Primary liver cancer, mostly hepatocellular carcinoma, remains a difficult-to-treat cancer. Incidence of liver cancer varies geographically and parallels with the geographic prevalence of viral hepatitis. A number of staging systems have been developed, reflecting the heterogeneity of primary liver cancer, regional preferences, and regional variations in resectability or transplant eligibility. Multimodality treatments are available for this heterogeneous malignancy, and there are variations in the management recommendations for liver cancers across specialties and geographic regions. Novel treatment strategies have merged with the advance of new treatment modalities. This work focuses on reviewing the incidence, staging, and treatment of liver cancer.

Hepatocellular carcinoma (HCC) is one of the most common potentially lethal human malignancies worldwide. Sorafenib, a tyrosine kinase inhibitor, was recently approved by the United States Food and Drug Administration for HCC. In this study, we established two sorafenib-resistant HCC cell lines from Huh7, a human HCC cell line, by long-term exposure of cells to sorafenib. Sorafenib induced significant apoptosis in Huh7 cells; however, Huh7-R1 and Huh7-R2 showed significant resistance to sorafenib-induced apoptosis at the clinical relevant concentrations (up to 10 μM). Thorough comparisons of the molecular changes between Huh7 and resistant cells showed that the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway played a significant role in mediating acquired resistance to sorafenib in Huh7-R1 and Huh7-R2 cells. Phospho-Akt and p85 (a regulatory subunit of PI3K) were up-regulated, whereas tumor suppressor phosphatase and tensin homolog were down-regulated in these resistant cells. In addition, ectopic expression of constitutive Akt in Huh7 demonstrated similar resistance to sorafenib. The knockdown of Akt by RNA interference reversed resistance to sorafenib in Huh7-R1 cells, indicating the importance of Akt in drug sensitivity. Furthermore, the combination of 8-[4-(1-aminocyclobutyl)phenyl]-9-phenyl-1,2,4-triazolo[3,4-f][1,6]naphthyridin-3(2H)-one dihydrochloride (MK-2206), a novel allosteric Akt inhibitor, and sorafenib restored the sensitivity of resistant cells to sorafenib-induced apoptosis. In conclusion, activation of PI3K/Akt signaling pathway mediates acquired resistance to sorafenib in HCC, and the combination of sorafenib and MK-2206, an Akt inhibitor, overcomes the resistance at clinical achievable concentrations.

Regarding the involvement of cyclooxygenase-2 (COX-2)-independent pathways in celecoxib-mediated antineoplastic effects, the following two issues remain outstanding: identity of the non-COX-2 targets and relative contributions of COX-2-dependent versus -independent mechanisms. We use a close celecoxib analog deficient in COX-2-inhibitory activity, DMC {4-[5-(2,5-dimethylphenyl)-3(trifluoromethyl)-1H-pyrazol-1-yl]benzene-sulfonamide}, to examine the premise that Akt signaling represents a major non-COX-2 target. Celecoxib and DMC block Akt activation in PC-3 cells through the inhibition of phosphoinositide-dependent kinase-1 (PDK-1) with IC50 of 48 and 38 μm, respectively. The consequent effect on Akt activation is more pronounced (IC50 values of 28 and 20 μm, respectively), which might be attributed to the concomitant dephosphorylation by protein phosphatase 2A. In serum-supplemented medium, celecoxib and DMC cause G1 arrest, and at higher concentrations, they induce apoptosis with relative potency comparable with that in blocking Akt activation. Moreover, the effect of daily oral celecoxib and DMC at 100 and 200 mg/kg on established PC-3 xenograft tumors is assessed. Celecoxib at both doses and DMC at 100 mg/kg had marginal impacts. However, a correlation exists between the in vitro potency of DMC and its ability at 200 mg/kg to inhibit xenograft tumor growth through the inhibition of Akt activation. Analysis of the tumor samples indicates that a differential reduction in the phospho-Akt/Akt ratio was noted in celecoxib- and DMC-treated groups vis-à-vis the control group. Together, these data underscore the role of 3-phosphoinositide-dependent protein kinase-1/Akt signaling in celecoxib-mediated in vitro antiproliferative effects in prostate cancer cells.

Certain members of the thiazolidenedione family of the peroxisome proliferator-activated receptor γ (PPARγ) agonists, such as troglitazone and ciglitazone, exhibit antitumor effects; however, the underlying mechanism remains inconclusive. This study shows that the effect of these thiazolidenedione members on apoptosis in prostate cancer cells is independent of PPARγ activation. First, close structural analogues of thiazolidenediones, whereas devoid of PPARγ activity, retain the ability to induce apoptosis with equal potency. Second, both PC-3 (PPARγ-expressing) and LNCaP (PPARγ-deficient) cells are sensitive to apoptosis induction by troglitazone and its PPARγ-inactive analogue irrespective of their PPARγ expression status. Third, rosiglitazone and pioglitazone, potent PPARγ agonists, show marginal effects on apoptosis even at high concentrations. Evidence indicates that the apoptotic effect of troglitazone, ciglitazone, and their PPARγ-inactive analogues 5-[4-(6-hydroxy-2,5,7,8-tetramethyl-chroman-2-ylmethoxy)-benzylidene]-2,4-thiazolidine-dione (Δ2-TG) and 5-[4-(1-methyl-cyclohexylmethoxy)-benzylidene]-thiazolidine-2,4-dione, respectively, is in part attributable to their ability to inhibit the anti-apoptotic functions of Bcl-xL and Bcl-2. Treatment of PC-3 cells with troglitazone or Δ2-TG led to reduced association of Bcl-2 and Bcl-xL with Bak, leading to caspase-dependent apoptosis. Bcl-xL overexpression protects LNCaP cells from apoptosis induction by troglitazone and Δ2-TG in an expression level–dependent manner. Considering the pivotal role of Bcl-xL/Bcl-2 in regulating mitochondrial integrity, this new mode of mechanism provides a framework to account for the PPARγ-independent action of thiazolidenediones in inducing apoptosis in cancer cells. Moreover, dissociation of these two pharmacologic activities provides a molecular basis to develop novel Bcl-xL/Bcl-2 inhibitors, of which the proof of principle is illustrated by a Δ2-TG analogue with potent in vivo antitumor activities.

We investigated the molecular mechanisms underlying the effect of sorafenib and SC-59, a novel sorafenib derivative, on hepatocellular carcinoma (HCC). Sorafenib activated autophagy in a dose- and time-dependent manner in the HCC cell lines PLC5, Sk-Hep1, HepG2 and Hep3B. Sorafenib downregulated phospho-STAT3 (P-STAT3) and subsequently reduced the expression of myeloid cell leukemia-1 (Mcl-1). Inhibition of Mcl-1 by sorafenib resulted in disruption of the Beclin 1-Mcl-1 complex; however, sorafenib did not affect the amount of Beclin 1, suggesting that sorafenib treatment released Beclin 1 from binding with Mcl-1. Silencing of SHP-1 by small interference RNA (siRNA) reduced the effect of sorafenib on P-STAT3 and autophagy. Ectopic expression of Mcl-1 abolished the effect of sorafenib on autophagy. Knockdown of Beclin 1 by siRNA protected the cells from sorafenib-induced autophagy. Moreover, SC-59, a sorafenib derivative, had a more potent effect on cancer cell viability than sorafenib. SC-59 downregulated P-STAT3 and induced autophagy in all tested HCC cell lines. Furthermore, our in vivo data showed that both sorafenib and SC-59 inhibited tumor growth, downregulated P-STAT3, enhanced the activity of SHP-1 and induced autophagy in PLC5 tumors, suggesting that sorafenib and SC-59 activate autophagy in HCC. In conclusion, sorafenib and SC-59 induce autophagy in HCC through a SHP-1-STAT3-Mcl-1-Beclin 1 pathway.

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. Clin Cancer Res; 16(21); 5189–99. ©2010 AACR.