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

PI3Kγ promotes obesity-associated hepatocellular carcinoma by regulating metabolism and inflammation

Background & Aims

Phosphatidylinositides-3 kinases (PI3Ks) are promising drug targets for cancer therapy, but blockage of PI3K-AKT signalling causes hyperglycaemia, hyperinsulinaemia, and liver damage in patients, and hepatocellular carcinoma (HCC) in mice. There are 4 PI3Ks: PI3Kα, PI3Kβ, PI3Kδ, and PI3Kγ. The role of PI3Kγ in HCC is unknown.

Methods

We performed histopathological, metabolic, and molecular phenotyping of mice with genetic ablation of PI3Kγ using models where HCC was initiated by the carcinogen diethylnitrosamine (DEN) and promoted by dietary or genetic obesity (ob/ob). The role of PI3Kγ in leucocytes was investigated in mice lacking PI3Kγ in haematopoietic and endothelial cells.

Results

Loss of PI3Kγ had no effects on the development of DEN-induced HCC in lean mice. However, in mice injected with DEN and placed on an obesogenic diet, PI3Kγ ablation reduced tumour growth, which was associated with reduced insulinaemia, steatosis, and expression of inflammatory cytokines. ob/ob mice lacking PI3Kγ, and mice with diet-induced obesity lacking PI3Kγ in leucocytes and endothelial cells did not display improved insulin sensitivity, steatosis, metabolic inflammation, or reduced tumour growth. However, these mice showed a reduced number of tumours, reduced liver infiltration by neutrophils, and reduced hepatocyte proliferation acutely induced by DEN.

Conclusions

Loss of PI3Kγ reduces tumour development in obesity-promoted HCC through multiple cell types and mechanisms that include improved insulinaemia, steatosis, and metabolic inflammation as well as the regulation of acute neutrophil infiltration and compensatory hepatocyte proliferation. PI3Kγ-selective inhibition may represent a novel therapeutic approach to reduce HCC initiation and slow HCC progression.

Lay summary

Class-1 phosphatidylinositides-3 kinases (PI3Ks) are critical targets in cancer therapy, but complete inhibition of all isoforms causes liver damage, hyperglycaemia, and insulinaemia. Here we show that selective ablation of the PI3Kγ isoform dampens tumour initiation and growth in a mouse model of carcinogen-initiated and obesity-promoted hepatocellular carcinoma (HCC). The effect of PI3Kγ ablation on reduced tumour growth was explained by reduced tumour cell proliferation, which was associated with reduced insulin levels, liver lipids, and reduced expression of tumour-promoting cytokines. PI3Kγ ablation in leucocytes of obese mice had no effects on tumour size. However, it reduced tumour number in association with reduced carcinogen-induced neutrophil infiltration and hepatocyte proliferation in livers of obese mice. Inhibition of PI3Kγ may thus reduce HCC initiation and growth in obese subjects by a mechanism involving reduced metabolic stress and insulinaemia and reduced carcinogen-induced neutrophil infiltration to the fatty liver.

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PI3Kγ ablation does not affect carcinogen-induced liver cancer in lean mice.

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PI3Kγ ablation reduces carcinogen-induced liver cancer in obese mice.

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Systemic PI3Kγ ablation reduces hyperinsulinaemia, steatosis, metabolic inflammation, and growth of liver tumours.

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PI3Kγ ablation in leucocytes and endothelial cells reduces neutrophil infiltration and hepatocyte proliferation acutely induced by carcinogen in the fatty liver.

Hormonally Induced Hepatocellular Carcinoma in Diabetic Wild Type and Carbohydrate Responsive Element Binding Protein Knockout Mice

OBJECTIVE

In the rat, the pancreatic islet transplantation model is an established method to induce hepatocellular carcinomas (HCC), due to insulin-mediated metabolic and molecular alterations like increased glycolysis and de novo lipogenesis and the oncogenic AKT/mTOR pathway including upregulation of the transcription factor Carbohydrate-response element-binding protein (ChREBP). ChREBP could therefore represent an essential oncogenic co-factor during hormonally induced hepatocarcinogenesis.

METHODS

Pancreatic islet transplantation was implemented in diabetic C57Bl/6J (wild type, WT) and ChREBP-knockout (KO) mice for 6 and 12 months. Liver tissue was examined using histology, immunohistochemistry, electron microscopy and Western blot analysis. Finally, we performed NGS-based transcriptome analysis between WT and KO liver tumor tissues.

RESULTS

Three hepatocellular carcinomas were detectable after 6 and 12 months in diabetic transplanted WT mice, but only one in a KO mouse after 12 months. Pre-neoplastic clear cell foci (CCF) were also present in liver acini downstream of the islets in WT and KO mice. In KO tumors, glycolysis, de novo lipogenesis and AKT/mTOR signalling were strongly downregulated compared to WT lesions. Extrafocal liver tissue of diabetic, transplanted KO mice revealed less glycogen storage and proliferative activity than WT mice. From transcriptome analysis, we identified a set of transcripts pertaining to metabolic, oncogenic and immunogenic pathways that are differentially expressed between tumors of WT and KO mice. Of 315 metabolism-associated genes, we observed 199 genes that displayed upregulation in the tumor of WT mice, whereas 116 transcripts showed their downregulated expression in KO mice tumor.

CONCLUSIONS

The pancreatic islet transplantation model is a suitable method to study hormonally induced hepatocarcinogenesis also in mice, allowing combination with gene knockout models. Our data indicate that deletion of ChREBP delays insulin-induced hepatocarcinogenesis, suggesting a combined oncogenic and lipogenic function of ChREBP along AKT/mTOR-mediated proliferation of hepatocytes and induction of hepatocellular carcinoma.

Metformin in the prevention of hepatocellular carcinoma in diabetic patients: A systematic review

.: Preventive effect of metformin in hepatocellular carcinoma (HCC) is not entirely clear. We aimed to evaluate the use of metformin as a protective factor of HCC in diabetic patients. .: We carried out an electronic search on PUBMED/MEDLINE, Web of Science and LILACS databases, with no limit of date, from April 2017 to January 2019. Eligible studies included cohort and case-control studies. We adressed data about the use of metformin on the risk of HCC development. Two independent reviewers extracted the data. We evaluated the quality of studies by using the Newcastle-Ottawa scale and carried out a meta-analysis using random-effects models. .: The electronic searches identified 747 studies. After reading abstracts and titles, we excluded 327 duplicated papers and 383 irrelevant references. Eight studies were selected; four case-control and four cohort studies. All studies have observed that the therapy with metformin was associated with a lower risk of HCC, compared with non-metformin therapy. Five articles reported that patients treated with insulin, or insulin secretagogues, presented increased risk of HCC compared to those treated with metformin. One study found that not only statin but also aspirin reduced the risk of HCC, if combined with metformin. A meta-analysis, using the case-control studies, found a combined Odds Ratio of 0.468; 95% CI 0.275-0.799 for the association between HCC and the use of metformin. .: The use of metformin was associated with a reduced risk of HCC, and it may be a relevant factor for preventing HCC in diabetic patients.

Hyperinsulinemia in Obesity, Inflammation, and Cancer

The relative insufficiency of insulin secretion and/or insulin action causes diabetes. However, obesity and type 2 diabetes mellitus can be associated with an absolute increase in circulating insulin, a state known as hyperinsulinemia. Studies are beginning to elucidate the cause-effect relationships between hyperinsulinemia and numerous consequences of metabolic dysfunctions. Here, we review recent evidence demonstrating that hyperinsulinemia may play a role in inflammation, aging and development of cancers. In this review, we will focus on the consequences and mechanisms of excess insulin production and action, placing recent findings that have challenged dogma in the context of the existing body of literature. Where relevant, we elaborate on the role of specific signal transduction components in the actions of insulin and consequences of chronic hyperinsulinemia. By discussing the involvement of hyperinsulinemia in various metabolic and other chronic diseases, we may identify more effective therapeutics or lifestyle interventions for preventing or treating obesity, diabetes and cancer. We also seek to identify pertinent questions that are ripe for future investigation.

Advances in Pancreatic Islet Transplantation Sites for the Treatment of Diabetes

Diabetes is a complex disease that affects over 400 million people worldwide. The life-long insulin injections and continuous blood glucose monitoring required in type 1 diabetes (T1D) represent a tremendous clinical and economic burdens that urges the need for a medical solution. Pancreatic islet transplantation holds great promise in the treatment of T1D; however, the difficulty in regulating post-transplantation immune reactions to avoid both allogenic and autoimmune graft rejection represent a bottleneck in the field of islet transplantation. Cell replacement strategies have been performed in hepatic, intramuscular, omentum, and subcutaneous sites, and have been performed in both animal models and human patients. However more optimal transplantation sites and methods of improving islet graft survival are needed to successfully translate these studies to a clinical relevant therapy. In this review, we summarize the current progress in the field as well as methods and sites of islet transplantation, including stem cell-derived functional human islets. We also discuss the contribution of immune cells, vessel formation, extracellular matrix, and nutritional supply on islet graft survival. Developing new transplantation sites with emerging technologies to improve islet graft survival and simplify immune regulation will greatly benefit the future success of islet cell therapy in the treatment of diabetes.

[Preneoplastic glycogenotic lesions of the liver and kidney : Metabolic and molecular alterations in preneoplastic clear cell lesions of the liver and the kidney in experimental and human carcinogenesis]

AIM

The focus of these five studies was on human clear cell, glycogen-storing lesions of the liver and kidney, which pertain to preneoplastic lesions of hepatocellular carcinoma and renal cell carcinoma in animal models of diabetes-associated carcinogenesis.

MATERIAL AND METHODS

Noncirrhotic hepatic and renal tissue of humans, rats, and mice were analyzed with histology, immunohistochemistry, electron microscopy, and molecular biologic methods.

RESULTS

In humans, clear cell lesions often occur in noncirrhotic liver and renal tissue. They resemble preneoplastic lesions of experimental hepato- and nephrocarcinogenesis regarding glycogen storage, increased proliferative activity, upregulation of glycolysis and de novo lipogenesis (lipogenic phenotype), and activated protooncogenic signaling pathway of AKT/mTOR. In two models of murine hepatocarcinogenesis, the important role of the transcription factor ChREBP as a "metabolic oncogene" was characterized.

CONCLUSION

In these studies, the significance of small glycogen storing parenchymal alterations for carcinogenesis in human noncirrhotic liver and kidney was demonstrated due to their already present metabolic and molecular alterations. Therefore, they have to represent indicator lesions for an increased risk of carcinogenesis. Activation of the protooncogenic pathway AKT/mTOR as well as the transcription factor ChREBP and the manifestation of the lipogenic phenotype are crucial during the processes of carcinogenesis.

Hyperinsulinaemia in cancer

Elevated circulating insulin levels are frequently observed in the setting of obesity and early type 2 diabetes, as a result of insensitivity of metabolic tissues to the effects of insulin. Higher levels of circulating insulin have been associated with increased cancer risk and progression in epidemiology studies. Elevated circulating insulin is believed to be a major factor linking obesity, diabetes and cancer. With the development of targeted cancer therapies, insulin signalling has emerged as a mechanism of therapeutic resistance. Although metabolic tissues become insensitive to insulin in the setting of obesity, a number of mechanisms allow cancer cells to maintain their ability to respond to insulin. Significant progress has been made in the past decade in understanding the insulin receptor and its signalling pathways in cancer, and a number of lessons have been learnt from therapeutic failures. These discoveries have led to numerous clinical trials that have aimed to reduce the levels of circulating insulin and to abrogate insulin signalling in cancer cells. With the rising prevalence of obesity and diabetes worldwide, and the realization that hyperinsulinaemia may contribute to therapeutic failures, it is essential to understand how insulin and insulin receptor signalling promote cancer progression.

Transcriptomic and Proteomic Analysis of Clear Cell Foci (CCF) in the Human Non-Cirrhotic Liver Identifies Several Differentially Expressed Genes and Proteins with Functions in Cancer Cell Biology and Glycogen Metabolism

Clear cell foci (CCF) of the liver are considered to be pre-neoplastic lesions of hepatocellular adenomas and carcinomas. They are hallmarked by glycogen overload and activation of AKT (v-akt murine thymoma viral oncogene homolog)/mTOR (mammalian target of rapamycin)-signaling. Here, we report the transcriptome and proteome of CCF extracted from human liver biopsies by laser capture microdissection. We found 14 genes and 22 proteins differentially expressed in CCF and the majority of these were expressed at lower levels in CCF. Using immunohistochemistry, the reduced expressions of STBD1 (starch-binding domain-containing protein 1), USP28 (ubiquitin-specific peptidase 28), monad/WDR92 (WD repeat domain 92), CYB5B (Cytochrome b5 type B), and HSPE1 (10 kDa heat shock protein, mitochondrial) were validated in CCF in independent specimens. Knockout of Stbd1, the gene coding for Starch-binding domain-containing protein 1, in mice did not have a significant effect on liver glycogen levels, indicating that additional factors are required for glycogen overload in CCF. Usp28 knockout mice did not show changes in glycogen storage in diethylnitrosamine-induced liver carcinoma, demonstrating that CCF are distinct from this type of cancer model, despite the decreased USP28 expression. Moreover, our data indicates that decreased USP28 expression is a novel factor contributing to the pre-neoplastic character of CCF. In summary, our work identifies several novel and unexpected candidates that are differentially expressed in CCF and that have functions in glycogen metabolism and tumorigenesis.

Considerations for an Alternative Site of Islet Cell Transplantation

Islet cell transplantation has been limited most by poor graft survival. Optimizing the site of transplantation could improve clinical outcomes by minimizing required donor cells, increasing graft integration, and simplifying the transplantation and monitoring process. In this article, we review the history and significant human and animal data for clinically relevant sites, including the liver, spleen, and kidney subcapsule, and identify promising new sites for further research. While the liver was the first studied site and has been used the most in clinical practice, the majority of transplanted islets become necrotic. We review the potential causes for graft death, including the instant blood-mediated inflammatory reaction, exposure to immunosuppressive agents, and low oxygen tension. Significant research exists on alternative sites for islet cell transplantation, suggesting a promising future for patients undergoing pancreatectomy.

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.

Hepatocellular glycogenotic foci after combined intraportal pancreatic islet transplantation and knockout of the carbohydrate responsive element binding protein in diabetic mice

Aims

The intraportal pancreatic islet transplantation (IPIT) model of diabetic rats is an insulin mediated model of hepatocarcinogenesis characterized by the induction of clear cell foci (CCF) of altered hepatocytes, which are pre-neoplastic lesions excessively storing glycogen (glycogenosis) and exhibiting activation of the AKT/mTOR protooncogenic pathway. In this study, we transferred the IPIT model to the mouse and combined it with the knockout of the transcription factor carbohydrate responsive element binding protein (chREBP).

Methods

C57BL/6J Wild-type (WT) and chREBP-knockout (chREBP-KO) mice (n = 297) were matched to 16 groups (WT/ chREBP-KO, experimental/control, streptozotocine-induced diabetic/not diabetic, one/four weeks). Experimental groups received the intraportal transplantation of 70 pancreatic islets. Liver and pancreatic tissue was examined using histology, morphometry, enzyme- and immunohistochemistry and electron microscopy.

Results

CCF emerged in the liver acini downstream of the transplanted islets. In comparison to WT lesions, CCF of chREBP-KO mice displayed more glycogen accumulation, reduced activity of the gluconeogenic enzyme glucose-6-phosphatase, decreased glycolysis, lipogenesis and reduced levels of the AKT/mTOR cascade members. Proliferative activity of CCF was ∼two folds higher in WT mice than in chREBP-KO mice.

Conclusions

The IPIT model is applicable to mice, as murine CCF resemble preneoplastic liver lesions from this hepatocarcinogenesis model in the rat in terms of morphological, metabolic and molecular alterations and proliferative activity, which is diminished after chREBP knockout. chREBP appears to be an essential component of AKT/mTOR mediated cell proliferation and the metabolic switch from a glycogenotic to lipogenic phenotype in precursor lesions of hepatocarcinogenesis.

Insulin Receptor Isoforms in Physiology and Disease: An Updated View

The insulin receptor (IR) gene undergoes differential splicing that generates two IR isoforms, IR-A and IR-B. The physiological roles of IR isoforms are incompletely understood and appear to be determined by their different binding affinities for insulin-like growth factors (IGFs), particularly for IGF-2. Predominant roles of IR-A in prenatal growth and development and of IR-B in metabolic regulation are well established. However, emerging evidence indicates that the differential expression of IR isoforms may also help explain the diversification of insulin and IGF signaling and actions in various organs and tissues by involving not only different ligand-binding affinities but also different membrane partitioning and trafficking and possibly different abilities to interact with a variety of molecular partners. Of note, dysregulation of the IR-A/IR-B ratio is associated with insulin resistance, aging, and increased proliferative activity of normal and neoplastic tissues and appears to sustain detrimental effects. This review discusses novel information that has generated remarkable progress in our understanding of the physiology of IR isoforms and their role in disease. We also focus on novel IR ligands and modulators that should now be considered as an important strategy for better and safer treatment of diabetes and cancer and possibly other IR-related diseases.

Role of insulin receptor substrates in the progression of hepatocellular carcinoma

Several cellular signaling pathways, including insulin/IGF signaling, are known to be activated in hepatocellular carcinoma (HCC). Here, we investigated the roles of insulin receptor substrate (Irs) 1 and Irs2, both of which are the major molecules to be responsible for transducing insulin/IGF signaling in the liver, in the development of HCC by inducing chemical carcinogenesis using diethylnitrosamine (DEN) in mice. The Irs1 mRNA and protein expressions were upregulated in the tumors, along with enhanced insulin signaling. Liver-specific Irs1-knockout (LIrs1KO) mice exhibited suppression of DEN-induced HCC development, accompanied by reduced cancer cell proliferative activity and reduced activation of Akt. Gene expression analyses revealed that the tumors in the DEN-treated LIrs1KO mice showed modest metabolic alterations during hepatocarcinogenesis as well as decreased inflammation and invasion potentials. On the other hand, liver-specific Irs2-knockout (LIrs2KO) mice showed a similar pattern of HCC development to the DEN-treated control wild-type mice. Based on the knowledge that Wnt/β-catenin signaling is activated in HCC, we focused on Wnt/β-catenin signaling and demonstrated that Irs1 expression was induced by Wnt3a stimulation in the primary hepatocytes, associated with insulin-stimulated Akt activation. These data suggest that upregulated Irs1 by Wnt/β-catenin signaling plays a crucial role in the progression of HCC.

Association of fasting serum insulin and cancer mortality in a healthy population - 28-year follow-up of the French TELECOM Study

AIMS

Epidemiologic, pharmacoepidemiologic and pathophysiologic evidence points consistently to an association between type 2 diabetes and cancer. This association could be explained by hyperinsulinemia induced by insulin resistance. We studied the association between fasting serum insulin (FSI) and cancer mortality in a population of non-diabetic individuals.

METHODS

We followed 3117 healthy workers (50.2% women), included in the TELECOM cohort study, between 1985 and 1987; their median age was 38 years (Q1-Q3=30-50). Baseline FSI was measured by radioimmunoassay, the INSI-PR method. People with diabetes or cancer at baseline were excluded. Vital status and causes of death were available until December 2013. The association between FSI and cancer deaths was analysed by sex, using a Cox proportional hazards model with age as the time scale, adjusting for body mass index, smoking habits, alcohol consumption, occupational category and ethnic origin.

RESULTS

After a 28-year follow-up, 330 (10.6%) deaths were reported, among which, 150 were cancer-related (80 men, 70 women). In men, the association between FSI and death by cancer was J-shaped: compared to the average FSI of 7.1mU/L, men with 5mU/L and 12.9mU/L had respectively adjusted hazard-ratios (HR) of 1.88 (95% confidence interval, 1.00-3.56) and 2.30 (95% CI, 1.34-3.94). Among women, no significant association was found (adjusted HR, 1.03; 95% CI, 0.96-1.11) for an increase of 1mU/L in FSI.

CONCLUSION

These results strengthen the hypothesis of an independent risk of cancer death associated with extreme values of FSI, mainly the highest, among men, but not among women.

A preclinical evaluation of alternative site for islet allotransplantation

The bone marrow cavity (BMC) has recently been identified as an alternative site to the liver for islet transplantation. This study aimed to compare the BMC with the liver as an islet allotransplantation site in diabetic monkeys. Diabetes was induced in Rhesus monkeys using streptozocin, and the monkeys were then divided into the following three groups: Group1 (islets transplanted in the liver with immunosuppressant), Group 2 (islets transplanted in the tibial BMC), and Group 3 (islets transplanted in the tibial BMC with immunosuppressant). The C-peptide and blood glucose levels were preoperatively measured. An intravenous glucose tolerance test (IVGTT) was conducted to assess graft function, and complete blood cell counts were performed to assess cell population changes. Cytokine expression was measured using an enzyme-linked immune sorbent assay (ELISA) and MILLIPLEX. Five monkeys in Group 3 exhibited a significantly increased insulin-independent time compared with the other groups (Group 1: 78.2 ± 19.0 days; Group 2: 58.8 ± 17.0 days; Group 3: 189.6 ± 26.2 days) and demonstrated increases in plasma C-peptide 4 months after transplantation. The infusion procedure was not associated with adverse effects. Functional islets in the BMC were observed 225 days after transplantation using the dithizone (DTZ) and insulin/glucagon stains. Our results showed that allogeneic islets transplanted in the BMC of diabetic Rhesus monkeys remained alive and functional for a longer time than those transplanted in the liver. This study was the first successful demonstration of allogeneic islet engraftment in the BMC of non-human primates (NHPs).

The Epidermal Growth Factor Receptor (EGFR) Inhibitor Gefitinib Reduces but Does Not Prevent Tumorigenesis in Chemical and Hormonal Induced Hepatocarcinogenesis Rat Models

Activation of the epidermal growth factor receptor (EGFR) signaling pathway promotes the development of hepatocellular adenoma (HCA) and carcinoma (HCC). The selective EGFR inhibitor Gefitinib was found to prevent hepatocarcinogenesis in rat cirrhotic livers. Thus, Gefitinib might reduce progression of pre-neoplastic liver lesions to HCC. In short- and long-term experiments, administration of N-Nitrosomorpholine (NNM) or intrahepatic transplantation of pancreatic islets in diabetic (PTx), thyroid follicles in thyroidectomized (TTx) and ovarian fragments in ovariectomized (OTx) rats was conducted for the induction of foci of altered hepatocytes (FAH). Gefitinib was administered for two weeks (20 mg/kg) or three and nine months (10 mg/kg). In NNM-treated rats, Gefitinib administration decreased the amount of FAH when compared to controls. The amount of HCA and HCC was decreased, but development was not prevented. Upon all transplantation models, proliferative activity of FAH was lower after administration of Gefitinib in short-term experiments. Nevertheless, the burden of HCA and HCC was not changed in later stages. Thus, EGFR inhibition by Gefitinib diminishes chemical and hormonal also induced hepatocarcinogenesis in the initiation stage in the non-cirrhotic liver. However, progression to malignant hepatocellular tumors was not prevented, indicating only a limited relevance of the EGFR signaling cascade in later stages of hepatocarcinogenesis.

Formation of Cholangiogenic Cysts Following Intrahepatic Islet Transplantation in Streptozotocin Diabetic Rats

Permanent hyperinsulinemia and the resulting overstimulation of the insulin receptor signaling pathway is suspected as a trigger of cancer genesis in the livers of type 2 diabetic patients. Liver tissue (LT) surrounding transplanted pancreatic islets (PI) can be permanently exposed to insulin in even higher concentrations than in type 2 diabetic patients. Therefore, this study examines the effect of PI transplantation (Tx) on LT in animals with streptozotocin (STZ)-induced diabetes mellitus. The suboptimal mass (400 or 1000) of isogeneic PI was transplanted into either the portal vein or under the kidney capsule of diabetic Brown Norway (BN) rats. Healthy BN rats treated with 400 isogeneic PI transplanted in the portal vein served as a control group. During the first 6 months after PI Tx, small and infrequent cystic lesions developed in animals with STZ diabetes, irrespective of the Tx site. In 10 months, frequent and complex cystic lesions appeared in these animals. In the control group, several small lesions were detected but not until 10 months after the PI Tx. In summary, STZ is the likely main inductor of hepatic cystic lesions, but the contribution of PI was not confirmed.

Hyperinsulinaemia and insulin signalling in the pathogenesis and the clinical course of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most prevalent cancer and is one of the leading causes of cancer-related death. The risk factors for HCC include cirrhosis, chronic viral hepatitis, heavy alcohol intake and metabolic diseases such as obesity, type 2 diabetes and metabolic syndrome. Insulin resistance is a common denominator of all of these conditions and is tethered to hyperinsulinaemia. Here, we give an overview of the recent advances linking hyperinsulinaemia to HCC development and progression. In particular, we summarise the underlying causes of hyperinsulinaemia in the setting of chronic liver diseases. We present epidemiological evidence linking metabolic diseases to HCC risk and HCC-related mortality, as well as the pathogenic cellular and molecular mechanisms explaining this relation. A better understanding of the mechanisms by which insulin participates in HCC biology might ultimately provide novel opportunities for prevention and treatment.

Nutrition and metabolism in hepatocellular carcinoma

Hepatocellular carcinoma is the fifth most common human cancer worldwide, with an overall 5-year survival in the range of 10%. In addition to the very substantial role of chronic viral hepatitis in causing hepatocellular carcinoma, nutritional status and specific nutritional factors appear to influence disease risk. This is apparent in the increased risk associated with non-alcoholic hepatic cirrhosis occurring in the context of obesity, the metabolic syndrome, and type 2 diabetes. Specific nutrients and ingested toxins, including ethanol, aflatoxin, microcystins, iron, and possibly components of red meat, also are associated with increased hepatocellular carcinoma risk. Other dietary components, including omega-3 fatty acids and branched chain amino acids, may have protective effects. Recent data further suggest that several metabolic regulatory drugs, including metformin, pioglitazone, and statins, may have the potential to decrease the risk of hepatocellular carcinoma. The available data on these nutritional and metabolic factors in causing hepatocellular carcinoma are reviewed with the goal of identifying the strength of current knowledge and directions for future investigation.

Molecular and metabolic changes in human liver clear cell foci resemble the alterations occurring in rat hepatocarcinogenesis

BACKGROUND & AIMS

Activation of the AKT/mTOR and Ras/MAPK pathways and the lipogenic phenotype occurs in both a rat model of insulin-induced hepatocarcinogenesis and in human hepatocellular carcinoma (HCC). In the rat model, activation of these pathways is evident within the earliest morphologic detectable alterations, i.e., clear cell foci (CCF) of altered hepatocytes. CCF have also been described in the human liver, but molecular and metabolic alterations within these foci remain to be determined.

METHODS

A collection of human liver specimens was examined using electron microscopy, histology, enzyme- and immunohistochemistry, and molecular analysis. Human data were compared to rat preneoplastic CCF and HCC induced by N-nitrosomorpholine administration.

RESULTS

CCF occurred in ∼33% of extrafocal tissues of human non-cirrhotic livers. Electron microscopy showed massive glycogen storage within CCF, largely due to the reduced activity of the glycogenolytic enzyme glucose-6-phosphatase. Hepatocytes in CCF overexpressed the insulin receptor and glucose transporter proteins. AKT/mTOR and Ras/MAPK pathways as well as enzymes of glycolysis, de novo lipogenesis, beta-oxidation, and cholesterol synthesis were upregulated, both in human CCF, and in CCF and HCC of N-nitrosomorpholine-treated rats. The Ki-67 proliferation index was 2-fold higher in human CCF than in extrafocal tissue.

CONCLUSIONS

The high degree of similarity between human CCF and pre-neoplastic lesions from experimental models of hepatocarcinogenesis in terms of morphologic, molecular and metabolic features suggests a low-grade dysplastic nature of these lesions in human non-cirrhotic livers.

A stochastic mathematical model to study the autoimmune progression towards type 1 diabetes

BACKGROUND

The integrity of the interactions and the 3D architecture among beta cell populations in pancreatic islets is critical for proper biosynthesis, storage and release of insulin. The aim of this study was to evaluate the effect on electrophysiological signalling of beta cells that is produced by progressive lymphocytic islet cell infiltration (insulitis), by modelling the disruption of pancreatic islet anatomy as a consequence of insulitis and altered glucose concentrations.

METHODS

On the basis of histopathological images of murine islets from non-obese diabetic mice, we simulated the electrophysiological dynamics of a 3D cluster of mouse beta cells via a stochastic model. Progressive damage was modelled at different glucose concentrations, representing the different glycaemic states in the autoimmune progression towards type 1 diabetes.

RESULTS

At 31% of dead beta cells (normoglycaemia) and 69% (hyperglycaemia), the system appeared to be biologically robust to maintain regular Ca(2+) ion oscillations guaranteeing an effective insulin release. Simulations at 84%, 94% and 98% grades (severe hyperglycemia) showed that intracellular calcium oscillations were absent. In such conditions, insulin pulsatility is not expected to occur.

CONCLUSIONS

Our results suggest that the islet tissue is biophysically robust enough to compensate for high rates of beta cell loss. These predictions can be experimentally tested in vitro by quantifying space and time electrophysiological dynamics of animal islets kept at different glucose gradients. The model indicates the necessity of maintaining glycaemia within the physiological range as soon as possible after diabetes onset to avoid a dramatic interruption of Ca(2+) pulsatility and the consequent drop of insulin release.

Islet transplantation in type 1 diabetes: ongoing challenges, refined procedures, and long-term outcome

Remarkable progress has been made in islet transplantation over a span of 40 years. Once just an experimental curiosity in mice, this therapy has moved forward, and can now provide robust therapy for highly selected patients with type 1 diabetes (T1D), refractory to stabilization by other means. This progress could not have occurred without extensive dynamic international collaboration. Currently, 1,085 patients have undergone islet transplantation at 40 international sites since the Edmonton Protocol was reported in 2000 (752 allografts, 333 autografts), according to the Collaborative Islet Transplant Registry. The long-term results of islet transplantation in selected centers now match registry data of pancreas-alone transplantation, with 6 sites reporting five-year insulin independence rates ≥50%. Islet transplantation has been criticized for the use of multiple donor pancreas organs, but progress has also occurred in single-donor success, with 10 sites reporting increased single-donor engraftment. The next wave of innovative clinical trial interventions will address instant blood-mediated inflammatory reaction (IBMIR), apoptosis, and inflammation, and will translate into further marked improvements in single-donor success. Effective control of auto- and alloimmunity is the key to long-term islet function, and high-resolution cellular and antibody-based assays will add considerable precision to this process. Advances in immunosuppression, with new antibody-based targeting of costimulatory blockade and other T-B cellular signaling, will have further profound impact on the safety record of immunotherapy. Clinical trials will move forward shortly to test out new human stem cell derived islets, and in parallel trials will move forward, testing pig islets for compatibility in patients. Induction of immunological tolerance to self-islet antigens and to allografts is a difficult challenge, but potentially within our grasp.

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 2 gene methylation in peripheral blood mononuclear cells of patients with hepatitis C related cirrhosis or hepatocellular carcinoma

Igf2 gene specific hypomethylation has been demonstrated in hepatocellular carcinoma (HCC) cells and in non-tumoral liver samples from patients with HCV-related cirrhosis who further developed HCC. In patients with colorectal cancers, Igf2 hypomethylation is found in peripheral blood mononuclear cells (PBMC) even prior to the occurrence of cancer.

AIM

To compare Igf2 methylation in PBMC from healthy donors and patients with HCV-related cirrhosis without or with history of HCC.

PATIENTS AND METHODS

After DNA extraction from frozen PBMC samples of 52 healthy blood donors and 121 patients with HCV-related cirrhosis either without (n=59) or with past or present HCC (n=62), and sodium bisulfite treatment, unbiased PCR amplification and Denaturing High Performance Liquid Chromatography (DHPLC) analysis were used for methylation analysis at the differentially methylated region 2 of Igf2. Methylation profiles were classified in three groups (unmethylated, U; methylated, M; and intermediate, UM) according to the proportions of M and U alleles, blindly to clinical data. In addition, 677C-T mutation of Methylenetetrahydrofolate Reductase (MTHFR) was investigated by fluorescent probes.

RESULTS

Prevalences of U, UM and M Igf2 profiles were: 8%, 65% and 27% in blood donors, 0%, 81% and 19% in patients with HCV-related cirrhosis without HCC, 71%, 29% and 0% in patients with HCC (P<0.0001). Igf2 methylation profile was independent from gender, age, body mass index, and presence of 677C-T mutation of MTHFR.

CONCLUSION

These observations suggest a decrease of Igf2 methylation from cirrhosis to HCC in patients with HCV infection, which may be an additional risk factor for HCC.

V-AKT murine thymoma viral oncogene homolog/mammalian target of rapamycin activation induces a module of metabolic changes contributing to growth in insulin-induced hepatocarcinogenesis

Mounting epidemiological evidence supports a role for insulin-signaling deregulation and diabetes mellitus in human hepatocarcinogenesis. However, the underlying molecular mechanisms remain unknown. To study the oncogenic effect of chronically elevated insulin on hepatocytes in the presence of mild hyperglycemia, we developed a model of pancreatic islet transplantation into the liver. In this model, islets of a donor rat are transplanted into the liver of a recipient diabetic rat, with resulting local hyperinsulinism that leads to the development of preneoplastic lesions and hepatocellular carcinoma (HCC). Here, we investigated the metabolic and growth properties of the v-akt murine thymoma viral oncogene homolog/mammalian target of rapamycin (AKT/mTOR) pathway, a major downstream effector of insulin signaling, in this model of insulin-induced hepatocarcinogenesis. We found that activation of insulin signaling triggers a strong induction of the AKT/mTOR cascade that is paralleled by increased synthesis of fatty acids, cholesterol, and triglycerides, induction of glycolysis, and decrease of fatty acid oxidation and gluconeogenesis in rat preneoplastic and neoplastic liver lesions, when compared with the healthy liver. AKT/mTOR metabolic effects on hepatocytes, after insulin stimulation, were found to be mTORC1 dependent and independent in human HCC cell lines. In these cells, suppression of lipogenesis, glycolysis, and the pentose phosphate pathway triggered a strong growth restraint, despite insulin administration. Noticeably, metabolic abnormalities and proliferation driven by insulin were effectively reverted using the dual PI3K/mTOR inhibitor, NVP-BEZ235, both in vitro and in vivo.

CONCLUSIONS

The present results indicate that activation of the AKT/mTOR cascade by unconstrained insulin signaling induces a defined module of metabolic alterations in hepatocytes contributing to aberrant cell growth. Thus, inhibition of AKT/mTOR and related metabolic changes might represent a novel preventive and therapeutic approach to effectively inhibit insulin-induced hepatocarcinogenesis.

Metformin and hepatic carcinogenesis

Retrospective, hypothesis-generating population studies suggest that diabetics treated with metformin have a substantially reduced risk of several cancers, including hepatoma, relative to diabetics on other therapies. In this issue of the journal (beginning on page 544), Bhalla and colleagues contribute to the growing literature on metformin effects in experimental carcinogenesis models, showing reduced carcinogen-induced hepatoma in mice. The clinical need to develop novel prevention strategies for hepatoma is obvious, given an increasing prevalence and poor prognosis. The clues that metformin or related biguanides may have utility in this area justify accelerated laboratory research, as more data concerning mechanism, pharmacokinetics, and predictors of efficacy will help to optimize the design of clinical trials.

Alternative transplantation sites for pancreatic islet grafts

The liver is the current site of choice for pancreatic islet transplantation, even though it is far from being an ideal site because of immunologic, anatomic, and physiologic factors leading to a significant early graft loss. A huge amount of alternative sites have been used for islet transplantation in experimental animal models to provide improved engraftment and long-term survival minimizing surgical complications. The pancreas, gastric submucosa, genitourinary tract, muscle, omentum, bone marrow, kidney capsule, peritoneum, anterior eye chamber, testis, and thymus have been explored. Site-specific differences exist in term of islet engraftment, but few alternative sites have potential clinical translation and generally the evidence of a post-transplant islet function better than that reached after intraportal infusion is still lacking. This review discusses site-specific benefits and drawbacks taking into account immunologic, metabolic, and technical aspects to identify the ideal microenvironment for islet function and survival.

Promoting Effects of Streptozotocin-induced Diabetes on Induction of Hepatic Preneoplastic Lesions by Diethylnitrosamine in Rats

The effects of streptozotocin (STZ)-induced diabetes on induction of hepatic preneoplastic lesions by diethylnitrosamine (DEN) were investigated in male Fischer rats. A single dose of STZ was injected intravenously either 2 weeks before or after initiation with DEN. The blood glucose levels were significantly elevated from 1 week after STZ-injection until autopsy. The numbers of GST-P positive foci at 1 week after DEN administration in the STZ-injected rats were similar to those in the non-diabetic rats. In contrast, both the numbers and areas of GST-P positive foci > 2 mm in diameter 8 weeks after DEN administration were increased significantly in the rats treated with STZ after DEN exposure compared with the non-diabetic control rats. The results suggest that hepatic preneoplastic lesions initiated with DEN are promoted by STZ treatment-inducing diabetes.

Comparison of four pancreatic islet implantation sites

Although the liver is the most common site for pancreatic islet transplantation, it is not optimal. We compared kidney, liver, muscle, and omentum as transplantation sites with regard to operative feasibility, and the efficiency of implantation and glycemic control. Islets from C57BL/6 mice were transplanted into diabetic syngeneic recipients. The mean operative time and mortality were measured to assess feasibility. To assess implantation efficiency, the marginal mass required to cure diabetes and the mean time taken to achieve normoglycemia were measured. A glucose tolerance test was performed to assess glycemic control efficiency. The data are listed in the order of the kidney, liver, muscle, and omentum, respectively. The mean mortality rate was 6.7, 20.0, 7.1, and 12.5%; the mean operative time was 10.2, 27.4, 11.2, and 19.8 min; the marginal islet mass was 100, 600, 600, and 200 islet equivalence units and the mean time to reach euglycemia was 3.0, 15.1, 26.6, and 13.9 days. The glucose kinetics of omental pouch islets was the most similar to controls. Thus, a strategic approach is required for deciding on the best transplantation recipient sites after considering donor sources and islet volume. Alternatives can be chosen based on safety or efficacy.

Insulin-independent promotion of chemically induced hepatocellular tumor development in genetically diabetic mice

Diabetes mellitus has been proposed as an epidemiological risk factor for human liver cancer development. One reasonable possibility is that this is attributable to hyperinsulinemia compensatory for obesity-related insulin resistance. However, diabetes mellitus is a complex disease with multiple abnormal conditions essentially caused by hyperglycemia. Therefore, it is not evident whether hyperinsulinemia is prerequisite for the elevated cancer risk. To gain a clue to answer this question, we characterized chemically induced hepatocarcinogenesis in diabetic model mice genetically deficient for insulin. Akita inbred mice originating from the C57BL/6 strain carry a heterozygous germline mutation of the insulin II gene and suffer from inherited insulin deficiency and diabetes in an autosomal dominant manner. They were mated with normal C3H/HeJ mice with high sensitivity to liver carcinogenesis and the resultant F(1) littermates, which were either normal or insulin deficient, were exposed to diethylnitrosamine and induced hepatocellular tumors were evaluated for number, size, proliferative activity, and apoptosis. Unexpectedly, both mean and total volumes of hepatocellular tumors in the insulin-deficient animals were more than twofold larger than those in the normal controls, with no significant difference in tumor number. The tumors in insulin-deficient mice showed a significantly lower frequency of apoptosis but no alteration in cell proliferation. In conclusion, our results indicate that insulin-independent liver tumor promotion occurred in diabetic mice. Clearly, insulin-independent mechanisms for the human case also deserve consideration.

Delayed improvement of insulin secretion after autologous islet transplantation in partially pancreatectomized patients

The purpose of this study was to evaluate the effects of autologous islet transplantation (ITx) on glucose homeostasis and insulin secretory function after partial pancreatectomy (Px). Fourteen nondiabetic patients who underwent distal Px and autologous ITx for benign pancreatic tumors were enrolled in the study (Px + ITx group). Fourteen normal glucose-tolerant controls and 6 Px without ITx controls were recruited, and all groups were followed over a 24-month period. They performed the 75-g oral glucose tolerance test and the 1-mg glucagon stimulation test. Hemoglobin A(1c) was measured, and indices of insulin secretion were calculated. In the Px + ITx group, insulin secretion increased after a nadir at 6 months. Glucose tolerance, which had been abruptly impaired immediately after Px, recovered until 6 months and stabilized thereafter. As a result, differences in glucose intolerance emerged between the subjects in the Px group and those in the Px + ITx group at 24 months after Px. Characteristic variables in the better insulin secretory subjects in the Px + ITx group included younger age, less extensive pancreas resection, and a greater number of total islets. In summary, delayed amelioration of glucose intolerance was induced by autologous ITx after partial Px, even with a small number of islets.

Bone marrow as an alternative site for islet transplantation

The liver is the current site for pancreatic islet transplantation, but has many drawbacks due to immunologic and nonimmunologic factors. We asked whether pancreatic islets could be engrafted in the bone marrow (BM), an easily accessible and widely distributed transplant site that may lack the limitations seen in the liver. Syngeneic islets engrafted efficiently in the BM of C57BL/6 mice rendered diabetic by streptozocin treatment. For more than 1 year after transplantation, these animals showed parameters of glucose metabolism that were similar to those of nondiabetic mice. Islets in BM had a higher probability to reach euglycemia than islets in liver (2.4-fold increase, P = .02), showed a compact morphology with a conserved ratio between alpha and beta cells, and affected bone structure only very marginally. Islets in BM did not compromise hematopoietic activity, even when it was strongly induced in response to a BM aplasia-inducing infection with lymphocytic choriomeningitis virus. In conclusion, BM is an attractive and safe alternative site for pancreatic islet transplantation. The results of our study open a research line with potentially significant clinical impact, not only for the treatment of diabetes, but also for other diseases amenable to treatment with cellular transplantation.

Expression of xenobiotic and steroid hormone metabolizing enzymes in hepatocellular tumors of the non-cirrhotic liver

Hepatocellular adenomas (HCA) and some hepatocellular carcinomas (HCC) arise in the non-cirrhotic liver. Although the liver is involved in the metabolism of a huge number of exogenous and endogenous substances, little is known about the role of metabolic enzymes in the development of liver tumors in the absence of cirrhosis. We analyzed the expression of glutathione S-transferases (GST) and cytochrome P450 enzymes (CYP) in 23 HCA, 20 HCC, and 22 focal nodular hyperplasias (FNH) using immunohistochemistry. The liver tissue revealed consistent specific staining for GST alpha, CYP1A1, 1A2, 2E1, and 3A4. In HCA and HCC, GST alpha expression was significantly reduced (p<0.001 and 0.043). Reduced GST alpha expression was significantly associated with steatosis in HCA and HCC (n=12, p=0.006), but not in non-neoplastic liver tissue. CYP3A4 expression was also reduced in HCA and HCC (p=0.03 and 0.02), and this was correlated with diabetes mellitus type 2 (p=0.02). In conclusion, HCA and HCC revealed changes in the expression of certain metabolic enzymes as compared with the non-neoplastic liver tissue or FNH. Therefore, reduced expression of GST alpha and CYP3A4 may indicate specific metabolic defects in the tumor tissue characterizing subgroups of HCA and HCC.

[Hepatocellular carcinoma in the non-cirrhotic liver]

Of hepatocellular carcinomas (HCC), 15-20% occur in the non-cirrhotic liver. All factors which cause HCC when liver cirrhosis (LC) is present, can also lead to HCC without LC. On the basis of the relative frequency, HCC can be roughly differentiated into 3 groups: 1) HCC, rarely occurring without cirrhosis (e.g. virus hepatitis, alcohol abuse). 2) HCC, frequently occurring without LC (alpha1-antitrypsin deficiency, hemochromatosis, non-alcoholic fatty liver disease). 3) HCC, consistently occurring without LC (glycogen storage disease type 1, consumption of oral contraceptives/anabolic steroids). In groups 1 and 2 the level of hepatocellular toxicity necessary to reach LC is not yet achieved but the carcinogenic effect is already strong enough to induce HCC, possibly owing to the influence of additional carcinogens or host factors. In group 3, the carcinogenic effect is mediated by a long-standing alteration of the hepatocellular metabolism that is of low toxic effect and does not lead to cell death, but is nevertheless carcinogenic. In these cases, the initial formation of hepatocellular adenomas that subsequently transform into HCC is a common finding (adenoma-carcinoma sequence).

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.

Sustained reversal of diabetes following islet transplantation to striated musculature in the rat

BACKGROUND

There is an increasing emphasis in the islet transplant community on the development of alternative sites for islet implantation. Striated musculature constitutes a potential alternative, which has been successfully employed in autotransplantation of parathyroid glands for decades. In the present study, a technique for intramuscular islet transplantation was developed and compared with intraportal islet transplantation in a syngeneic rat model.

MATERIALS AND METHODS

Lewis rats were used. Pancreata were digested using Liberase. Islets were either transplanted into m. biceps femoris in a pearls-on-a-string fashion or intraportally, and the ability to reverse diabetes was compared. Eight weeks after transplantation an IVGTT was performed. Real-time quantitative RT-PCR was employed on muscle biopsies to investigate mRNA levels of cytokines in response to the transplant procedure. Explanted livers, muscles, and pancreata were harvested at the end of the experiment for histopathological analyses.

RESULTS

2000 IEQ repeatedly cured diabetic rats at the intraportal site, while 4000 IEQ was required at the intramuscular site. Time to reversal of diabetes, post-transplant weight development, and IVGTT curves did not differ between the groups. Normoglycemia was sustainable to the end of the study (>100 days) for all animals. The transplant procedure upregulated pro-inflammatory cytokines (IL-6 and IL-8) in striated muscle, and peri-islet fibrosis was observed in intramuscular grafts.

CONCLUSIONS

Islet transplantation into striated musculature is feasible; however, in its present form the intramuscular site is less efficient compared with the liver in rats. The intramuscular site allows manipulation of the graft and implantation site prior to transplantation and may therefore have implications for islet transplantation in humans.

Nonvirally modified autologous primary hepatocytes correct diabetes and prevent target organ injury in a large preclinical model

BACKGROUND

Current gene- and cell-based therapies have significant limitations which impede widespread clinical application. Taking diabetes mellitus as a paradigm, we have sought to overcome these limitations by ex vivo electrotransfer of a nonviral insulin expression vector into primary hepatocytes followed by immediate autologous reimplantation in a preclinical model of diabetes.

METHODS AND RESULTS

In a single 3-hour procedure, hepatocytes were isolated from a surgically resected liver wedge, electroporated with an insulin expression plasmid ex vivo and reimplanted intraparenchymally under ultrasonic guidance into the liver in each of 10 streptozotocin-induced diabetic Yorkshire pigs. The vector was comprised of a bifunctional, glucose-responsive promoter linked to human insulin cDNA. Ambient glucose concentrations appropriately altered human insulin mRNA expression and C-peptide secretion within minutes in vitro and in vivo. Treated swine showed correction of hyperglycemia, glucose intolerance, dyslipidemia and other metabolic abnormalities for > or = 47 weeks. Metabolic correction correlated significantly with the number of hepatocytes implanted. Importantly, we observed no hypoglycemia even under fasting conditions. Direct intrahepatic implantation of hepatocytes did not alter biochemical indices of liver function or induce abnormal hepatic lobular architecture. About 70% of implanted hepatocytes functionally engrafted, appeared histologically normal, retained vector DNA and expressed human insulin for > or = 47 weeks. Based on structural tissue analyses and transcriptome data, we showed that early correction of diabetes attenuated and even prevented pathological changes in the eye, kidney, liver and aorta.

CONCLUSIONS

We demonstrate that autologous hepatocytes can be efficiently, simply and safely modified by electroporation of a nonviral vector to express, process and secrete insulin durably. This strategy, which achieved significant and sustained therapeutic efficacy in a large preclinical model without adverse effects, warrants consideration for clinical development especially as it could have broader future applications for the treatment of other acquired and inherited diseases for which systemic reconstitution of a specific protein deficiency is critical.

Optimising islet engraftment is critical for successful clinical islet transplantation

Clinical islet transplantation is currently being explored as a treatment for persons with type 1 diabetes and hypoglycaemia unawareness. Although 'proof-of-principle' has been established in recent clinical studies, the procedure suffers from low efficacy. At the time of transplantation, the isolated islets are allowed to embolise the liver after injection in the portal vein, a procedure that is unique in the area of transplantation. A novel view on the engraftment of intraportally transplanted islets is presented that could explain the low efficacy of the procedure.

Evaluation of alternative sites for islet transplantation in the minipig: interest and limits of the gastric submucosa

Since the introduction of glucocorticoid-free immunosuppressive regimens, islet transplantation offers a less invasive alternative to pancreas transplantation. However, complications associated with intraportal islet injection and the progressive functional decline of intrahepatic islets encourage the exploration of alternative sites. Herein we evaluated, in the minipig, the use of the gastric submucosa (GS; group 1, n = 5) for islet transplantation compared with the kidney capsule (KC; group 2, n = 5). Subsequently we attempted to improve the vascularization of the submucosal graft (group 3, n = 5) by the addition of an extracellular matrix rich in growth factors (Matrigel). One month after grafting, we evaluated transplanted islet function in vivo and in vitro. Our study showed better function of islets engrafted in the GS than in the KC (P < .05). Despite the growth factors, Matrigel did not offer a more suitable environment to further improve engraftment (group 3, P < .05). Thus, even if the liver remains the gold standard, the GS represents a potential islet engraftment site, confirming the data obtained in vitro and in the rodent. Offering easy access by endoscopy, this site could constitute an interesting alternative for experimental studies in large mammals and, eventually, for clinical application.

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.

Association of diet-induced hyperinsulinemia with accelerated growth of prostate cancer (LNCaP) xenografts

BACKGROUND

Prior research suggested that energy balance and fat intake influence prostate cancer progression, but the influence of dietary carbohydrate on prostate cancer progression has not been well characterized. We hypothesized that hyperinsulinemia resulting from high intake of refined carbohydrates would lead to more rapid growth of tumors in the murine LNCaP xenograft model of prostate cancer.

METHODS

Athymic mice were injected subcutaneously with LNCaP human prostate cancer cells and, when tumors were palpable, were randomly assigned (n = 20 per group) to high carbohydrate-high fat or low carbohydrate-high fat diets. Body weight and tumor volume were measured weekly. After 9 weeks, serum levels of insulin and insulin-like growth factor 1 (IGF-1) were measured by enzyme immunoassay. AKT activation and the levels of the insulin receptor in tumor cells were determined by immunoblotting. The in vitro growth response of LNCaP cells to serum from mice in the two treatment groups was measured based on tetrazolium compound reduction. All statistical tests were two-sided.

RESULTS

After 9 weeks on the experimental diets, mice on the high carbohydrate-high fat diet were heavier (mean body weight of mice on the high carbohydrate-high fat diet = 34 g versus 29.1 g on the low carbohydrate-high fat diet, difference = 4.9 g, 95% CI = 3.8 to 6.0 g; P = .003), experienced increased tumor growth (mean tumor volume in mice on high carbohydrate-high fat diet = 1695 versus 980 mm3 on low carbohydrate-high fat diet, difference = 715 mm3, 95% CI = 608 to 822 mm3; P<.001), and experienced a statistically significant increase in serum insulin and IGF-1 levels. Tumors from mice on the high carbohydrate-high fat diet had higher levels of activated AKT and modestly higher insulin receptor levels than tumors from mice on the low carbohydrate-high fat diet. Serum from mice on the high carbohydrate-high fat diet was more mitogenic for LNCaP cells in vitro than serum from mice fed the low carbohydrate-high fat diet.

CONCLUSION

A diet high in refined carbohydrates is associated with increased tumor growth and with activation of signaling pathways distal to the insulin receptor in a murine model of prostate cancer.

Revelation of simple and complex liver acini after portal transplantation of pancreatic islets or thyroid follicles in rats

The microarchitecture of the liver is still not completely understood although various concepts of structural liver organization have been proposed. Among them, Rappaport's liver acinus stands out as one of the most accepted models. The correctness of this model, however, has also been doubted, and its applicability is hampered by the fact that the outlines of the liver acinus are disguised and nobody was ever able to give visual evidence by "unmasking" a simple liver acinus from the surrounding liver tissue. After intraportal transplantation of pancreatic islets or thyroid follicles into diabetic or thyroidectomized rats, respectively, the transplants engraft in small portal tracts and morphologically alter the downstream liver tissue due to excessive hormone secretion. Using a combined approach of perfusion fixation, stereomicroscopy, and light microscopy, we demonstrate in this study that these foci of altered liver tissue represent simple and complex liver acini, exactly as described by Rappaport. We present stereomicroscopical and histological examples of all important cut levels of altered simple and complex liver acini, including their topographical relation to the supplying and draining vessels and to the "central vein" liver lobule. Moreover, by computer-aided reconstruction of serial semi-thin sections, we were able to present the first 3-dimensional images of simple and complex liver acini.

CONCLUSION

Our results prove the correctness of Rappaport's acinus model and confirm the simple liver acinus as the principal microcirculatory unit of the liver.

Assessment of islet function following islet and pancreas transplantation

Pancreas and islet transplant recipients are monitored using various metabolic and imaging methods. The inaccessibility of the transplanted whole pancreas and of the isolated islets poses specific problems (eg, all assessment techniques are indirect). Although successful pancreas transplantation typically restores normal glucose homeostasis, islet transplantation into the liver does not completely normalize islet hormone secretion and glucose metabolism. Development of better testing strategies, such as direct islet imaging, will significantly advance the field.

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.