Liver carcinogenesis by diethylnitrosamine in the rat

A systematic review on multipotent carcinogenic agent, N-nitrosodiethylamine (NDEA), its major risk assessment, and precautions

The International Agency for Research on Cancer has classified N-nitrosodiethylamine (NDEA) as a possible carcinogen and mutagenic substances, placing it in category 2A of compounds that are probably harmful to humans. It is found in nature and tobacco smoke, along with its precursors, and is also synthesized endogenously in the human body. The oral or parenteral administration of a minimal quantity of NDEA results in severe liver and kidney organ damage. The NDEA required bioactivation by CYP450 enzyme to form DNA adduct in the alkylation mechanism. Thus, this bioactivation directs oxidative stress and injury to cells due to the higher formation of reactive oxygen species and alters antioxidant system in tissues, whereas free radical scavengers guard the membranes from NDEA-directed injury in many enzymes. This might be one of the reasons in the etiology of cancer that is not limited to a certain target organ but can affect various organs and organ systems. Although there are various possible approaches for the treatment of NDEA-induced cancer, their therapeutic outcomes are still very dismal. However, several precautions were considered to be taken during handling or working with NDEA, as it considered being the best way to lower down the occurrence of NDEA-directed cancers. The present review was designed to enlighten the general guidelines for working with NDEA, possible mechanism, to alter the antioxidant line to cause malignancy in different parts of animal body along with its protective agents. Thus, revelation to constant, unpredictable stress situations even in common life may remarkably augment the toxic potential through the rise in the oxidative stress and damage of DNA.

Ferulic acid interventions ameliorate NDEA-CCl4-induced hepatocellular carcinoma via Nrf2 and p53 upregulation and Akt/PKB-NF-κB-TNF-α pathway downregulation in male Wistar rats

Hepatocellular carcinoma is a prevalent form of liver cancer that is life threatening. Many chemically synthesized anti-cancer drugs have various degrees of side effects. Hence, this study investigated the effect of FEAC interventions on NDEA-CCl4-induced HCAR in male Wistar rats. HCAR was induced by intraperitoneal administration of 200 mg/kg of NDEA and 0.5 mL/kg CCl4 (as a promoter of HCAR). Following the induction of HCAR, rats were treated differently with two different doses (25 and 50 mg/kg) of FEAC. HCAR induction was confirmed by the significant elevation of serum levels of ALT, AST, and α-FP. Also elevated significantly were liver levels of Akt/PKB, NF-κB, TNF-α, MDA, GSH, and activities of GST, SOD, and CAT, while levels of liver p53 and Nrf2 were significantly lowered compared with normal rats. Treatment interventions with both 25 and 50 mg/kg of FEAC against the DEN-CCl4-induced HCAR gave comparable effects, marked by a significant reduction in the levels of serum ALT, AST and α-FP, as well as liver levels of MDA, GSH, Akt/PKB, NF-κB, TNF-α, GST, SOD, and CAT, while levels of liver p53 and Nrf2 were significantly elevated compared with normal rats. Put together and judging by the outcomes of this study, FEAC being a potent antioxidant may also be potent against chemical-induced HCAR via upregulation of p53 and Nrf2, as well as downregulation of the Akt/PKB-NF-κB pathway in rats.

An overview of mouse models of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has become a severe burden on global health due to its high morbidity and mortality rates. However, effective treatments for HCC are limited. The lack of suitable preclinical models may contribute to a major failure of drug development for HCC. Here, we overview several well-established mouse models of HCC, including genetically engineered mice, chemically-induced models, implantation models, and humanized mice. Immunotherapy studies of HCC have been a hot topic. Therefore, we will introduce the application of mouse models of HCC in immunotherapy. This is followed by a discussion of some other models of HCC-related liver diseases, including non-alcoholic fatty liver disease (NAFLD), hepatitis B and C virus infection, and liver fibrosis and cirrhosis. Together these provide researchers with a current overview of the mouse models of HCC and assist in the application of appropriate models for their research.

Current progress of pig models for liver cancer research

Preclinical trials play critical roles in assessing the safety and efficiency of novel therapeutic strategies for human diseases including live cancer. However, most therapeutic strategies that were proved to be effective in preclinical cancer models failed in human clinical trials due to the lack of appropriate disease animal models. Therefore, it is of importance and urgent to develop a precise animal model for preclinical cancer research. Liver cancer is one of the most frequently diagnosed cancers with low 5-year survival rate. Recently, porcine attracted increasing attentions as animal model in biomedical research. Porcine liver cancer model may provide a promising platform for biomedical research due to their similarities to human being in body size, anatomical characteristics, physiology and pathophysiology. In this review, we comprehensively summarized and discussed the advantages and disadvantages, rationale, current status and progress of pig models for liver cancer research.

Risk assessment of N-nitrosamines in food

EFSA was asked for a scientific opinion on the risks to public health related to the presence of N-nitrosamines (N-NAs) in food. The risk assessment was confined to those 10 carcinogenic N-NAs occurring in food (TCNAs), i.e. NDMA, NMEA, NDEA, NDPA, NDBA, NMA, NSAR, NMOR, NPIP and NPYR. N-NAs are genotoxic and induce liver tumours in rodents. The in vivo data available to derive potency factors are limited, and therefore, equal potency of TCNAs was assumed. The lower confidence limit of the benchmark dose at 10% (BMDL10) was 10 μg/kg body weight (bw) per day, derived from the incidence of rat liver tumours (benign and malignant) induced by NDEA and used in a margin of exposure (MOE) approach. Analytical results on the occurrence of N-NAs were extracted from the EFSA occurrence database (n = 2,817) and the literature (n = 4,003). Occurrence data were available for five food categories across TCNAs. Dietary exposure was assessed for two scenarios, excluding (scenario 1) and including (scenario 2) cooked unprocessed meat and fish. TCNAs exposure ranged from 0 to 208.9 ng/kg bw per day across surveys, age groups and scenarios. 'Meat and meat products' is the main food category contributing to TCNA exposure. MOEs ranged from 3,337 to 48 at the P95 exposure excluding some infant surveys with P95 exposure equal to zero. Two major uncertainties were (i) the high number of left censored data and (ii) the lack of data on important food categories. The CONTAM Panel concluded that the MOE for TCNAs at the P95 exposure is highly likely (98-100% certain) to be less than 10,000 for all age groups, which raises a health concern.

Safety and Feasibility of Contrast-Enhanced Computed Tomography with a Nanoparticle Contrast Agent for Evaluation of Diethylnitrosamine-Induced Liver Tumors in a Rat Model

RATIONALE AND OBJECTIVES

Safety and feasibility of contrast-enhanced computed tomography (CECT) with a nanoparticulate contrast agent, ExiTron nano 12000, was evaluated in a rat liver tumor model.

MATERIALS AND METHODS

This study employed eighteen 8-week-old male F344 rats. Six rats given tap water for 8 weeks further divided into two: Control group and Normal Liver with CECT group. Six rats each were given tap water containing diethylnitrosamine (DEN) at 100 ppm for 8 or 14 weeks; Adenoma group and Hepatocellular carcinoma (HCC) group, respectively. Biochemical marker values and adverse events were evaluated after CT imaging. ExiTron nano 12000 was evaluated for the hepatic contrast enhancement, and the detection and measurement of liver nodules by CECT after 8- and 14-weeks administration of DEN. Post-mortem liver specimens were evaluated by hematoxylin-eosin (HE) staining, and the number and size of liver nodules were measured. The HCC group was evaluated for diagnostic concordance between HE-stained and CECT-detected nodules.

RESULTS

The contrast agent enhanced liver and was tolerated after CECT in 15 rats. Biochemical parameter values did not differ significantly between the Control and Normal Liver groups. The numbers of CECT-detected nodules in the Adenoma and HCC groups were 14.8 ± 5.1, and 32.4 ± 8.1, respectively. The HCC group had 3.6 ± 2.7 of pathological HCCs, which were identified by CECT. The size of CECT-detected HCCs correlated significantly with that of pathological HCCs (r = 0.966, p < 0.0001).

CONCLUSION

CECT with ExiTron nano 12000 is a safe and feasible method to measure tumors in a rat liver tumor model.

Two distinct Notch signals, Delta-like 4/Notch1 and Jagged-1/Notch2, antagonistically regulate chemical hepatocarcinogenesis in mice

Notch signaling is one of the most common drivers of carcinogenesis in many types of cancers, including hepatocellular carcinoma (HCC); however, it occasionally suppresses tumor progression. Moreover, it is virtually unknown how different sets of Notch ligands and receptors regulate the HCC development. In this study, we demonstrate that the expression of the Notch ligands, Delta-like 4 (Dll4) and Jagged-1 (Jag1), is upregulated during diethylnitrosamine-induced hepatocarcinogenesis. Dll4 is detected in the preneoplastic hepatocytes and HCC cells, but not in the normal hepatocytes, while Jag1 is expressed in the desmin-positive mesenchymal cells. Hepatocyte-specific Dll4 knockout abolishes the Notch1 signaling and suppresses the tumor progression. In contrast, Jag1 deletion induces the ectopic expression of Dll4 in hepatocytes along with the loss of Notch2 signaling, leading to the tumor progression. These results indicate that the two distinct Notch signals, Dll4/Notch1 and Jag1/Notch2, are antagonistic to each other, exerting opposite effects on HCC progression.

Dll4/Notch1 signal promotes the progression of HCC, while Jag1/Notch2 signal antagonistically suppresses it in murine chemical hepatocarcinogenesis. Nakano et al. report that two distinct Notch signals regulate the progression of hepatocellular carcinoma (HCC) using tissue specific loss of function mouse mutants. They find Dll4/Notch1 signal promotes HCC progression, while the Jag1/Notch2 signal antagonistically suppresses it.

Centrosome dysfunction associated with somatic expression of the synaptonemal complex protein TEX12

The synaptonemal complex (SC) is a supramolecular protein scaffold that mediates chromosome synapsis and facilitates crossing over during meiosis. In mammals, SC proteins are generally assumed to have no other function. Here, we show that SC protein TEX12 also localises to centrosomes during meiosis independently of chromosome synapsis. In somatic cells, ectopically expressed TEX12 similarly localises to centrosomes, where it is associated with centrosome amplification, a pathology correlated with cancer development. Indeed, TEX12 is identified as a cancer-testis antigen and proliferation of some cancer cells is TEX12-dependent. Moreover, somatic expression of TEX12 is aberrantly activated via retinoic acid signalling, which is commonly disregulated in cancer. Structure-function analysis reveals that phosphorylation of TEX12 on tyrosine 48 is important for centrosome amplification but not for recruitment of TEX12 to centrosomes. We conclude that TEX12 normally localises to meiotic centrosomes, but its misexpression in somatic cells can contribute to pathological amplification and dysfunction of centrosomes in cancers.

Sandhu et al. report that the synaptonemal complex (SC) protein, TEX12, localises to centrosomes independently of the SC during meiosis. They also show that it provokes centrosome amplification in somatic cells, a pathology associated with cancer development.

Identification of Gene-Set Signature in Early-Stage Hepatocellular Carcinoma and Relevant Immune Characteristics

Background

The incidence of hepatocellular carcinoma (HCC) is rising worldwide, and there is limited therapeutic efficacy due to tumor microenvironment heterogeneity and difficulty in early-stage screening. This study aimed to develop and validate a gene set-based signature for early-stage HCC (eHCC) patients and further explored specific marker dysregulation mechanisms as well as immune characteristics.

Methods

We performed an integrated bioinformatics analysis of genomic, transcriptomic, and clinical data with three independent cohorts. We systematically reviewed the crosstalk between specific genes, tumor prognosis, immune characteristics, and biological function in the different pathological stage samples. Univariate and multivariate survival analyses were performed in The Cancer Genome Atlas (TCGA) patients with survival data. Diethylnitrosamine (DEN)-induced HCC in Wistar rats was employed to verify the reliability of the predictions.

Results

We identified a Cluster gene that potentially segregates patients with eHCC from non-tumor, through integrated analysis of expression, overall survival, immune cell characteristics, and biology function landscapes. Immune infiltration analysis showed that lower infiltration of specific immune cells may be responsible for significantly worse prognosis in HCC (hazard ratio, 1.691; 95% CI: 1.171–2.441; p = 0.012), such as CD8 Tem and cytotoxic T cells (CTLs) in eHCC. Our results identified that Cluster C1 signature presented a high accuracy in predicting CD8 Tem and CTL immune cells (receiver operating characteristic (ROC) = 0.647) and cancerization (ROC = 0.946) in liver. As a central member of Cluster C1, overexpressed PRKDC was associated with the higher genetic alteration in eHCC than advanced-stage HCC (aHCC), which was also connected to immune cell-related poor prognosis. Finally, the predictive outcome of Cluster C1 and PRKDC alteration in DEN-induced eHCC rats was also confirmed.

Conclusions

As a tumor prognosis-relevant gene set-based signature, Cluster C1 showed an effective approach to predict cancerization of eHCC and its related immune characteristics with considerable clinical value.

Combine effect of exposure to petrol, kerosene and diesel fumes: On hepatic oxidative stress and haematological function in rats

Petroleum product fumes (PPFs) containing toxic organic components are pervasive in the environment, emanating from anthropogenic activities, including petroleum exploration and utilization by end-user activities from petrol-gasoline stations. Petrol station attendants are exposed to PPF through inhalation and dermal contact with consequent toxicological implications. We investigated the effects of chronic exposure (60 and 90 days) to petrol (P), kerosene (K) and diesel (D) alone and combined exposure to petrol, kerosene and diesel (PKD) fumes on hepatotoxicity, haematological function and oxidative stress in rats. Following sacrifice, we evaluated hepatic damage biomarkers, blood glucose, oxidative stress and haematological function. Chronic exposure to PPF significantly increased organo-somatic indices, blood glucose, biomarkers of hepatic toxicity and oxidative stress in an exposure duration-dependent manner. There was a simultaneous decrease in the protective capacity of antioxidants. Furthermore, exposure to PPF increased pro-inflammatory biomarkers in rats (90 > 60 days). Regardless of exposure duration, plateletcrit, mean platelet volume, platelet distribution width and red cell distribution width in the coefficient of variation increased, whereas red blood cell count, haemoglobin, packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, white blood cell, lymphocyte, monocyte-basophil-eosinophil mixed counts and platelet count decreased after 60 and 90 days exposure. Microscopic examination of the liver demonstrated hepatic pathological changes paralleling the duration of exposure to PKD fumes. However, the injury observed was lesser to that of rats treated with the diethylnitrosamine - positive control. Our results expanded previous findings and further demonstrated the probable adverse effect on populations' health occasioned by persistent exposure to PPF. Individuals chronically exposed by occupation to PPF may be at greater risk of developing disorders promoted by continuous oxido-inflammatory perturbation and suboptimal haematological-immunologic function - thereby enabling a permissive environment for pathogenesis notwithstanding the limitation of quantifying PPF absolute values in our model system.

MicroRNAs in Animal Models of HCC

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related mortality. Molecular heterogeneity and absence of biomarkers for patient allocation to the best therapeutic option contribute to poor prognosis of advanced stages. Aberrant microRNA (miRNA) expression is associated with HCC development and progression and influences drug resistance. Therefore, miRNAs have been assayed as putative biomarkers and therapeutic targets. miRNA-based therapeutic approaches demonstrated safety profiles and antitumor efficacy in HCC animal models; nevertheless, caution should be used when transferring preclinical findings to the clinics, due to possible molecular inconsistency between animal models and the heterogeneous pattern of the human disease. In this context, models with defined genetic and molecular backgrounds might help to identify novel therapeutic options for specific HCC subgroups. In this review, we describe rodent models of HCC, emphasizing their representativeness with the human pathology and their usefulness as preclinical tools for assessing miRNA-based therapeutic strategies.

NLRP12 suppresses hepatocellular carcinoma via downregulation of cJun N-terminal kinase activation in the hepatocyte

Hepatocellular carcinoma (HCC) is a deadly human cancer associated with chronic inflammation. The cytosolic pathogen sensor NLRP12 has emerged as a negative regulator of inflammation, but its role in HCC is unknown. Here we investigated the role of NLRP12 in HCC using mouse models of HCC induced by carcinogen diethylnitrosamine (DEN). Nlrp12^-/- mice were highly susceptible to DEN-induced HCC with increased inflammation, hepatocyte proliferation, and tumor burden. Consistently, Nlrp12^-/- tumors showed higher expression of proto-oncogenes cJun and cMyc and downregulation of tumor suppressor p21. Interestingly, antibiotics treatment dramatically diminished tumorigenesis in Nlrp12^-/- mouse livers. Signaling analyses demonstrated higher JNK activation in Nlrp12^-/- HCC and cultured hepatocytes during stimulation with microbial pattern molecules. JNK inhibition or NLRP12 overexpression reduced proliferative and inflammatory responses of Nlrp12^-/- hepatocytes. In summary, NLRP12 negatively regulates HCC pathogenesis via downregulation of JNK-dependent inflammation and proliferation of hepatocytes.

Extracts of Qizhu decoction inhibit hepatitis and hepatocellular carcinoma in vitro and in C57BL/6 mice by suppressing NF-κB signaling

Hepatitis and hepatocellular carcinoma are serious human diseases. Here, we examined the in vivo and in vitro inhibitory effect of extracts of Qizhu decoction (a traditional Chinese medicine) on hepatitis caused by diethylnitrosamine or hepatitis B virus and on diethylnitrosamine-induced hepatocellular carcinoma. The results showed that both the aqueous and ethanol extracts (QC and QS, respectively) of Qizhu decoction significantly inhibited hepatic inflammation and liver cancer induced by diethylnitrosamine or hepatitis B virus by suppressing NF-κB signaling and decreasing the levels of TNF-α and IL-1β. Both QC and QS inhibited the proliferation and migration of primary cancer hepatocytes by reducing cyclin B1, cyclin D1 and N-cadherin expression and increasing E-cadherin expression. QC and QS also promoted the apoptosis of primary cancer hepatocytes by upregulating caspase-3 and downregulating BCL-2 expression. The knockdown of p65 in NF-κB signaling inhibited the ability of QC and QS to significantly reduce the colony formation ability of liver cancer cells. Additionally, QC and QS might significantly inhibit the DNA replication of hepatitis B virus in vivo and in vitro, and we found that corilagin and polydatin were the active compounds of QC and QS. Taken together, our in vitro findings and our results in C57BL/6 mice showed that extracts of Qizhu decoction might inhibit hepatitis and hepatocellular carcinoma by suppressing NF-κB signaling.

Metabolomic analysis of serum from rats following long-term intake of Chinese sausage

Introduction

Owing to the contamination of chemical pollutants, especially nitrosamines and their precursors, in Chinese sausage, long-term intake of Chinese sausage may have potential health effects.

Objection

This study investigated the effects of long-term intake of Chinese sausage with different contaminations of N-nitrosodimethylamine (NDMA) on rat liver and the potential biomarkers in the serum.

Methods

Serum metabolomic analysis was performed by gas chromatography–mass spectrometry at weeks 7, 17, 25, and 33; simultaneously, liver histopathological examination was conducted and its relationship with the serum metabolomics was also investigated.

Results

In the study, long-term intake of Chinese sausage with different NDMA contents induced significant changes in serum metabolites and liver histopathology in rats. Metabonomic analysis showed that seven metabolites – β-alanine, 3-aminoisobutyric acid, aminooxyacetic acid, D-alanyl-D-alanine, pelargonic acid, palmitic acid (PA), and linoleic acid (LA) – in three sausage diet groups were significantly decreased at four time points, where three other metabolites were notably increased, which included putrescine, ethanolamine phosphate, and taurine. Among the various treatments, the NDMA (sausage-free) group demonstrated the most remarkable changes. Phenylalanine was decreased followed by an increase, and tyrosine persistently declined, both of which were elevated in the NDMA group. In addition, the histopathological result was consistent with that of the serum metabolomic analysis, and the changes in serum metabolites in each sausage diet group and the NDMA group were consistently associated with disorders of lipids, amino acid, and energy metabolism.

Conclusion

This work indicates that excessive NDMA content in sausage may cause liver damage.

A Study on the Role of Compensatory Hyperplasia in Renal Carcinogenesis with Dimethylnitrosamine in the Rat

Two experiments of renal carcinogenesis with dimethylnitrosamine (DMN) are described. In experiment I, the carcinogenicity of a single neonatal injection of DMN was compared in 34 intact rats and in 38 rats right-nephrectomized at 8–10 weeks of age. A total of 37 tumor-bearing kidneys were seen: both tubular and anaplastic; tumor incidence and time of observation showed no significant differences between intact and nephrectomized animals. Liver tumors were seen in 38 of 72 rats. In experiment II, 64 adult rats were given DMN in the drinking water for 2 weeks at a concentration corresponding to half an effective dose: 20 rats were used as non-nephrectomized controls; the others were right nephrectomized either on the 7th - 8th day of treatment with DMN or 15 days prior to the beginning of the treatment with the carcinogen. In no case did unilateral nephrectomy have a modifying effect upon carcinogenesis. In nephrectomized rats nonneoplastic nephritic changes were more severe than in intact animals. The design of the present experiments is compared with that of previous studies on the role of either partial hepatectomy or unilateral nephrectomy in carcinogenesis.

Molecular and proteomic insight into Notch1 characterization in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) ranks fifth in frequency worldwide amongst all human cancers causing one million deaths annually. Despite many promising treatment options, long-term prognosis remains dismal for the majority of patients who develop recurrence or present with advanced disease. Notch signaling is an evolutionarily conserved pathway crucial for the development and homeostasis of many organs including liver. Herein we showed that aberrant Notch1 is linked to HCC development, tumor recurrence and invasion, which might be mediated, at least in part, through the Notch1-E-Cadherin pathway. Collectively, these findings suggest that targeting Notch1 has important therapeutic value in hepatocellular carcinoma. In this regard, comparative analysis of the secretome of HepG2 and HepG2 Notch1 depleted cells identified novel secreted proteins related to Notch1 expression. Soluble E-Cadherin (sE-Cad) and Thrombospondin-1 (Thbs1) were further validated in human serum as potential biomarkers to predict response to Notch1 inhibitors for a tailored individualized therapy.

Combined use of alcohol in conventional chemical-induced mouse liver cancer model improves the simulation of clinical characteristics of human hepatocellular carcinoma

Liver cancer is the one of most common types of cancer and the 2nd cause of cancer-associated mortalities worldwide. Establishing appropriate animal models of liver cancer is essential for basic and translational studies. The present study evaluated the effects of the combined use of alcohol with a conventional chemical-induced mouse liver cancer model. The treatment of alcohol/diethylnitrosamine (DEN)/carbon tetrachloride (CCl₄) in the mice of experimental groups resulted in a series of pathological changes in the liver. Liver inflammation, fibrosis, cirrhosis and hepatocellular carcinoma were identified, and this method used less time (1–5 months) for inducement compared with the conventional chemical-induced method alone. In addition, murine α-fetoprotein (mAFP) was expressed throughout and ultrastructural features met the criteria for liver cancer. Fatty degeneration of pancreas, reduced blood glucose levels, and increased spleen weight were observed. These results indicated that an AFP-secreting hepatocellular carcinoma model of BALB/c mouse was successfully developed. The disease process and morphological changes met the criterion of the liver cancer process. Therefore the model developed in the present study may be an ideal animal model for studying the occurrence and development of liver cancer.

Chemopreventive Strategies for Inflammation-Related Carcinogenesis: Current Status and Future Direction

A sustained and chronically-inflamed environment is characterized by the presence of heterogeneous inflammatory cellular components, including neutrophils, macrophages, lymphocytes and fibroblasts. These infiltrated cells produce growth stimulating mediators (inflammatory cytokines and growth factors), chemotactic factors (chemokines) and genotoxic substances (reactive oxygen species and nitrogen oxide) and induce DNA damage and methylation. Therefore, chronic inflammation serves as an intrinsic niche for carcinogenesis and tumor progression. In this article, we summarize the up-to-date findings regarding definitive/possible causes and mechanisms of inflammation-related carcinogenesis derived from experimental and clinical studies. We also propose 10 strategies, as well as candidate agents for the prevention of inflammation-related carcinogenesis.

Hippo signaling interactions with Wnt/β-catenin and Notch signaling repress liver tumorigenesis

Malignant tumors develop through multiple steps of initiation and progression, and tumor initiation is of singular importance in tumor prevention, diagnosis, and treatment. However, the molecular mechanism whereby a signaling network of interacting pathways restrains proliferation in normal cells and prevents tumor initiation is still poorly understood. Here, we have reported that the Hippo, Wnt/β-catenin, and Notch pathways form an interacting network to maintain liver size and suppress hepatocellular carcinoma (HCC). Ablation of the mammalian Hippo kinases Mst1 and Mst2 in liver led to rapid HCC formation and activated Yes-associated protein/WW domain containing transcription regulator 1 (YAP/TAZ), STAT3, Wnt/β-catenin, and Notch signaling. Previous work has shown that abnormal activation of these downstream pathways can lead to HCC. Rigorous genetic experiments revealed that Notch signaling forms a positive feedback loop with the Hippo signaling effector YAP/TAZ to promote severe hepatomegaly and rapid HCC initiation and progression. Surprisingly, we found that Wnt/β-catenin signaling activation suppressed HCC formation by inhibiting the positive feedback loop between YAP/TAZ and Notch signaling. Furthermore, we found that STAT3 in hepatocytes is dispensable for HCC formation when mammalian sterile 20-like kinase 1 and 2 (Mst1 and Mst2) were removed. The molecular network we have identified provides insights into HCC molecular classifications and therapeutic developments for the treatment of liver tumors caused by distinct genetic mutations.

Hippo signaling interactions with Wnt/β-catenin and Notch signaling repress liver tumorigenesis

Malignant tumors develop through multiple steps of initiation and progression, and tumor initiation is of singular importance in tumor prevention, diagnosis, and treatment. However, the molecular mechanism whereby a signaling network of interacting pathways restrains proliferation in normal cells and prevents tumor initiation is still poorly understood. Here, we have reported that the Hippo, Wnt/β-catenin, and Notch pathways form an interacting network to maintain liver size and suppress hepatocellular carcinoma (HCC). Ablation of the mammalian Hippo kinases Mst1 and Mst2 in liver led to rapid HCC formation and activated Yes-associated protein/WW domain containing transcription regulator 1 (YAP/TAZ), STAT3, Wnt/β-catenin, and Notch signaling. Previous work has shown that abnormal activation of these downstream pathways can lead to HCC. Rigorous genetic experiments revealed that Notch signaling forms a positive feedback loop with the Hippo signaling effector YAP/TAZ to promote severe hepatomegaly and rapid HCC initiation and progression. Surprisingly, we found that Wnt/β-catenin signaling activation suppressed HCC formation by inhibiting the positive feedback loop between YAP/TAZ and Notch signaling. Furthermore, we found that STAT3 in hepatocytes is dispensable for HCC formation when mammalian sterile 20-like kinase 1 and 2 (Mst1 and Mst2) were removed. The molecular network we have identified provides insights into HCC molecular classifications and therapeutic developments for the treatment of liver tumors caused by distinct genetic mutations.

Thyroid hormone suppresses hepatocarcinogenesis via DAPK2 and SQSTM1-dependent selective autophagy

Recent studies have demonstrated a critical association between disruption of cellular thyroid hormone (TH) signaling and the incidence of hepatocellular carcinoma (HCC), but the underlying mechanisms remain largely elusive. Here, we showed that disruption of TH production results in a marked increase in progression of diethylnitrosamine (DEN)-induced HCC in a murine model, and conversely, TH administration suppresses the carcinogenic process via activation of autophagy. Inhibition of autophagy via treatment with chloroquine (CQ) or knockdown of ATG7 (autophagy-related 7) via adeno-associated virus (AAV) vectors, suppressed the protective effects of TH against DEN-induced hepatic damage and development of HCC. The involvement of autophagy in TH-mediated protection was further supported by data showing transcriptional activation of DAPK2 (death-associated protein kinase 2; a serine/threonine protein kinase), which enhanced the phosphorylation of SQSTM1/p62 (sequestosome 1) to promote selective autophagic clearance of protein aggregates. Ectopic expression of DAPK2 further attenuated DEN-induced hepatoxicity and DNA damage though enhanced autophagy, whereas, knockdown of DAPK2 displayed the opposite effect. The pathological significance of the TH-mediated hepatoprotective effect by DAPK2 was confirmed by the concomitant decrease in the expression of THRs and DAPK2 in matched HCC tumor tissues. Taken together, these findings indicate that TH promotes selective autophagy via induction of DAPK2-SQSTM1 cascade, which in turn protects hepatocytes from DEN-induced hepatotoxicity or carcinogenesis.

The metabolic gene HAO2 is downregulated in hepatocellular carcinoma and predicts metastasis and poor survival

BACKGROUND & AIMS

l-2-Hydroxy acid oxidases are flavin mononucleotide-dependent peroxisomal enzymes, responsible for the oxidation of l-2-hydroxy acids to ketoacids, resulting in the formation of hydrogen peroxide. We investigated the role of HAO2, a member of this family, in rat, mouse and human hepatocarcinogenesis.

METHODS

We evaluated Hao2 expression by qRT-PCR in the following rodent models of hepatocarcinogenesis: the Resistant-Hepatocyte, the CMD and the chronic DENA rat models, and the TCPOBOP/DENA and TCPOBOP only mouse models. Microarray and qRT-PCR analyses were performed on two cohorts of human hepatocellular carcinoma (HCC) patients. Rat HCC cells were transduced by a Hao2 encoding lentiviral vector and grafted in mice.

RESULTS

Downregulation of Hao2 was observed in all investigated rodent models of hepatocarcinogenesis. Interestingly, Hao2 mRNA levels were also profoundly downregulated in early preneoplastic lesions. Moreover, HAO2 mRNA levels were strongly downregulated in two distinct series of human HCCs, when compared to both normal and cirrhotic peri-tumoral liver. HAO2 levels were inversely correlated with grading, overall survival and metastatic ability. Finally, exogenous expression of Hao2 in rat cells impaired their tumorigenic ability.

CONCLUSION

Our work identifies for the first time the oncosuppressive role of the metabolic gene Hao2. Indeed, its expression is severely decreased in HCC of different species and etiology, and its reintroduction in HCC cells profoundly impairs tumorigenesis. We also demonstrate that dysregulation of HAO2 is a very early event in the development of HCC and it may represent a useful diagnostic and prognostic marker for human HCC.

Mice with hepatocyte-specific FXR deficiency are resistant to spontaneous but susceptible to cholic acid-induced hepatocarcinogenesis

Farnesoid X receptor (FXR) belongs to the nuclear receptor superfamily with its endogenous ligands bile acids. Mice with whole body FXR deficiency develop liver tumors spontaneously, but the underlying mechanism is unclear. Moreover, it is unknown whether FXR deficiency in liver alone serves as a tumor initiator or promoter during liver carcinogenesis. This study aims to evaluate the effects of hepatocyte-specific FXR deficiency (FXR(hep-/-)) in liver tumor formation. The results showed that FXR(hep-/-) mice did not show spontaneous liver tumorigenesis with aging (up to 24 mo of age). Therefore FXR(hep-/-) mice were fed a bile acid (cholic acid)-containing diet alone or along with a liver tumor initiator, diethylnitrosamine (DEN). Thirty weeks later, no tumors were found in wild-type or FXR(hep-/-) mice without any treatment or with DEN only. However, with cholic acid, while only some wild-type mice developed tumors, all FXR(hep-/-) mice presented with severe liver injury and tumors. Interestingly, FXR(hep-/-) mouse livers increased basal expression of tumor suppressor p53 protein, apoptosis, and decreased basal cyclin D1 expression, which may prevent tumor development in FXR(hep-/-) mice. However, cholic acid feeding reversed these effects in FXR(hep-/-) mice, which is associated with an increased cyclin D1 and decreased cell cycle inhibitors. More in-depth analysis indicates that the increased in cell growth might result from disturbance of the MAPK and JAK/Stat3 signaling pathways. In conclusion, this study shows that hepatic FXR deficiency may only serve as a tumor initiator, and increased bile acids is required for tumor formation likely by promoting cell proliferation.

Suppression of p53 by Notch3 is mediated by Cyclin G1 and sustained by MDM2 and miR-221 axis in hepatocellular carcinoma

To successfully target Notch receptors as part of a multidrug anticancer strategy, it will be essential to fully characterize the factors that are modulated by Notch signaling. We recently reported that Notch3 silencing in HCC results in p53 up-regulation in vitro and, therefore, we focused on the mechanisms that associate Notch3 to p53 protein expression. We explored the regulation of p53 by Notch3 signalling in three HCC cell lines HepG2, SNU398 and Hep3B.We found that Notch3 regulates p53 at post-transcriptional level controlling both Cyclin G1 expression and the feed-forward circuit involving p53, miR-221 and MDM2. Moreover, our results were validated in human HCCs and in a rat model of HCC treated with Notch3 siRNAs. Our findings are becoming an exciting area for further in-depth research toward targeted inactivation of Notch3 receptor as a novel therapeutic approach for increasing the drug-sensitivity, and thereby improving the treatment outcome of patients affected by HCC. Indeed, we proved that Notch3 silencing strongly increases the effects of Nutilin-3.With regard to therapeutic implications, Notch3-specific drugs could represent a valuable strategy to limit Notch signaling in the context of hepatocellular carcinoma over-expressing this receptor.

Segmental Transarterial Embolization in a Translational Rat Model of Hepatocellular Carcinoma

PURPOSE

To develop a clinically relevant, minimally invasive technique for transarterial embolization in a translational rat model of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Oral diethylnitrosamine was administered to 53 male Wistar rats ad libitum for 12 weeks. Tumor induction was monitored using magnetic resonance imaging. Minimally invasive lobar or segmental transarterial embolization was performed through a left common carotid artery approach. Necropsy was performed to evaluate periprocedural mortality. Histologic analysis of tumors that received embolization was performed to assess percent tumor necrosis.

RESULTS

Severe cirrhosis and autochthonous HCCs were characterized in a cohort of rats composed of two groups of rats identically treated with diethylnitrosamine with median survival times of 101 days and 105 days (n = 10/group). A second cohort was used to develop minimally invasive transarterial embolization of HCCs (n = 10). In a third cohort, lobar embolization was successfully performed in 9 of 10 rats and demonstrated a high rate of periprocedural mortality (n = 5). Necropsy performed for periprocedural mortality after lobar embolization demonstrated extensive tissue necrosis within the liver (n = 3) and lungs (n = 2), indicating nontarget embolization as the likely cause of mortality. In a fourth cohort of rats, a segmental embolization technique was successfully applied in 10 of 13 rats. Segmental embolization resulted in a reduction in periprocedural mortality (P = .06) relative to selective embolization and a 19% increase in average tumor necrosis (P = .04).

CONCLUSIONS

Minimally invasive, segmental embolization mimicking the currently applied clinical approach is feasible in a translational rat model of HCC and offers the critical advantage of reduced nontarget embolization relative to lobar embolization.

Diethylnitrosamine (DEN)-induced carcinogenic liver injury in mice

The toxic properties of various nitrosamines in animals and humans are well established. The parenteral or oral administration of the smallest quantities of diethylnitrosamine (DEN) or dimethylnitrosamine (DMN) results in severe liver damage. Most prominent are intense neutrophilic infiltration, extensive centrilobular haemorrhagic necrosis, bile duct proliferation, fibrosis, and bridging necrosis that ends in hepatocarcinogenesis. Due to the robustness of the induced hepatic alterations, the application of DEN in rodents has become an attractive experimental model for studies aimed at understanding the pathogenetic alterations underlying the formation of liver cancer, which represents one of the most common malignancies in humans worldwide. However, several studies have shown that the hepatocarcinogenic effects of nitrosamines might vary with the genetic background of the animals, their sex, their age, and other factors that might impact the outcome of experimentation. We present general guidelines for working with DEN, and a detailed protocol that allows the establishment of highly reproducible liver cancer in mice. The outcome of liver injury after the application of DEN in mice, as estimated by the formation of cirrhosis and cancer, appears to be a suitable animal model for the analysis of some aspects and processes that promote the pathogenesis of hepatocellular carcinoma in humans.

Albumin-drug conjugates in the treatment of hepatic disorders

INTRODUCTION

This review deals with the use of serum albumin (SA) as a carrier for the selective delivery of drugs to liver cells.

AREAS COVERED

The synthesis and properties of the SA conjugates prepared to enhance the performance of the drugs used in the treatment of viral hepatitis, hepatocellular carcinoma (HCC), liver micrometastases and hepatic fibrosis are reported.

EXPERT OPINION

Studies in humans and laboratory animals demonstrated the capacity of SA conjugates to accomplish a liver targeting of the drugs, but at the same time underscored their limits and drawbacks, which can explain why to date these complexes did not reach a practical application. The major drawback is the need of administration by intravenous route, which prevents long-term daily treatments as required by some liver pathologies, such as chronic virus hepatitis and fibrosis. At present, only a conjugate carrying doxorubicin and addressed to the treatment of HCC showed in laboratory animals a solid potentiality to improve the value of the coupled drug. In the future, conjugation to SA could remain a successful strategy to permit the administration of drugs with rapid resolutive effects inside liver cells without causing severe extrahepatic adverse reactions.

Two-stage model of chemically induced hepatocellular carcinoma in mouse

The aim of this study was to develop an efficient and reproducible mouse model for hepatocellular carcinoma (HCC) research and assess the expression of two proto-oncogenes (c-myc and N-ras) and tumor suppressor gene p53 in the carcinogenic process. In this study, we found that diethylnitrosamine initiation with CCl4 and ethanol promotion could induce a short-term, two-stage liver carcinogenesis model in male BALB/c mice, the process of hepatocarcinogenesis including liver damage, liver necrosis/cell death, liver inflammation, liver proliferation, liver hyperplasia, liver steatosis, and liver cirrhosis and hepatocellular nodules, which mimicked the usual sequence of events observed in human HCC. We also identified that the increase in expression of the p53 gene is related to the proliferation of hepatocytes, whereas overexpression of the c-myc and N-ras genes is associated with hepatocarcinogenesis. This animal model may serve as a basis for recapitulating the molecular pathogenesis of HCC seen in humans.

p53 promotes inflammation-associated hepatocarcinogenesis by inducing HMGB1 release

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) develops in response to chronic hepatic injury. Although induced cell death is regarded as the major component of p53 tumor-suppressive activity, we recently found that sustained p53 activation subsequent to DNA damage promotes inflammation-associated hepatocarcinogenesis. Here we aim at exploring the mechanism linking p53 activation and hepatic inflammation during hepatocarcinogenesis.

METHODS

p53(-/-) hepatocytes expressing inducible p53 and primary wild type hepatocytes were treated to induce p53 expression. The supernatants were collected and analyzed for the presence of released inflammatory cytokines. Ethyl pyruvate was used in a rat model of carcinogen-induced hepatocarcinogenesis to examine its effect on p53-dependent chronic hepatic injury, inflammation, and tumorigenesis.

RESULTS

Here we show that cytoplasmic translocation and circulating levels of potent inflammatory molecule high-mobility group protein 1 (HMGB1) were greater in wild type rats than in p53(+/-) rats following carcinogen administration. Restoration of p53 expression in p53-null hepatocytes or induction of endogenous p53 in wild type hepatocytes gives rise to the release of HMGB1. Administration of the HMGB1 release inhibitor ethyl pyruvate, which does not affect p53-mediated hepatic apoptosis, substantially prevented carcinogen-induced cirrhosis and tumorigenesis in rat livers.

CONCLUSIONS

These results suggest that although p53 is usually regarded as a tumor suppressor, its constant activation can promote pro-tumorigenic inflammation, at least in part, via inducing HMGB1 release. Application of HMGB1 inhibitors when restoring p53 in cancer therapy might protect against pro-tumorigenic effects while leaving p53-mediated clearance of malignant cells intact.

Immunomodulatory effect of Stichopus japonicus acid mucopolysaccharide on experimental hepatocellular carcinoma in rats

Stichopus japonicus acid mucopolysaccharide (SJAMP) is an important biologically active compound that can be extracted from the body wall of the sea cucumber. The present study investigated the anti-tumor and immunomodulatory effects of SJAMP in an experimental hepatocellular carcinoma (HCC) model in rats. Three doses of SJAMP (17.5 mg/kg, 35 mg/kg, and 70 mg/kg administered 5 days/week via oral gavage) were given to rats with diethylnitrosamine (DEN)-induced HCC. SJAMP treatment significantly inhibited DEN-induced HCC by reducing both the number and mean volume of nodules, decreasing serum a-fetoprotein (AFP) levels and proliferating cell nuclear antigen (PCNA) expression in liver, and increasing p21 expression. Furthermore, SJAMP decreased the serum levels of ALT, AST, GGT and TNF-α and increased serum IL-2. SJAMP administration also improved indices of spleen and thymus function and improved both macrophage phagocytosis and NK cell-mediated tumoricidal activity. Moreover, CD3+ and CD4+ T lymphocyte levels recovered significantly and the CD4+/CD8+ T cell ratio normalized in a dose-dependent manner. In conclusion, SJAMP effectively inhibited the growth of HCC through the stimulation of immune organs and tissue proliferation, leading to the enhancement of cellular immunity pathways in rats.

Paradoxical role of autophagy in the dysplastic and tumor-forming stages of hepatocarcinoma development in rats

Many reports have shown that autophagy has a role as both a promoter and inhibitor in tumor development. However, the mechanism of this paradox is unknown. Tumor development is a multistep process. Therefore, we investigated whether the role of autophagy in hepatocarcinoma formation depended on the stage of tumor development. Based on our results, autophagy inhibition by chloroquine had a tumor-promotive effect in the rat model with N-diethylnitrosamine-induced hepatocarcinogenesis in its dysplastic stage (Ds) and a tumor-suppressive effect in its tumor-forming stage (Ts). In the Ds, autophagy inhibition enhanced cell proliferation, DNA damage and inflammatory cytokines expression in liver. These changes were dependent on the upregulation of reactive oxygen species (ROS) that was resulted from autophagy inhibition, and ultimately accelerated the process of hepatocarcinogenesis. However, in the Ts, autophagy inhibition restrained tumor formation by decreasing tumor cell survival and proliferation. In this stage, autophagy inhibition led to excessive ROS accumulation in the tumor, which promoted cell apoptosis, and prominently suppressed tumor cell metabolism. Taken together, our data suggested that autophagy suppressed hepatocarcinogenesis in the Ds by protecting normal cell stability and promoted hepatocarcinogenesis in the Ts by supporting tumor cells growth. Autophagy always had a role as a protector throughout the process of hepatocarcinoma development.

Mouse models for liver cancer

Hepatocellular carcinoma (HCC), the most common form of primary liver cancer is the third leading cause of cancer-related cell death in human and the fifth in women worldwide. The incidence of HCC is increasing despite progress in identifying risk factors, understanding disease etiology and developing anti-viral strategies. Therapeutic options are limited and survival after diagnosis is poor. Therefore, better preventive, diagnostic and therapeutic tools are urgently needed, in particular given the increased contribution from systemic metabolic disease to HCC incidence worldwide. In the last three decades, technological advances have facilitated the generation of genetically engineered mouse models (GEMMs) to mimic the alterations frequently observed in human cancers or to conduct intervention studies and assess the relevance of candidate gene networks in tumor establishment, progression and maintenance. Because these studies allow molecular and cellular manipulations impossible to perform in patients, GEMMs have improved our understanding of this complex disease and represent a source of great potential for mechanism-based therapy development. In this review, we provide an overview of the current state of HCC modeling in the mouse, highlighting successes, current challenges and future opportunities.

DNA damage-induced sustained p53 activation contributes to inflammation-associated hepatocarcinogenesis in rats

The tumor suppressor p53 has an important role in inducing cell-intrinsic responses to DNA damage, including cellular senescence or apoptosis, which act to thwart tumor development. It has been shown, however, that senescent or dying cells are capable of eliciting inflammatory responses, which can have pro-tumorigenic effects. Whether DNA damage-induced p53 activity can contribute to senescence- or apoptosis-associated pro-tumorigenic inflammation is unknown. Recently, we generated a p53 knock-out rat via homologous recombination in rat embryonic stem cells. Here we show that in a rat model of inflammation-associated hepatocarcinogenesis, heterozygous deficiency of p53 resulted in attenuated inflammatory responses and ameliorated hepatic cirrhosis and tumorigenesis. Chronic administration of hepatocarcinogenic compound, diethylnitrosamine, led to persistent DNA damage and sustained induction of p53 protein in the wild-type livers, and much less induction in p53 heterozygous livers. Sustained p53 activation subsequent to DNA damage was accompanied by apoptotic rather than senescent hepatic injury, which gave rise to the hepatic inflammatory responses. In contrast, the non-hepatocarcinogenic agent, carbon tetrachloride, failed to induce p53, and caused a similar degree of chronic hepatic inflammation and cirrhosis in wild type and p53 heterozygous rats. These results suggest that although p53 is usually regarded as a tumor suppressor, its constant activation can promote pro-tumorigenic inflammation, especially in livers exposed to agents that inflict lasting mutagenic DNA damage.

RB restricts DNA damage-initiated tumorigenesis through an LXCXE-dependent mechanism of transcriptional control

The LXCXE peptide motif facilitates interaction between the RB tumor suppressor and a large number of cellular proteins that are expected to impinge on diverse biological processes. In vitro and in vivo analyses demonstrated that LXCXE binding function is dispensable for RB promoter association and control of basal gene expression. Dependence on this function of RB is unmasked after DNA damage, wherein LXCXE binding is essential for exerting control over E2F3 and suppressing cell-cycle progression in the presence of genotoxic stress. Gene expression profiling revealed that the transcriptional program coordinated by this specific aspect of RB is associated with progression of human hepatocellular carcinoma and poor disease outcome. Consistent with these findings, biological challenge revealed a requirement for LXCXE binding in suppression of genotoxin-initiated hepatocellular carcinoma in vivo. Together, these studies establish an essential role of the LXCXE binding motif for RB-mediated transcriptional control, response to genotoxic insult, and tumor suppression.

Tumor models and specific contrast agents for small animal imaging in oncology

Despite the widespread use of various imaging modalities in clinical and experimental oncology without or with combined application of commercially available nonspecific contrast agents (CAs), development of tissue- or organ- or disease-specific CAs has been a continuing effort for pursuing ever-improved sensitivity, specificity, and applicability. This is particularly true with magnetic resonance imaging (MRI) due to its intrinsic superb spatial/temporal/contrast resolutions and adequate detectability for tiny amount of substances. In this context, research using small animal tumor models has played an indispensible role in preclinical exploration of tissue specific CAs. Emphasizing more on methodological and practical aspects, this article aims to share our cumulated experiences on how to create tumor models for evaluation and development of new tissue specific MRI CAs and how to apply such models in imaging-based research studies. With the results that are repeatedly confirmed by later clinical applications in cancer patients, some of our early preclinical studies have contributed to the designs of subsequent clinical trials on the new CAs, some studies have predicted new utilities of these CAs; and other studies have led to the discoveries of new tissue- or disease-specific CAs with novel diagnostic or even therapeutic potentials. Among commonly adopted tumor models, the chemically induced and surgically implanted nodules in the liver prove very useful to simulate primary and metastatic intrahepatic tumors, respectively in clinical patients. The methods to create tumor models have eased procedures and yielded high success rates. The specific properties of the new CAs could be outshined by intraindividual comparison to the commercial CAs as nonspecific controls. Meticulous imaging-microangiography-histology matching techniques guaranteed colocalization of the lesion on in vivo MRI and postmortem tissue specimen, hence correct imaging interpretation and longstanding conclusions. As exemplified in the real study cases, the present experimental set-up proves applicable in small animals for imaging-based oncological investigations, and may provide a platform for the currently booming molecular imaging in a multimodality environment.

Doxorubicin coupled to lactosaminated human albumin: a hepatocellular carcinoma targeted drug

Hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide. There is a substantial need for new chemotherapeutic drugs effective against this tumor. Doxorubicin (DOXO), used for chemoembolization of HCCs, is poorly efficacious when administered systemically at conventional doses; dose escalation is hindered by unacceptable toxicity. Here, we review preclinical experiments showing that the efficacy of DOXO against HCCs and its safety increased following conjugation to lactosaminated human albumin (L-HSA). L-HSA-DOXO was initially prepared to improve the anticancer activity of the drug on well-differentiated HCCs, which actively internalize L-HSA by means of the asialoglycoprotein receptor. Unexpectedly, it was found that the conjugate enhanced DOXO concentrations in all forms of HCCs, independently of their differentiation grade.

Dual therapeutic effects of interferon-alpha gene therapy in a rat hepatocellular carcinoma model with liver cirrhosis

Human hepatocellular carcinoma (HCC) often arises from a background of liver cirrhosis. Therefore, in order to develop therapeutic strategies for HCC, an animal model bearing multifocal liver tumors accompanied by liver cirrhosis is a preferred experimental setting. In this study, we developed a rapid and reproducible method for generating such a model in rats by weekly administration of diethylnitrosamine (DEN) at doses based on body weight (BW). By adjusting the duration of administration of DEN, the animals could be induced to develop HCC alone, or HCC and liver cirrhosis simultaneously. The latter model was used for evaluating the therapeutic effects of adenoviral delivery of interferon-alpha (IFN-alpha). Our results demonstrated that targeting of IFN-alpha expression to the liver significantly reduced liver tumor volume and ameliorated liver cirrhosis. Mechanistic studies revealed that IFN-alpha gene therapy induced immunomodulatory, antiproliferative, and proapoptotic activities that were effective in the control of tumor growth, and reduced the expressions of transforming growth factor-beta (TGF-beta) and tissue inhibitor of metalloproteinase-1 (TIMP-1), leading to amelioration of liver cirrhosis. These results suggest that IFN-alpha gene therapy is a promising strategy to treat HCC patients who have concomitant liver cirrhosis.

Efficacy of doxorubicin coupled to lactosaminated albumin on rat hepatocellular carcinomas evaluated by ultrasound imaging

BACKGROUND/AIMS

Doxorubicin was conjugated with lactosaminated human albumin, a hepatotropic drug carrier, in order to increase its efficacy in the treatment of hepatocellular carcinoma. In rats bearing hepatocellular carcinomas induced by diethylnitrosamine, lactosaminated human albumin coupled doxorubicin enhanced the drug concentrations in the tumours and lowered those in extrahepatic tissues. The aim of the present study was to investigate the effects of lactosaminated human albumin coupled doxorubicin on the growth of established rat hepatocellular carcinomas induced by diethylnitrosamine.

METHODS

Lactosaminated human albumin coupled doxorubicin and the free drug were i.v. administered to rats twice a week for 4 weeks at the single dose of 1 microg/g. Growth of individual tumours was followed through time by ultrasonography.

RESULTS

In the control animals injected with saline the mean area of the tracked tumours significantly increased during the whole period of treatment. In the group of rats treated with lactosaminated human albumin coupled doxorubicin the mean area of the followed hepatocellular carcinomas remained practically unchanged. The free drug inhibited tumour growth only in the first period of drug administration. Lactosaminated human albumin coupled doxorubicin also hindered the development of new neoplastic nodules, which was unaffected by the free drug.

CONCLUSIONS

The results support lactosaminated human albumin coupled doxorubicin as a promising agent for a systemic chemotherapy of hepatocellular carcinomas to treat noncurable patients.

Doxorubicin coupled to lactosaminated albumin: effect of heterogeneity in drug load on conjugate disposition and hepatocellular carcinoma uptake in rats

Coupling to lactosaminated human albumin (L-HSA) makes doxorubicin (DOXO) an effective drug against chemically induced rat hepatocellular carcinomas (HCCs). In the conjugate there is a large heterogeneity in the number of DOXO molecules bound to one L-HSA molecule. After lyophilization, the molecules with the higher DOXO load form large complexes (C-DOXOL), whereas those with low drug load (C-DOXOS) have the size of the carrier L-HSA. In the present experiments, we demonstrated that in C-DOXOL the molecules are not linked by covalent bonds, but are strongly aggregated probably because of mutual drug-drug interaction between the DOXO residues. In healthy rats and in animals with HCCs which received the same dose (1 microg/g) of DOXO injected in C-DOXOL or in C-DOXOS forms, penetration of the drug in tumors and in tissues was more rapid after administration of the former complex. Three hours after injection of both conjugate forms the intracellular release of DOXO from the carrier was completed. The AUCs from 0.5 to 4h of the levels of the released DOXO in HCCs, surrounding liver and bone marrow of animals injected with C-DOXOL were similar to those calculated in animals given C-DOXOS. This suggests that after administration of the dose of DOXO used in the present experiments the conjugate molecules with lower or higher drug load can exert comparable pharmacological and toxic effects.

Coupling of lactose molecules to the carrier protein hinders the spleen and bone marrow uptake of doxorubicin conjugated with human albumin

Several attempts have been made to enhance doxorubicin (DOXO) concentrations in tumour cells by drug conjugation with human albumin (HSA). HSA-DOXO has the drawback of causing DOXO accumulation in spleen and bone marrow, with a consequent leucopoenia not produced when lactose molecules are coupled to the carrier protein. In the present experiments we demonstrated that the effect of HSA lactosamination is not a consequence of a more rapid disappearance from the bloodstream of the lactosaminated conjugate (L-HSA-DOXO), which is rapidly internalized by the liver through the asialoglycoprotein receptor, but is due to a hindered uptake by spleen and bone marrow cells caused by the coupled lactose molecules. Experiments in vitro showed that HSA-DOXO produced an inhibition of murine macrophage proliferation not caused by L-HSA-DOXO. This result can be explained by higher amounts of the former conjugate entering in these cells and suggests macrophages as the cell type responsible for the spleen and bone marrow internalization of HSA-DOXO hindered by lactose coupling. Importantly, lactosamination of HSA did not reduce the marked uptake of HSA-DOXO by chemically induced rat hepatocellular carcinoma. L-HSA-DOXO, by avoiding DOXO accumulation in bone marrow is an attractive candidate for clinical trials against tumors which were found to actively internalize this conjugate in laboratory animals, such as hepatocellular carcinoma.

A conjugate of doxorubicin with lactosaminated albumin enhances the drug concentrations in all the forms of rat hepatocellular carcinomas independently of their differentiation grade

BACKGROUND/AIMS

Doxorubicin (DOXO) was coupled to lactosaminated human serum albumin (L-HSA) in order to enhance the drug concentration in the well differentiated hepatocellular carcinomas (HCCs), which can accumulate L-HSA through the asialoglycoprotein receptor. In the present experiments we compared the DOXO concentrations produced by this conjugate (L-HSA-DOXO) and by the uncoupled drug in the well, moderately, and poorly differentiated rat HCCs.

METHODS

The same dose (1 microg/g) of free or L-HSA coupled-DOXO was injected in rats with HCCs induced by diethylnitrosamine. At different times, the animals were killed and the neoplastic nodules of liver were isolated. Their differentiation grade was determined histologically and their DOXO content was measured.

RESULTS

Unexpectedly, we found that also in the poorly differentiated forms of HCCs, which display no or only a poor capacity of accumulating L-HSA, the conjugate raised DOXO levels that were approximately twofold higher than those produced by the free drug.

CONCLUSIONS

The conjugate L-HSA-DOXO could improve the potential of DOXO in the treatment of all HCCs, including the poorly differentiated tumors that are the common forms in the advanced disease for which an effective chemotherapy is particularly needed.

Doxorubicin coupled to lactosaminated albumin inhibits the growth of hepatocellular carcinomas induced in rats by diethylnitrosamine

BACKGROUND/AIMS

The hepatocyte receptor for asialoglycoproteins internalizes galactosyl terminating macromolecules which can be used as hepatotropic drug carriers. Since this receptor is also expressed on the cells of well differentiated human hepatocellular carcinomas (HCCs), we studied whether conjugation of doxorubicin (DOXO) with lactosaminated human albumin (L-HSA) increases the drug efficacy on HCCs induced in rats by diethylnitrosamine (DENA).

METHODS

DENA was given in the drinking water for 8 weeks. One week after the last day of DENA administration, animals were randomly assigned to three groups. Each group was administered with either saline, free or coupled DOXO (1 microg/g). Rats received 4 weekly intravenous injections. One week after the last administration, rats were killed and HCC development was evaluated by counting the tumor nodules on the surface of hepatic lobes.

RESULTS

In rats treated with L-HSA coupled DOXO the number of neoplastic nodules was significantly lower (P < 0.05) than that counted in animals injected with saline or with free DOXO. Coupled DOXO did not decrease body rat weight, which was markedly reduced by the free drug.

CONCLUSIONS

Conjugation with L-HSA increased the antineoplastic efficacy and decreased the systemic toxicity of DOXO administered to rats with HCCs produced by DENA.

Enhanced uptake of lactosaminated human albumin by rat hepatocarcinomas: implications for an improved chemotherapy of primary liver tumors

BACKGROUND/AIMS

The hepatocyte receptor for asialoglycoproteins (ASGP-R) internalizes macromolecules exposing galactosyl residues (MEGRs) which can be used as liver-addressed drug carriers. This receptor was also found on the cells of the large majority of well differentiated hepatocarcinomas (HCCs). The aim of the present experiments was to ascertain whether ASGP-R of HCCs is functionally active and these tumors can internalize higher quantities of MEGRs than extra-hepatic tissues.

METHODS

We injected radioactive lactosaminated human albumin (L-HSA) in rats with HCCs produced by nitroso-diethylamine and measured the radioactivity of tumors, surrounding liver, heart, intestine and kidney. L-HSA is a MEGR successfully used in humans as a hepatotropic drug carrier.

RESULTS

The levels of radioactivity of HCCs were two to three times lower than those of surrounding liver, but several times higher than those of extra-hepatic tissues. L-HSA accumulation in the tumors mainly occurred via the ASGP-R, as indicated by the 20 times lower penetration of non-lactosaminated HSA. L-HSA uptake by the well-differentiated tumors were four times higher compared with that by the poorly differentiated forms.

CONCLUSIONS

The present results suggest that in the chemotherapy of HCCs expressing the ASGP-R the extra-hepatic toxicity of anticancer agents can be reduced by conjugation to L-HSA.

Long-term radioiodine retention and regression of liver cancer after sodium iodide symporter gene transfer in wistar rats

Radioiodine therapy of nonthyroid cancers after sodium iodide symporter (NIS) gene delivery has been proposed as a potential application of gene therapy. However, it seems to be precluded by the rapid efflux of taken up iodine from most transduced xenografted tumors. We present an in vivo kinetic study of NIS-related hepatic iodine uptake in an aggressive model of hepatocarcinoma induced by diethylnitrosamine in immunocompetent Wistar rats. We followed the whole-body iodine distribution by repeated imaging of live animals. We constructed a rat NIS (rNIS) adenoviral vector, Ad-CMV-rNIS, using the cytomegalovirus (CMV) as a promoter. Injected in the portal vein in 5 healthy and 25 hepatocarcinoma-bearing rats and liver tumors in 9 hepatocarcinoma-bearing rats, Ad-CMV-rNIS drove expression of a functional NIS protein by hepatocytes and allowed marked (from 20 to 30% of the injected dose) and sustained (>11 days) iodine uptake. This contrasts with the massive iodine efflux found in vitro in human hepatic tumor cell lines. In vivo specific inhibition of NIS by sodium perchlorate led to a rapid iodine efflux from the liver, indicating that the sustained uptake was not attributable to an active retention mechanism but to permanent recycling of the effluent radioiodine via the high hepatic blood flow. Radioiodine therapy after Ad-CMV-rNIS administration achieved a strong inhibition of tumor growth, the complete regression of small nodules, and prolonged survival of hepatocarcinoma-bearing rats. This demonstrates for the first time the efficacy of NIS-based radiotherapy in a relevant preclinical model of nonthyroid human carcinogenesis.