<p>Liver cancer is a devastating disease that is the 5th most common cancer in men, 7th most common cancer in women, and the 3rd leading cause of cancer-related mortality. This disease arises from multiple etiological factors, including hepatitis viruses, environmental toxins, alcohol abuse, and metabolic syndrome, which induce a state of chronic inflammation. This diseased liver tissue background is a drastically different microenvironment from the healthy liver, especially with regards to immune cell prevalence and presence of mediators of immune function. It has been well-established that this altered tissue background contributes significantly to the tumorigenic process, yet its effects on the progression of the disease are more poorly understood. </p><p>To better understand the consequences of liver disease on tumor growth and the interplay with its microenvironment, we first utilized two standard methods of fibrosis induction and orthotopic implantation of tumors into the inflamed and fibrotic liver to mimic the liver condition in human HCC patients, and examined the immune infiltrate. Compared to non-diseased controls, tumor growth is significantly enhanced under fibrotic conditions. The immune cells that infiltrated the tumors are also drastically different, with decreased proportions of natural killer cells but greatly increased numbers of immune-suppressive CD11b+ Gr1hi myeloid cells in both models of fibrosis. In addition, there are model-specific differences: increased proportions of CD11b+ myeloid cells and CD4+ CD25+ T-cells are found in tumors in the bile duct ligation model but not in the carbon tetrachloride model. Importantly, the skewed immune infiltration into the tumor, while having some commonalities with the non-tumor tissue, had several distinct, tumor-specific populations. Induction of fibrosis also alters the cytokine production of implanted tumor cells, which could have far-reaching consequences on the immune infiltrate and its functionality. Taken together, this work demonstrates that the combination of fibrosis induction with orthotopic tumor implantation results in a markedly different tumor microenvironment and tumor growth kinetics. </p><p>Appreciating that the altered immune microenvironment dramatically shifts tumor progression, we sought to further explore the effects of individual inflammatory mediators on the development of the disease. Interleukin 18 (IL-18) is an inflammatory cytokine that is markedly increased in the circulation of patients with HCC correlated with poor prognosis. However, the precise role for IL-18 in HCC remains unclear, with reports presenting both pro- and anti-tumorigenic activities. To answer this question definitively, we interrogated in more detail the expression profiles of IL-18 in tissue specimens from HCC patients and conducted experimentation using multiple clinically relevant mouse models to explore the functional role of this cytokine in the context of HCC. Our results indicate that IL-18 exerts a tumor-suppressive effect mediated in large part by alterations in survival and functionality of T-lymphocytes which infiltrated the tumor microenvironment. This tumor-suppressive effect is however dependent upon the inflammatory milieu: In the absence of an inflammatory environment, whether from a chemical carcinogenesis model or a fibrosis induction model, loss of IL-18 signaling does not affect tumor growth. This effect is also stage-dependent. Taken together, our findings establish a tumor-suppressive role for IL-18 in established HCC and provide a mechanistic explanation for the complex relationship between its expression pattern and HCC prognosis. </p><p>In summary, this work demonstrates a dramatic shift in the microenvironment of developing HCC tumors in the presence of chronic inflammatory stimuli. This microenvironment, which more accurately models the situation in which tumors develop and progress in patients, alters the presence and functionality of many immune mediators. In particular, IL-18 signaling is a powerful mediator of tumor progression, however observation of its functionality is dependent on an inflammatory context. This work provides new insight into the complex processes underlying HCC tumor progression, and emphasizes the necessity for more accurate modeling of HCC progression in mice which takes into account the drastic changes in the tissue caused by chronic liver disease.</p> / Dissertation

Η ηπατική καρκινογένεση είναι μια πολυσταδιακή διαδικασία που οδηγεί προοδευτικά στον κακοήθη μετασχηματισμό του ηπατικού κυττάρου, μέσω ποικίλων μοριακών μηχανισμών. Πρόσφατα αναδεικνύεται ολοένα και σε μεγαλύτερο βαθμό, η τεράστια σημασία που έχει για την ανάπτυξη και εξέλιξη του καρκίνου το μικροπεριβάλλον του όγκου, η αλληλεπίδραση δηλαδή των καρκινικών κυττάρων με την εξωκυττάρια ουσία. Ιδιαίτερο ενδιαφέρον παρουσιάζει η αλληλεπίδραση των καρκινικών κυττάρων με την εξωκυττάρια ουσία μέσω των ιντεγκρινών, η οποία φαίνεται ότι εμπλέκεται σε όλα τα στάδια καρκινογένεσης. Σημαντικό μόριο στην προαναφερθείσα διαδικασία αποτελεί η ILK (Integrin-Linked Kinase), μία κινάση σερίνης-θρεονίνης που παρεμβάλλεται στα σηματοδοτικά μονοπάτια που ξεκινούν από ιντεγκρίνες, αυξητικούς παράγοντες και συμμετέχει στη ρύθμιση κομβικών για το καρκινικό κύτταρο λειτουργιών όπως έλεγχο του κυτταρικού κύκλου, απώλεια των δομών συνοχής του κυττάρου, αναστολή της απόπτωσης και ενεργοποίηση της αγγειογένεσης. Διαπιστώθηκε πως το σηματοδοτικό μονοπάτι ILK/p-Akt διαδραματίζει κομβικό ρόλο τόσο στη βιολογία της κίρρωσης όσο και του ηπατοκυτταρικού καρκίνου και πιθανόν αποτελεί μοριακό σύνδεσμο μεταξύ των δύο καταστάσεων, επιβεβαιώνοντας τη διατυπωμένη θεωρία περί άξονα χρόνιας φλεγμονής-ίνωσης (κίρρωσης)-καρκίνου. Επίσης στην παθογένεια της κίρρωσης και του καρκίνου ήπατος, φαίνεται πως ρόλο έχει το φαινόμενο της επιθηλιακής προς μεσεγχυματική μετατροπή (EMT-epithelial to mesenchymal transition). Αυτό αποδεικνύεται από την απώλεια έκφρασης της E-καντχερίνης και τη μεταφορά της β-κατενίνης στον πυρήνα που οδηγούν σε απώλεια των κυτταρικών συνδέσεων από τη μεμβράνη καθώς και από την υπερέκφραση των μορίων ILK και p-Akt. Τέλος η υπερέκφραση survivin και κυκλίνης-D1 στην κίρρωση και στο ηπακυτταρικό καρκίνωμα καταδεικνύουν τη σημασία της αντιαποπτωτικής δραστηριότητας και του αυξημένου κυτταρικού πολλαπλασιασμού στις συγκεκριμένες νοσολογικές οντότητες. / The hepatic carcinogenesis is a many phased process that leads progressively to the malignant transformation of hepatic cell via various molecular mechanisms. Recently, the enormous importance of the tumor microenvironment for the growth and development of cancer, i.e. the interaction between cancer cells and the extacellular matrix, has been proven. Particular interest is presented in the interaction of tumor cells with the extracellular matrix via integrins, which appears to be involved in all the stages of carcinogenesis. An important molecule in the aforementioned process is the ILK (Integrin-Linked Kinase), a serine-threonine kinase that is implicated in the signal transduction pathways that begin from integrines, growth factors and participate in the regulation of nodal for the tumor cell functions, such as control of cell cycle, loss of cell adhesion structures, suppresion of apoptosis and activation of angiogenesis. It has been realized that the signal transduction pathway ILK /p-Akt plays a nodal role so much in the biology of cirrhosis as well as in hepatocellular cancer and probably constitutes a molecular connection between the two conditions, confirming the formulated theory of axis of chronic inflamation-chirrosis-cancer. Also in the pathogenicity of cirrhosis and liver cancer, it appears that the epithelial to mesenchymal transition (EMT) phenomenon plays a role. This is proven by the loss of expression of E-cadherin and the transport of b-catenin in the nucleus that leads to loss of cellular connections from the membrane as well as from the overexpression of molecules ILK and p-Akt. Finally, the overexpression of survivin and cyclin-D1 in cirrhosis and hepatocellular carcinoma show the importance of antiapoptotic activity and increased cellular proliferation in the particular disease entities.

Το ηπατοκυτταρικό καρκίνωμα (ΗΚΚ) είναι η πιο σημαντική πρωτοπαθής νεοπλασία του ήπατος παγκοσμίως. Πολλοί αιτιολογικοί παράγοντες έχουν συσχετιστεί με την ανάπτυξη του ΗΚΚ, όπως η κίρρωση, οι ιοί της ηπατίτιδας και το αλκοόλ. Χρόνια λοίμωξη με ηπατίτιδα Β (HBV) και C (HCV) συχνά καταλήγει σε κίρρωση και ενισχύει την πιθανότητα ανάπτυξης ΗΚΚ. Ωστόσο οι υποκείμενοι μηχανισμοί που οδηγούν στην κακοήθη εξαλλαγή των κυττάρων παραμένουν αδιευκρίνιστοι. Ο HBV είναι ένας DNA ιός που ενσωματώνεται στο γονιδίωμα του ξενιστή και θεωρείται ότι με τον τρόπο αυτό προκαλεί καρκινογένεση. Επιπρόσθετα, ο ιός κωδικοποιεί μία πρωτεΐνη 17 kDa,την HBx, η οποία είναι γνωστό ότι αποτελεί αιτιολογικό παράγοντα ανάπτυξης ΗΚΚ. Η παρούσα ανασκόπηση αναλύει το ρόλο της HBx στους μοριακούς μηχανισμούς που σχετίζονται με την παθογένεση της επαγόμενης από τον HBV ηπατικής καρκινογένεσης. / Hepatocellular carcinoma (HCC) is the most important primary hepatic cancer, being a common cancer type worldwide. Many aetiological factors have been related with HCC development, such as cirrhosis, hepatitis viruses and alcohol. Chronic infection with hepatitis B (HBV) and C viruses (HCV) often results in cirrhosis and enhances the probability of developing HCC. The underlying mechanisms that lead to malignant transformation of infected cells, however, remain unclear. HBV is a DNA virus that integrates into the host genome, and this integration is believed, in part, to be carcinogenic. Besides, the virus encodes a 17 kDa protein, HBx, which is known to be a causative agent in the formation of HCC. This review examines the role of HBx in the molecular mechanisms involved in the pathogenesis of HBV-induced hepatocarcinogenesis.

Woodchucks are the preferred animal model to study chronic viral hepatitis and the development of hepatocellular carcinoma (HCC), which occurs as a result of infection with woodchuck hepatitis virus. Significant elevations in the phosphomonoester peak in 31P-MRS spectrum correlated to the presence of HCC. Ex vivo 31P-NMR determined that HCC tissue had significantly elevated concentrations of PC compared to uninfected control tissues, confirming that PME is specific to the tumour’s growth. Finally, a recombinant vaccinia virus was constructed to stimulate the immune systems of infected woodchucks against cells expressing core antigens. Despite reductions in surface antigen expression and viral load, elevations in serum GGT and the PME in 31P-MRS indicated that there was tumour growth in treated woodchucks. In conclusion, the PME peak represents a potential biomarker of cancerous growth when used in conjunction with serological tests to detect HCC in the liver due to chronic hepatitis virus infection.

Hereditary tyrosinemia type 1 (HT1) is an autosomal recessive disorder of the tyrosine degradation pathway. The defective fumarylacetoacetate hydrolase enzyme causes the accumulation of upstream metabolites such as fumarylacetoacetate (FAA), maleylacetoacetate (MAA), succinylacetone (SA) and p-hydroxyphenylpyruvic acid (pHPPA). In vitro and in vivo studies showed that the accumulation of these metabolites are detrimental to cell homeostasis, by inducing cell cycle arrest, apoptosis, and endoplasmic reticulum stress, depleting GSH, inhibiting DNA ligase, causing chromosomal instability, etc. For in vivo studies different models of HT1 were developed. Most notably was the fah deficient mouse, whose neonatally lethal phenotype is rescued by the administration of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC). Although, this model most closely resembles the human phenotype with elevated tyrosine levels and the development of hepatocellular carcinoma (HCC), the model is not human genome based. Both the in vitro and in vivo studies suggested that DNA repair is affected in HT1. However, it is not yet clear which DNA repair mechanisms are affected and if only protein functionality is affected, or if expression of DNA repair proteins are also affected. Characteristic of HT1 is the high prevalence of HCC and the presence of liver mosaicism. The liver mosaicism observed in HT1 patients are the result of reversion of the inherited mutation to wild-type. The general consensus is that the reversion is the result of a true back mutation. However, the mechanism underlying the back mutation is still unresolved. It was suggested that cancer develops either through a chromosomal instability mutator phenotype, a microsatellite instability mutator phenotype, or a point mutation instability mutator phenotype. In HT1 only chromosomal instability was reported. The aims of this study were to contribute to the understanding of the molecular basis of the genetic mosaicism in hereditary tyrosinemia type 1. More specifically, determine whether baseand nucleotide DNA repair mechanisms are affected and to what extent, and to determine if microsatellite instability is found in HT1. To achieve these aims, a parallel approach was followed: i.e. to develop a HT1 hepatic cell model and to use HT1 related models and HT1 patient material. To assess the molecular basis of the genetic mosaicism in HT1, the comet assay, gene expression assays, microsatellite instability assays, high resolution melting and dideoxy sequencing techniques were employed. Results from the comet assay showed that the HT1 accumulating metabolites, SA and pHPPA, decreased the capacity of cells for base- and nucleotide excision repair. Gene expression assays showed that short term exposure to SA and/or pHPPA do not affect expression of hOGG1 or ERCC1. The expression of these genes were, however, low in HT1 patient samples. Microsatellite instability assays showed allelic imbalance on chromosome 7 of the mouse genome, and microsatellite instability in the lymphocytes of HT1 patients. Although high resolution melt and sequencing results did not reveal any de novo mutations in fah or hprt1, the appearance of de novo mutations on other parts of the genome can not be ruled out. To conclude, results presented in this thesis, for the first time show that in HT1 the initiating proteins of the base- and nucleotide repair mechanisms are affected, the gene expression of DNA repair proteins are low, and microsatellite instability is found in HT1. By contributing to the elucidation of the mechanism underlying the development of HT1-associated HCC, and providing evidence for the development of a mutator phenotype, the results presented in this thesis contributes to the understanding of the molecular mechanisms underlying the genetic mosaicism in HT1. In addition to these contributions, a hypothesis is posited, which suggests that a point mutation instability (PIN) mutator phenotype is the mechanism underlying the mutation reversions seen in HT1. / Thesis (Ph.D. (Biochemistry))--North-West University, Potchefstroom Campus, 2012

Woodchucks are the preferred animal model to study chronic viral hepatitis and the development of hepatocellular carcinoma (HCC), which occurs as a result of infection with woodchuck hepatitis virus. Significant elevations in the phosphomonoester peak in 31P-MRS spectrum correlated to the presence of HCC. Ex vivo 31P-NMR determined that HCC tissue had significantly elevated concentrations of PC compared to uninfected control tissues, confirming that PME is specific to the tumour’s growth. Finally, a recombinant vaccinia virus was constructed to stimulate the immune systems of infected woodchucks against cells expressing core antigens. Despite reductions in surface antigen expression and viral load, elevations in serum GGT and the PME in 31P-MRS indicated that there was tumour growth in treated woodchucks. In conclusion, the PME peak represents a potential biomarker of cancerous growth when used in conjunction with serological tests to detect HCC in the liver due to chronic hepatitis virus infection.

We previously observed that postnatal exposure of mice to the procarcinogen 4-aminobiphenyl (ABP) produced liver tumors only in wild-type males, while arylamine N-acetyltransferase deficient males and females of either strain were protected. Others have also observed a sex difference in liver tumors in mice using the procarcinogen diethylnitrosamine (DEN). Reasons for these sex and strain differences are unclear, but differences in acute hepatotoxicity and inflammation may be involved. In this thesis we found that neither ABP nor DEN produced overt hepatotoxicity in postnatally exposed mice, and only DEN caused an increase in levels of the pro-inflammatory cytokine interleukin-6 but was not sex-dependent. The lack of sex difference suggests that sex hormone modulation of inflammation following sexual maturation might favour growth of initiated cells in males. However, the lack of detectable inflammation following ABP exposure may be due to localized responses, or that inflammation may be a DEN-specific effect.

We previously observed that postnatal exposure of mice to the procarcinogen 4-aminobiphenyl (ABP) produced liver tumors only in wild-type males, while arylamine N-acetyltransferase deficient males and females of either strain were protected. Others have also observed a sex difference in liver tumors in mice using the procarcinogen diethylnitrosamine (DEN). Reasons for these sex and strain differences are unclear, but differences in acute hepatotoxicity and inflammation may be involved. In this thesis we found that neither ABP nor DEN produced overt hepatotoxicity in postnatally exposed mice, and only DEN caused an increase in levels of the pro-inflammatory cytokine interleukin-6 but was not sex-dependent. The lack of sex difference suggests that sex hormone modulation of inflammation following sexual maturation might favour growth of initiated cells in males. However, the lack of detectable inflammation following ABP exposure may be due to localized responses, or that inflammation may be a DEN-specific effect.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 6 uppsatser.

Diss. (sammanfattning) Umeå : Univ., 2009. / Härtill 4 uppsatser.