The Enhanced metastatic potential of hepatocellular carcinoma (HCC) cells with sorafenib resistance

Molecular bases of the poor response of liver cancer to chemotherapy

A characteristic shared by most frequent types of primary liver cancer, i.e., hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) in adults, and in a lesser extent hepatoblastoma (HB) mainly in children, is their high refractoriness to chemotherapy. This is the result of synergic interactions among complex and diverse mechanisms of chemoresistance (MOC) in which more than 100 genes are involved. Pharmacological treatment, although it can be initially effective, frequently stimulates the expression of MOC genes, which results in the relapse of the tumor, usually with a more aggressive and less chemosensitive phenotype. Identification of the MOC genetic signature accounting for the "resistome" present at each moment of tumor life would prevent the administration of chemotherapeutic regimens without chance of success but still with noxious side effects for the patient. Moreover, a better description of cancer cells strength is required to develop novel strategies based on pharmacological, cellular or gene therapy to overcome liver cancer chemoresistance.

CD44 positive and sorafenib insensitive hepatocellular carcinomas respond to the ATP-competitive mTOR inhibitor INK128

The mTOR pathway is activated in about 50% of patients with hepatocellular carcinoma (HCC). In an effort to identify new pathways and compounds to treat advanced HCC, we considered the ATP-competitive mTOR inhibitor INK128. ATP-competitive mTOR inhibitors attenuate both mTORC1 and mTORC2. INK128 was evaluated in sorafenib sensitive and insensitive HCC cell lines, CD44low and CD44high HCC and those cell lines with acquired sorafenib resistance. CD44 was significantly increased in Huh7 cells made resistant to sorafenib. Forced expression of CD44 enhanced cellular proliferation and migration, and rendered the cells more sensitive to the anti-proliferative effects of INK128. INK128 suppressed CD44 expression in HCC cells while allosteric mTOR inhibitors did not. CD44 inhibition correlated with 4EBP1 phosphorylation status. INK128 showed better anti-proliferative and anti-migration effects on the mesenchymal-like HCC cells, CD44high HCC cells compared to the allosteric mTOR inhibitor everolimus. Moreover, a combination of INK128 and sorafenib showed improved anti-proliferative effects in CD44high HCC cells. INK128 was efficacious at reducing tumor growth in CD44high SK-Hep1 xenografts in mice when given as monotherapy or in combination with sorafenib. Since the clinical response to sorafenib is highly variable, our findings suggest that ATP-competitive mTOR inhibitors may be effective in treating advanced, CD44-expressing HCC patients who are insensitive to sorafenib.

Comparative proteomics of side population cells derived from human hepatocellular carcinoma cell lines with varying metastatic potentials

Metastasis and recurrence following surgery are major reasons for the high mortality rate and poor prognosis associated with hepatocellular carcinoma (HCC). Cancer stem cells (CSCs) are thought to be able to cause cancer, and to be the primary cause of tumor recurrence and metastasis. The underlying mechanisms of the metastatic potential of CSCs is poorly understood. In the present study, side population (SP) cells were isolated from 4 HCC cell lines, and their self-renewal and migratory abilities were compared. The results demonstrate that SP cells from different cell lines exhibited similar self-renewal abilities but different metastatic potentials. Furthermore, the overall proteomes of the SP cells were systematically quantified. This revealed 11 and 19 differentially expressed proteins (DEPs), upregulated and downregulated, respectively, associated with increased metastatic potential. These proteins were involved in the ‘regulation of mRNA processing’ and ‘cytoskeleton organization’ biological processes. The majority of the proteins were involved in ‘cell proliferation’, ‘migration’ and ‘invasion of cancer’, and may promote HCC metastasis in a synergistic manner. The AKT and nuclear factor-κB signaling pathways may contribute to the regulation of HCC metastasis through regulating the DEPs in SP cells. To the best of our knowledge, the present study is the first to demonstrate the overall proteome difference among SP cells from the different HCC cell lines with different metastatic potentials. The present study provides novel information regarding the metastatic potential of CSCs, which will facilitate further investigation of the topic.

Differential regulation of AKT1 contributes to survival and proliferation in hepatocellular carcinoma cells by mediating Notch1 expression

The RAC serine/threonine-protein kinase (AKT) family of serine/threonine protein kinases, particularly the AKT1 isoform, has been identified abnormally expressed in hepatocellular carcinoma (HCC) cells, and is highly associated with cell behavior, including proliferation, survival, metabolism, and tumorigenesis. However, the specific mechanism by which AKT1 elicits these effects requires further study. The purpose of the present study was to reveal the effects of AKT1 on the survival and proliferation of HCC cells, and to investigate the mechanisms involved. Western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to evaluate the expression levels of AKT1 in HCC SMMC-7721 cell line. Molecular mechanisms and the influences of different regulation the expression of AKT1 on HCC cell growth, proliferation were determined by western blotting, MTT and colony formation assays, cell cycle and apoptosis were investigated by flow cytometry. The activation of AKT1 suppressed the expression of phosphatase and tensin homolog and increased the activation of Notch1. The inhibition of AKT1 effectively suppressed the expression of Notch1. Furthermore, the data of the present study indicated that B-cell lymphoma 2 and cyclin D1 is involved in the regulation of AKT1 expression.

Silencing activating transcription factor 2 promotes the anticancer activity of sorafenib in hepatocellular carcinoma cells

The present study aimed to investigate the anticancer effect of sorafenib combined with silencing of activating transcription factor 2 (ATF2) in hepatocellular carcinoma (HCC) cells and to assess the underlying molecular mechanisms. Huh-7 HCC cell line was selected for the present study. Small interfering RNA (siRNA)-ATF2 sequence was constructed to silence ATF2 expression. The experiment was divided into 6 groups: i) Control; ii) vector; iii) sorafenib (6.8 µM); iv) vector+sorafenib; v) siRNA-ATF2; and vi) siRNA-ATF2+sorafenib groups. Cell proliferation, apoptosis, migration and invasion were detected following treatments with sorafenib and/or ATF2 silencing. Additionally, expression of tumor necrosis factor (TNF)-α and c-Jun N-terminal kinase 3 (JNK3) was detected using reverse transcription-quantitative polymerase chain reaction and western blotting. The current findings revealed that siRNA-ATF2 significantly reduced ATF2 expression. Cell proliferation, migration and invasion abilities in the sorafenib and siRNA-ATF2 groups were significantly reduced compared with the control group (P<0.05). Apoptotic rate in the sorafenib and siRNA-ATF2 groups was significantly increased compared with the control group (P<0.05). The mRNA and protein expression levels of ATF2 in the sorafenib or siRNA-ATF2 groups was significantly reduced when compared with control group. The phosphorylation of ATF2 was also reduced following sorafenib treatment or ATF2 silence. Although JNK3 mRNA expression level was not affected, the phosphorylation level of JNK3 was significantly promoted following sorafenib treatment or ATF2 silencing. Additionally, TNF-α mRNA and protein expression levels were increased following sorafenib treatment or ATF2 silencing. It is of note that siRNA-ATF2 treatment promoted the anticancer activity of sorafenib in Huh-7 cells. Additionally, siRNA-ATF2+sorafenib treatment combined additionally promoted TNF-α expression and phosphorylation of JNK3. Combined siRNA-ATF2 and sorafenib treatment had a greater anticancer effect compared with sorafenib or ATF2 silencing alone. The possible mechanism involved in the anticancer effect of sorafenib and ATF2 silencing may be associated with the activation of the TNF-α/JNK3 signaling pathway.

Inhibition of the PI3K/Akt signaling pathway reverses sorafenib-derived chemo-resistance in hepatocellular carcinoma

Long-term sorafenib treatment triggers resistance to chemotherapy in patients with hepatocellular carcinoma (HCC). In order to investigate the mechanisms of sorafenib resistance in HCC, the aim of the present study was to develop a resistant human liver cell line via long-term exposure to sorafenib. The cytotoxicity cell counting kit-8 assay was used to evaluate drug sensitivity. Reverse transcription-quantitative polymerase chain reaction and western blotting were used to examine the molecular mechanisms underpinning sorafenib resistance. Migratory and invasive properties in resistant cells were assessed using Transwell assays. The results from the present study revealed that resistant cells became insensitive to sorafenib treatment and exhibited increased migratory and invasive capacities. Activation of the phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway and epithelial-mesenchymal transition was characteristic of resistant cells. The use of LY294002, a PI3K inhibitor, was able to suppress the activation of Akt and extracellular signal-regulated kinase 1/2, attenuated the migratory and invasive capacities of resistant cells. Data from the present study indicates that inhibition of the PI3K signaling pathway with LY294002 exerts suppressive effects on sorafenib resistance and provides an attractive novel therapeutic regime in patients with advanced HCC.

YY1 promotes HDAC1 expression and decreases sensitivity of hepatocellular carcinoma cells to HDAC inhibitor

YY1 is a DNA-binding transcription factor and reported to be involved in cancer progression. Histone deacetylase inhibitor (HDACi) could inhibit proliferation and promote apoptosis of Hepatocellular carcinoma (HCC) cells. However, it is unclear about the roles of YY1 in the sensitivity of HCC cells to HDACi. In this study, firstly, we identified two drug-response profiles to HDACi in HCC cell lines, while our results showed that HDAC1 expression was positively correlated with YY1 in HCC cell lines and primary tumor tissues. Secondly, YY1 decreased the sensitivity of HCC cells to HDACi in vitro and in vivo. Furthermore, we found that YY1 promoted HDAC1 expression by binding to its promoter, while HDAC1 in turn up-regulated the expression of YY1. In conclusion, our results showed that YY1 could reduce the sensitivity of HCC cells to HDACi and might be a potential therapeutic target in HCC.

Inhibition of sirtuins 1 and 2 impairs cell survival and migration and modulates the expression of P-glycoprotein and MRP3 in hepatocellular carcinoma cell lines

Sirtuins (SIRTs) 1 and 2 deacetylases are overexpressed in hepatocellular carcinoma (HCC) and are associated with tumoral progression and multidrug resistance (MDR). In this study we analyzed whether SIRTs 1 and 2 activities blockage was able to affect cellular survival and migration and to modulate p53 and FoxO1 acetylation in HepG2 and Huh7 cells. Moreover, we analyzed ABC transporters P-glycoprotein (P-gp) and multidrug resistance-associated protein 3 (MRP3) expression. We used cambinol and EX-527 as SIRTs inhibitors. Both drugs reduced cellular viability, number of colonies and cellular migration and augmented apoptosis. In 3D cultures, SIRTs inhibitors diminished spheroid growth and viability. 3D culture was less sensitive to drugs than 2D culture. The levels of acetylated p53 and FoxO1 increased after treatments. Drugs induced a decrease in ABC transporters mRNA and protein levels in HepG2 cells; however, only EX-527 was able to reduce MRP3 mRNA and protein levels in Huh7 cells. This is the first work demonstrating the regulation of MRP3 by SIRTs. In conclusion, both drugs decreased HCC cells survival and migration, suggesting SIRTs 1 and 2 activities blockage could be beneficial during HCC therapy. Downregulation of the expression of P-gp and MRP3 supports the potential application of SIRTs 1 and 2 inhibitions in combination with conventional chemotherapy.

Inhibition of N-acetyltransferase 10 using remodelin attenuates doxorubicin resistance by reversing the epithelial-mesenchymal transition in breast cancer

Development of resistance to doxorubicin-based chemotherapy limits curative effect in breast cancer (BC). N-acetyltransferase 10 (NAT10), a nucleolar protein involved in histone acetylation, is overexpressed in several cancers. We investigated whether NAT10 is involved in doxorubicin resistance in BC and explored the potential mechanisms. Remodelin, a NAT10 inhibitor, and a NAT10 small interfering RNA (siRNA) were used to inhibit NAT10; both remodelin and the NAT10 siRNA reduced cell viability and attenuated doxorubicin resistance in four BC cell lines. Remodelin and doxorubicin synergistically reduced cell viability, though knockdown of NAT10 and remodelin did not exert a synergistic effect in doxorubicin-treated cells. Remodelin upregulated E-cadherin and downregulated vimentin, canonical markers of the epithelial-mesenchymal transition (EMT), whereas doxorubicin had the opposite effects. Moreover, both remodelin and knockdown of NAT10 reversed the doxorubicin-induced EMT. Finally, when the EMT was blocked using a siRNA targeting Twist, remodelin could not alleviate doxorubicin resistance. Collectively, these findings demonstrate that inhibition of NAT10 attenuates doxorubicin resistance by reversing the EMT in BC. This represents a novel mechanism of doxorubicin resistance in BC and indicates remodelin may have potential clinical value to increase the efficacy of doxorubicin-based chemotherapy in BC.

MicroRNA-30a suppresses autophagy-mediated anoikis resistance and metastasis in hepatocellular carcinoma

MiRNA-30a (miR-30a) was previously reported as one of metastatic hepatocellular carcinoma (HCC)-related microRNAs. However, the function of miR-30a on enhancing our biological understanding of HCC metastasis is not clear. This study demonstrated that miR-30a was significantly down-regulated in HCC tissues and cell lines, and was associated with vascular invasion, metastasis potential and recurrent disease in HCC. Functional studies confirmed that miR-30a could inhibit the metastasis of HCC in a well-established nude mouse model of lung metastasis. Moreover, miR-30a was proved to prevent anoikis inhibition of HCC cells in vivo and in vitro. Mechanically, autophagy related protein Beclin 1 and Atg5 were direct downstream targets of miR-30a, and mediated autophagy activity influence of miR-30a in HCC. Taken together, downregulated miR-30a in metastatic HCC mediates Beclin 1 and Atg5-dependent autophagy, which confers anoikis resistance in HCC cells. The molecular basis of autophagy action during this process partly contributes to the HCC metastasis, suggesting that targeting autophagy via miR-30a may have therapeutic implications for the prevention of HCC recurrence/metastasis.

New insights into sorafenib resistance in hepatocellular carcinoma: Responsible mechanisms and promising strategies

It is disappointing that only a few patients with hepatocellular carcinoma (HCC) obtain a significant survival benefit from the sorafenib treatment, which is currently regarded as a first-line chemotherapeutic therapy in patients with advanced HCC. Most patients are highly refractory to this therapy. Therefore, it is necessary to identify resistant factors and explore potential protocols that can be used to overcome the resistance or substitute sorafenib once the resistance is formed. In fact, a growing body of studies has been focusing on the resistance mechanisms or the method to overcome it. The limitation of sorafenib efficacy has been partially but not fully elucidated. Moreover, some protocols have shown encouraging outcomes but still need to be further verified in clinical trials. In this review, we summarize the recent findings on the potential mechanisms that contribute to sorafenib resistance and discuss strategies that can be used to improve the treatment outcome.

Dihydroartemisinin inhibits EMT induced by platinum-based drugs via Akt-Snail pathway

Artemisinin and its derivatives exhibit a high activity against a range of cancer cell types both in vitro and in vivo. In clinical practice, platinum-based anti-cancer chemotherapy is widely used to treat tumors. However, a large proportion of patients receiving these treatments will relapse because of metastasis and drug resistance. The purpose of this study is to explore the combinational anti-metastatic effect of platinum-based drugs and dihydroartemisinin (DHA). Both DDP and oxaliplatin (OXA) at low doses could induce epithelial–mesenchymal transition (EMT) in HCC. Meanwhile, co-administration of DHA could enhance DDP and OXA chemosensitivity in HCC and reverse drug resistance. DHA reversed the morphological changes induced by DDP or OXA and reversed the changes in EMT biomarkers induced by DDP and OXA in HCC in vitro and in vivo via AKT–Snail signaling. DHA significantly increased platinum-based drug sensitivity and suppressed EMT induced by platinum-based drugs via AKT–Snail signaling in HCC. DHA is expected to become the new adjuvant for chemotherapy.

Activation of phosphatidylinositol 3-kinase/AKT/snail signaling pathway contributes to epithelial-mesenchymal transition-induced multi-drug resistance to sorafenib in hepatocellular carcinoma cells

Sorafenib, an orally available kinase inhibitor, is the standard first-line systemic drug for advanced hepatocellular carcinoma (HCC), and it exerts potent inhibitory activity against epithelial–mesenchymal transition (EMT) and multidrug resistance (MDR) by inhibiting mitogen-activated protein kinase (MAPK) signaling in HCC. However, after long-term exposure to sorafenib, HCC cells exhibit EMT and resistance to sorafenib. The activation of AKT by sorafenib is thought to be responsible for the development of these characteristics. The present study aims to examine the underlying mechanism and seek potential strategies to reverse this resistance and the progression to EMT. Sorafenib-resistant cells showed increased metastatic and invasive ability, with a higher expression of P-glycoprotein (P-gp), compared with the parental cells. This phenomenon was at least partially due to EMT and the appearance of MDR in sorafenib-resistant HCC cells. Moreover, MDR was a downstream molecular event of EMT. Silencing Snail with siRNA blocked EMT and partially reversed the MDR, thereby markedly abolishing invasion and metastasis in sorafenib-resistant HCC cells, but silencing of MDR1 had no effect on the EMT phenotype. Additionally, HCC parental cells that were stably transfected with pCDNA3.1-Snail exhibited EMT and MDR. Two sorafenib-resistant HCC cell lines, established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition but were sensitive to MK-2206, a novel allosteric AKT inhibitor. Thus, the combination of sorafenib and MK-2206 led to significant reversion of the EMT phenotype and P-gp-mediated MDR by downregulating phosphorylated AKT. These findings underscore the significance of EMT, MDR and enhanced PI3K/AKT signaling in sorafenib-resistant HCC cells.

The potential of cell sheet technique on the development of hepatocellular carcinoma in rat models

BACKGROUND

Hepatocellular carcinoma (HCC) is considered the 3rd leading cause of death by cancer worldwide with the majority of patients were diagnosed in the late stages. Currently, there is no effective therapy. The selection of an animal model that mimics human cancer is essential for the identification of prognostic/predictive markers, candidate genes underlying cancer induction and the examination of factors that may influence the response of cancers to therapeutic agents and regimens. In this study, we developed a HCC nude rat models using cell sheet and examined the effect of human stromal cells (SCs) on the development of the HCC model and on different liver parameters such as albumin and urea.

METHODS

Transplanted cell sheet for HCC rat models was fabricated using thermo-responsive culture dishes. The effect of human umbilical cord mesenchymal stromal cells (UC-MSCs) and human bone marrow mesenchymal stromal cells (BM-MSCs) on the developed tumour was tested. Furthermore, development of tumour and detection of the liver parameter was studied. Additionally, angiogenesis assay was performed using Matrigel.

RESULTS

HepG2 cells requires five days to form a complete cell sheet while HepG2 co-cultured with UC-MSCs or BM-MSCs took only three days. The tumour developed within 4 weeks after transplantation of the HCC sheet on the liver of nude rats. Both UC-MSCs and BM-MSCs improved the secretion of liver parameters by increasing the secretion of albumin and urea. Comparatively, the UC-MSCs were more effective than BM-MSCs, but unlike BM-MSCs, UC-MSCs prevented liver tumour formation and the tube formation of HCC.

CONCLUSIONS

Since this is a novel study to induce liver tumour in rats using hepatocellular carcinoma sheet and stromal cells, the data obtained suggest that cell sheet is a fast and easy technique to develop HCC models as well as UC-MSCs have therapeutic potential for liver diseases. Additionally, the data procured indicates that stromal cells enhanced the fabrication of HepG2 cell sheets. This provides the foundation for future research using stromal cells in preclinical and clinical investigations.

Sorafenib induced alteration of protein glycosylation in hepatocellular carcinoma cells

Sorafenib is a multikinase inhibitor and is effective in treating hepatocellular carcinoma (HCC). However, it remains unknown whether sorafenib induces the alteration of protein glycosylation. The present study treated HCC MHCC97L and MHCC97H cells with a 50% inhibitory concentration of sorafenib. Following this treatment, alteration of protein glycosylation was detected using a lectin microarray. Compared with the controls, the binding capacity of glycoproteins extracted from sorafenib-treated HCC cells to the lectins Bauhinia purpurea lectin, Dolichos biflorus agglutinin, Euonymus europaeus lectin, Helix aspersa lectin, Helix pomatia lectin, Jacalin, Maclura pomifera lectin and Vicia villosa lectin were enhanced; while, the binding capacities to the lectins Caragana arborescens lectin, Lycopersicon esculentum lectin, Limulus polyphemus lectin, Maackia amurensis lecin I, Phaseolus vulgaris leucoagglutinin, Ricinus communis agglutinin 60, Sambucus nigra lectin and Solanum tuberosum lectin were reduced (spot intensity median/background intensity median ≥2, P<0.05). This difference in glycoprotein binding capacity indicates that cells treated with sorafenib could increase α-1,3GalNAc/Gal, β-1,3 Gal, GalNAcα-Ser/Thr(Tn) and α-GalNAc structures and decrease GlcNAc, sialic acid, tetra-antennary complex-type N-glycan and β-1,4Gal structures. These results were additionally confirmed by lectin blotting. Expression levels of signaling molecules including erythroblastosis 26–1 (Ets-1), extracellular signal-related kinases (ERK) and phosphorylated-ERK were measured by western blotting. There was a reduction in the expression of Ets-1 and ERK phosphorylation in sorafenib or 1,4-Diamino-2,3-dicyano-1,4-bis (2-aminophenylthio) butadiene treated cells suggesting that sorafenib may reduce the expression levels of Ets-1 by blocking the Ras/Raf/mitogen activated protein kinase signaling pathway. In the present study, it was clear that sorafenib could inhibit the proliferation of HCC cells and alter protein glycosylation. The findings of this study may lead to providing a novel way of designing new anti-HCC drugs.

Tumour initiating cells and IGF/FGF signalling contribute to sorafenib resistance in hepatocellular carcinoma

OBJECTIVE

Sorafenib is effective in hepatocellular carcinoma (HCC), but patients ultimately present disease progression. Molecular mechanisms underlying acquired resistance are still unknown. Herein, we characterise the role of tumour-initiating cells (T-ICs) and signalling pathways involved in sorafenib resistance.

DESIGN

HCC xenograft mice treated with sorafenib (n=22) were explored for responsiveness (n=5) and acquired resistance (n=17). Mechanism of acquired resistance were assessed by: (1) role of T-ICs by in vitro sphere formation and in vivo tumourigenesis assays using NOD/SCID mice, (2) activation of alternative signalling pathways and (3) efficacy of anti-FGF and anti-IGF drugs in experimental models. Gene expression (microarray, quantitative real-time PCR (qRT-PCR)) and protein analyses (immunohistochemistry, western blot) were conducted. A novel gene signature of sorafenib resistance was generated and tested in two independent cohorts.

RESULTS

Sorafenib-acquired resistant tumours showed significant enrichment of T-ICs (164 cells needed to create a tumour) versus sorafenib-sensitive tumours (13 400 cells) and non-treated tumours (1292 cells), p<0.001. Tumours with sorafenib-acquired resistance were enriched with insulin-like growth factor (IGF) and fibroblast growth factor (FGF) signalling cascades (false discovery rate (FDR)<0.05). In vitro, cells derived from sorafenib-acquired resistant tumours and two sorafenib-resistant HCC cell lines were responsive to IGF or FGF inhibition. In vivo, FGF blockade delayed tumour growth and improved survival in sorafenib-resistant tumours. A sorafenib-resistance 175 gene signature was characterised by enrichment of progenitor cell features, aggressive tumorous traits and predicted poor survival in two cohorts (n=442 patients with HCC).

CONCLUSIONS

Acquired resistance to sorafenib is driven by T-ICs with enrichment of progenitor markers and activation of IGF and FGF signalling. Inhibition of these pathways would benefit a subset of patients after sorafenib progression.

Accumulation of low-dose BIX01294 promotes metastatic potential of U251 glioblastoma cells

BIX01294 (Bix) is known to be a euchromatic histone-lysine N-methyltransferase 2 inhibitor and treatment with Bix suppresses cancer cell survival and proliferation. In the present study, it was observed that sequential treatment with low-dose Bix notably increases glioblastoma cell migration and metastasis. It was demonstrated that U251 cells sequentially treated with low-dose Bix exhibited induced characteristic changes in critical epithelial-mesenchymal transition (EMT) markers, including E-cadherin, N-cadherin, β-catenin and zinc finger protein SNAI2. Notably, sequential treatment with Bix also increased the expression of cancer stem cell-associated markers, including sex determining region Y-box 2, octamer-binding transcription factor 4 and cluster of differentiation 133. Neurosphere formation was significantly enhanced in cells sequentially treated with Bix, compared with control cells (control: P=0.011; single treatment of Bix, P=0.045). The results of the present study suggest that accumulation of low-dose Bix enhanced the migration and metastatic potential of glioblastoma cells by regulating EMT-associated gene expression, which may be the cause of the altered properties of glioblastoma stem cells.

Quinoides and VEGFR2 TKIs influence the fate of hepatocellular carcinoma and its cancer stem cells

Bioactivities of quinoides 1-5 and VEGFR2 TKIs 6-10 in hepatocellular cancer (HCC) and cancer stem cells (HCSCs) were studied. The compounds exhibited IC50 values in μM concentrations in HCC cells. Quinoide 3 was able to eradicate cancer stem cells, similar to the action of the stem cell inhibitor DAPT. However, the more cytotoxic VEFGR TKIs (IC50: 0.4-3.0 μM) including sorafenib, which is the only FDA approved drug for the treatment of HCC, enriched the hepatocellular cancer stem cell population by 2-3 fold after treatment. An aggressiveness factor (AF) was proposed to quantify the characteristics of drug candidates for their ability to eradicate the CSC subpopulation. Considering the tumour heterogeneity and marker positive cancer stem cell like subpopulation enrichment upon treatments in patients, this study emphasises the importance of the chemotherapeutic agent choice acting differentially on all the subpopulations including marker-positive CSCs.

Targeting glucosylceramide synthase upregulation reverts sorafenib resistance in experimental hepatocellular carcinoma

Evasive mechanisms triggered by the tyrosine kinase inhibitor sorafenib reduce its efficacy in hepatocellular carcinoma (HCC) treatment. Drug-resistant cancer cells frequently exhibit sphingolipid dysregulation, reducing chemotherapeutic cytotoxicity via the induction of ceramide-degrading enzymes. However, the role of ceramide in sorafenib therapy and resistance in HCC has not been clearly established. Our data reveals that ceramide-modifying enzymes, particularly glucosylceramide synthase (GCS), are upregulated during sorafenib treatment in hepatoma cells (HepG2 and Hep3B), and more importantly, in sorafenib-resistant cell lines. GCS silencing or pharmacological GCS inhibition sensitized hepatoma cells to sorafenib exposure. GCS inhibition, combined with sorafenib, triggered cytochrome c release and ATP depletion in sorafenib-treated hepatoma cells, leading to mitochondrial cell death after energetic collapse. Conversely, genetic GCS overexpression increased sorafenib resistance. Of interest, GCS inhibition improved sorafenib effectiveness in a xenograft mouse model, recovering drug sensitivity of sorafenib-resistant tumors in mice. In conclusion, our results reveal GCS induction as a mechanism of sorafenib resistance, suggesting that GCS targeting may be a novel strategy to increase sorafenib efficacy in HCC management, and point to target the mitochondria as the subcellular location where sorafenib therapy could be potentiated.

Understanding the role of PIN1 in hepatocellular carcinoma

PIN1 is a peptidyl-prolyl cis/trans isomerase that binds and catalyses isomerization of the specific motif comprising a phosphorylated serine or threonine residue preceding a proline (pSer/Thr-Pro) in proteins. PIN1 can therefore induce conformational and functional changes of its interacting proteins that are regulated by proline-directed serine/threonine phosphorylation. Through this phosphorylation-dependent prolyl isomerization, PIN1 fine-tunes the functions of key phosphoproteins (e.g., cyclin D1, survivin, β-catenin and x-protein of hepatitis B virus) that are involved in the regulation of cell cycle progression, apoptosis, proliferation and oncogenic transformation. PIN1 has been found to be over-expressed in many cancers, including human hepatocellular carcinoma (HCC). It has been shown previously that overexpression of PIN1 contributes to the development of HCC in-vitro and in xenograft mouse model. In this review, we first discussed the aberrant transcription factor expression, miRNAs dysregulation, PIN1 gene promoter polymorphisms and phosphorylation of PIN1 as potential mechanisms underlying PIN1 overexpression in cancers. Furthermore, we also examined the role of PIN1 in HCC tumourigenesis by reviewing the interactions between PIN1 and various cellular and viral proteins that are involved in β-catenin, NOTCH, and PI3K/Akt/mTOR pathways, apoptosis, angiogenesis and epithelial-mesenchymal transition. Finally, the potential of PIN1 inhibitors as an anti-cancer therapy was explored and discussed.

Implications of vessel co-option in sorafenib-resistant hepatocellular carcinoma

The reason why tumors generally have a modest or transient response to antiangiogenic therapy is not well understood. This poses a major challenge for sorafenib treatment of advanced hepatocellular carcinoma (HCC) where alternate therapies are lacking. We recently published a paper entitled “Co-option of liver vessels and not sprouting angiogenesis drives acquired sorafenib resistance in hepatocellular carcinoma” in the Journal of the National Cancer Institute, providing a potential explanation for this limited benefit. We found that in mice bearing HCCs that had acquired resistance to sorafenib, tumors had switched from using angiogenesis for growth to co-opting the liver vasculature by becoming more invasive. Accumulating evidence suggests that many human tumor types may use vessel co-option, which has profound implications for the use of anti-angiogenic agents for cancer treatment.

Angiopoietin-like protein 1 antagonizes MET receptor activity to repress sorafenib resistance and cancer stemness in hepatocellular carcinoma

Angiopoietin-like protein 1 (ANGPTL1) has been shown to act as a tumor suppressor by inhibiting angiogenesis, cancer invasion, and metastasis. However, little is known about the effects of ANGPTL1 on sorafenib resistance and cancer stem cell properties in hepatocellular carcinoma (HCC) and the mechanism underlying these effects. Here, we show that ANGPTL1 expression positively correlates with sorafenib sensitivity in HCC cells and human HCC tissues. ANGPTL1 significantly decreases epithelial-mesenchymal transition (EMT)-driven sorafenib resistance, cancer stemness, and tumor growth of HCC cells by repressing Slug expression. ANGPTL1 directly interacts with and inactivates MET receptor, which contributes to Slug suppression through inhibition of the extracellular receptor kinase/protein kinase B (ERK/AKT)-dependent early growth response protein 1 (Egr-1) pathway. ANGPTL1 expression inversely correlates with Slug expression, poor sorafenib responsiveness, and poor clinical outcomes in HCC patients.

CONCLUSION

ANGPTL1 inhibits sorafenib resistance and cancer stemness in HCC cells by repressing EMT through inhibition of the MET receptor-AKT/ERK-Egr-1-Slug signaling cascade. ANGPTL1 may serve as a novel MET receptor inhibitor for advanced HCC therapy. (Hepatology 2016;64:1637-1651).

APSA Awardee Submission: Tumor/cancer stem cell marker doublecortin-like kinase 1 in liver diseases

Liver diseases are the fourth leading cause of mortality among adults in the United States. Patients with chronic liver diseases such as viral hepatitis, fibrosis, and cirrhosis have significantly higher risks of developing hepatocellular carcinoma (HCC). With a dismal five-year survival rate of 11%, HCC is the third most common cause of cancer-related deaths worldwide. Regardless of the underlying cause, late presentation and a lack of effective therapy are the major impediments for successful treatment of HCC. Therefore, there is a considerable interest in developing new strategies for the prevention and treatment of chronic liver diseases at the early stages. Cancer stem cells (CSCs), a small cell subpopulation in a tumor, exhibit unlimited self-renewal and differentiation capacity. These cells are believed to play pivotal roles in the initiation, growth, metastasis, and drug-resistance of tumors. In this review, we will briefly discuss pivotal roles of the CSC marker doublecortin-like kinase 1 (DCLK1) in hepatic tumorigenesis. Recent evidence suggests that anti-DCLK1 strategies hold promising clinical potential for the treatment of cancers of the liver, pancreas, and colon.

Repression of Human Hepatocellular Carcinoma Growth by Regulating Met/EGFR/VEGFR-Akt/NF-κB Pathways with Theanine and Its Derivative, (R)-2-(6,8-Dibromo-2-oxo-2H-chromene-3-carboxamido)-5-(ethylamino)-5-oxopentanoic Ethyl Ester (DTBrC)

To explore the potential of theanine against cancer, we have studied the anticancer activities of theanine from tea and its semisynthesized derivative, (R)-2-(6,8-dibromo-2-oxo-2H-chromene-3-carboxamido)-5-(ethylamino)-5-oxopentanoic ethyl ester (DTBrC), in in vitro, ex vivo, and in vivo models of human hepatocellular carcinoma (HHC). Theanine and DTBrC displayed inhibitory effects on the growth and migration of HHC cells in vitro, ex vivo, and in vivo. Theanine and DTBrC significantly enhanced the repression of HHC cell growth in combination with anticancer drug pirarubicin. Theanine and DTBrC completely suppressed HGF- and EGF+HGF-induced migration with a reduction of p53 tumor suppressor level and enhanced the p53 protein expression in HHC cells. The Akt and NF-κB knockdown greatly reduced cancer cell migration with a decrease in CD44 expression. DTBrC and theanine significantly repressed the protein expressions in the Met/EGFR/VEGFR-Akt/NF-κB pathways, which might be the mechanism for their biologic effects.

Epithelial-to-mesenchymal plasticity of cancer stem cells: therapeutic targets in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains one of the most common and lethal malignancies worldwide despite the development of various therapeutic strategies. A better understanding of the mechanisms responsible for HCC initiation and progression is essential for the development of more effective therapies. The cancer stem cell (CSC) model has provided new insights into the development and progression of HCC. CSCs are specialized tumor cells that are capable of self-renewal and have long-term repopulation potential. As they are important mediators of tumor proliferation, invasion, metastasis, therapy resistance, and cancer relapse, the selective targeting of this crucial population of cells has the potential to improve HCC patient outcomes and survival. In recent years, the role of epithelial-to-mesenchymal transition (EMT) in the advancement of HCC has gained increasing attention. This multi-step reprograming process resulting in a phenotype switch from an epithelial to a mesenchymal cellular state has been closely associated with the acquisition of stem cell-like attributes in tumors. Moreover, CSC mediates tumor metastasis by maintaining plasticity to transition between epithelial or mesenchymal states. Therefore, understanding the molecular mechanisms of the reprograming switches that determine the progression through EMT and generation of CSC is essential for developing clinically relevant drug targets. This review provides an overview of the proposed roles of CSC in HCC and discusses recent results supporting the emerging role of EMT in facilitating hepatic CSC plasticity. In particular, we discuss how these important new insights may facilitate rational development of combining CSC- and EMT-targeted therapies in the future.

TLR3 agonist and Sorafenib combinatorial therapy promotes immune activation and controls hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is associated with high mortality and the current therapy for advanced HCC, Sorafenib, offers limited survival benefits. Here we assessed whether combining the TLR3 agonist: lysine-stabilized polyinosinic-polycytidylic-acid (poly-ICLC) with Sorafenib could enhance tumor control in HCC. Combinatorial therapy with poly-ICLC and Sorafenib increased apoptosis and reduced proliferation of HCC cell lines in vitro, in association with impaired phosphorylation of AKT, MEK and ERK. In vivo, the combinatorial treatment enhanced control of tumor growth in two mouse models: one transplanted with Hepa 1-6 cells, and the other with liver tumors induced using the Sleeping beauty transposon. Tumor cell apoptosis and host immune responses in the tumor microenvironment were enhanced. Particularly, the activation of local NK cells, T cells, macrophages and dendritic cells was enhanced. Decreased expression of the inhibitory signaling molecules PD-1 and PD-L1 was observed in tumor-infiltrating CD8⁺ T cells and tumor cells, respectively. Tumor infiltration by monocytic-myeloid derived suppressor cells (Mo-MDSC) was also reduced indicating the reversion of the immunosuppressive tumor microenvironment. Our data demonstrated that the combinatorial therapy with poly-ICLC and Sorafenib enhances tumor control and local immune response hence providing a rationale for future clinical studies.

(Z)-3,5,4'-Trimethoxystilbene Limits Hepatitis C and Cancer Pathophysiology by Blocking Microtubule Dynamics and Cell-Cycle Progression

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related deaths worldwide. Chronic hepatitis C virus (HCV) infection causes induction of several tumors/cancer stem cell (CSC) markers and is known to be a major risk factor for development of HCC. Therefore, drugs that simultaneously target viral replication and CSC properties are needed for a risk-free treatment of advanced stage liver diseases, including HCC. Here, we demonstrated that (Z)-3,5,4'-trimethoxystilbene (Z-TMS) exhibits potent antitumor and anti-HCV activities without exhibiting cytotoxicity to human hepatocytes in vitro or in mice livers. Diethylnitrosamine (DEN)/carbon tetrachloride (CCl4) extensively induced expression of DCLK1 (a CSC marker) in the livers of C57BL/6 mice following hepatic injury. Z-TMS exhibited hepatoprotective effects against DEN/CCl4-induced injury by reducing DCLK1 expression and improving histologic outcomes. The drug caused bundling of DCLK1 with microtubules and blocked cell-cycle progression at G2-M phase in hepatoma cells via downregulation of CDK1, induction of p21(cip1/waf1) expression, and inhibition of Akt (Ser(473)) phosphorylation. Z-TMS also inhibited proliferation of erlotinib-resistant lung adenocarcinoma cells (H1975) bearing the T790M EGFR mutation, most likely by promoting autophagy and nuclear fragmentation. In conclusion, Z-TMS appears to be a unique therapeutic agent targeting HCV and concurrently eliminating cells with neoplastic potential during chronic liver diseases, including HCC. It may also be a valuable drug for targeting drug-resistant carcinomas and cancers of the lungs, pancreas, colon, and intestine, in which DCLK1 is involved in tumorigenesis. Cancer Res; 76(16); 4887-96. ©2016 AACR.

Sorafenib treatment in children with relapsed and refractory neuroblastoma: an experience of four cases

Metastatic neuroblastoma is an aggressive malignancy with a poor prognosis. Recent findings have shown that sorafenib decreases cell viability and increases apoptosis in human neuroblastoma cell lines. We report an experience of compassionate use of sorafenib in children with treatment‐refractory neuroblastoma. Sorafenib showed transient anti‐tumor activity in all four patients without adverse effects. However, progression was observed after a short stabilization phase. While sorafenib showed minimal anti‐tumor activity in our patients, it might still be effective in patients with neuroblastoma in an earlier stage.

Transposon mutagenesis identifies genes and cellular processes driving epithelial-mesenchymal transition in hepatocellular carcinoma

Epithelial-mesenchymal transition (EMT) is thought to contribute to metastasis and chemoresistance in patients with hepatocellular carcinoma (HCC), leading to their poor prognosis. The genes driving EMT in HCC are not yet fully understood, however. Here, we show that mobilization of Sleeping Beauty (SB) transposons in immortalized mouse hepatoblasts induces mesenchymal liver tumors on transplantation to nude mice. These tumors show significant down-regulation of epithelial markers, along with up-regulation of mesenchymal markers and EMT-related transcription factors (EMT-TFs). Sequencing of transposon insertion sites from tumors identified 233 candidate cancer genes (CCGs) that were enriched for genes and cellular processes driving EMT. Subsequent trunk driver analysis identified 23 CCGs that are predicted to function early in tumorigenesis and whose mutation or alteration in patients with HCC is correlated with poor patient survival. Validation of the top trunk drivers identified in the screen, including MET (MET proto-oncogene, receptor tyrosine kinase), GRB2-associated binding protein 1 (GAB1), HECT, UBA, and WWE domain containing 1 (HUWE1), lysine-specific demethylase 6A (KDM6A), and protein-tyrosine phosphatase, nonreceptor-type 12 (PTPN12), showed that deregulation of these genes activates an EMT program in human HCC cells that enhances tumor cell migration. Finally, deregulation of these genes in human HCC was found to confer sorafenib resistance through apoptotic tolerance and reduced proliferation, consistent with recent studies showing that EMT contributes to the chemoresistance of tumor cells. Our unique cell-based transposon mutagenesis screen appears to be an excellent resource for discovering genes involved in EMT in human HCC and potentially for identifying new drug targets.

Multidrug Resistance-associated Protein-1 (MRP-1)-dependent Glutathione Disulfide (GSSG) Efflux as a Critical Survival Factor for Oxidant-enriched Tumorigenic Endothelial Cells

Endothelial cell tumors are the most common soft tissue tumors in infants. Tumor-forming endothelial (EOMA) cells are able to escape cell death fate despite excessive nuclear oxidant burden. Our previous work recognized perinuclear Nox-4 as a key contributor to EOMA growth. The objective of this work was to characterize the mechanisms by which EOMA cells evade oxidant toxicity and thrive. In EOMA cells, compared with in the cytosol, the nuclear GSSG/GSH ratio was 5-fold higher. Compared to the ratio observed in healthy murine aortic endothelial (MAE) cells, GSSG/GSH was over twice as high in EOMA cells. Multidrug resistance-associated protein-1 (MRP-1), an active GSSG efflux mechanism, showed 2-fold increased activity in EOMA compared with MAE cells. Hyperactive YB-1 and Ape/Ref-1 were responsible for high MRP-1 expression in EOMA. Proximity ligand assay demonstrated MRP-1 and YB-1 binding. Such binding enabled the nuclear targeting of MRP-1 in EOMA in a leptomycin-B-sensitive manner. MRP-1 inhibition as well as knockdown trapped nuclear GSSG, causing cell death of EOMA. Disulfide loading of cells by inhibition of GSSG reductase (bischoloronitrosourea) or thioredoxin reductase (auranofin) was effective in causing EOMA death as well. In sum, EOMA cells survive a heavy oxidant burden by rapid efflux of GSSG, which is lethal if trapped within the cell. A hyperactive MRP-1 system for GSSG efflux acts as a critical survival factor for these cells, making it a potential target for EOMA therapeutics.

Elevated hepatocyte growth factor expression as an autocrine c-Met activation mechanism in acquired resistance to sorafenib in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and the third leading cause of cancer‐related deaths worldwide. Limitations in HCC treatment result due to poor prognosis and resistance against traditional radiotherapy and chemotherapies. The multikinase inhibitor sorafenib is the only FDA approved drug available for advanced HCC patients, and development of second‐line treatment options for patients who cannot tolerate or develop resistance to sorafenib is an urgent medical need. In this study, we established sorafenib‐resistant cells from Huh7 and Mahlavu cell lines by long‐term sorafenib exposure. Sorafenib‐resistant HCC cells acquired spindle‐shape morphology, upregulated mesenchymal markers, and showed significant increase in both migration and invasion abilities compared to their parental counterparts. Moreover, after long‐term sorafenib treatment, HCC cells showed induction of hepatocyte growth factor (HGF) synthesis and secretion along with increased levels of c‐Met kinase and its active phosphorylated form, indicating autocrine activation of HGF/c‐Met signaling. Importantly, the combined treatment of the resistant cells with c‐Met kinase inhibitor SU11274 and HGF neutralizing antibody significantly reversed the increased invasion ability of the cells. The combined treatment also significantly augmented sorafenib‐induced apoptosis, suggesting restoration of sorafenib sensitivity. These results describe, for the first time, compensatory upregulation of HGF synthesis leading to autocrine activation of HGF/c‐Met signaling as a novel cellular strategy in the acquisition of sorafenib resistance. Therefore, we suggest that combinatorial therapeutic strategies with HGF and c‐Met inhibitors comprise promising candidates for overcoming sorafenib resistance.

Metabolic Modification in Gastrointestinal Cancer Stem Cells: Characteristics and Therapeutic Approaches

Currently, there is much interest in the characterization of metabolic profiling of cancer stem cells (CSCs), a small subset of tumor cells with self-renewal capacity. Indeed, ever-growing evidence indicate that metabolism and stemness are highly intertwined processes in tumor tissue. In this review, we analyze the potential metabolic targeting strategies for eradicating CSCs that could help to develop a more effective therapeutic approach for gastrointestinal cancers. Indeed, the successful elimination of a tumor requires an anticancer therapy that affects both cancer cells and CSCs. The observation that gastrointestinal CSCs possess higher inducible nitric oxide sinthase (iNOS) expression, lower reactive oxygen species (ROS) production, and a different metabolism respect to no-CSCs tumor cells has paved the way to develop drugs targeting CSC specific signaling. In particular, several studies have highlighted that metformin, aldehyde dehydrogenase 1, and iNOS inhibitors selectively suppressed CSC growth and that combinatorial therapy of them with standard chemotherapeutic drugs had a synergistic effect resulting in reduced tumor burden and delayed tumor recurrence. Thus, the possibility of combining specific CSC metabolism inhibitors with existing therapeutic approaches could have profound anticancer effects, changing the conventional treatment approaches to gastrointestinal cancers. J. Cell. Physiol. 231: 2081-2087, 2016. © 2016 Wiley Periodicals, Inc.

Epithelial-mesenchymal transition plays a critical role in drug resistance of hepatocellular carcinoma cells to oxaliplatin

Drug resistance is one characteristic of hepatocellular carcinoma (HCC) and can affect the prognosis of patients directly. To explore drug resistance well, we established an oxaliplatin (OXA)-resistant cell line Bel-7402/OXA by exposure to gradually increased concentration of OXA. Some biological characters, such as proliferation, migration, and invasion, were studied. Drug sensitivity and the mechanisms of drug resistance were also investigated. We found that the resistant index of Bel-7402/OXA was 8.3. In comparison with Bel-7402, the percentages of cells in S and G2/M phase were increased. The nature apoptosis rate and drug-after apoptosis rate were all decreased in Bel-7402/OXA, as compared to Bel-7402. Bel-7402/OXA acquired increased migration and invasion ability with epithelial-mesenchymal transition (EMT) phenotype. Knockdown of EMT transcription factor Snail could reverse EMT and sensitized Bel-7402/OXA cells to OXA. EMT was one mechanism of drug resistance and may be a novel target of treatment for drug resistance.

Nuclear factor kappa B-mediated CD47 up-regulation promotes sorafenib resistance and its blockade synergizes the effect of sorafenib in hepatocellular carcinoma in mice

Sorafenib is a new standard treatment for patients with advanced hepatocellular carcinoma (HCC). However, the survival benefit of this treatment is modest, partly owing to drug resistance. Recent evidence has demonstrated the existence of tumor-initiating cells (T-ICs) as the culprit for treatment resistance. To examine whether sorafenib resistance was a result of the presence of liver T-ICs, we developed sorafenib-resistant HCC cells both in vitro and in vivo through continuous exposure to sorafenib. Using these models, we found that sorafenib-resistant clones demonstrated enhanced T-IC properties, including tumorigenicity, self-renewal, and invasiveness. In addition, several T-IC markers were found to be up-regulated, among which CD47 was found to be most significant. Using chromatin immunoprecipitation assays and expression analyses, CD47 expression was found to be regulated by nuclear factor kappa B (NF-κB) through a specific response element in the promoter of CD47, and the site occupancy and expression were increased and decreased upon stimulation and inhibition of NF-κB, respectively. Consistently, NF-κB was activated in sorafenib-resistant HCC cells, and this finding was confirmed in clinical HCC samples, which showed a positive correlation between NF-κB and CD47 expression. Functional characterization of CD47 in sorafenib-resistant HCC cells was evaluated using a lentivirus-based knockdown approach and showed increased sensitization to sorafenib upon CD47 knockdown. Furthermore, blockade of CD47 using anti-CD47 antibody (Ab) showed a similar effect. Using a patient-derived HCC xenograft mouse model, we found that anti-CD47 Ab (500 μg/mouse) in combination with sorafenib (100 mg/kg, orally) exerted synergistic effects on tumor suppression, as compared with sorafenib and anti-CD47 Ab alone.

CONCLUSIONS

NF-κB-mediated CD47 up-regulation promotes sorafenib resistance, and targeting CD47 in combination with sorafenib is an attractive therapeutic regimen for the treatment of HCC patients.

Loss of microRNA-27b contributes to breast cancer stem cell generation by activating ENPP1

Cancer stem cells (CSCs) have been identified in various types of cancer; however, the mechanisms by which cells acquire CSC properties such as drug resistance and tumour seeding ability are not fully understood. Here, we identified microRNA-27b (miR-27b) as a key regulator for the generation of a side-population in breast cancer cells that showed CSC properties, and also found that the anti-type II diabetes (T2D) drug metformin reduced this side-population via miR-27b-mediated repression of ectonucleotide pyrophosphatase/phosphodiesterase family member 1 (ENPP1), which is involved in T2D development. ENPP1 induced the generation of the side-population via upregulation of the ABCG2 transporter. ENPP1 was also identified as a substrate of the 26S proteasome, the activity of which is downregulated in CSCs. Overall, these results demonstrate that a T2D-associated gene plays an important role in tumour development and that its expression is strictly controlled at the mRNA and protein levels.

MicroRNAs have a role in the acquisition of stem cell-like properties of cancer cells. Here the authors show that microRNA-27b mediates generation of a side-population of breast cancer stem cells, in part by regulating the protein ENPP1, which has been previously linked to the development of diabetes.

Role of anti-angiogenesis therapy in the management of hepatocellular carcinoma: The jury is still out

As the leading cause of disease-related deaths, cancer is a major public health threat worldwide. Surgical resection is still the first-line therapy for patients with early-stage cancers. However, postoperative relapse and metastasis remain the cause of 90% of deaths of patients with solid organ malignancies, including hepatocellular carcinoma (HCC). With the rapid development of molecular biology techniques in recent years, molecularly targeted therapies using monoclonal antibodies, small molecules, and vaccines have become a milestone in cancer therapeutic by significantly improving the survival of cancer patients, and have opened a window of hope for patients with advanced cancer. Hypervascularization is a major characteristic of HCC. It has been reported that anti-angiogenic treatments, which inhibit blood vessel formation, are highly effective for treating HCC. However, the efficacy and safety of anti-angiogenesis therapies remain controversial. Sorafenib is an oral multikinase inhibitor with anti-proliferative and anti-angiogenic effects and is the first molecular target drug approved for the treatment of advanced HCC. While sorafenib has shown promising therapeutic effects, substantial evidence of primary and acquired resistance to sorafenib has been reported. Numerous clinical trials have been conducted to evaluate a large number of molecularly targeted drugs for treating HCC, but most drugs exhibited less efficacy and/or higher toxicity compared to sorafenib. Therefore, understanding the mechanism(s) underlying sorafenib resistance of cancer cells is highlighted for efficiently treating HCC. This concise review aims to provide an overview of anti-angiogenesis therapy in the management of HCC and to discuss the common mechanisms of resistance to anti-angiogenesis therapies.

Association of Notch1 with vasculogenic mimicry in human hepatocellular carcinoma cell lines

BACKGROUND AND AIMS

According to recent findings, some tumor cells function as endothelial progenitor cells to initiate tumor vasculogenesis, known as "vasculogenic mimicry" (VM). Notch1, the key regulator of vasculogenesis and embryonic differentiation, has shown a correlation with a poor prognosis in hepatocellular carcinoma (HCC). We attempted to elucidate the relationship between Notch1 and the vascularization of HCC.

MATERIALS AND METHODS

HCC cell lines were assayed for tube formation and low-density lipoprotein (LDL) absorption. The translation level of targets of interest was verified using western blot. Notch1 was silenced in HepG2, BEL-7402 and HCCLM6 using lentivirus shRNA. A hypoxic culture was conducted in an anaerobic culture chamber to induce VM in HepG2. Samples from 53 patients with HCC, i.e., 5 with metastasis and 48 without were tested for Notch1(+) cells and CD34 negative plus Periodic Acid-Schiff (PAS) positive structures, respectively.

RESULTS

BEL-7402 and HCCLM6 were capable of tube formation and LDL absorption in vitro, while HepG2 was negative for both. Notch1 down-regulation suppressed endothelial marker expression and greatly impaired tube formation. After hypoxic culture, the tube formation capacity of HepG2 was significantly enhanced, along with an increase in Notch1 expression. Notch1 was strongly and profusely expressed in all 5 cases of distant metastasis, while 19 of the 48 cases without metastasis were sparsely positive (P < 0.05). Notch1 positivity was mainly seen in the cytoplasm and nuclei. VM structures were only found in 2 cases from the metastasis group (P < 0.05).

CONCLUSIONS

HCC is capable of VM. Notch1 might serve as a potential target for VM development in HCC.

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.