Study on the mechanism of epidermal growth factor-induced proliferation of hepatoma cells

How Dysregulated Ion Channels and Transporters Take a Hand in Esophageal, Liver, and Colorectal Cancer

Over the last two decades, the understanding of how dysregulated ion channels and transporters are involved in carcinogenesis and tumor growth and progression, including invasiveness and metastasis, has been increasing exponentially. The present review specifies virtually all ion channels and transporters whose faulty expression or regulation contributes to esophageal, hepatocellular, and colorectal cancer. The variety reaches from Ca²⁺, K⁺, Na⁺, and Cl^- channels over divalent metal transporters, Na⁺ or Cl^- coupled Ca²⁺, HCO₃^- and H⁺ exchangers to monocarboxylate carriers and organic anion and cation transporters. In several cases, the underlying mechanisms by which these ion channels/transporters are interwoven with malignancies have been fully or at least partially unveiled. Ca²⁺, Akt/NF-κB, and Ca²⁺- or pH-dependent Wnt/β-catenin signaling emerge as cross points through which ion channels/transporters interfere with gene expression, modulate cell proliferation, trigger epithelial-to-mesenchymal transition, and promote cell motility and metastasis. Also miRs, lncRNAs, and DNA methylation represent potential links between the misexpression of genes encoding for ion channels/transporters, their malfunctioning, and cancer. The knowledge of all these molecular interactions has provided the basis for therapeutic strategies and approaches, some of which will be broached in this review.

Grb7-derived calmodulin-binding peptides inhibit proliferation, migration and invasiveness of tumor cells while they enhance attachment to the substrate

The growth factor receptor bound protein 7 (Grb7) is a Ca²⁺-dependent calmodulin (CaM)-binding adaptor protein implicated, among other functions, in cell proliferation, migration and tumor-associated angiogenesis. The goal of this study was to determine whether a peptide based on the CaM binding site of Grb7 disrupts cellular processes, relevant for the malignancy of tumor cells, in which this adaptor protein is implicated. We designed synthetic myristoylated and non-myristoylated peptides corresponding to the CaM-binding domain of human Grb7 with the sequence ²⁴³RKLWKRFFCFLRRS²⁵⁶ and a variant peptide with the mutated sequence RKLERFFCFLRRE (W246E-ΔK247-S256E). The two non-myristoylated peptides bind dansyl-CaM with higher efficiency in the presence than in the absence of Ca²⁺ and they enter into the cell, as tested with 5(6)-carboxytetramethylrhodamine (TAMRA)-labeled peptides. The myristoylated and non-myristoylated peptides inhibit the proliferation, migration and invasiveness of A431 tumor cells while they enhance their adhesion to the substrate. The myristoylated peptides have stronger inhibitory effect than the non-myristoylated counterparts, in agreement with their expected higher cell-permeant capacity. The myristoylated and non-myristoylated W246E-ΔK247-S256E mutant peptide has a lesser inhibitory effect on cell proliferation as compared to the wild-type peptide. We also demonstrated that the myristoylated peptides were more efficient than the CaM antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) inhibiting cell migration and equally efficient inhibiting cell proliferation.

An Epitope on EGFR Loading Catastrophic Internalization Serve as a Novel Oncotarget for Hepatocellular Carcinoma Therapy

The precise role of Epidermal Growth Factor Receptor (EGFR) in Hepatocellular carcinoma (HCC) cells is unknown and EGFR inhibitors have not achieved positive clinical results. The rapid and drastic internalization of EGFR has been proved to successfully treat EGFR inhibitor-resistant patients in recent clinical trials. Here, the anti-tumor efficacy of a protein (rLZ-8) from Ganoderma lucidum was evaluated, it was demonstrated that rLZ-8 could bind to EGFR specifically, drastically enter into Hepatoma cells, abrogate endosomal recycling and induce HCC cell death. Surprisingly, we screened a monoclonal antibody which possesses competitive binding site with rLZ-8, it also trigger catastrophic EGFR internalization. This result suggests that it is necessary to investigate the interface of EGFR and rLZ-8 complex. An internalization related epitope (S222/K269) was identified on the dimerization arm of EGFR extracellular domain (ECD). These results suggest vulnerability of HCC cells to catastrophic EGFR internalization that can be targeted by a novel epitope and point to the possible exploitation in the design of anti-EGFR therapeutic biologics for HCC therapy.

Combination of cetuximab and rapamycin enhances the therapeutic efficacy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide. It is well known that the activation of PI3K/AKT/mTOR and the Ras/MAPK signaling pathway plays a critical role in cellular metabolism, growth and proliferation, and its inhibitors have been used as therapeutic drugs for hepatocellular carcinoma. Cetuximab, a chimerical monoclonal EGFR IgG1 antibody, can block the binding of EGF or other ligands to EGFR and thus inhibit ligands-induced receptor phosphorylation. In the present study, we found that rapamycin could enhance the antiproliferation effect of cetuximab in both HepG2 cells and Huh-7 cells and arrest the cell cycle. Cetuximab in combination with rapamycin had synergistic effects on inhibiting the phosphrylation of proteins in PI3K/AKT/mTOR and Ras/MAPK signaling pathway. Combination of cetuximab with rapamycin treatment significantly suppressed the HCC development in HepG2 cells-xenografted mice and improved the survival. Cetuximab and rapamycin inhibited the growth of HCC both in vitro and in vivo. These results suggest that the combination therapy using the inhibitors for both EGFR and PI3K/AKT/mTOR signaling pathways may be a novel therapeutic approach for HCC.

Bevacizumab and erlotinib in previously untreated inoperable and metastatic hepatocellular carcinoma

PURPOSE

To evaluate the combination of erlotinib and bevacizumab in subjects with hepatocellular carcinoma (HCC) who are not candidates for local therapy.

PATIENTS AND METHODS

Twenty-one subjects with metastatic or inoperable HCC who had not received local or systemic therapy were treated with 15 mg/kg bevacizumab every 3 weeks and a daily dose of 150 mg oral erlotinib. The primary endpoint was progression-free survival (PFS) at 27 weeks. The secondary endpoints were median time to progression and median overall survival.

RESULTS

Twenty-one subjects were enrolled. Eighteen were evaluable for the primary endpoint; all subjects were evaluable for toxicity. The median age was 60 years (range, 33 to 81 y). Five subjects (28%) were progression free at 27 weeks (90% confidence interval (CI), 12%-50%). Median time to progression was 2.57 months (95% CI, 2.13-4.20 mo). Median overall survival was 8.33 months (95% CI, 5.73-13.97 mo). Two subjects withdrew consent, and 1 subject did not have adequate baseline scans.

CONCLUSIONS

The 28% progression-free survival rate at 27 weeks was not significantly higher than the recent historical control rate of 20% observed on the placebo arm of the Sorafenib Hepatocellular Carcinoma Assessment Randomized Protocol trial (P=0.28). The combination of bevacizumab and erlotinib does not appear to have sufficient efficacy in patients with unresectable and metastatic HCC not amenable to local therapy, and may not warrant further investigation. However, this could be evaluated as an alternative to those intolerant to sorafenib therapy.

Hepatic cancer stem cells and drug resistance: Relevance in targeted therapies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of most common malignancies in the world. Systemic treatments for HCC, particularly for advanced stages, are limited by the drug resistance phenomenon which ultimately leads to therapy failure. Recent studies have indicated an association between drug resistance and the existence of the cancer stem cells (CSCs) as tumor initiating cells. The CSCs are resistant to conventional chemotherapies and might be related to the mechanisms of the ATP Binding Cassette (ABC) transporters and alterations in the CSCs signaling pathways. Therefore, to contribute to the development of new HCC treatments, further information on the characterization of CSCs, the modulation of the ABC transporters expression and function and the signaling pathway involved in the self renewal, initiation and maintenance of the cancer are required. The combination of transporters modulators/inhibitors with molecular targeted therapies may be a potent strategy to block the tumoral progression. This review summarizes the association of CSCs, drug resistance, ABC transporters activities and changes in signaling pathways as a guide for future molecular therapy for HCC.

Calmodulin-mediated regulation of the epidermal growth factor receptor

In this review, we first describe the mechanisms by which the epidermal growth factor receptor generates a Ca(2+) signal and, subsequently, we compile the available experimental evidence regarding the role that the Ca(2+)/calmodulin complex, formed after the rise in cytosolic free Ca(2+) concentration, exerts on the receptor. We focus not only on the indirect action that Ca(2+)/calmodulin exerts on the epidermal growth factor receptor, as a result of the activation of distinct calmodulin-dependent kinases, but also, and more extensively, on the direct interaction of Ca(2+)/calmodulin with the receptor. We also describe several mechanistic models that could account for the Ca(2+)/calmodulin-mediated regulation of epidermal growth factor receptor activity. The control exerted by calmodulin on distinct epidermal growth factor receptor-mediated cellular functions is also discussed. Finally, the phosphorylation of this Ca(2+) sensor by the epidermal growth factor receptor is highlighted.

Phytochemicals as potential chemopreventive and chemotherapeutic agents in hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the fifth commonest malignancy worldwide and the incidence is rising. Surgery, including transplantation resection, is currently the most effective treatment for HCC; however, recurrence rates are high and long-term survival is poor. Identifying novel chemopreventive and chemotherapeutic agents and targeting them to patients at high risk of developing HCC or following curative treatment may go some way towards improving prognosis. This review examines current knowledge regarding the chemopreventive and chemotherapeutic potential of phytochemicals in heptocarcinogenesis. Both in-vitro and animal studies demonstrate that several phytochemicals, including curcumin, resveratrol, green tea catechins, oltipraz and silibinin, possess promising chemopreventive and chemotherapeutic properties. Despite this, very few clinical trials have been performed. Problems regarding validation of biomarkers, agent delivery, side effects and patient selection are barriers that need to be overcome to determine the potential of such agents in clinical practice.

EGFR blockade by cetuximab alone or as combination therapy for growth control of hepatocellular cancer

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death worldwide. In light of the very poor 5 year survival new therapeutic approaches are mandatory. Several reports indicate that the epidermal growth factor receptor (EGFR) is expressed frequently in HCC, most likely contributing to the aggressive growth characteristics of these tumors. Cetuximab, a chimeric monoclonal IgG1 antibody directed against the EGFR, potently suppresses the growth of various cancers but its effect on HCC remains to be explored. We therefore studied the antineoplastic potency of cetuximab in human HCC cells alone and in combination with growth factor tyrosine-kinase inhibition (TKI) or HMG-CoA-reductase inhibiton or conventional cytostatics. Cetuximab inhibited growth of p53 wild-type HepG2 hepatocellular cancer cells in a time- and dose-dependent manner. Cetuximab treatment resulted in arresting the cell cycle in the G(1)/G(0)-phase due to an increase of expression of the cyclin-dependent kinase inhibitors p21(Waf1/CIP1) and p27(Kip1) and a decrease in cyclin D1 expression. Additionally, we observed a moderate increase in apoptosis as demonstrated by caspase-3 activation. Combining cetuximab with TKIs (erlotinib or AG1024) or the HMG-CoA-reductase inhibitor fluvastatin or doxorubicin resulted in synergistic antiproliferative effects. In contrast, p53 mutated Huh-7 hepatocellular cancer cells proved to be less sensitive towards cetuximab, but when combined with TKIs or fluvastatin or doxorubicin a pronounced reduction of cell growth was observed. To conclude, our study may provide a rationale for future clinical investigations of cetuximab combination therapy for growth control of hepatocellular cancer.

Erlotinib induces cell cycle arrest and apoptosis in hepatocellular cancer cells and enhances chemosensitivity towards cytostatics

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death worldwide. In light of the very poor 5-year-survival new therapeutic approaches are urgently needed. Recently, evidence has been accumulated that the epidermal growth factor receptor (EGFR) is a promising target for cancer therapy. Several reports indicate that EGFRs are expressed frequently in HCC, most likely contributing to the aggressive growth characteristics of these tumors.

METHODS

Erlotinib, an inhibitor of EGFR-tyrosine kinase, potently suppresses the growth of various tumors, but its effect on HCC remains to be explored. We therefore studied the antineoplastic potency of erlotinib in human HCC cells (Huh-7 and HepG2 cell lines).

RESULTS

We show that erlotinib inhibited HCC growth in a time- and dose-dependent manner. Moreover erlotinib treatment induced apoptosis and resulted in a dose-dependent arrest at the G1/S checkpoint of the cell cycle. Combining erlotinib with doxorubicin or docetaxel or SN-38 resulted in additive or even synergistic antiproliferative effects.

CONCLUSIONS

Our data demonstrate that in human HCC cells the inhibition of EGFR-tyrosine kinase by erlotinib induces growth inhibition, apoptosis and cell cycle arrest. Additionally, erlotinib enhances the antineoplastic activity of conventional cytostatic drugs. Thus, inhibiting EGFR-tyrosine kinase appears to be a promising treatment strategy in HCC.

Antitumor effect of Gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor, combined with cytotoxic agent on murine hepatocellular carcinoma

AIM: To investigate the inhibitory effect of gefitinib combined with cytotoxic agent cisplatin (CDDP) on hepatocellular carcinoma (HCC).

METHODS: Female Kunming mice and H22 hepatocarcinoma cells were used. Gefitinib at daily dose of 100 mg/kg body weight (BW) or lecithin liquid was given by gastrogavage once a day for 5 or 10 successive days. CDDP or normal saline (NS) was administered intraperitoneally (i.p.) once a day for 5 successive days. Mice were randomly divided into control group (lecithin, or NS, i.p.), CDDP group (daily dose, 1.2 mg/kg BW; d1-5, or d6-10), Gefitinib (d1-5, or d6-10, or d1-10), and Gefitinib combined with CDDP groups. The inhibitory rate (IR) of tumor, net BW, spleen index (SI), thymus index (TI) and the amount of peripheral blood cells of mice were detected on the 12th experiment day.

RESULTS: The growth of HCC in mice was inhibited by Gefitinib alone (IR: 41% in d1-10 group and 30% in d1-5 group, respectively) or CDDP alone (IR: 32-54% in d1-5 group or d6-10 group). The highest inhibitory effect (IR: 56%) on HCC growth was observed in Gefitinib (d1-10) combined with CDDP (d1-5) group. Higher inhibition was also observed in CDDP (d1-5) followed by Gefitinib (d6-10) group than that in Gefitinib (d1-5) followed by CDDP (d6-10) group (IR: 61% vs 36%, P<0.01) in the independent study. Net BW, SI, TI and the amount of blood cells of mice in Gefitinib alone group were not significantly different from those in control groups.

CONCLUSION: Gefitinib can significantly inhibit the growth of murine H22 hepatocellular carcinoma. If Gefitinib is used after CDDP treatment in animal experiments, the inhibitory effect could be enhanced.

The ErbB2/Neu/HER2 receptor is a new calmodulin-binding protein

We have demonstrated previously that the EGFR (epidermal growth factor receptor) is a calmodulin (CaM)-binding protein. To establish whether or not the related receptor ErbB2/Neu/HER2 also binds CaM, we used human breast adenocarcinoma SK-BR-3 cells, because these cells overexpress this receptor thus facilitating the detection of this interaction. In the present paper, we show that ErbB2 could be pulled-down using CaM-agarose beads in a Ca2+-dependent manner, as detected by Western blot analysis using an anti-ErbB2 antibody. ErbB2 was also isolated by Ca2+-dependent CaM-affinity chromatography. We also demonstrate using an overlay technique with biotinylated CaM that CaM binds directly to the immunoprecipitated ErbB2. The binding of biotinylated CaM to ErbB2 depends strictly on the presence of Ca2+, since it was prevented by the presence of EGTA. Moreover, the addition of an excess of free CaM prevents the binding of its biotinylated form, demonstrating that this was a specific process. We excluded any interference with the EGFR, as SK-BR-3 cells express considerably lower levels of this receptor, and no detectable EGFR signal was observed by Western blot analysis in the immunoprecipitated ErbB2 preparations used to perform the overlay assays with biotinylated CaM. We also demonstrate that treating living cells with W7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide], a cell-permeant CaM antagonist, down-regulates ErbB2 phosphorylation, and show that W7 does not interfere non-specifically with the activity of ErbB tyrosine kinases. We also show that W7 inhibits the phosphorylation (activation) of both ERK1/2 (extracellular-signal-regulated kinases 1 and 2) and Akt/PKB (protein kinase B), in accordance with the inhibition observed in ErbB2 phosphorylation. In contrast, W7 treatment increased the phosphorylation (activation) of CREB (cAMP-response-element-binding protein) and ATF1 (activating transcription factor-1), two Ca2+-sensitive transcription factors that operate downstream of these ErbB2 signalling pathways, most likely because of the absence of calcineurin activity. We conclude that ErbB2 is a new CaM-binding protein, and that CaM plays a role in the regulation of this receptor and its downstream signalling pathways in vivo.

Endogenous calmodulin interacts with the epidermal growth factor receptor in living cells

We have previously shown that exogenous calmodulin (CaM) binds to the epidermal growth factor receptor (EGFR) at its cytosolic juxtamembrane region inhibiting its tyrosine kinase activity. We demonstrate in this report that endogenous CaM binds to EGFR in intact cells as CaM co-immunoprecipitates with EGF-activated and non-activated receptors. We also show in living cells that cell-permeable CaM inhibitors prevent the full transphosphorylation of wild type EGFR but not the transphosphorylation of an insertional EGFR mutant in which the CaM-binding domain was divided into two parts. Overall these results suggest that CaM interacts with EGFR in vivo.

Protective effect of angelica sinensis polysaccharide on experimental immunological colon injury in rats

AIM: To study the effect of angelica sinensis polysaccharide (ASP) on immunological colon injury and its mechanisms in rats.

METHODS: Immunological colitis model of rats was induced by intracolon enema with 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) and ethanol. The experimental animals were randomly divided into normal control, model control, 5-aminosalicylic acid therapy groups and three doses of ASP therapy groups. The 6 groups were treated intracolonically with normal saline, normal saline, 5-aminosalicylic acid (100 mg·kg^-1), and ASP daily (8: 00 am) at the doses of 200, 400 and 800 mg·kg^-1 respectively for 21 days 7 d following induction of colitis. The rat colon mucosa damage index (CMDI), the histopathological score (HS), the score of occult blood test (OBT), and the colonic MPO activity were evaluated. The levels of SOD, MDA, NO, TNF-α, IL-2 and IL-10 in colonic tissues were detected biochemically and immunoradiometrically. The expressions of TGF-β and EGF in colonic tissues were also determined immunochemically.

RESULTS: Enhanced colonic mucosal injury, inflammatory response and oxidative stress were observed in colitis rats, which manifested as significant increases of CMDI, HS, OBT, MPO activity, MDA and NO contents, as well as the levels of TNF-α and IL-2 in colonic tissues, although colonic TGF-β protein expression, SOD activity and IL-10 content were significantly decreased compared with the normal control (P < 0.01). However, these parameters were found to be significantly ameliorated in colitis rats treated intracolicly with ASP at the doses of 400 and 800 mg·kg^-1 (P < 0.05-0.01). Meantime, colonic EGF protein expression in colitis rats was remarkably up-regulated.

CONCLUSION: ASP has a protective effect on immunological colon injury induced by TNBS and ethanol enema in rats, which was propably due to the mechanism of antioxidation, immunomodulation and promotion of wound repair.

FT-IR spectroscopic analysis of normal and cancerous tissues of esophagus

AIM: To investigate the special Fourier transform infrared spectroscopy (FT-IR) spectra in normal and cancerous tissues of esophagus.

METHODS: Twenty-seven pairs of normal and cancerous tissues of esophagus were studied by using FT-IR and the special spectra characteristics were analyzed in different tissues.

RESULTS: Different spectra were found in normal and cancerous tissues. The peak at 1550/cm was weak and wide in cancerous tissues but strong and high in normal tissues.The ratio of I 1647/I 1550 was 2.0 in normal tissues and 2.36 in cancerous tissues (P < 0.05). The ratio of I 1550/I 1080 was 4.5 in normal tissues and 3.4 in cancerous tissues (P < 0.01). The peak at 1453/cm was higher than at 1402/cm in normal tissue and lower than at 1402/cm in cancerous tissues.

CONCLUSION: The results indicate that FTIR may be used in clinical diagnosis.

Establishment of apoptotic model induced by hydroxyapatite nanoparticles in human hepatoma cell line BEL-7402

AIM

To establish an apoptotic model induced by hydroxyapatite (HAP) nanoparticles in human hepatoma cell line in vitro in order to explore the mechanism of nanoparticles-induced apoptosis.

METHODS

The selected human hepatoma cell line BEL-7402 was treated with HAP nanoparticles at different concentrations and for various durations of time. Growth suppression was evaluated by MTT method. Apoptosis-related alterations in morphology and biochemistry were ascertained under cytochemical staining (Hoechst 33 258), transmission electron microscopy (TEM), and DNA agarose gel electrophoresis. Flow cytometry (FCM) was used to investigate the apoptotic rate.

RESULTS

HAP nanoparticles inhibited the growth of hepatoma cells in a dose and time-dependent manner. After BEL-7402 cells were treated with 50-200 mg/L HAP nanoparticles for 48 h, apoptosis with nuclear chromatin condensation and fragmentation as well as cell shrinkage were observed using fluorescent staining and TEM. DNA ladder could be demonstrated on DNA electrophoresis. By FCM analysis, the apoptotic rates at concentrations of 0 mg/L, 50 mg/L,75 mg/L, 100 mg/L, 150 mg/L, 200 mg/L were 2.2%, 20.3%, 25.3%, 29.8%, 45.1% and 53.1%, respectively. Cell apoptosis began approximately at 12h after administration of 50 mg/L and peaked at 48 h following treatment. The rates at 12, 24, 36, and 48 h were 2.7%, 3.5%, 6.3%, and 21.4%, respectively.

CONCLUSION

HAP nanoparticles not only inhibit proliferation but also induce apoptosis of human hepatoma cell line BEL-7402 in vitro. The successful establishment of this model will help further explore the molecular mechanism of hepatoma cells apoptosis.

Effects of hydroxyapatite nanoparticles on proliferation and apoptosis of human hepatoma BEL-7402 cells

AIM: To study the effect of hydroxyapatite (HAP) nanoparticles on human hepatoma cell line BEL-7402 in vitro.

METHODS: The human hepatoma cell line BEL-7402 was cultured and treated with HAP nanoparticles at various concentrations. Growth suppression was detected with MTT colorimetric assay, cell apoptotic alterations were evaluated by cytochemical staining (Hoechst 33258), transmission electron microscopy (TEM), and flow cytometry (FCM).

RESULTS: HAP nanoparticles inhibited the growth of hepatoma cells in a dose-dependent manner, with IC₅₀ values of 29.30 mg/L. Treated with 50-200 mg/L HAP nanoparticles for 48 h, BEL-7402 cells apoptosis with nuclear chromatin condensation and fragmentation as well as cell shrinkage and the formation of apoptotic bodies were observed under cytochemical staining and transmission electron microscopy. FCM analysis showed hypodiploid peaks on histogram, the apoptotic rates at the concentrations of 50, 75, 100, 150 and 200 mg/L of HAP nanoparticles were 20.35 ± 2.23%, 25.35 ± 1.92%, 29.34 ± 4.61%, 44.92 ± 3.78% and 53.64 ± 3.49%, respectively, which were all significantly higher than that of control group 2.23 ± 0.14%. There was a significant correlation between HAP nanoparticle concentration and apoptotic rate (r = 0.994, P < 0.01).

CONCLUSION: HAP nanoparticles not only inhibit proliferation but also induce apoptosis of human hepatoma cell line BEL-7402 in vitro.