Molecular therapy and prevention of liver diseases

Molecular analyses have become an integral part of biomedical research as well as clinical medicine. The definition of the molecular and genetic basis of many human diseases has led to a better understanding of their pathogenesis and has in addition offered new perspectives for their diagnosis, therapy and prevention. Genetically, liver diseases can be classified as hereditary monogenic, acquired monogenic, complex genetic and diseases. Based on this classification, gene therapy is based on six concepts: gene repair, gene substitution, cell therapy, block of gene expression or function, DNA vaccination as well as gene augmentation. While recent developments are promising, various delivery, targeting and safety issues need to be addressed before gene therapy will enter clinical practice. In the future, molecular diagnosis and therapy liver diseases will be part of our patient management and complement existing diagnostic, therapeutic and preventive strategies.

[Regional therapy of liver tumors]

Malignant liver tumors are either originating from the liver, such as the primary liver tumors hepatocellular carcinoma and the cholangiocellular carcinoma, or metastases from extrahepatic malignancies. Apart from surgical procedures (resection, liver transplantation) percutaneous local-ablative (ethanol injection, radiofrequency thermal ablation as well as radiation therapy) and transarterial interventions are non-surgical therapeutic options. While these regional therapies have been shown in randomised controlled studies to be effective for hepatocellular carcinoma, their therapeutic efficacy in cholangiocellular carcinoma and liver metastases has not been shown. In the following we will summarize the regional therapeutic options in primary and secondary liver tumors.

Hepatitis C virus infection: in vivo and in vitro models

Major advances in the understanding of the molecular biology of hepatitis C virus (HCV) have been made recently. While the chimpanzee is the only established animal model of HCV infection, several in vivo and in vitro models have been established that allow us to study various aspects of the viral life cycle. In particular, the replicon system and the production of recombinant infectious virions revolutionized the investigation of HCV-RNA replication and rendered all steps of the viral life cycle, including entry and release of viral particles, amenable to systematic analysis. In the following we will review the different in vivo and in vitro models of HCV infection.

An error model for protein quantification

MOTIVATION

Quantitative experimental data is the critical bottleneck in the modeling of dynamic cellular processes in systems biology. Here, we present statistical approaches improving reproducibility of protein quantification by immunoprecipitation and immunoblotting.

RESULTS

Based on a large data set with more than 3600 data points, we unravel that the main sources of biological variability and experimental noise are multiplicative and log-normally distributed. Therefore, we suggest a log-transformation of the data to obtain additive normally distributed noise. After this transformation, common statistical procedures can be applied to analyze the data. An error model is introduced to account for technical as well as biological variability. Elimination of these systematic errors decrease variability of measurements and allow for a more precise estimation of underlying dynamics of protein concentrations in cellular signaling. The proposed error model is relevant for simulation studies, parameter estimation and model selection, basic tools of systems biology.

AVAILABILITY

Matlab and R code is available from the authors on request. The data can be downloaded from our website www.fdm.uni-freiburg.de/~ckreutz/data.

[The hepatocellular carcinoma: alternative therapeutical strategies]

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in some areas of the world. The prognosis of HCC patients is generally very poor with a 5-year survival rate of less than 5%. Therapeutic strategies include surgery (resection or liver transplantation) and non-surgical interventions, such as percutaneous ethanol injection or radiofrequency thermal ablation as well as transarterial embolization or chemoembolization. Therefore, the development and evaluation of novel HCC treatment strategies such as the use of antiangiogenic, antiproliferative or antiinflammatoric drugs, immune therapeuticals, gene therapy and internal or external radiation are of utmost importance. This review should give an overview of possible alternative therapies in HCC treatment.

Reversal of drug resistance of hepatocellular carcinoma cells by adenoviral delivery of anti-ABCC2 antisense constructs

Human cancers are characterized by a high degree of drug resistance. The multidrug resistance transporters MDR1-P-glycoprotein (ABCB1) and ABCC2 (MRP2) are expressed in a variety of human cancers, including hepatocellular carcinoma (HCC). The ABCC2 gene encodes a membrane protein involved in the ATP-dependent transport of conjugates of lipophilic substances. In this study we analyzed the effect of an ABCC2 antisense construct on the chemosensitization of HepG2 cells. Adenoviral vectors were constructed to allow an efficient expression of anti-ABCC2 antisense constructs. The effective target sequence comprised nucleotides 2543-2942 of the human ABCC2 cDNA. Adenoviral delivery of the ABCC2 antisense construct resulted in a reduced IC(50) for doxorubicin (12-fold), vincristine (50-fold), cisplatin (25-fold) and etoposide (VP-16) (25-fold). The adenoviral delivery of the ABCC2 antisense construct was so efficient that chemosensitization of HepG2 cells could even be demonstrated in mass cell cultures without a selection of transduced cells for single ABCC2 antisense-expressing HCC cell clones. After transfection of the ABCC2 antisense-expressing construct, HepG2 cells had significantly reduced ABCC2 mRNA and ABCC2 protein levels. Transduction of the ABCC2 antisense-expressing construct into HepG2 cells resulted in the accumulation of the high-affinity ABCC2 substrate Fluo-3. HepG2 tumors stably transfected with an anti-ABCC2 antisense construct regressed significantly in nude mice upon vincristine treatment. In addition, significant tumor regression was also observed when adenovirus-expressing anti-ABCC2 antisense construct was directly injected into HepG2 tumors in nude mice. Our study demonstrates the specific reversal of ABCC2-related drug resistance in adenovirus-transduced HepG2 cells and in HepG2 tumors in nude mice expressing this ABCC2 antisense construct.

[Stem cells--basic aspects and therapeutic perspectives]

Stem cells are somatic cells with different proliferation and differentiation potential. Embryonic stem cells (ESC) are derived from human blastocysts. Recently, human ESC (hESC) were generated by nuclear transfer from somatic cells from patients for individual cell or tissue replacement. Adult stem cells (ASC) are multipotent and are harvested postnatally. ASC are found in peripheral blood and many tissues and organs and can differentiate in vitro to many cell types and tissues that can be used for therapeutic purposes ("tissue engineering"). Preliminary clinical studies demonstrate the tremendous therapeutic potential of ESC and ASC. Before a routine clinical application in humans, apart from many technical questions, safety and ethical issues need to be addressed and the therapeutic benefit of ESC and ASC for human diseases has to be demonstrated by qualified clinical studies.

[Palliative medicine content in German-language medical textbooks]

BACKGROUND

There is a need for improved end-of-life care, especially in the light of demographic changes with an increased incidence of cancer. Although medical textbooks are central to the training of medical students and also serve as a reference for more experienced clinicians, only few data exist on the extent to which medical textbooks address end-of-life care. We analysed the quantity and quality of information on end-of-life care given in German textbooks on different medical disciplines.

MATERIAL AND METHODS

26 top-selling German medical textbooks were analysed for the presentation of end-of-life care in chapters that address the 13 most common causes of death worldwide

RESULTS

In the 159 chapters analysed for information on traditional topics, like risk factors or early diagnosis (group A), such information was provided in 52% compared with only 9% on end-of-life topics, such as symptom management or manner of death (group B) (p=0.0001). There was no statistically significant difference between the different medical specialities (p=0.22). Line-by-line analysis showed that the phrase death or related terms was mentioned in only 57 of 159 chapters dealing with the most common causes of death worldwide.

CONCLUSION

The top-selling German textbooks that were analysed generally offer little helpful information on end-of-life care of patients.

CD117 (c-kit) expression in human hepatocellular carcinoma

AIMS

Although various methods of treatment have been tried, treatment options for advanced hepatocellular carcinoma (HCC) remain limited. Expression of the platelet-derived growth factor has been shown in HCC, which may derive from hepatic stem cells that express the c-kit proto-oncogene. Because of the promising results of imatinib and the key role played by c-kit in gastrointestinal stromal tumours and other solid tumours, the aim of this study was to determine the prevalence of c-kit (CD117) overexpression in patients with HCC.

MATERIALS AND METHODS

A retrospective study of 258 archival specimens of subjects with histologically confirmed HCC was carried out. Expression of the c-kit proto-oncogene was evaluated by immunohistochemistry using rabbit anti-CD117 antibody A4502.

RESULTS

The overall percentage of positive immunohistochemical staining of HCCs was 2.3% (6/258).

CONCLUSIONS

Our results suggest that CD117 is not significantly overexpressed in HCC and there seems to be no role for the use of imatinib.

Serum markers of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in some areas of the world with increasing incidence worldwide. Most of patients with HCC are diagnosed at a late stage. Therefore, the prognosis of HCC patients is generally very poor with a 5-year survival rate of less than 5%. Screening strategies including alpha-fetoprotein (AFP) and ultrasound every 6 months in patients with liver cirrhosis, the major risk factor for HCC development, have been recommended to detect HCC at earlier stages amenable to effective treatment strategies. AFP, however, is a marker with poor sensitivity and specificity and the ultrasound is highly dependent on the operator's experience. Apart from AFP, lens culinaris agglutinin-reactive AFP and des-gamma carboxyprothrombin and several other biomarkers (e.g., glypican-3, human hepatocyte growth factor, and insulin-like growth factor) have been proposed as markers for HCC detection. In addition, with recently employed techniques, such as gene-expressing microarrays and proteomics, it is to be expected that new HCC-specific markers will become available in the near future. For all such proposed markers, however, the clinical usefulness has to be carefully evaluated and validated.

[Vasculitis and liver disease]

Extrahepatic manifestations of liver diseases especially the hepatitis B virus (HBV)-infection and hepatitis C virus (HCV)-infection may occur during acute and/or chronic viral hepatitis. Besides a serum like illness with fever, arthralgia and urticaria, haematological disorders with transient bone marrow suppression and cryoglobulinemia have been described. Vasculitis is a rare complication of viral hepatitis. However, HCV can trigger a cryoglobulinemic vasculitis and may clinically present with purpura, arthritis, neuropathy, glomerulonephritis and fatigue. Panarteritis nodosa is frequently associated with HBV infection, which is caused by deposits of immune complexes in the arterial wall. Therapy of both types of vasculitis depends on the severity of disease and may include immunosuppressive agents as well as antivirals.

[Therapy of chronic hepatitis C]

Hepatitis C virus (HCV) infection is a leading cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma worldwide. Here, we will briefly review current and evolving therapies for chronic hepatitis C. Standard therapy with pegylated interferon-alpha and ribavirin achieves sustained virologic response rates of up to 40-50% in genotype 1- and about 80% in genotype 2- and 3-infected patients. Comprehensive management of chronic hepatitis C takes into account cofactors of disease progression. Novel antiviral strategies will likely complement existing therapeutic modalities in the near future.

[Therapy of hepatitis B]

Worldwide, there are approximately 350 million carriers of hepatitis B virus (HBV), of whom half a million to 1 million die from liver disease. The goal of treatment is to prevent cirrhosis, hepatic failure, and hepatocellular carcinoma. Substantial progress has been made in the treatment for hepatitis B in the past decade. Currently approved therapeutic options include interferon alpha, lamivudine and adefovir. The efficacy ot the respective antivirals is affected by virological and clinical parameters, thus requiring individual treatment strategies that will be discussed in detail.

[Chronic liver disease--diagnostic work-up]

The diagnostic work-up of patients with liver diseases includes taking a past history, a physical examination, incl. an abdominal ultrasound examination or a duplex ultrasonography, general laboratory analyses, etiology-defining analyses, imaging studies and in special situations a percutaneous or transjugular liver biopsy or a laparoscopy. Following this algorithm it is possible to identify in most cases the etiology of the liver disease. The exact diagnosis is key for the understanding of the natural course and prognosis of the liver disease and for the indication for therapy, the choice of the optimal therapeutic strategy and the assessment of its response. Of particular importance is at the time of the first diagnosis of a liver disease to exclude or identify coexisting etiologies, e. g., alcohol use and HCV infection.

[Treatment of hepatocellular carcinoma]

Hepatocellular carcinoma is one of the most common cancers worldwide. The incidence of this disease is also increasing in the Western world. Typically, HCC is diagnosed when patients have already reached an advanced stage of the disease and the prognosis is poor. Potentially curative treatment options include surgical resection or liver transplantation and can be offered to patients with adequate liver function and tumour stage. Other non-surgical treatment options such as radiofrequency ablation, cryoablation, ethanol or acetic acid injection, transarteriel chemoembolisation radiation therapy and systemic chemotherapy can be offered either alone or in combination to selected groups of patients. These treatments can improve (tumour-free) survival and in a few cases even cure the patient.

Effect of vardenafil, an inhibitor of phosphodiesterase-5, on portal haemodynamics in normal and cirrhotic liver -- results of a pilot study

BACKGROUND

Dysregulation of the cyclic guanosine 3',5' monophosphate-nitric oxide system is in part responsible for portal hypertension in cirrhosis.

AIM

To test the effects of inhibitors of phosphodiesterase-5 on portal haemodynamics.

METHODS

To 18 healthy subjects and 18 patients with Child A liver cirrhosis, 10 mg of vardenafil, an inhibitor of phosphodiesterase-5, were administered orally. Doppler sonographic measurements of hepatic and splanchnic blood flow, systemic blood pressure and heart rate were recorded before, 1 h after, and 48 h after the application. Vardenafil plasma levels were determined after 1 h. In five patients, invasive registration of free and wedged hepatic vein pressure was performed.

RESULTS

Portal venous flow increased in patients from 0.82 +/- 0.30 L/min (mean +/- s.d.) by 26% (CI: 16-37%, P = 0.0004) and in healthy subjects from 0.75 +/- 0.20 L/min (mean +/- s.d.) by 19% (CI: 9-28%; P = 0.0010). Celiac and hepatic artery resistivity indices rose significantly. Systemic blood pressure decreased slightly in patients. The wedged hepatic venous pressure gradient decreased in four of five patients with liver cirrhosis. Vardenafil plasma levels were higher in patients (14 +/- 10 microg/L) than in healthy subjects (9 +/- 6 microg/L; n.s.).

CONCLUSIONS

Inhibition of phosphodiesterase-5 increases portal flow and lowers portal pressure by a decrease in sinusoidal resistance and may be a novel therapeutic strategy for portal hypertension.