Metabolic heterogeneity of human hepatocellular carcinoma: implications for personalized pharmacological treatment

Metabolic reprogramming is a characteristic feature of cancer cells, but there is no unique metabolic program for all tumors. Genetic and gene expression studies have revealed heterogeneous inter- and intratumor patterns of metabolic enzymes and membrane transporters. The functional implications of this heterogeneity remain often elusive. Here, we applied a systems biology approach to gain a comprehensive and quantitative picture of metabolic changes in individual hepatocellular carcinoma (HCC). We used protein intensity profiles determined by mass spectrometry in samples of 10 human HCCs and the adjacent noncancerous tissue to calibrate Hepatokin1, a complex mathematical model of liver metabolism. We computed the 24-h profile of 18 metabolic functions related to carbohydrate, lipid, and nitrogen metabolism. There was a general tendency among the tumors toward downregulated glucose uptake and glucose release albeit with large intertumor variability. This finding calls into question that the Warburg effect dictates the metabolic phenotype of HCC. All tumors comprised elevated β-oxidation rates. Urea synthesis was found to be consistently downregulated but without compromising the tumor's capacity for ammonia detoxification owing to increased glutamine synthesis. The largest intertumor heterogeneity was found for the uptake and release of lactate and the size of the cellular glycogen content. In line with the observed metabolic heterogeneity, the individual HCCs differed largely in their vulnerability against pharmacological treatment with metformin. Taken together, our approach provided a comprehensive and quantitative characterization of HCC metabolism that may pave the way for a computational a priori assessment of pharmacological therapies targeting metabolic processes of HCC

Analysis of molecular and structural characteristics of the liver to improve the diagnostic performance of a ¹³C-methacetin liver function breath test

Hintergrund: Der atembasierte Liver MAximum capacity (LiMAx)-Test erlaubt die nicht-invasive Messung der Cytochrom P450 1A2 (CYP1A2)-Gesamtleberfunktion. In Kombination mit Schnittbildverfahren wird der LiMAx-Test zur Einschätzung der Operabilität vor leberchirurgischen Eingriffen eingesetzt (Volumen-Funktionsplanung). Unklar ist bislang der Einfluss der CYP1A2-Aktivität hepatischer Tumoren auf die Genauigkeit der Volumen-Funktionsplanung, was im ersten Teil untersucht werden sollte. Darüber hinaus könnte der LiMAx-Test künftig allein oder in Kombination mit einem elastographischen Verfahren als diagnostisches Werkzeug, z. B. zur Fibrosedetektion, eingesetzt werden. Grundlegend ist dafür, den Zusammenhang zwischen strukturell-mechanischen Lebergewebeeigenschaften und dem LiMAx-Test zu untersuchen (Struktur-Funktionsanalyse), was Gegenstand des zweiten Teils der Arbeit sein sollte. Methoden: Die CYP1A2-Aktivität wurde experimentell in 38 Gewebeproben aus hepatozellulärem Adenom (HCA), Karzinom (HCC), kolorektalen Lebermetastasen (CRLM) sowie den korrespondierenden nicht-tumorösen Geweben bestimmt. Zur Struktur-Funktionsanalyse wurden bei 66 Patienten mit chronischen Lebererkrankungen sowie 20 lebergesunden Probanden simultan Lebersteifigkeit (zeitharmonische Elastographie, THE) und Leberfunktion (LiMAx-Test) erfasst. Zudem wurden die serologischen Fibrose-Scores Aspartate aminotransferase to Platelet Ratio Index (APRI) und Fibrosis-4 Index (FIB 4) berechnet und bei 47 Patienten der Fibrosegrad bestimmt. Ergebnisse: HCC und CRLM wiesen nahezu keine CYP1A2-Aktivität im Vergleich zum nicht-tumorösen Gewebe auf (< 1 %). HCA-Gewebe hingegen besaß eine Restaktivität (20,7 %), die sich auf die exemplarisch erstellte Volumen-Funktionsplanung auswirkte. Die Struktur-Funktionsanalyse zeigte eine stark negative Korrelation zwischen Lebersteifigkeit und LiMAx-Werten (r = -0,701). Eine fortschreitende Fibrosierung ging mit einer höheren Lebersteifigkeit und Fibrose-Scores sowie niedrigeren LiMAx-Werten einher. Nur schwere Leberfibrose war zuverlässig mit THE und LiMAx detektierbar. Schlussfolgerung: Zur exakten Volumen-Funktionsplanung sollte die CYP1A2-Aktivität in HCA Berücksichtigung finden. Zudem besteht ein signifikanter Zusammenhang zwischen strukturell-mechanischen und funktionellen Lebergewebeeigenschaften, der sich klinisch zur nicht-invasiven Diagnostik nutzen lässt.Background: The Liver MAximum capacity (LiMAx) test allows the non-invasive measurement of the overall hepatic cytochrome P450 1A2 (CYP1A2) activity. It is used, in combination with imaging techniques, for preoperative risk assessment in liver surgery (volume-function analysis). Yet, it remains unknown, to which extent the residual CYP1A2 activity of hepatic tumors influences the accuracy of the volume-function analysis, which was addressed in the first part. Moreover, the LiMAx test, alone or in combination with elastographic techniques, could be used as a diagnostic tool, e.g. for fibrosis detection. The relationship between structural characteristics of the hepatic tissue and the LiMAx test must be studied beforehand (structure-function relationship), which was the aim of the second part. Methods: CYP1A2 activity was measured in vitro in 38 paired samples of tumorous and adjacent nontumorous tissue of patients suffering from hepatocellular adenoma (HCA), carcinoma (HCC) or colorectal liver metastases (CRLM). To analyze the hepatic structure-function relationship, LiMAx test and liver stiffness measurements based on time-harmonic elastography (THE) were applied and the serological fibrosis scores Aspartate aminotransferase to Platelet Ratio Index (APRI) and Fibrosis-4 Index (FIB 4) were calculated in patients with chronic liver diseases (n = 66) and healthy control subjects (n = 20). Moreover, fibrosis was graded by histological examination. Results: CYP1A2 activity was found to be significantly decreased in HCC and CRLM tissues, compared to the adjacent nontumorous tissue (< 1 %). HCA tissue contained residual activity (20.7 %) which altered the results of the volume-function analysis in its currently used way. Concerning the structure-function relationship, there was a significant negative correlation between liver stiffness and LiMAx values (r = -0.701). Liver stiffness and serological fibrosis scores (APRI, FIB-4) increased progressively with the stage of fibrosis whereas LiMAx values decreased with fibrosis progression. THE and LiMAx were able to discriminate well between non-severe and severe fibrosis. Conclusion: The residual CYP1A2 activity should be considered especially in HCA cases for an improved volume-function analysis. Moreover, the strong relationship between structural and functional tissue characteristics should be further evaluated for non-invasive diagnostic applications

Characterization of Lipid and Lipid Droplet Metabolism in Human HCC

Human hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and the most common cause of death in people with cirrhosis. While previous metabolic studies of HCC have mainly focused on the glucose metabolism (Warburg effect), less attention has been paid to tumor-specific features of the lipid metabolism. Here, we applied a computational approach to analyze major pathways of fatty acid utilization in individual HCC. To this end, we used protein intensity profiles of eleven human HCCs to parameterize tumor-specific kinetic models of cellular lipid metabolism including formation, enlargement, and degradation of lipid droplets (LDs). Our analysis reveals significant inter-tumor differences in the lipid metabolism. The majority of HCCs show a reduced uptake of fatty acids and decreased rate of &#946;-oxidation, however, some HCCs display a completely different metabolic phenotype characterized by high rates of &#946;-oxidation. Despite reduced fatty acid uptake in the majority of HCCs, the content of triacylglycerol is significantly enlarged compared to the tumor-adjacent tissue. This is due to tumor-specific expression profiles of regulatory proteins decorating the surface of LDs and controlling their turnover. Our simulations suggest that HCCs characterized by a very high content of triglycerides comprise regulatory peculiarities that render them susceptible to selective drug targeting without affecting healthy tissue

LiMAx Prior to Radioembolization for Hepatocellular Carcinoma as an Additional Tool for Patient Selection in Patients with Liver Cirrhosis

Background and Aims: Radioembolization (RE) has recently demonstrated a non-inferior survival outcome compared to systemic therapy for advanced hepatocellular carcinoma (HCC). Therefore, current guidelines recommend RE for patients with advanced HCC and preserved liver function who are unsuitable for transarterial chemoembolization (TACE) or systemic therapy. However, despite the excellent safety profile of RE, post-therapeutic hepatic decompensation remains a serious complication that is difficult to predicted by standard laboratory liver function parameters or imaging modalities. LiMAx® is a non-invasive test for liver function assessment, measuring the maximum metabolic capacity for 13C-Methacetin by the liver-specific enzyme CYP 450 1A2. Our study investigates the potential of LiMAx® for predicting post-interventional decompensation of liver function. Patients and methods: In total, 50 patients with HCC with or without liver cirrhosis and not amenable to TACE or systemic treatments were included in the study. For patients prospectively enrolled in our study, LiMAx® was carried out one day before RE (baseline) and 28 and 90 days after RE. Established liver function parameters were assessed at baseline, day 28, and day 90 after RE. The relationship between baseline LiMAx® and pre-and post-interventional liver function parameters, as well as the ability of LiMAx® to predict hepatic decompensation, were analyzed. Results: We observed a strong association between baseline LiMAx® and bilirubin, albumin, ALBI grade, and MELD score. Patients presenting with Child–Pugh score B 28 days after RE or with a deterioration in Child–Pugh score by at least one point had a significantly lower baseline LiMAx® compared to those with Child–Pugh score A or with stable Child–Pugh score. The ability of LiMAx® to predict hepatic decompensation after RE was determined using ROC curve analysis and was compared to MELD score and ALBI grade. LiMAx® achieved a substantial AUC of 0.8117, comparable to MELD score and ALBI grade. Conclusion: Patients with lower LiMAx® values at baseline have a significantly increased risk for hepatic decompensation after RE, despite being categorized as Child–Pugh A. Therefore, LiMAx® can be used as an additional tool to identify patients at high risk of post-interventional hepatic failure