Analysis of the IGF axis in preneoplastic hepatic foci and hepatocellular neoplasms developing after low-number pancreatic islet transplantation into the livers of streptozotocin diabetic rats

Insulin Resistance and Cancer: In Search for a Causal Link

Insulin resistance (IR) is a condition which refers to individuals whose cells and tissues become insensitive to the peptide hormone, insulin. Over the recent years, a wealth of data has made it clear that a synergistic relationship exists between IR, type 2 diabetes mellitus, and cancer. Although the underlying mechanism(s) for this association remain unclear, it is well established that hyperinsulinemia, a hallmark of IR, may play a role in tumorigenesis. On the other hand, IR is strongly associated with visceral adiposity dysfunction and systemic inflammation, two conditions which favor the establishment of a pro-tumorigenic environment. Similarly, epigenetic modifications, such as DNA methylation, histone modifications, and non-coding RNA, in IR states, have been often associated with tumorigenesis in numerous types of human cancer. In addition to these observations, it is also broadly accepted that gut microbiota may play an intriguing role in the development of IR-related diseases, including type 2 diabetes and cancer, whereas potential chemopreventive properties have been attributed to some of the most commonly used antidiabetic medications. Herein we provide a concise overview of the most recent literature in this field and discuss how different but interrelated molecular pathways may impact on tumor development.

The IGF-1 Signaling Pathway in Viral Infections

Insulin-like growth factor-1 (IGF-1) and the IGF-1 receptor (IGF-1R) belong to the insulin-like growth factor family, and IGF-1 activates intracellular signaling pathways by binding specifically to IGF-1R. The interaction between IGF-1 and IGF-1R transmits a signal through a number of intracellular substrates, including the insulin receptor substrate (IRS) and the Src homology collagen (Shc) proteins, which activate two major intracellular signaling pathways: the phosphatidylinositol 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK) pathways, specifically the extracellular signal-regulated kinase (ERK) pathways. The PI3K/AKT kinase pathway regulates a variety of cellular processes, including cell proliferation and apoptosis. IGF1/IGF-1R signaling also promotes cell differentiation and proliferation via the Ras/MAPK pathway. Moreover, upon IGF-1R activation of the IRS and Shc adaptor proteins, Shc stimulates Raf through the GTPase Ras to activate the MAPKs ERK1 and ERK2, phosphorylate and several other proteins, and to stimulate cell proliferation. The IGF-1 signaling pathway is required for certain viral effects in oncogenic progression and may be induced as an effect of viral infection. The mechanisms of IGF signaling in animal viral infections need to be clarified, mainly because they are involved in multifactorial signaling pathways. The aim of this review is to summarize the current data obtained from virological studies and to increase our understanding of the complex role of the IGF-1 signaling axis in animal virus infections.

Islet transplantation modulates macrophage to induce immune tolerance and angiogenesis of islet tissue in type I diabetes mice model

Objective To investigate the dual mechanism of islet transplantation in T1D by regulating the immune tolerance of macrophages and inducing the neovascularization.

Methods NC group, T1D model group and T1D model + islet group were constructed. Then, the abdominal aorta blood of abdominal aorta and islet tissue were collected. ELISA was performed to detect the level of IL-1Rα, IL-1α, IL-1β, CXCL2, MCP1, TNF-α and IL-10. Flow cytometry was used to measure the content of M1 and M2 macrophages. HE staining indicated the pathological characteristics of islet. IHC and WB were applied to determine the protein levels of IGF1R, FGFR2 or VEGFA as well as IGF1R, GRB2, EGFR, PTPN1, JAK2, STAT3, Caspase-1, Bcl2 respectively.

Results Islet transplantation in T1D stimulated the expression of IL-1Rα, IL-1α, IL-1β, CXCL2, MCP1, TNF-α and IL-10 in abdominal aorta blood, changed the content of MHCII⁺CD206^-M1 and MHCII⁺CD206⁺M2 macrophages, reduced the pathological features and the infiltration of immunocytes, promoted the expression of IGF1R, FGFR2 and VEGFA, eliminated cell apoptosis and induced the neovascularization in islet grafts.

Conclusions Islet transplantation is an effective strategy for the treatment of T1D. It can increase the content of M2 macrophages whose immune tolerance can elevate the survival of islet grafts, reduce the inflammatory responses mediated by macrophages, promote the neovascularization and eliminate the cell apoptosis of islet grafts.

Diabetes and hepatocellular carcinoma: A pathophysiological link and pharmacological management

Both diabetes mellitus (DM) and cancer are multifarious, dissimilar, and long-lasting, fatal diseases with a remarkable influence on health worldwide. DM is not only related to cardiovascular diseases, neuropathy, nephropathy, and retinopathy, but also related to a number of liver diseases such as nonalcoholic fatty liver disease, steatohepatitis, and liver cirrhosis. Recently, it is hypothesized that DM has a greater risk for many forms of cancer, such as breast, colorectal, endometrial, pancreatic, gallbladder, renal, and liver cancer including hepatocellular carcinoma (HCC). Both DM and cancer have many common risk factors, but the association between these two is poorly stated. Several epidemiologic studies have revealed the association between pathogenic and prognostic characteristics of DM and a higher incidence of HCC, thus representing DM as an independent risk factor for HCC development. The etiological and pathophysiological relationship between DM and HCC has been presented in this review by linking hyperglycemia, hyperinsulinemia, insulin resistance, and activation of insulin-like growth factor signaling pathways and pharmacological management of HCC associated with DM.

Insulin-Like Growth Factor (IGF) System in Liver Diseases

Hepatocyte differentiation, proliferation, and apoptosis are affected by growth factors produced in liver. Insulin-like growth factor 1 and 2 (IGF1 and IGF2) act in response to growth hormone (GH). Other IGF family components include at least six binding proteins (IGFBP1 to 6), manifested by both IGFs develop due to interaction through the type 1 receptor (IGF1R). The data based on animal models and/or in vitro studies suggest the role of IGF system components in cellular aspects of hepatocarcinogenesis (cell cycle progression, uncontrolled proliferation, cell survival, migration, inhibition of apoptosis, protein synthesis and cell growth), and show that systemic IGF1 administration can reduce fibrosis and ameliorate general liver function. In epidemiologic and clinicopathological studies on chronic liver disease (CLD), lowered serum levels, decreased tissue expression of IGF1, elevated production of IGF1R and variable IGF2 expression has been noted, from the start of preneoplastic alterations up to the developed hepatocellular carcinoma (HCC) stage. These changes result in well-known clinical symptoms of IGF1 deficiency. This review summarized the current data of the complex role of IGF system components in the most common CLD (nonalcoholic fatty liver disease, cirrhosis, and hepatocellular carcinoma). Better recognition and understanding of this system can contribute to discovery of new and improved versions of current preventive and therapeutic actions in CLD.

Clear cell hepatocellular carcinoma: origin, metabolic traits and fate of glycogenotic clear and ground glass cells

Clear cell hepatocellular carcinoma (CCHCC) has hitherto been considered an uncommon, highly differentiated variant of hepatocellular carcinoma (HCC) with a relatively favorable prognosis. CCHCC is composed of mixtures of clear and/or acidophilic ground glass hepatocytes with excessive glycogen and/or fat and shares histology, clinical features and etiology with common HCCs. Studies in animal models of chemical, hormonal and viral hepatocarcinogenesis and observations in patients with chronic liver diseases prone to develop HCC have shown that the majority of HCCs are preceded by, or associated with, focal or diffuse excessive storage of glycogen (glycogenosis) which later may be replaced by fat (lipidosis/steatosis). In ground glass cells, the glycogenosis is accompanied by proliferation of the smooth endoplasmic reticulum, which is closely related to glycogen particles and frequently harbors the hepatitis B surface antigen (HBsAg). From the findings in animal models a sequence of changes has been established, commencing with preneoplastic glycogenotic liver lesions, often containing ground glass cells, and progressing to glycogen-poor neoplasms via various intermediate stages, including glycogenotic/lipidotic clear cell foci, clear cell hepatocellular adenomas (CCHCA) rich in glycogen and/or fat, and CCHCC. A similar process seems to take place in humans, with clear cells frequently persisting in CCHCC and steatohepatitic HCC, which presumably represent intermediate stages in the development rather than particular variants of HCC. During the progression of the preneoplastic lesions, the clear and ground glass cells transform into cells characteristic of common HCC. The sequential cellular changes are associated with metabolic aberrations, which start with an activation of the insulin signaling cascade resulting in pre-neoplastic hepatic glycogenosis. The molecular and metabolic changes underlying the glycogenosis/lipidosis are apparently responsible for the dramatic metabolic shift from gluconeogenesis to the pentose phosphate pathway and Warburg-type glycolysis, which provide precursors and energy for an ever increasing cell proliferation during progression.

Obesity and Liver Cancer

Obesity and related metabolic disorders have become globally prevalent posing a challenge for the chronically damaged liver and predisposing the development and progression of cancer. The rising phenomenon of "obesity epidemic" may provide means for understanding why liver cancer is one of the few malignancies with rising incidence in developed countries over the last decades. Non-alcoholic fatty liver disease associated with obesity, insulin resistance, and type 2 diabetes is an increasingly recognized trigger for liver cancer in Western populations characterized by low prevalence of established risk factors for liver cancer such as viral hepatitis and hepatotoxin exposure. Accumulating evidence has established an association between higher body mass index as an indicator of general obesity and higher risk of primary liver cancer. The associations are stronger in men, in patients with underlying liver disease and in white ethnic groups. Abdominal obesity, weight gain in adult life and metabolic factors related to visceral fat accumulation were also suggested as important risk factors for liver cancer; however, more studies are needed to evaluate these associations. The association of obesity and metabolic parameters with liver cancer survival remains controversial. It is unclear which exact mechanisms could provide links between obesity and liver cancer risk. Recent evidence has implicated several molecular pathways in obesity-associated liver cancer. These include insulin resistance leading to increased levels of insulin and insulin-like growth factors, chronic inflammation, adipose tissue remodeling, pro-inflammatory cytokine and adipokine secretion, and altered gut microbiota. These mechanisms coincide with inflammatory and metabolic processes occurring in non-alcoholic fatty liver disease predisposing cancer development and progression. In the context of the current evidence, better understanding of the role of obesity and related metabolic factors may help in improving current strategies for liver cancer prevention.

Diagnosis of hepatic glycogenosis in poorly controlled type 1 diabetes mellitus

Hepatic glycogenosis (HG) in type 1 diabetes is a underrecognized complication. Mauriac firstly described the syndrome characterized by hepatomegaly with altered liver enzymes, growth impairment, delay puberty and Cushingoid features, during childhood. HG in adulthood is characterized by the liver disorder (with circulating aminotransferase increase) in the presence of poor glycemic control (elevation of glycated hemoglobin, HbA1c levels). The advances in the comprehension of the metabolic pathways driving to the hepatic glycogen deposition point out the role of glucose transporters and insulin mediated activations of glucokinase and glycogen synthase, with inhibition of glucose-6-phosphatase. The differential diagnosis of HG consists in the exclusion of causes of liver damage (infectious, metabolic, obstructive and autoimmune disease). The imaging study (ultrasonography and/or radiological examinations) gives information about the liver alterations (hepatomegaly), but the diagnosis needs to be confirmed by the liver biopsy. The main treatment of HG is the amelioration of glycemic control that is usually accompanied by the reversal of the liver disorder. In selected cases, more aggressive treatment options (transplantation) have been successfully reported.

Emerging role of insulin-like growth factor-binding protein 7 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a vicious and highly vascular cancer with a dismal prognosis. It is a life-threatening illness worldwide that ranks fifth in terms of cancer prevalence and third in cancer deaths. Most patients are diagnosed at an advanced stage by which time conventional therapies are no longer effective. Targeted molecular therapies, such as the multikinase inhibitor sorafenib, provide a modest increase in survival for advanced HCC patients and display significant toxicity. Thus, there is an immense need to identify novel regulators of HCC that might be targeted effectively. The insulin-like growth factor (IGF) axis is commonly abnormal in HCC. Upon activation, the IGF axis controls metabolism, tissue homeostasis, and survival. Insulin-like growth factor-binding protein 7 (IGFBP7) is a secreted protein of a family of low-affinity IGF-binding proteins termed “IGFBP-related proteins” that have been identified as a potential tumor suppressor in HCC. IGFBP7 has been implicated in regulating cellular proliferation, senescence, and angiogenesis. In this review, we provide a comprehensive discussion of the role of IGFBP7 in HCC and the potential use of IGFBP7 as a novel biomarker for drug resistance and as an effective therapeutic strategy.

Curcumin regulates gene expression of insulin like growth factor, B-cell CLL/lymphoma 2 and antioxidant enzymes in streptozotocin induced diabetic rats

Background

The effects of curcumin on the activities and gene expression of antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione-S-transferase (G-ST), B-cell CLL/lymphoma 2 (Bcl-2) and insulin like growth factor-1 (IGF-1) in diabetic rats were studied.

Methods

Twenty four rats were assigned to three groups (8 rats for each). Rats of first group were non diabetic and rats of the second group were rendered diabetic by streptozotocin (STZ). Both groups received vehicle, corn oil only (5 ml/kg body weight) and served as negative and positive controls, respectively. Rats of the third group were rendered diabetic and received oral curcumin dissolved in corn oil at a dose of 15 mg/5 ml/kg body weight for 6 weeks.

Results

Diabetic rats showed significant increase of blood glucose, thiobarbituric acid reactive substances (TBARS) and activities of all antioxidant enzymes with significant reduction of reduced glutathione (GSH) compare to the control non diabetic group. Gene expression of Bcl2, SOD, CAT, GPX and GST was increased significantly in diabetic untreated rats compare to the control non diabetic group. The administration of curcumin to diabetic rats normalized significantly their blood sugar level and TBARS values and increased the activities of all antioxidant enzymes and GSH concentration. In addition, curcumin treated rats showed significant increase in gene expression of IGF-1, Bcl2, SOD and GST compare to non diabetic and diabetic untreated rats.

Conclusion

Curcumin was antidiabetic therapy, induced hypoglycemia by up-regulation of IGF-1 gene and ameliorate the diabetes induced oxidative stress via increasing the availability of GSH, increasing the activities and gene expression of antioxidant enzymes and Bcl2. Further studies are required to investigate the actual mechanism of action of curcumin regarding the up regulation of gene expression of examined parameters.

Glycogenotic hepatocellular carcinoma with glycogen-ground-glass hepatocytes: A heuristically highly relevant phenotype

Glycogenotic hepatocellular carcinoma (HCC) with glycogen-ground-glass hepatocytes has recently been described as an allegedly “novel variant” of HCC, but neither the historical background nor the heuristic relevance of this observation were put in perspective. In the present contribution, the most important findings in animal models and human beings related to the emergence and further evolution of excessively glycogen storing (glycogenotic) hepatocytes with and without ground glass features during neoplastic development have been summarized. Glycogenotic HCCs with glycogen-ground-glass hepatocytes represent highly differentiated neoplasms which contain subpopulations of cells phenotypically resembling those of certain types of preneoplastic hepatic foci and benign hepatocellular neoplasms. It is questionable whether the occurrence of glycogen-ground-glass hepatocytes in a glycogenotic HCC justifies its classification as a specific entity. The typical appearance of ground-glass hepatocytes is due to a hypertrophy of the smooth endoplasmic reticulum, which is usually associated with an excessive storage of glycogen and frequently also with an expression of the hepatitis B surface antigen. Sequential studies in animal models and observations in humans indicate that glycogen-ground-glass hepatocytes are a facultative, integral part of a characteristic cellular sequence commencing with focal hepatic glycogenosis potentially progressing to benign and malignant neoplasms. During this process highly differentiated glycogenotic cells including ground-glass hepatocytes are gradually transformed via various intermediate stages into poorly differentiated glycogen-poor, basophilic (ribosome-rich) cancer cells. Histochemical, microbiochemical, and molecular biochemical studies on focal hepatic glycogenosis and advanced preneoplastic and neoplastic lesions in tissue sections and laser-dissected specimens in rat and mouse models have provided compelling evidence for an early insulinomimetic effect of oncogenic agents, which is followed by a fundamental metabolic switch from gluconeogenesis towards the pentose-phosphate pathway and the Warburg type of glycolysis during progression from preneoplastic hepatic glycogenosis to the highly proliferative malignant phenotype.

Insulin-like growth factor-II is a useful marker to detect hepatocellular carcinoma?

BACKGROUND

Hepatocellular carcinoma (HCC) is a typical hypervascular tumor. The utility of serum alpha-fetoprotein (α-FP) in its detection is questionable. Over-expression and high circulating levels of insulin-like growth factor-II (IGF-II) were reported in tissue and in serum of patients with HCC. We investigated the diagnostic application of IGF-II in the diagnosis of HCC.

METHODS

Serum IGF-II and α-FP levels were measured in 178 patients (82 with HCC and 96 with liver cirrhosis) and in 30 healthy controls. Spearman test, non parametric combination test and confidence interval analysis were used for statistical evaluation of data.

RESULTS

The best cut-off values selected by ROC curves were 796 ng/ml for IGF-II and 132 ng/ml for α-FP. IGF-II mean values were higher in patients with HCC than in those with liver cirrhosis (LC) (p=0.0001) but lower in LC than in controls (p=0.0001). Serum IGF-II levels above cut-off were found in 22% of patients with HCC, in 9.3% of those with cirrhosis and in 20% of controls. α-FP serum levels >132 ng/ml were observed in 48% of HCC, in 3.1% of LC and in none of control group. By correlation study, serum IGF-II levels were significantly correlated with serum α-FP levels (r=0.427, p=0.0001) and with nodules' diameter (r=0.252, p=0.0130) but not with nodules' number (p>0.050). Finally, IGF-II showed lower sensitivity, specificity and predictive values than α-FP.

CONCLUSION

Circulating IGF-II is not a useful marker for HCC. Further researches are however needed to evaluate its diagnostic accuracy before and after nutritional adjustment.

Serum IGFBP-3 is a more effective predictor than IGF-1 and IGF-2 for the development of hepatocellular carcinoma in patients with chronic HCV infection

Hepatocellular carcinoma (HCC) contributes to 14.8% of all cancer mortality in Egypt, which has a high prevalence of hepatitis C virus (HCV). We have previously shown alterations in the insulin-like growth factor-1 (IGF-1) receptor signalling pathway during experimental hepatocarcinogenesis. The aim of this study was to determine whether serum levels of IGF-1, IGF-2 and IGFBP-3 can be used to discriminate between HCC and the stages of hepatic dysfunction in patients with liver cirrhosis assessed by the Child-Pugh (CP) score, and to correlate these levels with HCC stages. We recruited 241 subjects to the present study; 79 with liver cirrhosis, 62 with HCV-induced HCC and 100 age-matched controls. Results showed that serum levels of IGF-1, IGF-2 and IGFBP-3 were reduced significantly in cirrhosis and HCC patients in comparison to the controls, and that this reduction negatively correlated with the CP scores. However, only IGFBP-3 levels showed significant negative correlation with α-fetoprotein levels. The reduction in IGF-1 and IGFBP-3 but not IGF-2 levels was significant in HCC in comparison to patients with cirrhosis. None of the parameters significantly correlated with the HCC stage. IGFBP-3 levels discriminated between cirrhosis and HCC at a sensitivity of 87%, a specificity of 80% and a cut-off value of <682.6 ng/ml. In conclusion, although our results showed that serum IGF-1, IGF-2 and IGFBP-3 are reduced with the progression of hepatic dysfunction, only IGFBP-3 may be considered as the most promising serological marker for the prediction of the development of HCC in the chronic HCV patients with liver cirrhosis.

Targeting insulin-like growth factor axis in hepatocellular carcinoma

The insulin-like growth factor (IGF) axis contains ligands, receptors, substrates, and ligand binding proteins. The essential role of IGF axis in hepatocellular carcinoma (HCC) has been illustrated in HCC cell lines and in animal xenograft models. Preclinical evidence provides ample indication that all four components of IGF axis are crucial in the carcinogenic and metastatic potential of HCC. Several strategies targeting this system including monoclonal antibodies against the IGF 1 receptor (IGF-1R) and small molecule inhibitors of the tyrosine kinase function of IGF-1R are under active investigation. This review describes the most up-to-date understanding of this complex axis in HCC, and provides relevant information on clinical trials targeting the IGF axis in HCC with a focus on anti-IGF-1R approach. IGF axis is increasingly recognized as one of the most relevant pathways in HCC and agents targeting this axis can potentially play an important role in the treatment of HCC.

Targeting insulin-like growth factor axis in hepatocellular carcinoma

The insulin-like growth factor (IGF) axis contains ligands, receptors, substrates, and ligand binding proteins. The essential role of IGF axis in hepatocellular carcinoma (HCC) has been illustrated in HCC cell lines and in animal xenograft models. Preclinical evidence provides ample indication that all four components of IGF axis are crucial in the carcinogenic and metastatic potential of HCC. Several strategies targeting this system including monoclonal antibodies against the IGF 1 receptor (IGF-1R) and small molecule inhibitors of the tyrosine kinase function of IGF-1R are under active investigation. This review describes the most up-to-date understanding of this complex axis in HCC, and provides relevant information on clinical trials targeting the IGF axis in HCC with a focus on anti-IGF-1R approach. IGF axis is increasingly recognized as one of the most relevant pathways in HCC and agents targeting this axis can potentially play an important role in the treatment of HCC.

Upregulation of the insulin receptor and type I insulin-like growth factor receptor are early events in hepatocarcinogenesis

The molecular mechanisms underlying the development of hepatocellular carcinoma (HCC) are not yet fully understood. Preneoplastic foci of altered hepatocytes regularly precede HCC in various species. The predominant earliest type of foci of altered hepatocytes, the glycogen storage focus (GSF), shows an excess of glycogen (glycogenosis) in the cytoplasm. During progression from GSF to HCC, the stored glycogen is gradually reduced, resulting in complete loss in basophilic HCC. We have previously shown that in N-nitrosomorpholine-induced hepatocarcinogenesis, insulin receptor substrate (IRS-1) is strongly expressed in GSF and reduced during progression to HCC, thus correlating with the glycogen content. In the present study, we observed increased levels of insulin receptor, IGF-I receptor (IGF-IR), IRS-2, and mitogen-activated kinase/extracellular regulated kinase-1 in GSF, following the same pattern of expression as IRS-1. We conclude that the abundance of IRS-1, IRS-2, and mitogen-activated kinase/extracellular regulated kinase-1 coincides with a concerted upregulation of both IR and IGF-IR induced by the hepatocarcinogen. Our data suggest that in early hepatocellular preneoplasia, the upregulation of IR elicits glycogenosis through IRS-1 and/or IRS-2, whereas the increased level of the IGF-IR may lead to the increased cell proliferation previously reported in GSF. Therefore, the concerted upregulation of both IR and IGF-IR may represent initial events in hepatocarcinogenesis.

Hepatocarcinogenesis following pancreatic islet transplantation in streptozotocin- and autoimmune-diabetic rats

Epidemiological studies assign a role to insulin signalling deregulation and diabetes mellitus in human hepatocarcinogenesis. The underlying mechanisms, however, remain largely unknown. To unravel the molecular pathogenesis of insulin-induced hepatocarcinogenesis, we generated an experimental animal model: after transplantation of only a low number of isologous pancreatic islets into the livers of diabetic rats, mild diabetes persists and the beta cells are maximally stimulated to permanently secrete insulin. As a consequence, liver acini, draining the hyperinsulinemic blood from islet grafts, show insulin-induced adaptive alterations simultaneously resembling preneoplastic foci of chemically-induced hepatocarcinogenesis models. These lesions progress to hepatocellular tumours within 6 and 24 months. Hepatocarcinogenesis is accompanied by alterations in hepatocytes metabolisms and changes in signal transduction pathways that, in the beginning, can be attributed solely to insulin action. In this review, we summarize our findings that may help understanding the oncogenic potential of diabetes mellitus in the human liver.

Glypican-3-mediated oncogenesis involves the Insulin-like growth factor-signaling pathway

Glypican-3 (gpc3) is the gene responsible for Simpson-Golabi-Behmel overgrowth syndrome. Previously, we have shown that GPC3 is overexpressed in hepatocellular carcinoma (HCC). In this study, we demonstrated the mechanisms for GPC3-mediated oncogenesis. Firstly, GPC3 overexpression in NIH3T3 cells gave to cancer cell phenotypes including growing in serum-free medium and forming colonies in soft agar, or on the other way, GPC3 knockdown in HuH-7 cells decreased oncogenecity. We further demonstrated that GPC3 bound specifically through its N-terminal proline-rich region to both Insulin-like growth factor (IGF)-II and IGF-1R. GPC3 stimulated the phosphorylation of IGF-1R and the downstream signaling molecule extracellular signal-regulated kinase (ERK) in an IGF-II-dependent way. Also, GPC3 knockdown in HCC cells decreased the phosphorylation of both IGF-1R and ERK. Therefore, GPC3 confers oncogenecity through the interaction between IGF-II and its receptor, and the subsequent activation of the IGF-signaling pathway. This data are novel to the current understanding of the role of GPC3 in HCC and will be important in future developments of cancer therapy.

Renal carcinogenesis in models of diabetes in rats: metabolic changes are closely related to neoplastic development

AIMS/HYPOTHESIS

There is an increased risk of renal cell carcinoma (RCC) in human diabetes mellitus. We therefore examined the influence of hyperglycaemia and glucose-lowering treatment on nephrocarcinogenesis in rats.

METHODS

Rats (n = 850), which were either spontaneously diabetic, streptozotocin-diabetic or normoglycaemic, were examined with special reference to Armanni-Ebstein lesions (AEL).

RESULTS

Irrespective of the cause of diabetes, diabetic but not normoglycaemic rats developed typical glycogenotic clear-cell AEL. AEL showed strong proliferative activity, which was nearly completely inhibited by EGF receptor blockade (Gefitinib treatment). Many findings suggested a stepwise development of RCCs from AEL. Whereas the number and size of RCCs gradually increased in all diabetic groups, beginning at 6 months after onset of diabetes, normoglycaemic controls did not developed RCC. After 28 months, up to 82% of diabetic animals had at least one RCC. In contrast to the proximal tubules, the distal tubular system, including glycogenotic AEL, had the same levels of enzyme activities as RCC (e.g. high glycogen phosphorylase and synthase activity, lack of glucose 6-phosphatase activity) and the same expression patterns of cytokeratin 7 and several growth factors, along with their receptors and signal transduction proteins (TGF-alpha, EGF receptor, IGF-I, IGF-I receptor, IGF-II receptor, insulin receptor substrate 1, v-raf-1 murine leukemia viral oncogene homologue 1 and mitogen activated protein kinase kinase 1). In addition, direct morphological transitions between distal tubules, AEL and RCCs were frequently observed. All these findings indicate a common origin and a precursor-product relationship of AEL and RCCs.

CONCLUSIONS/INTERPRETATION

Nephrocarcinogenesis in diabetic rats results from sustained hyperglycaemia, resulting in an adaptive metabolic response, altered growth factor signalling and subsequent neoplastic transformation of the tubular epithelial cells.

Screening candidate longevity therapeutics using gene-expression arrays

BACKGROUND

We review studies showing that CR acts rapidly, even in late adulthood, to extend health- and lifespan in mice. These rapid physiological effects are closely linked to patterns of gene expression in liver and heart. Non-human primate and human studies suggest that the signal transduction pathways responsible for the lifespan and health effects of caloric restriction (CR) may also be involved in human longevity. Thus, pharmaceuticals capable of mimicking the effects of CR (and other methods of lifespan extension) may have application to human health.

OBJECTIVE

We show that lifespan studies are an inefficient and theoretically problematic way of screening for longevity therapeutics. We review studies suggesting that rapid changes in patterns of gene expression can be used to identify pharmaceuticals capable of mimicking some positive effects of caloric restriction.

RESULTS

We present a traditional study of the effects of melatonin, melatonin and pregnenolone, aminoguanidine, aminoguanidine and alpha-lipoic acid, aminoguanidine, alpha-lipoic acid, pregnenolone, and coenzyme-Q(10) on the lifespan of mice. No treatment extended lifespan. However, because the mice die mostly of cancer, only chemopreventives active against specific cancers can be identified by such studies. The studies were also time-consuming and expensive. We discuss high-density microarray studies of the effectiveness of glucoregulatory drugs and putative cancer chemopreventatives at reproducing the hepatic gene-expression profiles of long-term and short-term CR. We describe the identification of one compound, metformin, which reproduces a subset of the gene-expression and physiological effects of CR.

CONCLUSION

Taken together, our results suggest that gene-expression biomarkers may be superior to lifespan studies for initial screening of candidate longevity therapeutics.

Pleiotropic effects of PI-3' kinase/Akt signaling in human hepatoma cell proliferation and drug-induced apoptosis

IGF-II and type I-IGF receptor (IGF-IR) gene expression is increased in primary liver tumors, and transgenic mice overexpressing IGF-II in the liver develop hepatocellular carcinoma (HCC) spontaneously, suggesting that alterations of IGF-IR signaling in vivo may play a role in the auto/paracrine control of hepatocarcinogenesis. We have addressed the contribution of PI-3'K/Akt signaling on the proliferation of HepG2 human hepatoma cells and on their protection against doxorubicin-induced apoptosis. Both basal HepG2 cell DNA replication and that stimulated by IGF-IR signaling were inhibited by the specific PI-3'K inhibitor Ly294002 (Ly). In the former case, PI-3'K signaling overcame cell cycle arrest in G1 via increased cyclin D1 protein and decreased p27kip1 gene expression. Doxorubicin treatment induced apoptosis in HepG2 cells and was concomitant with the proteolytic cleavage of Akt-1 and -2. Drug-induced apoptosis was reversed by IGF-I and this effect was (i) dependent on Akt-1 and -2 phosphorylation and (ii) accompanied by the inhibition of initiator caspase-9 activity, suggesting that IGF-IR signaling interferes with mitochondria-dependent apoptosis. Accordingly, Ly enhanced doxorubicin-induced apoptosis and suppressed its reversal by IGF-I. Altogether, the data emphasize the crucial role of PI-3'K/Akt signaling (i) in basal as well as IGF-IR-stimulated HepG2 cell proliferation and (ii) in controlling both doxorubicin-induced apoptosis (e.g., drug-induced cleavage of Akt) and its reversal by IGF-I (protection against apoptosis parallels the extent of Akt phosphorylation). They suggest that targeting Akt activity or downstream Akt effectors (e.g., GSK3-beta, FOXO transcription factors) may help define novel therapeutic strategies of increased efficacy in the treatment of HCC-bearing patients.

Correlations of insulin-like growth factor-II expression with hepatitis B virus DNA replication and clinical pathological characteristics in human hepatocelullar carcinoma

AIM: To investigate the expression of insulin-like growth factor-II (IGF-II) in hepatocellular carcinoma (HCC) as well as its correlations with the pathogenesis, development and prognosis of HCC.

METHODS: IGF-II expression was detected by immunohistochemistry in 30 HCC and their corresponding non-cancerous tissues. Liver HBV DNA was detected by in situ molecular hybridization technique and the relationship was analyzed between IGF-II expression and HBV replication or the clinical pathological characteristics.

RESULTS: The stronger expression of IGF-II was found in liver cancer tissues. The positive rate of IGF-II expression was 83.3% in HCC, and 46.7% in non-cancerous liver tissues (P < 0.01), respectively. The expression of IGF-II was significantly higher in HCC with moderate or low differentiation than that with well differentiation (90.0%, 100% vs 42.9%, P < 0.05 or P < 0.01). IGF-II expression was markedly lower in HCC without serosa invasion than that with serosa invasion (95.0% vs 60.0%, P < 0.05). IGF-II expression was also correlated with tumor size (< 5 cm vs ≥ 5 cm: 58.3% vs 100%, P < 0.01), but with tumor number (P > 0.05). The level of IGF-II expression in HBV DNA-positive HCC was significantly higher than that in HBV DNA-negative ones (94.7% vs 63.6%, P < 0.05).

CONCLUSION: IGF-II is highly expressed in HCC, and the aberrant expression of IGF-II is correlated with the degree of differentiation, invasion and tumor size, and it may be used as a marker for development and prognosis of HCC.

Cystic cholangiomas after transplantation of pancreatic islets into the livers of diabetic rats

Islet transplantation is increasingly used as a therapy for human type 1 diabetes mellitus. In our study, we investigated the effect of the transplantation of a low number (n = 350) of pancreatic islets into the right liver part on the neighboring portal bile ducts. Male streptozotocin- diabetic Lewis or autoimmune-diabetic BB/Pfd rats (n = 1065) were subdivided into 11 experimental groups. A few days after low-number islet transplantation, cholangiocytes adjacent to the grafts showed an increase in proliferative activity. During the next 12-24 months, many peri-insular ductules progressed via tumor-like cystic lesions to large cystic cholangiomas, accompanied by a translocation of the insulin receptor into the cytoplasm and an increase in expression of insulin-related signaling proteins (Insulin-receptor-substrate-1, Raf-1, Mek-1). After 24 months, 53% of rats with low-number transplantation exhibited at least one cholangioma >10 mm, significantly outnumbering tumor development in the transplant-free left liver part and in any control group. No cholangiocarcinomas emerged. A graft cell origin of the tumors was excluded by Y chromosome in situ hybridization in cross-gender transplantations. Conclusively, low-number intrahepatic islet transplantation, most likely acting by permanent local hyperinsulinism, leads to prolonged cholangiocellular proliferation in streptozotocin- and in autoimmune-diabetic rats, resulting in the development of benign cystic cholangiomas.

Hepatocellular neoplasms after intrahepatic transplantation of ovarian fragments into ovariectomized rats

Intrahepatic transplantation of ovarian fragments in ovariectomized rats results in morphological abnormalities. The liver acini draining blood from ovarian grafts show alterations resembling chemically induced amphophilic hepatocellular preneoplasias. We investigated the long-term development of these estrogen-induced foci of altered hepatocytes (FAH). We divided 451 Lewis rats into one main group (MG) and 11 (7 female, 4 male) control groups and observed them for up to 30 months. MG animals were ovariectomized and received ovarian transplants into the right liver part. Different combinations of castration, transplantation of ovarian or testicular fragments, and administration of antiestrogenic toremifene were used in controls. In the MG, transplants showed signs of gonadotropic stimulation, and estrogen levels were strongly increased in the downstream liver acini. After 6 and 12 months, FAH developed in hepatocytes downstream of the transplants. After 18 months, 27% of the MG animals showed transformation of FAH into hepatocellular adenomas; this figure increased to 42% after 24 months (8/19), significantly outnumbering four spontaneous adenomas that developed between 18 and 30 months in 258 control animals. Hepatocellular carcinoma (HCC) appeared only in the MG. At 24 and 30 months, 18 HCCs developed; thus, 78% of MG animals showed at least one carcinoma. Administration of toremifene in ovariectomized and transplanted animals completely prevented hepatocarcinogenesis. Testicular grafts showed no influence on liver tissue. In conclusion, initially adaptive but preneoplastic alterations in hepatocytes downstream of intrahepatically transplanted ovarian fragments may transform into HCC, indicating a strong hepatocarcinogenic potential of high local levels of endogenous estrogens in the rat liver.

Insulin-like growth factor-I stimulates H4II rat hepatoma cell proliferation: Dominant role of PI-3′K/Akt signaling

Although hepatocytes are the primary source of endocrine IGF-I and -II in mammals, their autocrine/paracrine role in the dysregulation of proliferation and apoptosis during hepatocarcinogenesis and in hepatocarcinomas (HCC) remains to be elucidated. Indeed, IGF-II and type-I IGF receptors are overexpressed in HCC cells, and IGF-I is synthesized in adjacent non-tumoral liver tissue. In the present study, we have investigated the effects of type-I IGF receptor signaling on H4II rat hepatoma cell proliferation, as estimated by 3H-thymidine incorporation into DNA. IGF-I stimulated the rate of DNA synthesis of serum-deprived H4II cells, stimulation being maximal 3 h after the onset of IGF-I treatment and remaining elevated until at least 6 h. The IGF-I-induced increase in DNA replication was abolished by LY294002 and only partially inhibited by PD98059, suggesting that phosphoinositol-3' kinase (PI-3'K) and to a lesser extent MEK/Erk signaling were involved. Furthermore, the 3- to 19-fold activation of the Erks in the presence of LY294002 suggested a down-regulation of the MEK/Erk cascade by PI-3'K signaling. Finally, the effect of IGF-I on DNA replication was almost completely abolished in clones of H4II cells expressing a dominant-negative form of Akt but was unaltered by rapamycin treatment of wild-type H4II cells. Altogether, these data support the notion that the stimulation of H4II rat hepatoma cell proliferation by IGF-I is especially dependent on Akt activation but independent on the Akt/mTOR signaling.

Hepatocellular neoplasms induced by low-number pancreatic islet transplants in autoimmune diabetic BB/Pfd rats

It has been shown that combined high local hyperinsulinism and hyperglycemia after low-number islet transplantation into the livers of streptozotocin-diabetic rats lead to the development of hepatocellular neoplasms but a substantial cocarcinogenic effect of genotoxic streptozotocin could not be ruled out completely. Thus, we herein investigated this model in BB/Pfd rats (n = 805; nine experimental groups), which develop spontaneous autoimmune diabetes similar to human type 1 diabetes. After low-number islet transplantation (n = 450), the liver acini downstream of the islets show insulin-induced alterations: massive glycogen and/or fat accumulation, translocation of the insulin receptor, decrease in glucose-6-phosphatase activity, increase in expression of insulin-like growth factor (IGF)-I, IGF-II/mannose-6-phosphate receptor, insulin receptor substrate-1, Raf-1, and Mek-1, corresponding to clear cell preneoplastic foci of altered hepatocytes known from chemical hepatocarcinogenesis and identical to that in streptozotocin-diabetic Lewis rats. After 6 months, many altered liver acini progressed to other types of preneoplasias often accompanied by an overexpression of the glutathione-S transferase (placental form), IGF-I receptor, and transforming growth factor (TGF)-alpha. After 12 to 15 and 15 to 18 months, 52% and 100% of the animals showed one or multiple hepatocellular adenomas or hepatocellular carcinomas (HCCs), respectively. Conclusively, this study identifies combined hyperinsulinism and hyperglycemia as a carcinogenic mechanism for the development of HCCs in diabetic rats. Hepatocarcinogenesis is independent from additional genotoxic compounds (i.e., streptozotocin), but is primarily triggered by increased intracellular insulin signaling via pathways associated with cell growth and proliferation, such as the Ras-Raf-mitogen-activated protein kinase pathway and the IGF system, and secondarily involves other growth factors, such as TGF-alpha.

Expression of insulin-like growth factor-I and insulin-like growth factor binding proteins during thioacetamide-induced liver cirrhosis in rats

OBJECTIVE

The liver plays a central role in insulin-like growth factor (IGF) homeostasis providing the majority of circulating IGF-I and some of its binding proteins (IGFBPs). In liver cirrhosis the IGF axis is severely disturbed, and these alterations are associated with reduced IGF-I, IGFBP-3 but elevated IGFBP-1 serum levels.

METHODS

By Northern blotting and in situ hybridization (ISH), hepatic expression of IGF-I and of IGFBP was studied in a rat model of liver cirrhosis induced by thioacetamide.

RESULTS

ISH revealed a homogeneous distribution of IGFBP-1, IGFBP-4 and IGF-I mRNA over hepatic parenchyma in normal and cirrhotic liver. Fibrous septa of cirrhotic liver were IGFBP-1 mRNA negative, whereas IGFBP-4 and IGF-I transcripts were detected in single cells. In normal liver, IGFBP-3 mRNA was distributed within nonparenchymal cells of the hepatic lobule and in the wall of the portal vein. In cirrhotic liver, IGFBP-3 transcripts were abundant in mesenchymal cells of fibrous tissue. IGFBP-3 mRNA expression was also prominent in cells at the septal-nodular interface most likely representing monocyte infiltration. IGFBP-3 mRNA expression was reduced in nonparenchymal liver cells located more distantly from the septal-nodular interface in the cirrhotic nodule that correlated with reduced IGFBP-3 mRNA expression observed in Kupffer cells (KC) and sinusoidal endothelial cells (SEC) isolated from macronodular cirrhotic livers.

CONCLUSION

Cirrhosis is accompanied by an altered spatial expression of IGFBP-3 in liver tissue, which is characterized by decreased levels of IGFBP-3 mRNA in KC and SEC, but elevated IGFBP-3 expression in myofibroblast-like cells and inflammatory infiltrate.

Expression and alteration of insulin-like growth factor II-messenger RNA in hepatoma tissues and peripheral blood of patients with hepatocellular carcinoma

AIM: To investigate the clinical values of serum free insulin-like growth factor II (IGF-II) levels and IGF-II mRNA in hepatocellular carcinoma (HCC) tissues and peripheral blood for diagnosis of HCC and monitoring of extrahepatic metastasis.

METHODS: Total RNAs were extracted from HCC tissues or peripheral blood mononuclear cells from patients with HCC, liver diseases devoid of cancer, non-hepatic tumors, and healthy controls, respectively. IGF-II cDNAs were synthesized through random primers and reverse-transcriptase, amplified by polymerase chain reaction (PCR), and confirmed by DNA sequencing analysis. Serum free IGF-II levels in patients with different liver diseases were analyzed by an enzyme-linked immunosorbent assay.

RESULTS: The amplified fragments of IGF-II mRNA by RT-PCR were identical to originally designed ones with a size of 170 bp and confirmed by sequencing analysis. The dilution experiments revealed that the lowest sensitivity of our system was 2 ng/L of total RNA. The positive frequencies of IGF-II mRNA were 100% in HCC tissues, 53.3% in para-cancerous tissues, and 0% in non-cancerous tissues, respectively. The serum free IGF-II levels were significantly higher in HCC than those in chronic hepatitis or liver cirrhosis. The positive frequency of circulating IGF-II mRNA was 34.2% in HCC, no amplified fragment was found in other liver diseases, extrahepatic tumors, and normal controls, respectively. The circulating IGF-II mRNA correlated with the stage of HCC, and its positive rate was 100% in HCC with extrahepatic metastasis and 35.5% in HCC with AFP-negative. No significant correlation was found between tumor sizes and circulating IGF-II mRNA fragment.

CONCLUSION: The abnormal expressions of free IGF-II and IGF-II mRNA are useful tumor markers for HCC diagnosis, differentiation of extrahepatic metastasis and monitoring postoperative recurrence.

Cocarcinogenic Effects of Islet Hormones and N-Nitrosomorpholine in Hepatocarcinogenesis after Intrahepatic Transplantation of Pancreatic Islets in Streptozotocin-Diabetic Rats

In contrast to high local insulin levels obtained after low-number transplantation (n = 350) of islets of Langerhans into the livers of diabetic rats, low insulin levels after high-number transplantation (n = 1,000) do not suffice to induce hepatocarcinogenesis. Herein, we investigated the possible cocarcinogenic potential of high and, in particular, low insulin levels, combining this in vivo model with a chemical model of hepatocarcinogenesis after administration of N-nitrosomorpholine (NNM). In three main experiments, different schemes of single or continuous NNM administration were combined with different transplantation procedures in diabetic or nondiabetic animals, i.e., low-number and high-number islet transplantation, transplantation of polystyrene particles, and sham transplantation. Animals were sacrificed between 3 and 53 weeks after transplantation procedures. Evidence for the cocarcinogenic effects of NNM and insulin was provided in each main experiment. NNM treatment after low-number islet transplantation resulted in an increase in the number of preneoplastic hepatocellular foci, and a significant increase in the number and an earlier appearance of hepatocellular adenomas and carcinomas compared with controls. Most intriguing was the increase in preneoplastic foci after combined NNM treatment and high-number islet transplantation, proving that insulin, even in lower doses, has at least cocarcinogenic effects on the downstream hepatocytes and thus promotes an otherwise initiated hepatocarcinogenic process. Conclusively, intrahepatic transplantation of pancreatic islets acts as a strong cocarcinogenic factor together with NNM in streptozotocin-diabetic rats.

Role of constitutively activated and insulin-like growth factor-stimulated ERK1/2 signaling in human hepatoma cell proliferation and apoptosis: evidence for heterogeneity of tumor cell lines

Enhanced insulin-like growth factor II (IGF-II) and type I IGF receptor (IGF-IR) gene expression in liver tumors and the development of liver tumors in transgenic mice overexpressing IGF-II in the liver suggest that the IGFs and underlying signaling cascades may play auto/paracrine roles in the control of hepatocarcinoma (HCC) cell proliferation and in their protection against apoptosis. We have focused on the role of mitogen-activated protein kinase (ERK1/2) signaling on human HepG2 and Huh-7 hepatoma cell proliferation and on the protection of these cells against drug-induced apoptosis. Physiological concentrations of IGF-I stimulated DNA replication in HepG2 cells (1.5-fold) but not in Huh-7 cells, and this effect was abolished by PD98059 (MEK-1 inhibitor). Doxorubicin or cisplatin treatment induced apoptosis (caspase-dependent poly[ADP-ribose]polymerase cleavage) in both cell lines, but dose-dependent reversion of drug-induced apoptosis (57-84%) by IGF-I was only observed in HepG2 cells. The very low level of IGF-IR at the plasma membrane of Huh-7 cells may account for their unresponsiveness to IGF-I. We have shown that drug treatment enhanced (17-fold) or did not modify constitutive ERK1/2 activity in cultured HepG2 or Huh-7 cells, respectively. In both cell lines, inhibition of constitutive and drug-induced ERK1/2 activity by PD98059 yielded a complete inhibition of drug-induced apoptosis. Altogether, our data demonstrate the heterogeneous response of human hepatoma cells to an IGF stimulus and suggest (1) that auto/paracrine effects of IGF-I/-II might contribute to the proliferation of HCC cells and to their protection against apoptosis in vivo and (2) that drug-induced activation of ERK1/2 plays a role in drug-induced apoptosis in human hepatoma cells.

Microarray data analysis of mouse neoplasia

Microarray gene expression analysis offers great promise to help us understand the molecular events of experimental carcinogenesis, but have such promises been fulfilled? Studies of gene expression profiles of rodent are being published and demonstrate that yes, indeed, gene array data is furthering our understanding of tumor biology. Recent studies have identified differentially expressed genes in rodent mammary, colon, lung, and liver tumors. Although relatively few genes on the rodent arrays have been fully characterized, information has been generated to better identify signatures of histologic type and grade, understand invasion and metastasis, identify candidate biomarkers of early development, identify gene networks in carcinogenesis, understand responses to therapy, and decifer overlap with molecular events in human cancers. Data from mouse lung, mammary gland, and liver tumor studies are reviewed as examples of how to approach and interpret gene array data. Methods of gene array data analysis were also applied for discovery of genes involved in the regression of mouse liver tumors induced by chlordane, a nongenotoxic murine hepatocarcinogen. Promises are beginning to be fulfilled and it is clear that pathologists and toxicologists, in collaboration with molecular biologists, bioinformatists,and other scientists are making great strides in the design, analysis, and interpretation of microarray data for cancer studies.

Overexpression of fatty acid synthase in chemically and hormonally induced hepatocarcinogenesis of the rat

Fatty acid synthase (FAS) is the key enzyme of de novo fatty acid synthesis and has been shown to be involved in carcinogenesis of numerous human malignancies, including breast, colorectal, and prostate carcinomas, often associated with a worse prognosis. Although FAS is mainly expressed in the liver, an implication of FAS in hepatocarcinogenesis, has not yet been investigated. FAS expression is stimulated by insulin and glucose, and insulin is also the primary trigger of hepatocarcinogenesis in an endocrine experimental model, which is induced by low-number transplantation of islets of Langerhans into the livers of diabetic rats. We therefore investigated, whether FAS is implicated in hepatocarcinogenesis in this model and in comparison to chemically induced hepatocarcinogenesis after N-nitrosomorpholine (NNM) treatment in diabetic and normoglycemic rats. Preneoplastic clear-cell foci of altered hepatocytes (FAH), harvested after laser-microdissection of kryostat sections, showed an overexpression of FAS messenger RNA in gene expression profiles, done by array-hybridization, and in quantitative RT-PCR (Light-Cycler). Virtually, all (96-98%) of the subsequently investigated FAH and the glycogenotic hepatocellular adenomas and carcinomas showed an additional strong FAS protein overexpression. In the NNM-model, FAS protein was also overexpressed in the vast majority (87%) of glycogenotic FAH and neoplasms, in particular in the diabetic animals. Also two spontaneous glycogenotic FAH in control animals displayed strong FAS overexpression. Basophilic lesions and neoplasms, which occasionally develop out of the primary clear-cell FAH at later stages of carcinogenesis, however, lost FAS overexpression. In conclusion, FAS overexpression is an early phenonemon in spontaneous, hormonally and chemically induced rat hepatocarcinogenesis, demonstrable in early clear-cell (glycogenotic) FAH and hepatocellular neoplasms. FAS overexpression can be attributed to the local hyperinsulinemia in the transplantation model and belongs to cellular and metabolic alterations in the chemical model, which are induced by an insulinomimetic but yet unknown mechanism.

Insulin receptor, insulin receptor substrate-1, Raf-1, and Mek-1 during hormonal hepatocarcinogenesis by intrahepatic pancreatic islet transplantation in diabetic rats

Low-number transplantation of pancreatic islets into the livers of diabetic rats leads to transformation of the downstream liver acini into clear-cell foci of altered hepatocytes (FAHs). These FAHs correspond to the glycogen-storing (clear-cell) phenotype of hepatocellular preneoplasias and develop into hepatocellular adenomas (HCAs) and hepatocellular carcinomas (HCCs) within 6 to 24 months. In addition, they show metabolic alterations that resemble well-known insulin effects, most likely constituting the result of the local hyperinsulinemia. Thus, we investigated FAHs, HCAs, and HCCs for altered expression of insulin receptor, insulin receptor substrate-1 (IRS-1), Raf-1 and Mek-1. Light and electron microscopic immunohistochemistry revealed a translocation of insulin receptor from the plasma membrane (normal tissue) into the cytoplasm in clear-cell FAHs and an increase in insulin receptor expression in HCAs and HCCs. FAHs also showed an increase in IRS-1 gene expression, investigated by in situ hybridization and quantitative reverse transcription-PCR. IRS-1, Raf-1, and Mek-1 proteins were strongly overexpressed in FAHs and tumors, as compared with the unaltered liver tissue. These overexpressions were closely linked to the clear-cell phenotype of preneoplastic and neoplastic hepatocytes, because basophilic FAHs (later stages) and basophilic tumors showed no overexpressions. In this endocrine model of hepatocarcinogenesis, severe alterations of insulin signaling were induced by the pathological local action of islet hormones in the livers and may substantially contribute to the carcinogenic process.

An evaluation of the role of insulin-like growth factors (IGF) and of type-I IGF receptor signalling in hepatocarcinogenesis and in the resistance of hepatocarcinoma cells against drug-induced apoptosis

Strong evidence emphasizes the role of the insulin-like growth factor (IGF) system and of type-I IGF receptor (IGF-IR) signalling in tumourigenesis. In this connection: (i) changes in the expression pattern of components of the IGF system (autocrine/paracrine expression of IGF-I and -II, overexpression of IGF-IR, decreased expression of IGF-binding proteins (IGFBPs) and of type-II IGF receptor/cation-independent mannose-6-phosphate receptor (IGF-II/M6PR) and (ii) increased serum concentrations of proteases that cleave the IGFBPs (e.g., cathepsin D) were observed in patients with hepatocellular carcinomas (HCC), in human hepatoma cell lines and in their conditioned culture medium, as well as in rodent models of hepatocarcinogenesis. Accordingly, studies carried out with animal models do suggest that the IGF system and IGF-IR signalling may play a role in hepatocarcinogenesis and in deregulated proliferation and apoptosis of HCC cells. Finally the instrumental role of Raf/MEK/ERK, one of the signalling cascades stimulated by IGF-IR, in anthracycline-induced apoptosis of HepG2 and Huh-7 human hepatoma cell lines emphasizes that care must be taken when designing combinations of antitumoural molecules for antineoplastic treatment. This review addresses the putative roles of the IGF system in primary HCC, with a special focus on the underlying molecular mechanisms. In a second part it emphasizes the putative interference of IGF-IR signalling with chemotherapeutic drug-induced apoptosis in human hepatoma cells.

Insulin-like growth factor (IGF)-binding protein-1 is highly induced during acute carbon tetrachloride liver injury and potentiates the IGF-I-stimulated activation of rat hepatic stellate cells

Hepatic stellate cells (HSC) play a pivotal role in hepatic tissue repair and fibrogenesis. IGF-I has been considered a mitogenic signal for activation and proliferation of HSC in vitro. In the present study IGF-I and IGF-binding protein (IGFBP) gene expression was studied in a model of acute liver injury induced by a single intragastric dose of carbon tetrachloride (CCl(4)) in adult rats. Northern blot analysis revealed a marked increase in IGFBP-1 mRNA levels, with a maximum between 3 and 9 h after CCl(4) application, whereas steady state mRNA levels of IGF-I were only moderately altered. In situ hybridization experiments demonstrated that this increase in IGFBP-1 mRNA was due to a strong expression of IGFBP-1 in the perivenous region 6-12 h after CCl(4) application, extending to the midzonal region of the acinus within 24-48 h. Consequently, a prominent immunostaining for IGFBP-1 was observed in perivenous areas, with a maximum 24-48 h after intoxication. Preincubation of early cultured HSC with a nonphosphorylated IGFBP-1 from human amniotic fluid resulted in a 3.4-fold increase in IGF-I-induced DNA synthesis. The mitogenic effect of IGF-I was also potentiated when HSC were cocultivated with IGFBP-1-overexpressing BHK-21 cells compared with nontransfected cells. These data suggest that IGFBP-1 released during the early steps of liver tissue damage and repair may interact with HSC and potentiate the sensitivity of IGF-I to mitogenic signals.

Expression of liver insulin-like growth factor 1 gene and its serum level in rats with diabetes

AIM: To explore the effect of diabetic duration and blood glucose level on insulin like growth factor 1 (IGF-1) gene expression and serum IGF-1 level.

METHODS: Diabetes was induced into Sprague Dawley rats by alloxan and then the rats were subdivided into different groups with varying blood glucose level and diabetic duration. The parameters were measured as follows: IGF-1 mRNA by reverse transcriptase- polymerase chain reaction (RT-PCR), IGF-1 peptide and serum IGF-1 concentration by enzyme-linked immunosorbent assay (ELISA).

RESULTS: During early diabetic stage (week 2), in comparison with normal control group (NC), IGF-1 mRNA (1.17 ± 0.069 vs 0.79 ± 0.048, P < 0.001; 1.17 ± 0.069 vs 0.53 ± 0.023, P < 0.0005, respectively), IGF-1 peptide contents [(196.66 ± 14.9) ng·mg^-1vs (128.2 ± 11.25) ng·mg^-1, P < 0.0005; (196.66 ± 14.9) ng·mg^-1vs (74.43 ± 5.33) ng·mg^-1, P < 0.0001, respectively] were reduced in liver tissues of diabetic rats. The IGF-1 gene downregulation varied with glucose control level of the diabetic state, and deteriorated gradually further with duration of diabetes. By month 6, hepatic tissue IGF-1mRNA was 0.71 ± 0.024 vs 1.12 ± 0.056, P < 0.001; 0.47 ± 0.021 vs 1.12 ± 0.056, P < 0.0005, respectively. IGF-1 peptide was (114.35 ± 8.09) ng·mg^-1vs (202.05 ± 15.73) ng·mg^-1, P < 0.0005; (64.58 ± 3.89) ng·mg^-1vs (202.05 ± 15.73) ng·mg^-1, P < 0.0001 respectively. Serum IGF-1 was also lowered in diabetic group with poor control of blood glucose. On week 2, serum IGF-1 concentrations were (371.0 ± 12.5) ng·mg^-1vs (511.2 ± 24.7) ng·mg^-1, P < 0.0005, (223.2 ± 9.39) ng·mg^-1vs (511.2 ± 24.7) ng·mg^-1, P < 0.0001 respectively. By month 6, (349.6 ± 18.62) ng·mg^-1vs (520.7 ± 26.32) ng·mg^-1, P < 0.0005, (188.5 ± 17.35 vs 520.7 ± 26.32) ng·mg^-1, P < 0.0001, respectively. Serum IGF-1 peptide change was significantly correlated with that in liver tissue (r = 0.99, P < 0.001). Furthermore, No difference was found in the above parameters between diabetic rats with euglycemia and non-diabetic control group.

CONCLUSION: The influence of diabetic status on IGF-1 gene expression in liver tissues is started from early diabetic stage, causing down regulation of IGF-1 expression, and progresses with the severity and duration of diabetic state. Accordingly serum IGF-1 level decreases. This might indicate that liver tissue IGF-1 gene expression is greatly affected in diabetes, thus contributing to reduction of serum IGF-1 level.

Expression and regulation of the insulin-like growth factor axis components in rat liver myofibroblasts

Apart from hepatic stellate cells (HSC), liver myofibroblasts (MF) represent a second mesenchymal cell population involved in hepatic fibrogenesis. The IGF system including the insulin-like growth factors I and II (IGF-I, -II), their receptors (IGF-I receptor, IGF-IR; IGF-II/mannose 6-phosphate receptor, IGF-II/M6-PR), and six high affinity IGF binding proteins (IGFBPs) participate in the regulation of growth and differentiation of cells of the fibroblast lineage, possibly contributing to the fibrogenic process. The aim of this work was to study the expression and regulation of the IGF axis components in rat liver MF.

METHODS

Cultures of MF from passages 1 to 4 (P1-4) were studied. IGFBP secretion was analyzed by [(125)I]-IGF-I ligand and immunoblotting. IGF-I, IGF-IR, IGF-II/M6-PR, and IGFBP messenger RNA (mRNA) expression was assessed by Northern blot hybridization. DNA synthesis was evaluated by 5-bromo-2'-deoxyuridine (BrdU) incorporation assay.

RESULTS

MF from P1 to 4 constitutively expressed mRNA transcripts specific for IGF-I, IGF-IR, and IGF-II/M6-PR. In MF, biosynthesis of IGFBP-3 and -2 was observed that was stimulated by IGF-I, insulin, and transforming growth factor beta (TGF-beta), whereas platelet-derived growth factor (PDGF-BB) revealed inhibitory effects. IGF-I and to a lesser extent insulin increased DNA synthesis of MF. Simultaneous addition of recombinant human IGFBP-2 or -3 with IGF-I diminished the mitogenic effect of IGF-I on MF whereas preincubation of MF with IGFBP-2 or -3 further potentiated the IGF-I stimulated DNA synthesis. In conclusion, the present study demonstrates that the IGF axis may play a role in the regulation of MF proliferation in vitro which might be relevant in vivo for the process of fibrogenesis during acute and chronic liver injury.

cDNA microarray analysis of macroregenerative and dysplastic nodules in end-stage hepatitis C virus-induced cirrhosis

Hepatocellular carcinoma is a common malignancy causing significant morbidity and mortality worldwide. In this study we use expression microarray technology to identify novel genes that consistently displayed altered expression levels in the earliest identifiable precursors to hepatocellular carcinoma, dysplastic and macroregenerative nodules. The gene expression profiles from nine patients with end-stage hepatitis C cirrhosis that contained a combined 11 dysplastic or macroregenerative nodules were compared to the patient's matched cirrhotic liver tissue. A total of 53 genes were consistently dysregulated in the patient liver specimens. Six of seven genes were validated by quantitative real-time reverse transcriptase-polymerase chain reaction, or by immunohistochemical studies performed on an independent set of lesions. The novel genes, including caveolin-1, semaphorin E, and FMS-like tyrosine kinase 3 ligand, have putative roles in carcinogenesis but have not been reported in hepatocellular carcinogenesis. Microarray expression analysis of dysplastic and macroregenerative liver nodules provide insight into the earliest changes in hepatocellular carcinogenesis.

Insulin-like growth factor binding protein-1 over-expression in transgenic mice inhibits hepatic preneoplasia

Insulin-like growth factor binding protein-1 (IGFBP-1) is synthesized in the liver and regulates the mitogenic effects of the insulin-like growth factors (IGFs). The evidence that IGFBP-1 plays a role in hepatocarcinogenesis, however, is equivocal. We have, therefore, investigated the development of preneoplastic hepatic lesions in transgenic mice in which the human IGFBP-1 gene is under the control of the mouse metallothionein promoter. The lesions were induced by treating 15-d-old male mice with a single intraperitoneal injection of 5 mg/kg diethylnitrosamine (DENA). Lesions were scored when the mice were 28 wk of age. Quantitative microscopy of liver sections revealed that significantly fewer transgenic mice treated with zinc to activate the transgene had focal lesions compared to either transgenic mice not treated with zinc or wild-type mice treated with zinc (36.4% versus 85.7% and 83.3%, respectively, P < 0.05 in each case). Zinc-treated transgenic mice also had significantly fewer lesions per liver (11.5 +/- 5.0 versus 74.7 +/- 18.4 and 59.4 +/- 15.6, respectively, P < 0.01 in each case) and a smaller percentage of liver volume occupied by lesions (0.2 +/- 0.1 versus 1.4 +/- 0.3 and 1.1 +/- 0.4 respectively, P < 0.05 in each case). Immunohistochemical staining showed that both IGF-I and IGF-II were overexpressed in most of the lesions. These results show that expression of the IGFBP-1 transgene leads to a marked inhibition of hepatic preneoplasia, possibly by decreasing the mitogenic activity of IGF-I and/or IGF-II. This study adds new evidence to the notion that the IGF axis plays an important role in liver cancer development.

Expression of IGF-II in early experimental hepatocellular carcinomas and its significance in early diagnosis

AIM: To investigate the serum level and expression of insulin growth factor II (IGF-II) in liver tissues of rats with early experimental hepatocellular carcinomas (HCC) and its significance in early diagnosis.

METHODS: Early experimental hepatocellular carcinomas were induced by diethylnitrosamine (DENA) in 180 male SD rats. Another 20 male SD rats served as control. The IGF-II serum level was measured by ELISA. Immunohistochemistry and electron microscopic immunohistochemistry were used to observe the expression of IGF-II in normal and tumor liver tissues and its ultrastructural location in malignant hepatocytes. The expressions of IGF-II in human hepatoma cell lines HepG2, SMMC7721 and human embryonic liver cell line L-02 were measured by immunocytochemistry. IGF-II mRNA level was studied by in situ hybridization.

RESULTS: IGF-II was expressed in the cytoplasm of both sinusoidal cells in paracancerous cirrhotic liver tissue and malignant hepatocytes in early experimental HCC tissues. Gold particles were seen on the rough endoplasmic reticulum and the mitochondrion in malignant hepatocytes. IGF-II was expressed in the human hepatoma cell lines. The mRNA level of IGF-II was higher in rat liver tumor tissue than in normal rat liver tissue. The serum IGF-II level of the early experimental HCC group was 34.67 ± 10.53 ng·mL^-1 and that of the control group was 11.75 ± 5.84 ng·mL^-1. The rank sum test was used for statistical analysis. There was a significant difference between the two groups (P < 0.01).

CONCLUSION: During the induction of early experimental HCC by DENA, IGF-II may promote hepatocytic proliferation via a paracrine mechanism in the pre-cancerous stage. When hepatocytes are transformed into malignant cells, they may secrete IGF-II and promote malignant cell proliferation by an autocrine mechanism. IGF-II may be a possible biological marker in the early diagnosis of HCC.

Epidermal growth factor-induced activation of the insulin-like growth factor I receptor in rat hepatocytes

Insulin-like growth factor I (IGF-I) plays a critical role in the induction of cell cycle progression and survival in many cell types. However, there is minimal IGF-I binding to hepatocytes, and a role for IGF-I in hepatocyte signaling has not been elucidated. The dynamics of IGF-I receptor (IGF-IR) activation were examined in freshly isolated rat hepatocytes. IGF-I did not activate the IGF-IR. However, des(1-3)IGF-I, which weakly binds IGF binding protein-3 (IGFBP-3), induced IGF-IR phosphorylation. IGFBP-3 surface coating was identified by confocal immunofluorescence microscopy. In contrast with the inactivity of IGF-I, epidermal growth factor (EGF) induced the tyrosine phosphorylation of the IGF-IR in parallel with EGF receptor phosphorylation. Transactivation of the IGF-IR by EGF was inhibited by tyrphostin I-Ome-AG538, a tyrosine kinase inhibitor with high specificity for the IGF-IR. Src kinase inhibitors pyrazolopyrimidine PP-1 and PP-2 inhibited transactivation of the IGF-IR by EGF. EGF stimulated the tyrosine phosphorylation of Src, and induced its association with the IGF-IR. EGF-induced phosphorylations of insulin-related substrate (IRS)-1, IRS-2, Akt, and p42/44 mitogen-activated protein kinases (MAPKs) were inhibited variably by I-Ome-AG538. In conclusion, the data show an EGF- and Src-mediated transactivation pathway for IGF-IR activation in hepatocytes, and indicate a role for the IGF-IR in hepatocyte intracellular signaling. The findings also show a role for IGFBP-3 in the inhibition of IGF-I signaling in hepatocytes.

Cirrhotic livers reveal genetic changes in the MDM2-P14ARF system of cell cycle regulators

The genesis of hepatocellular carcinoma is promoted by changes in the regulatory MDM2-P14ARF system. The incidence of such changes has to date not been analysed in non-tumourous livers showing regenerative proliferation. In the present study, 24 cirrhotic livers of alcohol-, autoimmue disorder- or HCV-caused genesis were screened for MDM2-P14ARF alterations at the level of protein, DNA and mRNA. Using confocal laser scanning microscopy, the absence of MDM2 and P14ARF expression was detected in all samples except three HCV-infected livers (four livers) which contained hepatocytes overexpressing MDM2 (P14ARF) protein. In two of the samples lacking P14ARF expression, laser microdissection and PCR demonstrated deletion of the P14ARF gene. The P14ARF gene amplified from other specimens did not carry mutations. MDM2 splicing variants were present in tissues from alcohol- and autoimmune disorder-induced cirrhoses. Sequencing of full-size mRNA revealed a MDM2 mis-sense mutation in an alcohol-induced cirrhosis. One sample contained regenerative nodules with genetic instability occurring at MDM2 locus D12S83 according to the data of automatic PCR fragment analysis. In summary, this study gives first evidence for different types of MDM2 and P14ARF alterations in cirrhotic livers. We suggest that the changes impair the regulatory MDM2-P14ARF system, thus possibly favouring regenerative proliferation and transformation.

The IGF axis and hepatocarcinogenesis

Deregulation of the insulin-like growth factor (IGF) axis, including the autocrine production of IGFs, IGF binding proteins (IGFBPs), IGFBP proteases, and the expression of the IGF receptors, has been identified in the development of hepatocellular carcinoma (HCC). Characteristic alterations detected in HCC and hepatoma cell lines comprise the increased expression of IGF-II and the IGF-I receptor (IGF-IR), which have emerged as crucial events in malignant transformation and the growth of tumours. Alterations of IGFBP production and the proteolytic degradation of IGFBPs resulting in an excess of bioactive IGFs, as well as the defective function of the IGF degrading IGF-II/mannose 6-phosphate receptor (IGF-II/M6PR), may further potentiate the mitogenic effects of IGFs in the development of HCC.

Regulation of the components of the 150 kDa IGF binding protein complex in cocultures of rat hepatocytes and Kupffer cells by 3',5'-cyclic adenosine monophosphate

In the circulation, most of IGFs are bound to a high molecular mass complex of 150 kDa that consists of IGF-I (or IGF-II), IGFBP-3 and the acid-labile subunit (ALS). Within rat liver, biosynthesis of these components has been localized to different cell populations with hepatocytes as source of ALS and nonparenchymal cells (endothelial and Kupffer cells (KC)) as source of IGFBP-3. In the present study, the regulatory effects of the cAMP analogs dibutyryl-cAMP (db-cAMP) and 8-bromo-cAMP (8-br-cAMP) on IGF-I, ALS, and IGFBP expression were evaluated in primary cultures of rat hepatocytes, KC as well as in cocultures of hepatocytes and KC. In cocultures, biosynthesis of IGFBP-3 and ALS was inhibited dose-dependently by db-cAMP and 8-br-cAMP while that of IGF-I, IGFBP-1, and -4 was stimulated as demonstrated by ligand and Northern blotting. IGFBP-3 expression in primary cultures of pure KC did not respond to cAMP treatment indicating the importance of a cellular interaction between KC and hepatocytes for the decreased IGFBP-3 synthesis. The inhibition of IGFBP-3 in db-cAMP-treated cocultures was due to a decrease of IGFBP-3 mRNA level accompanied by a reduced cellular degradation of IGFBP-3. We conclude that cAMP stimulate the biosynthesis of IGF-I, IGFBP-1, and -4 in cocultures of hepatocytes and KC thereby enabling the formation of binary IGF/IGFBP complexes while the formation of the 150 kDa complex is impaired through downregulation of IGFBP-3 and ALS. This complex regulation may be a prerequisite for the effects of cAMP-dependent hormones on the transfer of IGFs from circulation to peripheral tissues.