment of hepatocellular carcinoma (HCC). This retrospective study assessed whether the administration of sorafenib can result in a reduction of the hepatopulmonary shunt (HPS) before selective internal radiation therapy (SIRT). After exclusion from SIRT because of high HPS, computed tomography scan indicated a shunt reduction in seven patients with HCC receiving sorafenib. Repeated measurements revealed HPS reduction (from 26.5% to 7.5% on average), and subsequent SIRT became possible. In conclusion, sorafenib may reduce HPS in patients with advanced HCC in some cases.

18β-glycyrrhetinic acid inhibits hepatocellular carcinoma development by reversing hepatic stellate cell-mediated immunosuppression in mice

Hepatic stellate cells (HSCs) have immunosuppressive capabilities and contribute to the occurrence and development of hepatocellular carcinoma (HCC). Thus, activated HSCs may be a suitable target for HCC therapy. Our study used mixed leukocyte reactions (MLR) in vitro to demonstrate that 18β-glycyrrhetinic acid (GA) could reverse HSC-mediated immunosuppression by reducing T-cell apoptosis and regulatory T (Treg) cells expression, thereby enhancing the ability of T cells to attack tumor cells and attenuating HCC cell invasiveness. Moreover, we established a HCC orthotopic implantation model in immunocompetent C57BL/6 mice, which suggested that GA played a protective role in HCC development by reducing immunosuppression mediated by HSCs in the tumor microenvironment.

Enhanced erythrocyte membrane exposure of phosphatidylserine following sorafenib treatment: an in vivo and in vitro study

BACKGROUND

Sorafenib (Nexavar(®)), a polytyrosine kinase inhibitor, stimulates apoptosis and is thus widely used for chemotherapy in hepatocellular carcinoma (HCC). Hematological side effects of Nexavar(®) chemotherapy include anemia. Erythrocytes may undergo apoptosis-like suicidal death or eryptosis, which is characterized by cell shrinkage and phosphatidylserine-exposure at the cell surface. Signaling leading to eryptosis include increase in cytosolic Ca(2+)activity ([Ca(2+)](i)), formation of ceramide, ATP-depletion and oxidative stress. The present study explored, whether sorafenib triggers eryptosis in vitro and in vivo.

METHODS

[Ca(2+)](i )was estimated from Fluo3-fluorescence, cell volume from forward scatter, phosphatidylserine-exposure from annexin-V-binding, hemolysis from hemoglobin release, ceramide with antibody binding-dependent fluorescence, cytosolic ATP with a luciferin-luciferase-based assay, and oxidative stress from 2',7' dichlorodihydrofluorescein diacetate (DCFDA) fluorescence.

RESULTS

A 48 h exposure of erythrocytes to sorafenib (≥0.5 µM) significantly increased Fluo 3 fluorescence, decreased forward scatter, increased annexin-V-binding and triggered slight hemolysis (≥5 µM), but did not significantly modify ceramide abundance and cytosolic ATP. Sorafenib treatment significantly enhanced DCFDA-fluorescence and the reducing agents N-acetyl-L-cysteine and tiron significantly blunted sorafenib-induced phosphatidylserine exposure. Nexavar(®) chemotherapy in HCC patients significantly enhanced the number of phosphatidylserine-exposing erythrocytes.

CONCLUSIONS

The present observations disclose novel effects of sorafenib, i.e. stimulation of suicidal erythrocyte death or eryptosis, which may contribute to the pathogenesis of anemia in Nexavar(®)-based chemotherapy.

Combined anti-tumor effects of IFN-α and sorafenib on hepatocellular carcinoma in vitro and in vivo

Hepatocellular carcinoma (HCC) is among the most common and aggressive cancers worldwide, and novel therapeutic strategies are urgently required to improve clinical outcome. Interferon-alpha (IFN-α) and sorafenib are widely used as anti-tumor agents against various malignancies. In this study, we investigated the combined effects of IFN-α and sorafenib against HCC. We demonstrated that the combination therapy synergistically suppressed HCC cellular viability, arrested cell cycle propagation and induced apoptosis in HCC cells. Further research revealed that IFN-α and sorafenib collaboratively regulated the expression levels of cell cycle-related proteins Cyclin A and Cyclin B as well as the pro-survival Bcl-2 family proteins Mcl-1, Bcl-2 and Bcl-X(L). Moreover, sorafenib inhibited IFN-α induced oncogenic signaling of STAT3, AKT and ERK but not the activation of the tumor suppressor STAT1. Xenograft experiments also confirmed the combined effects of IFN-α and sorafenib on tumor growth inhibition and apoptosis induction in vivo. In conclusion, these results provide rationale for the clinical application of IFN-α and sorafenib combination therapy in HCC treatment.