Expression of transforming growth factor alpha and epidermal growth factor receptor in human hepatocellular carcinoma

The impact of new data in the treatment of advanced hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide, causing 500,000 deaths yearly. The risk factors mostly responsible for the rising incidence of HCC in the Western hemisphere are hepatitis C, alcoholic cirrhosis, and nonalcoholic steatohepatitis, which most commonly leads to HCC in the setting of cirrhosis. Over the past 30 years, several chemotherapeutic single agents and combinations have been tested in HCC, yet none have demonstrated any improvement in survival. Recently, the multitargeted anti-angiogenic and Raf kinase inhibitor sorafenib has shown a survival advantage as a single agent and improved outcomes in combination with doxorubicin. Other novel agents have also shown intriguing outcomes as single agents (sunitinib) or in combination (bevacizumab and erlotinib). The encouraging results and clinical information gathered in recent trials are generating important clinical questions regarding which patients to treat, how to accommodate concurrent cirrhosis, and which parameters to use to monitor efficacy and the potential benefit from therapy.

[Molecular pathogenesis of hepatocellular carcinoma: new therapeutic approaches and predictive pathology]

Hepatocellular carcinoma is one of the most prevalent malignancies worldwide and its incidence is increasing. Multimodal strategies directed towards this carcinoma include primary (e.g. immunisation) and secondary (e.g. antiviral therapy) prevention, surgical approaches, novel specific systemic therapies (targeted therapy), and the treatment of comorbidity (cirrhosis). New molecular approaches are currently under development. These tackle several specific targets, with pathology being challenged in many aspects: experimental evaluation, the development of valid tumor-relevant diagnostic tests as well as morphological evaluation in the context of clinical studies, and finally in routine diagnosis.

Epidermal growth factor receptor expression and gene copy number in conventional hepatocellular carcinoma

Epidermal growth factor receptor (EGFR) is frequently overexpressed in hepatocellular carcinoma, but its relationship with EGFR gene copy number has not been studied. This study examined EGFR expression and gene copy number in hepatocellular carcinoma and evaluated their relationship to clinicopathologic features in 76 tumors. Moderate to strong expression of EGFR was observed by immunohistochemical analysis in 50 (66%) of 76 hepatocellular carcinomas. Fluorescence in situ hybridization (FISH) showed extra EGFR gene copies in 17 (45%) of 38 tumors. This was accompanied by gains of chromosome 7, indicating that this was the result of balanced polysomy rather than gene amplification. There was no correlation between EGFR expression by immunohistochemical analysis and gene copy number by FISH. EGFR expression showed borderline association with cirrhosis but not with other clinicopathologic parameters examined. EGFR overexpression is present in a majority of hepatocellular carcinomas, suggesting a role for EGFR antagonists in therapy. The increased expression does not correlate with an increase in the EGFR gene copy number.

Development of sorafenib and other molecularly targeted agents in hepatocellular carcinoma

It is well appreciated that hepatocellular carcinoma (HCC) represents one of the most challenging malignancies of worldwide importance. In fact, HCC is the fifth most common cancer and the third most common cause of cancer-related death globally. The incidence rates for HCC in the U.S. and Western Europe have been rising. Unresectable or metastatic HCC carries a poor prognosis, and systemic therapy with cytotoxic agents provides marginal benefit. Because of the poor track record of systemic therapy in HCC, there has been a sense of nihilism for this disease in the oncology community for decades. However, with the arrival of newly developed, molecularly targeted agents and the success of some of these agents in other traditionally challenging cancers, such as renal cell carcinoma, there has been renewed interest in developing novel systemic therapy in HCC. At the recent Annual Meeting of the American Society of Clinical Oncology, results of a phase 3, randomized, placebo-controlled trial were presented in which sorafenib demonstrated improved survival in patients with advanced HCC. This landmark study represents the first agent that has demonstrated an improved overall survival benefit in this disease and sets the new standard for first-line treatment of advanced HCC. For this review, the author concisely summarized the current status of molecularly targeted agents that are under clinical development in advanced HCC.

Phase 2 study of cetuximab in patients with advanced hepatocellular carcinoma

BACKGROUND

Epidermal growth factor receptor (EGFR) and ligand expression is frequently seen in hepatocellular carcinoma (HCC). A phase 2 study was performed with cetuximab, a chimeric monoclonal antibody that binds specifically to EGFR, in patients with advanced HCC.

METHODS

Eligibility criteria included unresectable or metastatic measurable HCC, an Eastern Cooperative Oncology Group performance status <or=2, Cancer of the Liver Italian Program (CLIP) score <or=3, and adequate organ functions. The initial dose of cetuximab was 400 mg/m(2) given intravenously followed by weekly intravenous infusions at 250 mg/m(2). Each cycle was defined as 6 consecutive weekly treatments. EGFR expression was assayed by immunohistochemistry and trough serum concentrations of cetuximab were determined during the first cycle.

RESULTS

Thirty patients were enrolled and assessable for efficacy and toxicity. No responses were seen. Five patients had stable disease (median time, 4.2 months; range, 2.8-4.2 months). The median overall survival was 9.6 months (95% confidence interval [CI], 4.3-12.1 months) and the median progression-free survival (PFS) was 1.4 months (95% CI, 1.2-2.6 months). The treatment was generally well tolerated. No treatment-related grade 4-5 toxicities occurred. Grade 3 (according to the National Cancer Institute's Common Terminology Criteria for Adverse Events [version 3.0]) aspartate aminotransferase, hypomagnesemia, and fever without neutropenia were noted in 1 patient (3.3%) each. On Week 6 of Cycle 1, arithmetic mean serum cetuximab concentrations for patients with Child-Turcotte-Pugh (CTP) A and CTP B disease were 47.6 mcg/mL and 66.9 mcg/mL, respectively.

CONCLUSIONS

Although cetuximab could be safely administered with tolerable toxicity profiles, it demonstrated no antitumor activity in HCC in this phase 2 study. Cetuximab trough concentrations were not notably altered in patients with mild to moderate hepatic dysfunction.

Hepatocellular carcinoma: epidemic and treatment

Hepatocellular carcinoma remains a worldwide epidemic. Survival rates are poor; however, oncologists are able to offer regional therapies to those patients who present with early disease. Prevention through vaccination remains a mainstay of this epidemic. New staging systems that incorporate important information about tumor characteristics and liver disease improve our ability to prognosticate and treat these patients.

Cimetidine inhibits epidermal growth factor-induced cell signaling

BACKGROUND

Cimetidine, a histamine-2 (H2) receptor antagonist, has been demonstrated to have anticancer effects on colorectal cancer, melanoma and renal cell carcinoma. In the current study, we clarified that cimetidine inhibits both epidermal growth factor (EGF)-induced cell proliferation and migration in hepatocellular carcinoma (HCC) cell lines.

METHOD

HCC cell lines (Hep3B, HLF, SK-Hep-1, JHH-2, PLC/PRF/5 and HLE) were used and cell proliferation was assessed by [3H]-thymidine incorporation assay. Cell migration was measured by in vitro cell migration assay. Biological effects of cimetidine were assessed with human EGF receptor (EGFR)-expressing mouse fibroblast cells (NR6-WT). The autophosphorylation of EGFR and the activation of other downstream effectors were analyzed by immunoprecipitation and immunoblotting. The concentration of intracellular cyclic AMP (cAMP) was measured by competitive enzyme immunoassay.

RESULTS

Cimetidine inhibited both EGF-induced cell proliferation and migration in Hep3B, HLF, SK-Hep-1 and JHH-2, while cimetidine did not affect EGF-induced cell proliferation and migration in PLC/PRF/5 and HLE. Cimetidine was revealed to disrupt the EGF-induced autophosphorylation of EGFR and its downstream effectors, mitogen activated protein kinases and phospholipase C-gamma. To define the molecular basis of this negative regulation, we identified that cimetidine significantly decreased intracellular cAMP levels and that decrement of cAMP inhibited autophosphorylation of EGFR. The cell permeable cAMP analog, CPT-cAMPS reversed the cimetidine-induced inhibition of EGF-induced cell proliferation and cell migration by restoring autophosphorylation of EGFR.

CONCLUSION

Cimetidine inhibited EGF-induced cell proliferation and migration in HCC cell lines by decreasing the concentration of intracellular cAMP levels. Cimetidine may be a candidate chemopreventive agent for HCC.

New molecular targets for hepatocellular carcinoma: the ErbB1 signaling system

Hepatocellular carcinoma (HCC) is a major cause of cancer-related deaths. This malignancy is often diagnosed at an advanced state, when most potentially curative therapies are of limited efficacy. In addition, HCC is a type of tumor highly resistant to available chemotherapeutic agents, which leaves HCC patients with no effective therapeutic options and a poor prognosis. From a molecular perspective, HCC is a heterogeneous type of tumor. However, in most cases, HCC emerges on a background of persistent liver injury, inflammation and hepatocellular proliferation, which is characteristic of chronic hepatitis and cirrhosis. Recent studies have revealed that dysregulation of a limited number of growth and survival-related pathways can play a key role in HCC development. The epidermal growth factor receptor (ErbB1) can be bound and activated by a broad family of ligands, and can also engage in extensive cross talk with other signaling pathways. This system is considered as an important defense mechanism for the liver during acute tissue injury; however, accumulating evidences suggest that its chronic stimulation can participate in the neoplastic conversion of the liver. Agents that target the ErbB1 receptor have shown antineoplastic activity in other types of tumors, but their efficacy either alone or in combination with other compounds has just started to be tested in experimental and human HCC. Here, we review the evidences that support the involvement of the ErbB1 in HCC development and that provide a rationale for ErbB1 targeting in HCC prevention and treatment.

COX-2 expression in hepatocellular carcinoma is an initiation event; while EGF receptor expression with downstream pathway activation is a prognostic predictor of survival

INTRODUCTION

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is a leading cause of cancer mortality with over 90% of HCC patients succumbing to the disease. Current systemic therapies have had no measurable impact on survival in this disease; however there are small subsets of patients who benefit from systemic therapy who have been difficult to identify. Improvements in patient stratification and the development of biological therapies have resulted from the elucidation of the molecular mechanisms integral to tumor development and progression. Recent studies have found that COX-2 and EGFR are frequently inappropriately expressed in HCC compared to normal liver expression; however the presence of surface receptors does not always mean that the downstream pathway is active. In this study, we investigate the incidence and impact of activated EGFR downstream messengers phosphorylated akt (pakt) and/or phosphorylated MAPK (pMAPK) on survival in patients with HCC.

METHOD

Thirty consecutive HCC patients treated at a single institution were retrospectively reviewed. Patient data including age, sex, Child's score, histological type, grade, stage, and survival were analyzed. Immunohistochemical staining was performed on formalin fixed, paraffin embedded tissues using monoclonal antibodies to COX-2, EGF receptor, pMAPK, and pakt. Histoscores were determined for each marker and evaluated for impact in survival, stage, and tumor grade.

RESULTS

The median age was 67 years (39-83) and 67% of patients were male. Median survival was 9.8 months (1-47 months) for the whole group. COX-2 and EGFR expression was present in 90 and 67% of the tumors, respectively. Expression of activated downstream EGFR messengers was present in 53% of tumors (pMAPK 41%, pakt 31%). Median survival was significantly better in patients with downstream messenger expression, 24.4 months, compared to no expression, 4.7 months (P = 0.03). These groups were matched in age, stage, and Child's score.

CONCLUSION

COX-2 and EGFR expression are commonly seen in HCC. Activated downstream EGFR expression is also common in HCC and is a predictor of improved survival. There may be a therapeutic role for EGFR tyrosine kinase inhibitors in this subset of patients and further investigation is warranted.

EGFR is phosphorylated at Ty845 in hepatocellular carcinoma

Epidermal growth factor receptor (EGFR) is overexpressed in a significant proportion of hepatocellular carcinomas. Recent studies of EGFR inhibitors to treat hepatocellular carcinoma have been encouraging and better understanding of EGFR signaling may lead to more effective strategies for inhibiting this key pathway. The EGFR can be phosphorylated at different tyrosine sites, leading to subsequent activation of different pathways. Cell line and animal studies have shown that MAPK and STAT-3 are important mediators of the EGFR signal in liver cells. However, little is known about EGFR phosphorylation and subsequent signaling in primary hepatocellular carcinoma. We investigated the site of EGFR phosphorylation by Western blot in 18 hepatocellular carcinomas. Fourteen of 18 hepatocellular carcinomas had detectable EGFR by Western blotting and 13 of 14 showed phosphorylation at tyrosine 845. In contrast, no EGFR phosphorylation was detected at tyrosine 998, tyrosine 1045, or tyrosine 1068, which signal through other pathways including STAT-3 and MAPK. These findings were further explored by examination of EGFR expression and signaling pathway activation in tissue arrays comprised of 73 hepatocellular carcinomas using antibodies that recognize phosphorylated (or activated) proteins. Tissue array studies also found no correlation between EGFR expression (29% of cases) and STAT-3 nuclear positivity (16%), AKT (4%), MAPK (3%), or STAT-5 (3%) positivity, all P>0.05. EGFR expression was correlated with hepatitis B infection, but not with tumor size, nuclear grade, or proliferative rate. We conclude that EGFR is phosphorylated at tyrosine 845 in most hepatocellular carcinomas and that EGFR expression by immunohistochemistry does not correlate well with STAT-3, STAT-5, MAPK, or AKT immunostaining.

Gene expression profile related to the progression of preneoplastic nodules toward hepatocellular carcinoma in rats

In this study, we investigated the time course gene expression profile of preneoplastic nodules and hepatocellular carcinomas (HCC) to define the genes implicated in cancer progression in a resistant hepatocyte model. Tissues that included early nodules (1 month, ENT-1), persistent nodules (5 months, ENT-5), dissected HCC (12 months), and normal livers (NL) from adult rats were analyzed by cDNA arrays including 1185 rat genes. Differential genes were derived in each type of sample (n = 3) by statistical analysis. The relationship between samples was described in a Venn diagram for 290 genes. From these, 72 genes were shared between tissues with nodules and HCC. In addition, 35 genes with statistical significance only in HCC and with extreme ratios were identified. Differential expression of 11 genes was confirmed by comparative reverse transcription-polymerase chain reaction, whereas that of 2 genes was confirmed by immunohistochemistry. Members involved in cytochrome P450 and second-phase metabolism were downregulated, whereas genes involved in glutathione metabolism were upregulated, implicating a possible role of glutathione and oxidative regulation. We provide a gene expression profile related to the progression of nodules into HCC, which contributes to the understanding of liver cancer development and offers the prospect for chemoprevention strategies or early treatment of HCC.

Signaling pathways involved in the inhibition of epidermal growth factor receptor by erlotinib in hepatocellular cancer

AIM: To examine the underlying mechanisms of erlotinib-induced growth inhibition in hepatocellular carcinoma (HCC).

METHODS: Erlotinib-induced alterations in gene expression were evaluated using cDNA array technology; changes in protein expression and/or protein activation due to erlotinib treatment as well as IGF-1-induced EGFR transactivation were investigated using Western blotting.

RESULTS: Erlotinib treatment inhibited the mitogen activated protein (MAP)-kinase pathway and signal transducer of activation and transcription (STAT)-mediated signaling which led to an altered expression of apoptosis and cell cycle regulating genes as demonstrated by cDNA array technology. Overexpression of proapoptotic factors like caspases and gadds associated with a down-regulation of antiapoptotic factors like Bcl-2, Bcl-X_L or jun D accounted for erlotinib's potency to induce apoptosis. Downregulation of cell cycle regulators promoting the G₁/S-transition and overexpression of cyclin-dependent kinase inhibitors and gadds contributed to the induction of a G₁/G₀-arrest in response to erlotinib. Furthermore, we displayed the transactivation of EGFR-mediated signaling by the IGF-1-receptor and showed erlotinib’s inhibitory effects on the receptor-receptor cross talk.

CONCLUSION: Our study sheds light on the under-standing of the mechanisms of action of EGFR-TK-inhibition in HCC-cells and thus might facilitate the design of combination therapies that act additively or synergistically. Moreover, our data on the pathways responding to erlotinib treatment could be helpful in predicting the responsiveness of tumors to EGFR-TKIs in the future.

Expression of betacellulin and epidermal growth factor receptor in hepatocellular carcinoma: implications for angiogenesis

Hepatocellular carcinoma (HCC) is becoming one of the common malignant tumors worldwide and is characterized by high vascularity. Angiogenesis (formation of new microvessels) is critical for growth and progression of various human solid tumors. Betacellulin (BTC) is a member of the epidermal growth factor (EGF) family, and its signal action is mediated through EGF receptors (EGFR). In this study, to understand the role of BTC in relation to EGFR in HCC, we examined localization, expression, and involvement in angiogenesis of BTC and EGFR. The results revealed that expression of BTC, EGFR, and tumor growth factor-alpha messenger RNA in HCC was increased by 80%, 60%, and 40%, respectively, as compared with those in the nontumorous tissues. Increased expression of BTC protein was observed in 31 (61%) of 51 HCC specimens, and the level of tumor growth factor-alpha protein was higher in 17 (33%) of 51 HCC specimens than in nonmalignant hepatocytes. Betacellulin was predominantly expressed in HCC cells, whereas EGFR was observed in sinusoidal endothelial cells of HCC in 25 tumors (49%). Betacellulin was secreted in all 4 examined HCC cell lines. The HCC specimens showing positive EGFR expression in tumor endothelial cells had a significantly higher microvessel density than those without EGFR expression (P < .005). A strong correlation was found between BTC expression in cancer cells and EGFR expression in tumor endothelial cells (P < .001). These findings suggest that overexpression of BTC by HCC cells and EGFR by tumor endothelial cells enhance vascularity in a paracrine manner.

Systemic Therapy of Advanced Hepatocellular Carcinoma: How Hopeful Should We Be?

Worldwide, hepatocellular carcinoma (HCC) is the fifth most common cancer and the third most common cause of cancer-related death. In the U.S., 18,510 new cancers of the liver and intrahepatic bile duct are expected in 2006, with an estimated 16,200 deaths. The incidence rates for HCC in the U.S. continued to rise steadily through 1998 and doubled during the period 1975-1995. Unresectable or metastatic HCC carries a poor prognosis, and systemic therapy with cytotoxic agents provides marginal benefit. A majority of HCC patients (>80%) presents with advanced or unresectable disease. Even for those with resected disease, the recurrence rate can be as high as 50% at 2 years. Because of the poor track record of systemic therapy in HCC, there has been a sense of nihilism for this disease in the oncology community for decades. However, with the arrival of newly developed molecularly targeted agents and the success of some of these agents in other traditionally challenging cancers, like renal cell carcinoma, there has recently been renewed interest in developing systemic therapy for HCC. This review attempts to concisely summarize the historical perspective and the current status of systemic therapy development in HCC.

Dysregulation of growth factor signaling in human hepatocellular carcinoma

Dysregulation of pleiotropic growth factors, receptors and their downstream signaling pathway components represent a central protumorigenic principle in human hepatocarcinogenesis. Especially the Insulin-like Growth Factor/IGF-1 receptor (IGF/IGF-1R), Hepatocyte Growth Factor (HGF/MET), Wingless (Wnt/beta-catenin/FZD), Transforming Growth Factor alpha/Epidermal Growth Factor receptor (TGFalpha/EGFR) and Transforming Growth Factor beta (TGFbeta/TbetaR) pathways contribute to proliferation, antiapoptosis and invasive behavior of tumor cells. This review focuses on the relevant alterations in these pathways identified in human human hepatocellular carcinomas (HCCs). Resultant functional effects are modulated by multiple cross-talks between the different signaling pathways and additional tumor-relevant factors, such as cyclooxygenase-2 and p53. Several specific strategies are currently under development such as receptor kinase inhibitors, neutralizing antibodies and antagonistic proteins, which may improve the systemic treatment of human HCCs.

Prevention of rat hepatocarcinogenesis by acyclic retinoid is accompanied by reduction in emergence of both TGF-alpha-expressing oval-like cells and activated hepatic stellate cells

We investigated the preventive effects of a synthetic acyclic retinoid, NIK-333, on the early and late events of hepatocarcinogenesis in male F344 rats treated with 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB). NIK-333 was administered once a day on consecutive days at a dose of 10, 40, or 80 mg/kg body weight along with the supplementation with 3'-MeDAB-containing diet for 16 wk. Animals from each group were sacrificed at 4 and 16 wk after the commencement of the experiment to determine the effect of NIK-333 on the early and late stages of carcinogenesis, respectively. NIK-333 suppressed the emergence of both oval-like cells expressing transforming growth factor (TGF)-alpha, putative progenitors of hepatocellular carcinoma (HCC), and activated hepatic stellate cells, major matrix-producing cells of the liver, in the early stage and inhibited the incidence of HCC in the late phase. These results suggest that NIK-333 is a promising drug for the chemoprevention of HCC by uniquely suppressing the early events of hepatocarcinogenesis, that is, development of both oval-like cells and fibrogenesis.

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.

Greater expression of transforming growth factor alpha and proliferating cell nuclear antigen staining in mouse hepatoblastomas than hepatocellular carcinomas induced by a diethylnitrosamine-sodium phenobarbital regimen

Transforming growth factor alpha (TGF-alpha) is a potent stimulator of normal hepatocyte proliferation, considered to have relationship to the liver regeneration or carcinogenesis. In this study, we investigated immunohistochemically the association between expression of TGF-alpha and cell proliferation activity in mouse hepatoblastomas (HBs) and hepatocellular carcinomas (HCCs) induced in B6C3F1 mice by diethylnitrosamine and sodium phenobarbital. The TGF-alpha-positive rate in HBs (29.2%) was significantly higher than that in HCCs (12.7%). Likewise, the proliferating cell nuclear antigen-positive rate (22.2%) was higher than the HCC value (14.5%). On the individual data for both TGF-alpha and PCNA, most of the HBs showed higher positive rates than HCCs. In HBs, TGF-alpha was localized only in the nuclei, whereas some HCC cells stained positive both in their nuclei and cytoplasm (0.6%). These results suggest expression of TGF-alpha and its localization might be linked to cell proliferation and play a role in malignant progression of mouse HBs.

Expression and clinical significance of the erbB family in intrahepatic cholangiocellular carcinoma

The type I family of growth factor receptors is known to play a role in the development of several carcinomas, but its role in hepatic malignancies is not clearly understood. In this study we investigated the expression of this family of EGF-R, c-erbB-2, c-erbB-3 and c-erbB-4 in 38 intrahepatic cholangiocellular carcinomas (CCC) by means of immunohistochemistry. EGF-R expression was related to lymph node metastasis, aberrant p53 expression, proliferating activity, and carcinoma differentiation. c-erbB-2 expression was observed in more than 50% of the cases, but was not related to any clinicopathological features, c-erbB-3 expression was linked to lymph node metastasis, and c-erbB-4 expression was directly related to proliferating activity and lymph node metastasis. These results indicate that: 1) EGF-R contributes greatly to CCC progression, and c-erbB-3 and c-erbB-4 have roles similar to but less than that of EGFR, and 2) c-erbB-2 is expressed in CCC in high incidence, but its clinical role in CCC remains unclear.

Alterations in metastatic properties of hepatocellular carcinoma cell following H-ras oncogene transfection

AIM: To demonstrate the relationship between H-ras oncogene and hepatocellular carcinoma (HCC) metastasis.

METHODS: Activated H-ras oncogene was transfected into SMMC 7721, a cell line derived from human HCC, by calcium phosphate transfection method. Some metastasis-related parameters were detected in vitro, including adhesion assay, migration assay, expression of collagenase IV (cIVase) and epidermal growth factor receptor (EGFR).

RESULTS: The abilities of H-ras-transfected cell clones in adhesion to laminin (LN) or fibronectin (FN), migration, cIVase secretion increased markedly, and the expression of EGFR elevated moderately. More importantly, these alterations were consistent positively with the expression of p21, the protein product of H-ras oncogene.

CONCLUSION: H-ras oncogene could induce the metastatic phenotype of HCC cell in vitro to raise its metastatic potential.

Expression and clinical significance of erb-B receptor family in hepatocellular carcinoma

In order to elucidate the clinical significance of the erbB family, epidermal growth factor receptor (EGF-R), c-erbB-2, c-erbB-3 and c-erbB-4 in hepatocellular carcinoma (HCC), we investigated the expression of these proteins by means of immunohistochemistry for HCC as well as adjacent noncancerous lesions. EGF-R was expressed in 68% of the HCC examined and showed correlation with the proliferating activity, stage, intrahepatic metastasis and carcinoma differentiation. c-erbB-2 was expressed in only 21% of the cases and showed no relationships with the clinicopathological parameters. c-erbB-3 protein was observed in 84% of the HCC and 38.1% of the noncancerous lesions. Its expression in HCC was equal to or greater than noncancerous lesions in 90.5% of the cases, and was related to the stage, portal invasion, cell proliferating activity, tumour size, intrahepatic metastasis and carcinoma differentiation. c-erbB-4 protein was expressed in 61.0% of HCC and in as much as 86.1% of the noncancerous lesions. Unlike the expression of c-erbB-3, that of c-erbB-4 in HCC was less than that of the adjacent noncancerous lesions in 51.2% of the cases. No statistical significance could be established between this protein expression in HCC and clinicopathological features. EGF-R and c-erbB-3 affected disease-free survival, but were not recognized as independent prognostic factors by multivariate analysis. The present study suggests that, of the four receptors, EGF-R and c-erbB-3 play important roles in the progression of HCC.

Expression of transforming growth factor-alpha mRNA in livers of patients with chronic viral hepatitis and hepatocellular carcinoma

BACKGROUND

Transforming growth factor-alpha (TGFalpha) is an important autocrine growth factor of hepatocytes. The authors evaluated the roles of TGFalpha in chronic viral hepatitis (CVH) and hepatocellular carcinoma (HCC).

METHODS

The authors measured the amounts of TGFalpha mRNA in liver tissues from 18 patients with HCC, 31 patients with CVH, and 7 normal controls. " Hot-start" reverse transcription-polymerase chain reaction (RT-PCR) using oligo-dT and specific primers detected TGFalpha mRNA in total cellular RNA extracted from liver tissues. The levels of TGFalpha mRNA were determined by the end point titers of serial, two-fold dilutions of cDNA. The amounts of hepatitis B virus RNA (HBV-RNA) in livers of patients with chronic hepatitis B also were measured by Northern blot hybridization.

RESULTS

TGFalpha mRNA levels were extremely higher in patients with HCC compared with patients with CVH and normal controls, and the levels in patients with CVH also were elevated compared with normal controls. The levels of TGFalpha mRNA were overexpressed in the underlying livers of patients with HCC compared with patients with CVH, although they were lower than those found in HCC tissues. The levels of TGFalpha mRNA were higher in samples from patients with chronic hepatitis B than in samples from patients with chronic hepatitis C. The levels of TGFalpha mRNA were not correlated with serum alanine aminotransferase or HBV-RNA levels in liver tissues in patients with chronic hepatitis B. However, the expression of TGFalpha mRNA tended to be higher in the livers of patients with raised serum alpha-fetoprotein levels.

CONCLUSIONS

The overexpression of TGFalpha mRNA in the liver seems to be associated with the regeneration of hepatocytes rather than hepatic necrosis or viral replication. Also, it may be related closely to the development or progression of HCC, especially in the livers of patients with chronic hepatitis B.

Immunohistochemical localization of transforming growth factor alpha in chemically induced rat hepatocellular carcinomas with reference to differentiation and proliferation

Hepatocellular carcinomas (HCCs) were induced in male Fischer 344 rats with dietary 3'-methyl-4-(dimethylamino)-azobenzene treatment and were classified into solid, glandular (well- or poorly differentiated), and trabecular types. Investigation of cell proliferation kinetics and immunohistochemical localization of transforming growth factor alpha (TGF-alpha) demonstrated all solid (n = 24) and poorly differentiated glandular type (n = 6) HCCs to have TGF-alpha-positive nuclei. Nuclear staining of TGF-alpha was also observed in 13 of 28 (46%) trabecular-type HCCs, whereas 12 (43%) exhibited cytoplasmic staining, and 3 (11%) were negative. As for well-differentiated glandular HCCs, 7 of 20 (35%) were positively stained in their nucleus, another 7 (35%) demonstrated antibody binding in the cytoplasm, and 6 (30%) were negative. The order for growth rate evaluated by bromodeoxyuridine (BrdU) labeling was solid (38.22%), poorly differentiated glandular (26.82%), trabecular (7.98%), and well-differentiated glandular (2.57%) types. For trabecular HCCs with nuclear, cytoplasmic, or negative TGF reactions, values were 13.39% (n = 13), 3.61% (n = 12), and 2.01% (n = 3), respectively. Likewise, BrdU-labeling indices for the counterpart groups of well-differentiated glandular type HCCs were 4.53, 1.91, and 1.29%, respectively. The results indicate that TGF-alpha expression might be linked to histopathological differentiation and cell proliferation in rat HCCs.

Transforming growth factor-alpha and epidermal growth factor receptor in chronic liver disease and hepatocellular carcinoma

AIMS/BACKGROUND

Transforming growth factor-alpha (TGF-alpha) is a potent mitogen of normal and neoplastic hepatocytes. In addition, TGF-alpha has been reported to play a pivotal role in hepatocarcinogenesis. To evaluate the significance of TGF-alpha in chronic liver diseases and hepatocellular carcinoma, we examined serum TGF-alpha, and expression of TGF-alpha, epidermal growth factor receptor (EGFR) and proliferating cell nuclear antigen (PCNA) mRNA in liver tissues.

METHODS

Thirty-five patients with chronic hepatitis (CH), 33 with liver cirrhosis (LC), 55 with hepatocellular carcinoma (HCC) and 53 normal controls (C) were enrolled in this study. Serum TGF-alpha levels were measured by an enzyme-linked immunosorbent assay. Expression of TGF-alpha, EGFR, PCNA and beta-actin mRNA in liver tissues were examined by reverse transcription polymerase chain reaction.

RESULTS

Serum TGF-alpha levels in C, CH, LC and HCC were 5.6+/-2.1, 33.2+/-8.3, 404.0+/-173.0 and 100.3+/-39.2 pg/ml, respectively. Serum TGF-alpha level in LC was higher than in other diseases (p<0.01, compared to CH, HCC and C, respectively). Serum TGF-alpha levels exhibited a significant positive correlation with total bilirubin, ICGR15 and Pugh score (p<0.01, p<0.01 and p<0.05, respectively), and increased in parallel with severity of disease according to Child classification. Although the ratios of TGF-alpha, EGFR and PCNA mRNA to beta-actin mRNA were not significantly different among the diseases, the TGF-alpha/beta-actin ratio correlated with EGFR/beta-actin and PCNA/beta-actin ratios (p<0.001 and p<0.0001, respectively), and EGFR/beta-actin ratio was related to PCNA/beta-actin ratio in all patients, especially with HCC.

CONCLUSION

The results of the present study suggest that serum TGF-alpha levels are closely related to severity of liver dysfunction, and that hepatic expression of TGF-alpha and EGFR correlates with proliferation of normal and neoplastic hepatocytes.