Na+/K+-ATPase α1 subunit,a novel therapeutic target for hepatocellular carcinoma

We aimed to identify the expression patterns of Na⁺/K⁺-ATPase (NKA) α subunits in human hepatocellular carcinoma (HCC) samples and evaluate these subunits as potential targets for HCC treatment. The mRNA expression profiles of NKA α subunits in human HCC samples were analyzed. We found that the mRNA expression for NKA α1 subunit (ATP1A1) was higher than that for other NKA α subunits. Also, ATP1A1 gene expression was markedly higher in HCC samples than in adjacent nontumor tissue samples. Western blotting data suggested that 6 of 14 (43%) HCC samples had elevated ATP1A1 protein expression. Furthermore, knockdown of ATP1A1 expression in human HCC HepG2 and MHCC97H cells markedly reduced their proliferation in vitro and suppressed the tumorigenicity of MHCC97H cells in vivo. Downregulation of ATP1A1 expression resulted in cell-cycle arrest at G2/M phase and apoptosis in HepG2 cells as well as decreased migration in Hep3B cells. We further validated that ATP1A1 downregulation caused intracellular accumulation of reactive oxygen species. Pretreatment with N-acetyl cysteine blocked cell-growth inhibition induced by ATP1A1 downregulation. Collectively, these data suggested that targeting ATP1A1 is a novel approach to the treatment of HCC.     

Na+/K+-ATPase β2-subunit (AMOG) expression abrogates invasion of glioblastoma-derived brain tumor-initiating cells

Background

Mechanisms of glioma invasion remain to be fully elucidated. Glioma cells within glioblastoma multiforme (GBM) range from well-differentiated tumor cells to less-differentiated brain tumor-initiating cells (BTICs). The β2-subunit of Na⁺/K⁺-ATPase, called the adhesion molecule on glia (AMOG), is highly expressed in normal glia but is thought to be universally downregulated in GBM. To test our hypothesis that expression of AMOG is heterogeneous in GBM and confers a less invasive phenotype, we compared it between BTICs and differentiated cells from patient-matched GBM and then tested GBM invasion in vitro after AMOG overexpression.

Methods

Immunohistochemistry, immunoblotting, and real-time PCR were used to characterize AMOG protein and mRNA expression in tumor samples, BTICs, and differentiated cells. Matrigel invasion assay, scratch assay, and direct cell counting were used for testing in vitro invasion, migration, and proliferation, respectively.

Results

While AMOG expression is heterogeneous in astrocytomas of grades II–IV, it is lost in most GBM. BTICs express higher levels of AMOG mRNA and protein compared with patient-matched differentiated tumor cells. Overexpression of AMOG decreased GBM cell and BTIC invasion without affecting migration or proliferation. Knockdown of AMOG expression in normal human astrocytes increased invasion.

Conclusions

AMOG expression inhibits GBM invasion. Its downregulation increases invasion in glial cells and may also represent an important step in BTIC differentiation. These data provide compelling evidence implicating the role of AMOG in glioma invasion and provide impetus for further investigation.     

The α7-nicotinic acetylcholine receptor mediates the sensitivity of gastric cancer cells to taxanes

Tumor Biology - Gastric cancer is difficult to cure because most patients are diagnosed at an advanced disease stage. Systemic chemotherapy remains an important therapy for gastric cancer, but both...     

Role of Na+, K+-ATPase α1 subunit in the intracellular accumulation of cisplatin

The present study was undertaken to identify what regulates intracellular cisplatin (CDDP) accumulation and what changes in membrane fraction of CDDDP-resistant cell line. The CDDP-resistant rat hepatoma cell line, H4-II-E/CDDP, shows a significant decrease in intracellular platinum accumulation compared with parental H4-II-E cells, although there was no difference in the efflux of CDDP between these two cell lines. In this study, we examined the contribution of functional change in active transport to the CDDP resistance of H4-II-E/CDDP cells. Compared with the resistant cells, platinum accumulation in the parental cells was clearly decreased by low temperature or ATP depletion. In addition, the Na⁺, K⁺-ATPase inhibitor ouabain and the K⁺ channel inhibitor tetraethylammonium decreased platinum accumulation in parental cells but did not change the accumulation in resistant cells. Amphotericin B, an antifungal agent, increased the intracellular platinum accumulation in resistant cells to the same level as in parent cells. Western blot analysis demonstrated that the Na⁺, K⁺-ATPase α₁ subunit was reduced in resistant cells compared with the parental cells, although there was no difference in the expression of the β1 subunit between the two cell lines. Furthermore, the Na⁺, K⁺-ATPase α1 subunit of H4-II-E was decreased following a 24-h exposure to CDDP. These results suggest that Na⁺, K⁺-ATPase-dependent active transport of CDDP does not occur in resistant cells, and, furthermore, our findings provide the first evidence that the Na⁺, K⁺-ATPase α1 subunit plays an important role in the transport of CDDP.     

Acquired tolerance of hepatocellular carcinoma cells to selenium deficiency: a selective survival mechanism?

Selenium is essential to human health, and its deficiency is associated with different diseases including liver necrosis. Selenium is protective against viral hepatitis and hepatocellular carcinoma (HCC). The underlying molecular mechanisms of selenium effects are not well known. In this study, in vitro response of HCC-derived cell lines to selenium deficiency is examined alone or in conjunction with Vitamin E and copper/zinc. Here, we show that in vitro selenium deficiency in a subset of HCC-derived cell lines causes oxidative stress and cytochrome c release with subsequent cell death by apoptosis. The oxidative stress and consequent cell death induced by selenium deficiency on these cells are reverted by the antioxidant effect of Vitamin E. However, most HCC cell lines (10 of 13) tolerate selenium deficiency. Consequently, they escape apoptosis. Moreover, nine of these tolerant cell lines have integrated hepatitis B Virus (HBV) DNA in their genomes, and some display p53-249 mutation, indicating past exposure to HBV or aflatoxins, established factors for oxidative stress and cancer risk in liver. An HBV-transfected clone (2.2.15) of the sensitive HepG2 cell line has gained tolerance to selenium deficiency. Our findings indicate that selenium deficiency induces apoptosis in some "hepatocyte-like" cells. However, most HCC cells, particularly HBV-related ones, tolerate selenium deficiency and escape its deadly consequences. Thus, as demonstrated by the gain of survival capacity of apoptosis-sensitive cell lines with Vitamin E, such malignant cells have acquired a selective survival advantage that is prominent under selenium-deficient and oxidative-stress conditions.     

Lack of ex vivo peripheral and intrahepatic α-fetoprotein-specific CD4+ responses in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies with a poor prognosis and limited therapeutic options that is often characterized by the expression of the tumor-associated antigen α-fetoprotein (AFP). CD4+ helper T cells are important in generating potent anticancer immunity as they prime and expand CD8+ T-cell memory and may also have direct antitumor activity. However, very little information is currently available about the relative frequency, immunodominance and peripheral versus intratumoral distribution of AFP-specific CD4+ T-cell responses in patients with HCC. We, therefore, analyzed AFP-specific CD4+ responses in blood and tumor tissue of patients with HCC by using overlapping peptides spanning the entire AFP protein and novel sensitive approaches such as antigen-specific upregulation of CD154. We found that AFP-specific CD4+ T-cell responses were not detectable in the peripheral blood ex vivo. However, after in vitro stimulation, AFP-specific CD4+ T-cell responses were detectable in a large fraction of patients targeting different previously unreported epitopes with no clear immunodominance. These results indicate that AFP-specific CD4+ T-cell responses are not completely deleted but only present at very low frequencies. Importantly, AFP-specific CD4+ T-cell responses were also rarely detectable in tumor tissue, suggesting that the relative absence of these cells in the circulation ex vivo is not due to a rapid accumulation to the tumor side. Taken together, these results suggest that the lack of sufficient CD4+ T-cell help, especially within the tumor tissue, may be one central mechanism responsible for the failure of AFP-specific immune responses to control HCC progression.     

The possible role of signal regulatory protein α1 in hepatocellular carcinoma

Objective: To study the relationship between signal regulatory protein α₁ (SIRPα₁) and hepatocellular carcinoma (HCC) and explore the possible molecular mechanisms.Methods: Total RNA was extracted from normal hepatocyte cell line Hs680, Hepatocellular carcinoma cell lines HepG2, H4–H7, Chang liver and SK-Hep1. The SIRPTα₁ was detected in 42 pathologically confirmed hepatocellular carcinoma tissue samples and 6 normal liver tissues by Northern blot and immunohistochemical staining. The association of SIRPα1 and HGF was determined in HuH7.Results: SIRPα1 was highly expressed in Hs680, HepG2 and H4–H7, but weakly expressed in SK-Hep1 and Chang liver cell lines. Northern blot and Western blot both detected the reduced expression of SIRPα1 in hepatocellular carcinoma tissue as compare to paracancerous and normal tissues.In vitro experiments showed HGF stimulation elevated SIRPα1 phosphorylation. Over-expression of wild type SIRPα1 promoted cell proliferation in the presence of HGF.Conclusion: SIRPα1 might be involved in HCC development and metastasis. The underlying mechanisms may be related to regulatory tyrosine phosphorylation of SIRPα1 by HGF stimulation. These authors contributed equally to these work     

MicroRNA-21 induces resistance to the anti-tumour effect of interferon-α/5-fluorouracil in hepatocellular carcinoma cells

Background:

We reported recently the clinical efficiency of interferon (IFN)-α/5-fluorouracil (5-FU) combination therapy in advanced hepatocellular carcinoma (HCC). However, prediction of the response to the combination therapy remains unsatisfactory. The aim of this study was to investigate the anti-tumour effects of microRNA (miR)-21 on the sensitivity of HCC cells to IFN-α/5-FU and whether miR-21 can be used as a predictor of the response to such therapy in HCC.

Methods:

Changes in the sensitivity of HCC cells (PLC/PRF/5 and HepG2) to IFN-α/5-FU were examined after transfection with pre-miR-21 or anti-miR-21. The correlation between miR-21 expression level, evaluated by qRT–PCR, and response to the therapy was also investigated in clinical HCC specimens.

Results:

Hepatocellular carcinoma cells transfected with pre-miR-21 were significantly resistant to IFN-α/5-FU. Annexin V assay showed that the percentage of apoptotic cells was significantly lower in cells transfected with pre-miR-21 than control cells. Transfection of anti-miR-21 rendered HCC cells sensitive to IFN-α/5-FU, and such sensitivity was weakened by transfection of siRNAs of target molecules, PETN and PDCD4. miR-21 expression in clinical HCC specimens was significantly associated with the clinical response to the IFN-α/5-FU combination therapy and survival rate.

Conclusions:

The miR-21 in HCC cell lines and clinical HCC samples is a significant modulator of the anti-tumour effect of IFN-α and 5-FU. This suggests that miR-21 is a potentially suitable marker for the prediction of the clinical response to the IFN-α/5-FU combination therapy.     

Vitamin K2 augments 5-fluorouracil-induced growth inhibition of human hepatocellular carcinoma cells by inhibiting NF-κB activation

Although 5-fluorouracil (5-FU) is one of the most commonly used chemotherapeutic agents in various cancer including hepatocellular carcinoma (HCC), chemoresistance has precluded single use of 5-FU in clinical settings. Since menatetrenone, an analogue of vitamin K2 (VK2), inhibits growth of cancer cells including HCC cells in vitro and in vivo, we examined VK2 modulation of HCC cell response to 5-FU. VK2 pretreatment dose-dependently enhanced growth-inhibition by 5-FU through a G1 cell cycle arrest. VK2 inhibited 5-FU-induced NF-κB activation and cyclin D1 expression. Therefore, combination of VK2 and 5-FU might represent a new therapeutic strategy for patients with HCC.     

NDRG1 promotes growth of hepatocellular carcinoma cells by directly interacting with GSK-3β and Nur77 to prevent β-catenin degradation

The N-myc downstream regulated gene 1 (NDRG1) is significantly associated with advanced tumor stages and poor survival of hepatocellular carcinoma (HCC), thereby implicating it as a potential target for HCC treatment. We aim to further understand its biological roles in hepatocarcinogenesis, as a means to exploit it for therapeutic purposes. By screening using the ProtoArray^® Human Protein Microarrays, we identified glycogen synthase kinase 3β (GSK-3β) and the orphan nuclear receptor (Nur77) as potential interaction partners of NDRG1. These interactions were confirmed in HCC cell lines in vitro by co-immunoprecipitation; and co-localizations of NDRG1 with GSK-3β and Nur77 were observed by immunofluorescence staining. Additionally, high levels of NDRG1 competitively bind to GSK-3β and Nur77 to allow β-catenin to escape degradation, with consequent elevated levels of downstream oncogenic genes. In vivo, we consistently observed that NDRG1 suppression in HCC xenografts decreased β-catenin levels and its downstream target Cyclin D1, with concomitant tumor growth inhibition. Clinically, the over-expression of NDRG1 in HCC patient samples is positively correlated with GSK-3β-9ser (│R│= 0.28, p = 0.01), Nur77 (│R│= 0.42, p < 0.001), and β-catenin (│R│= 0.32, p = 0.003) expressions. In conclusion, we identified GSK-3β and Nur77 as novel interaction partners of NDRG1. These protein-protein interactions regulate the turnover of β-catenin and subsequent downstream signaling mediated by β-catenin in HCC cells, and provides potential targets for future therapeutic interventions.     

A new approach to the use of α-fetoprotein as surveillance test for hepatocellular carcinoma in patients with cirrhosis

Background:

Surveillance for hepatocellular carcinoma (HCC) is recommended in patients with cirrhosis. As α-fetoprotein (AFP) is considered a poor surveillance test, we tested the performance of its changes over time.

Methods:

Eighty patients were diagnosed with HCC (cases) during semiannual surveillance with ultrasonography and AFP measurement were recruited and matched for age, gender, etiology and Child-Pugh class with 160 contemporary cancer-free controls undergoing the same surveillance training group (TG). As a validation group (VG) we considered 36 subsequent patients diagnosed with HCC, matched 1 : 3 with contemporary cancer-free controls. α-Fetoprotein values at the time of HCC diagnosis (T0) and its changes over the 12 (Δ12) and 6 months (Δ6) before cancer detection were considered.

Results:

In both TG and VG, >80% of HCCs were found at an early stage. In TG, AFP significantly increased over time only in cases. T0 AFP and a positive Δ6 were independently associated with HCC diagnosis (odds ratio: 1.031 and 2.402, respectively). The area under the curve of T0 AFP was 0.76 and its best cutoff (BC) was 10 ng ml⁻¹ (sensitivity 66.3%, specificity 80.6%). The combination of AFP >10 ng ml⁻¹ or a positive Δ6 composite α-fetoprotein index (CAI) increased the sensitivity to 80% with a negative predictive value (NPV) of 86.2%. Negative predictive value rose to 99%, considering a cancer prevalence of 3%. In the VG, the AFP-BC was again 10 ng ml⁻¹ (sensitivity 66.7%, specificity 88.9%), and CAI sensitivity was 80.6% with a NPV value of 90.5%.

Conclusions:

CAI achieves adequate sensitivity and NPV as a surveillance test for the early detection of HCC in cirrhosis.     

DNA methylation-mediated silencing of matricellular protein dermatopontin promotes hepatocellular carcinoma metastasis by α3β1 integrin-Rho GTPase signaling

Dermatopontin (DPT), a tyrosine-rich, acidic matricellular protein, has been implicated in several human cancers. However, its biological functions and molecular mechanisms in cancer progression, particular hepatocellular carcinoma (HCC), remain unknown. We demonstrated that DPT was significantly down-regulated in 202 HCC clinical samples and that its expression level was closely correlated with cancer metastasis and patient prognosis. The overexpression of DPT dramatically suppressed HCC cell migration in vitro and intrahepatic metastasis in vivo. We further revealed that the down-regulation of DPT in HCC was due to epigenetic silencing by promoter DNA methylation. And the inhibitory effects of DPT on HCC cell motility were associated with dysregulated focal adhesion assembly, decreased RhoA activity and reduced focal adhesion kinase (FAK) and c-Src tyrosine kinase (Src) phosphorylation, and all of these alterations required the involvement of integrin signaling. Furthermore, we determined that the inhibitory effects of DPT on HCC cell motility were primarily mediated through α3β1 integrin. Our study provides new evidence for epigenetic control of tumor microenvironment, and suggests matricellular protein DPT may serve as a novel prognostic marker and act as a HCC metastasis suppressor.     

The α-iso-cubebenol compound isolated from Schisandra chinensis induces p53-independent pathway-mediated apoptosis in hepatocellular carcinoma cells

Schisandra chinensis (S. chinensis) plants are extensively used because of their anticancer, anti-inflammatory, antioxidant and antihepatic activities. However, their active compounds remain to be clearly determined. In this study, we investigated the antitumor functions of α-iso-cubebenol (αIC) isolated from S. chinensis using HepG2 hepatocellular carcinoma cells. HepG2 cells were exposed to αIC for 24 h, and apoptosis was assessed using standard viability and cell proliferation assays, flow cytometry and western blotting. HepG2 cell populations treated only with 340 μM of αIC showed markedly increased cell death, but lower concentrations induced minimal alterations of population viability and cell morphology. However, the results of flow cytometry showed that the majority of viable cells were undergoing apoptosis at all tested αIC concentrations. Western blot analysis results revealed a significant and αIC concentration-dependent reduction in the levels of the pro-caspase-3 apoptotic protein and the Bcl-2 anti-apoptotic protein. In particular, the Bax pro-apoptosis protein and p53 (which regulates Bax expression) showed different expression patterns after the application of αIC treatment to HepG2 cells. Bax expression was slightly increased in cells treated with the high concentration of αIC, while p53 expression was markedly reduced in a dose-dependent fashion, similar to that of Bcl-2. The results of this study suggest that αIC is an anticancer drug candidate by virtue of its apoptotic induction abilities in hepatocellular carcinoma cells, which occur via a p53-independent pathway.     

Urinary transforming growth factor α and serum α-fetoprotein as tumor markers of hepatocellular carcinoma

This case–control study aimed to evaluate the diagnostic application of urinary transforming growth factor (TGF) α and serum α-fetoprotein (AFP) in hepatocellular carcinoma (HCC). TGFα and AFP were determined in 90 pairs of age- and gender-matched patients with cirrhotic HCC and patients with cirrhosis alone and 60 healthy controls. The results indicated that TGFα and AFP levels in patients with HCC were higher than in those with cirrhosis alone or healthy controls (each P?=?0.0001). Multivariate analysis indicated that TGFα (odds ratio (OR) 1.03, 95 % confidence interval (CI) 1.05–1.16) and AFP (OR 1.03, 95 % CI 1.01–1.06) were closely associated, in a dose-related fashion, with the development of HCC. The optimal cutoff values, determined with the receiver operating characteristic (ROC) curves, were 29 μg/g creatinine for TGFα and 100 ng/ml for AFP, respectively. The areas under ROC curve (AUC) were 0.74 for TGFα and 0.78 for AFP, respectively. Both biomarkers showed the same sensitivity (52.2 %), high specificity, high positive predictive value, and moderate positive likelihood ratio. Determination of both markers in parallel significantly increased the AUC (0.91) and diagnostic accuracy (92.2 %), with a high sensitivity (86.7 %), specificity (97.8 %), positive predictive value (PPV; 97.5 %), and moderate positive likelihood ratio (PLR; 39.4). Among 31 cirrhotic HCC with AFP?≤?20 ng/ml, the calculated AUC for TGFα was 0.79, with a sensitivity of 64.5 %, specificity of 96.7 %, PPV of 87.0 %, and PLR of 19.5. In conclusion, urinary TGFα and serum AFP are complementary tumor markers for detection of HCC with low AFP production.