Carcinogen-induced alteration in liver epidermal growth factor receptor distribution during the promotion stage of hepatocarcinogenesis in rat

Immunohistochemical Expression of Epidermal Growth Factor Receptor in Hepatocellular Carcinoma

INTRODUCTION

Epidermal growth factor receptor (EGFR) signaling plays an important role in various cancers, including hepatocellular carcinoma (HCC). We aimed to evaluate immunoexpression of EGFR in HCC and surrounding non-tumor liver tissue and to correlate it to multiple clinicopathologic data.

MATERIAL AND METHODS

We analyzed 60 patients with HCC for multiple clinicopathologic characteristics and survival. Presence of the immunosignal and the percentage of positive tumor cells at the whole tumor tissue sample and adjacent cirrhotic liver tissue were semi-quantitatively determined.

RESULTS

Nineteen patients (31.67%) were female and 41 (68.33%) were male ranging in age from 31 to 85 years, median 61.88±10.51. Mean survival time for female patients was 8.86±1.76 months, for male 13.03±1.50 months and overall survival was 11.6051±1.19 months. The most patients had: T2 status (41.67%), no enlarged lymph nodes (90%), vascular invasion (63.33%) and well differentiated (43.33%) tumors. EGFR immunoexpression was determined in range from 0% to 100% in both tumor and non-tumor tissue with mean value of 39.58% in tumor and 86.86% in cirrhotic tissue (p<0.00). Higher percent of tumor EGFR positive cells were found in cases with higher T status, higher levels of AFP and poorly differentiated carcinoma, but not significantly. Lower percent of tumor EGFR positive cells were found in patients with vascular invasion and enlarged lymph nodes, but also not significantly. EGFR expression in tumor tissue significantly influenced survival of the patients (p<0.05).

CONCLUSION

The study showed that expression of EGFR in lower percentage of tumor cells was associated to favorable prognosis, making it a potential prognostic marker and therapeutic target.

Missense Mutations in Exons 18-24 of EGFR in Hepatocellular Carcinoma Tissues

Epidermal growth factor receptor (EGFR), a transmembrane tyrosine kinase receptor, plays important roles in various cancers. In nonsmall cell lung cancer (NSCLC), EGFR mutations cluster around the ATP-binding pocket (exons 18-21) and some of these mutations activate the kinase and induce an increased sensitivity to EGFR-tyrosine kinase inhibitors. Nevertheless, data of EGFR mutations in HCC are limited. In this study, we investigated EGFR expression by immunohistochemistry and EGFR mutations (exons 18-24) by PCR cloning and sequencing. EGFR overexpression in HCC and matched nontumor tissues were detected in 13/40 (32.5%) and 10/35 (28.6%), respectively. Moreover, missense and silent mutations were detected in 13/33 (39.4%) and 11/33 (33.3%) of HCC tissues, respectively. The thirteen different missense mutations were p.L730P, p.V742I, p.K757E, p.I780T, p.N808S, p.R831C, p.V851A, p.V897A, p.S912P, p.P937L, p.T940A, p.M947V, and p.M947T. We also found already known SNP, p.Q787Q (CAG>CAA), in 13/33 (39.4%) of HCC tissues. However, no significant association was detected between EGFR mutations and EGFR overexpression, tissue, age, sex, tumor size, AFP, HBsAg, TP53, and Ki-67. Further investigation is warranted to validate the frequency and activity of these missense mutations, as well as their roles in HCC tumorigenesis and in EGFR-targeted therapy.

Molecular imaging of hepatocellular carcinoma xenografts with epidermal growth factor receptor targeted affibody probes

Hepatocellular carcinoma (HCC) is a highly aggressive and lethal cancer. It is typically asymptomatic at the early stage, with only 10%–20% of HCC patients being diagnosed early enough for appropriate surgical treatment. The delayed diagnosis of HCC is associated with limited treatment options and much lower survival rates. Therefore, the early and accurate detection of HCC is crucial to improve its currently dismal prognosis. The epidermal growth factor receptor (EGFR) has been reported to be involved in HCC tumorigenesis and to represent an attractive target for HCC imaging and therapy. In this study, an affibody molecule, Ac-Cys-Z_EGFR:1907, targeting the extracellular domain of EGFR, was used for the first time to assess its potential to detect HCC xenografts. By evaluating radio- or fluorescent-labeled Ac-Cys-Z_EGFR:1907 as a probe for positron emission tomography (PET) or optical imaging of HCC, subcutaneous EGFR-positive HCC xenografts were found to be successfully imaged by the PET probe. Thus, affibody-based PET imaging of EGFR provides a promising approach for detecting HCC in vivo.

Growth suppression of human hepatocellular carcinoma xenografts by a monoclonal antibody CH12 directed to epidermal growth factor receptor variant III

Human hepatocellular carcinoma (HCC) is considered difficult to cure because it is resistant to radio- and chemotherapy and has a high recurrence rate after curative liver resection. Epidermal growth factor receptor variant III (EGFRvIII) has been reported to express in HCC tissues and cell lines. This article describes the efficacy of an anti-EGFRvIII monoclonal antibody (mAb CH12) in the treatment of HCC xenografts with EGFRvIII expression and the underlying mechanism of EGFRvIII as an oncogene in HCC. The results demonstrated that CH12 bound preferentially to EGFRvIII with a dissociation constant (K(d)) of 1.346 nm/liter. In addition, CH12 induces strong antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in Huh7-EGFRvIII (with exogenous expression of EGFRvIII) and SMMC-7721 (with endogenous expression of EGFRvIII) cells. Notably, CH12 significantly inhibited the growth of Huh7-EGFRvIII and SMMC-7721 xenografts in vivo with a growth inhibition ratio much higher than C225, a U. S. Food and Drug Administration-approved anti-EGFR antibody. Treatment of the two HCC xenografts with CH12 significantly suppressed tumor proliferation and angiogenesis. Mechanistically, in vivo treatment with CH12 reduced the phosphorylation of constitutively active EGFRvIII, Akt, and ERK. Down-regulation of the apoptotic protectors Bcl-x(L), Bcl-2, and the cell cycle regulator cyclin D1, as well as up-regulation of the cell-cycle inhibitor p27, were also observed after in vivo CH12 treatment. Collectively, these results indicate that the monoclonal antibody CH12 is a promising therapeutic agent for HCC with EGFRvIII expression.

Cellular Proliferation, Cell Death, and Liver Histology in Gambusia affinis After Dietary Exposure to Benzidine and 2-Aminofluorene

Chronic exposure to arylamines through diet and/or smoking has been associated with genetic changes and tumorigenesis. Cellular proliferation, apoptosis, and histological changes in liver tissue were investigated in Gambusia affinis ( G affinis) after chronic dietary exposure to 6.9 mM and 0.069 mM concentrations of benzidine (BZ), 2-aminofluorene (2AF), and their combination for 4, 8, and 12 weeks, respectively. The proliferation assay indicated non–dose-dependent increases in cellular proliferation over the controls for all treatment groups at 4 and 12 weeks but not at 8 weeks except for the low dose of 2AF. The apoptosis assay showed effects in the low-dose group of 2AF and BZ at 4 weeks only. Hematoxylin/eosin staining of liver tissue revealed an increase in oval/spindle cell proliferation and altered foci formation in the treated groups compared with controls. These results demonstrate a mammalian-like response to 2AF and BZ in G affinis liver.

HB-EGF is a paracrine growth stimulator for early tumor prestages in inflammation-associated hepatocarcinogenesis

BACKGROUND/AIMS

We studied the impact of heparin-binding epidermal growth factor-like growth factor (HB-EGF) on inflammation-driven hepatocarcinogenesis.

METHODS

HB-EGF expression was determined by qRT-PCR and immunodetection in hepatocellular adenoma and carcinoma and in mesenchymal (MC) and parenchymal liver cells obtained from different models of inflammation. The functions of HB-EGF in early hepatocarcinogenesis were assessed in co-cultures of unaltered and initiated/premalignant hepatocytes.

RESULTS

In human and rat (pre)malignant liver lesions, HB-EGF levels were comparable to that of the surrounding tissue. In inflamed livers HB-EGF was expressed predominantly in MC and was further increased by pro-inflammatory lipopolysaccharide (LPS) or linoleic acid hydroperoxide (LOOH). In culture, DNA-replication occurred rather in initiated/premalignant than unaltered hepatocytes and was further elevated by LOOH- or LPS-stimulated MC-supernatants. The supernatant effects were abrogated by pre-incubation with HB-EGF-neutralizing antisera. HB-EGF itself induced DNA-replication and mitosis preferentially in the initiated/premalignant cells. When transducing hepatocytes with a dominant-negative ErbB1-construct, HB-EGF-induced DNA-replications were blocked completely in unaltered hepatocytes but incompletely in initiated/premalignant cells, which suggests elevated ErbB-mediated signal transduction in first stages of hepatocarcinogenesis.

CONCLUSIONS

Pro-inflammatory stimuli induce the release of HB-EGF from MC, which stimulates DNA-replication in initiated/premalignant hepatocytes. Similar mechanisms may contribute to carcinogenesis in human inflammatory liver diseases.

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.

Targeting the epidermal growth factor receptor by gefitinib for treatment of hepatocellular carcinoma

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death worldwide. Due to very poor 5-year-survival new therapeutic approaches are mandatory. Gefitinib, an inhibitor of epidermal growth factor receptor tyrosine kinase (EGFR-TK), potently suppresses the growth of various tumors, but its effect on HCC remains unexplored. We therefore studied the antineoplastic potency of gefitinib in human HCC cells.

RESULTS

Gefitinib induced a time- and dose-dependent growth inhibition of the human HCC cell lines Huh-7 and HepG2. Gefitinib-treatment induced both mitochondria-dependent and -independent apoptosis. Changes in mitochondrial membrane potential and caspase-8 activation, followed by caspase-3 activation and nuclear degradation, were detected. Moreover, gefitinib induced cell cycle arrest at the G1/S checkpoint and decreased the phosphorylation of mitogen-activated protein kinase ERK1/2. Finally, gefitinib suppressed the expression of antiapoptotic Bcl-2 and Bcl-X(L), further rendering HCC cells prone to apoptosis.

CONCLUSIONS

Our data demonstrate that the inhibition of EGFR-TK by gefitinib induced growth inhibition, apoptosis and cell cycle arrest in human HCC cells. Thus, EGFR-TK inhibition appears to be a promising novel approach for future treatment strategies of HCC.

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

AIM: Many growth factors, such as epidermal growth factor (EGF), are associated with the carcinogenesis. EGF plays its role in the proliferation of hepatoma cells through binding with EGF receptor (EGFR) and a series of signal transduction. But the postreceptor pathway is still not clear. In the present experiment, we studied the effect of tyrosine kinase, protein kinase C, Na⁺/H⁺ exchange, calmodulin and voltage-dependent Ca²⁺ channel on EGF-induced hepatoma cell proliferation.

METHODS: Hepatoma cell line SMMC7721 was cultured in RPMI1640 serum-free medium. In order to study the effect of thyrosine kinase, protein kinase C, Na⁺/H⁺ exchange, calmodulin and voltage-dependent Ca²⁺ channel on human heptoma cell proliferation induced by epidermal growth factor (EGF), DNA synthesis rate of hepatoma cells was measured by the method of ³H-TdR incorporation.

RESULTS: EGF (10^-9 M) stimulated the proliferation of heptoma cells significantly (³H-TdR incorporation was 1880 ± 281 cpm/well, P < 0.05), and this effect was significantly inhibited by tyrosine kinase inhibitor genistein (³H-TdR incorporation was 808 ± 209 cpm/well, P < 0.001). Calmodulin inhibitor W-7, protein kinase C inhibitor H-7 and Na⁺/H⁺ exchange inhibitor amiloride individually had significant inhibiting effect on EGF-induced proliferation of hepatoma cells (³H-TdR incorporation was 978 ± 87.3 cpm/well, 1241 ± 147 cpm/well, 1380 ± 189 cpm/well, respectivly, P < 0.001, P < 0.01, P < 0.05), but they all had no effect on the basal level proliferation of cultured hepatoma cells (³H-TdR incorporation was 1284 ± 260 cpm/well, 1179 ± 150 cpm/well, 1392 ± 152 cpm/well, respectivly, ³H-TdR incorporation of the control was 1353 ± 175 cpm/well, P > 0.05). Voltage-dependent Ca²⁺ channel inhibitor verapamil had no inhibition on EGF-induced proliferation of hepatoma cells (³H-TdR incorporation was 1637 ± 133 cpm/well, P > 0.05), it also had no effect on the basal level proliferation of cultured hepatoma cells (³H-TdR incorporation was 1196 ± 12 cpm/well, P > 0.05).

CONCLUSION: Our data suggest that tyrosine kinase, Ca²⁺-calmodulin-dependent pathway, protein kinase C and Na⁺/H⁺ exchange play a critical role in EGF-induced proliferation of hepatoma cells and that the effect of EGF is independent of voltage-dependent Ca²⁺ channel.

Expression of epidermal growth factor and its receptor in cirrhotic liver disease

Polypeptide growth factors, including epidermal growth factor (EGF), play a central role in regulating hepatocyte growth both in vivo and in primary culture. To characterize EGF gene expression in the pathogenesis of regenerative cirrhotic fibrosis, we employed biotinylated antisense oligonucleotide probes to localize hepatic mRNA transcripts in situ. In control tissue and regenerative hepatic nodules, EGF receptor (EGFR) mRNA transcripts were expressed constitutively. In contrast, oligonucleotide probes targeting the human EGF coding region showed that EGF transcription was extremely low in control liver but was highly elevated and localized to regenerative hepatic nodules and bile duct epithelia of cirrhotic liver. To determine whether EGF mRNA accumulation accompanied a comparable increase in the EGF peptide, we performed immunohistochemistry using an antibody specific for the nonprocessed peptide aminoterminus. We observed that positive localized EGF staining paralleled its mRNA transcript. These results indicate that EGF upregulation is a characteristic of cirrhotic liver disease and suggest that persistent de novo ligand synthesis and its signaling contribute to an autocrine-mediated hepatocyte proliferation within the regenerative nodule.