Christoph P. Berg

Caspase-8/FLICE functions as an executioner caspase in anticancer drug-induced apoptosis

Caspase-8 plays an essential role in apoptosis triggered by death receptors. Through the cleavage of Bid, a proapoptotic Bcl-2 member, it further activates the mitochondrial cytochrome c/Apaf-1 pathway. Because caspase-8 can be processed also by anticancer drugs independently of death receptors, we investigated its exact role and order in the caspase cascade. We show that in Jurkat cells either deficient for caspase-8 or overexpressing its inhibitor c-FLIP apoptosis mediated by CD95, but not by anticancer drugs was inhibited. In the absence of active caspase-8, anticancer drugs still induced the processing of caspase-9, -3 and Bid, indicating that Bid cleavage does not require caspase-8. Overexpression of Bcl-xL prevented the processing of caspase-8 as well as caspase-9, -6 and Bid in response to drugs, but was less effective in CD95-induced apoptosis. Similar responses were observed by overexpression of a dominant-negative caspase-9 mutant. To further determine the order of caspase-8 activation, we employed MCF7 cells lacking caspase-3. In contrast to caspase-9 that was cleaved in these cells, anticancer drugs induced caspase-8 activation only in caspase-3 transfected MCF7 cells. Thus, our data indicate that, unlike its proximal role in receptor signaling, in the mitochondrial pathway caspase-8 rather functions as an amplifying executioner caspase.

Mesalazine inhibits activation of transcription factor NF-κB in inflamed mucosa of patients with ulcerative colitis

OBJECTIVES:The salicylate mesalazine is commonly used for the treatment of inflammatory bowel diseases, yet its precise mechanism of action is unknown. Because transcription factor NF-κB plays an important role in inflammatory bowel diseases, we investigated the effects of mesalazine therapy on NF-κB activation in patients with ulcerative colitis.METHODS:A total of 20 patients with moderately active ulcerative colitis received mesalazine for 8 wk. Biopsies were taken before and after drug administration and analyzed for NF-κB activation using an antibody specific for active NF-κB.RESULTS:In biopsies of active ulcerative colitis but not in noninflamed mucosa, activation of NF-κB was detected predominantly in macrophages. Mesalazine therapy resulted in a strong abrogation of NF-κB activation in situ.CONCLUSIONS:Our results suggest that the therapeutic properties of mesalazine rely at least in part on the inhibition of NF-κB activation, resulting in the suppression of proinflammatory gene expression in the inflamed mucosa.

Telaprevir‐based triple therapy in liver transplant patients with hepatitis C virus: A 12‐week pilot study providing safety and efficacy data

After liver transplantation (LT), the management of recurrent hepatitis C virus (HCV) infections still remains a major challenge. In HCV genotype 1 patients not undergoing transplantation, the introduction of protease inhibitor (PI)–based regimens has increased the sustained virological response rate significantly. This pilot study investigated both the safety and efficacy of telaprevir (TVR)‐based triple therapy in HCV‐infected LT patients with a special emphasis on drug‐drug interactions between immunosuppressants and PIs. Safety and efficacy data were gathered for 12 weeks for 9 HCV‐infected LT patients who were treated with a combination of TVR, pegylated interferon, and ribavirin (RBV) in parallel with immunosuppressive drugs such as tacrolimus (TAC; n = 4), cyclosporine A (CSA; n = 4), and sirolimus (SIR; n = 1). Seven of the transplant patients completed the 12 weeks of triple therapy. At week 4, 4 of the patients were found to be HCV RNA–negative, and importantly, 8 were found to be negative at week 12. During the 12‐week course of triple therapy, short‐term measurements of immunosuppressant trough levels required individual dose reductions in all patients (CSA, 2.5‐fold; SIR, 7‐fold; and TAC, 22‐fold). Furthermore, two‐thirds of the patients exhibited hematological side effects requiring RBV dose reductions, the administration of erythropoietin, or even blood transfusions. In conclusion, this pilot study provides evidence showing that TVR‐based triple therapy is effective within the first 4 to 12 weeks in LT patients suffering from HCV genotype 1 recurrence, and it also provides evidence showing that drug‐drug interactions between TVR and immunosuppressants can be handled appropriately through the close monitoring of trough levels and adequate dosage adjustments. Liver Transpl, 2012.

Early MRI response monitoring of patients with advanced hepatocellular carcinoma under treatment with the multikinase inhibitor sorafenib

BackgroundNew therapeutic principles in clinical oncology require the adjustment of response criteria to govern therapy decisions. For advanced hepatocellular carcinoma (HCC) a new era has recently begun by the approval of the multikinase inhibitor sorafenib. As a unique feature, HCC usually develops in a diseased liver and current imaging technologies employing classical response criteria have not been prospectively evaluated for this new treatment.MethodsMRI signal patterns were assessed in 21 advanced HCC patients receiving sorafenib. MRI was performed at baseline and in short-term intervals thereafter. Signal changes under therapy on T1WI, T2WI and post-gadolinium images including necrosis volume and its ratio to the entire tumor volume were compared to baseline imaging. To assess the association between the categorical variables, Fishers exact tests were applied for a statistical analysis. Survey time ranged from 2–65 weeks, and a total of 39 target lesions were evaluated.ResultsSignal abnormalities during sorafenib therapy were disclosed by T1WI and T2WI in 15/21 patients. The predominant tumor signal change was hyperintensity on both T1WI and T2WI. Interestingly, most patients developed MRI signal changes within 4 weeks of therapy; in contrast, two non-responders did not show any signal alteration at follow-up. Under therapy, 16/21 patients presented with new or progressive necrosis, whereas 7 patients achieved temporarily >75% tumor necrosis under sorafenib. Significantly associated MRI variables were increase in T1WI signal and tumor necrosis (p = 0.017) as well as increase of tumor necrosis with an elevated ratio of necrotic to vital tumor areas (p = 0.002). Remarkably, some (3/13) of the patients developing necrotic tumor areas showed a relevant (>20%) increase in tumor volume, which should be considered in the assessment of imaging studies.ConclusionAs sorafenib induces early intralesional necrosis with profound changes in T1WI/T2WI MRI signal intensities and measurable necrotic tumor areas in most HCC patients, early MRI-based evaluation could pave the way for its rationale and cost-effective application.

Daclatasvir combined with sofosbuvir or simeprevir in liver transplant recipients with severe recurrent hepatitis C infection

Daclatasvir (DCV) is a potent, pangenotypic nonstructural protein 5A inhibitor with demonstrated antiviral efficacy when combined with sofosbuvir (SOF) or simeprevir (SMV) with or without ribavirin (RBV) in patients with chronic hepatitis C virus (HCV) infection. Herein, we report efficacy and safety data for DCV‐based all‐oral antiviral therapy in liver transplantation (LT) recipients with severe recurrent HCV. DCV at 60 mg/day was administered for up to 24 weeks as part of a compassionate use protocol. The study included 97 LT recipients with a mean age of 59.3 ± 8.2 years; 93% had genotype 1 HCV and 31% had biopsy‐proven cirrhosis between the time of LT and the initiation of DCV. The mean Model for End‐Stage Liver Disease (MELD) score was 13.0 ± 6.0, and the proportion with Child‐Turcotte‐Pugh (CTP) A/B/C was 51%/31%/12%, respectively. Mean HCV RNA at DCV initiation was 14.3 × 6 log10 IU/mL, and 37% had severe cholestatic HCV infection. Antiviral regimens were selected by the local investigator and included DCV+SOF (n = 77), DCV+SMV (n = 18), and DCV+SMV+SOF (n = 2); 35% overall received RBV. At the end of treatment (EOT) and 12 weeks after EOT, 88 (91%) and 84 (87%) patients, respectively, were HCV RNA negative or had levels <43 IU/mL. CTP and MELD scores significantly improved between DCV‐based treatment initiation and last contact. Three virological breakthroughs and 2 relapses occurred in patients treated with DCV+SMV with or without RBV. None of the 8 patient deaths (6 during and 2 after therapy) were attributed to therapy. In conclusion, DCV‐based all‐oral antiviral therapy was well tolerated and resulted in a high sustained virological response in LT recipients with severe recurrent HCV infection. Most treated patients experienced stabilization or improvement in their clinical status. Liver Transplantation 22 446‐458 2016 AASLD

Mycoplasma antigens as a possible trigger for the induction of antimitochondrial antibodies in primary biliary cirrhosis.

Background: In primary biliary cirrhosis (PBC), autoreactivity mainly targets members of the pyruvate dehydrogenase complex (PDC). Because PDC subunits are expressed on the surface of mycoplasma and molecular mimicry may be one aetiological factor, we analysed the presence of mammalian and mycoplasma PDC‐specific antibodies in PBC patients.

Autoantibodies to asialoglycoprotein receptor (ASGPR) measured by a novel ELISA—Revival of a disease-activity marker in autoimmune hepatitis

BACKGROUND The liver-specific ASGPR is an autoantigen in autoimmune hepatitis (AIH) patients. Anti-ASGPR antibody correlates with disease activity, however, only in-house assays have been reported so far. METHODS Rabbit ASGPR was purified by affinity chromatography on galactose-Sepharose and used for standardised detection of anti-ASGPR by ELISA. Anti-ASGPR IgG was measured in sera from 45 patients with AIH, PBC (n=43), alcoholic liver disease (n=13), HBV infection (n=35), HCV infection (n=53), and 118 blood donors. Anti-ASGPR was correlated with biochemical parameters of disease activity in 22 AIH patients with consecutive samples. RESULTS Twenty-one of 30 untreated (70%) and five of 15 treated AIH patients (30%) showed elevated anti-ASGPR at first presentation. Only one blood donor demonstrated anti-ASGPR. ALD and PBC patients were all negative. ROC curve analysis of AIH and disease-control patients revealed a sensitivity of 77.8% and a specificity of 99.4%. Three (8.6%) of 35 HBV and 7 (13.2%) of 53 HCV patients demonstrated elevated anti-ASGPR. In AIH patients, anti-ASPGR correlated with liver-transaminases levels. In 22 follow-up patients, elevation of anti-ASPGR preceded liver-transaminases increase. CONCLUSIONS The novel anti-ASGPR ELISA is a readily available and specific diagnostic tool for anti-ASGPR detection in AIH. Quantification of anti-ASGPR is helpful in monitoring disease activity.

Apoptosis-associated antigens recognized by autoantibodies in patients with the autoimmune liver disease primary biliary cirrhosis

There is growing evidence that the onset of autoimmune disorders can be linked to the inefficient removal of apoptotic cells. Since defects in the elimination of apoptotic cells lead to secondary necrosis and subsequent release of intracellular components, this might explain the generation of autoantibodies against intracellular antigens. Accordingly, we wanted to investigate, whether antibodies from patients with the autoimmune liver disease primary biliary cirrhosis (PBC) recognize self-proteins generated and released during apoptosis. Using Western blot analyses we could detect intracellular antigens with serum IgG from PBC patients but not with serum IgG from healthy donors in lysates of Jurkat T-leukemia, HepG2 hepatoma, and HT-29 colon-carcinoma cells. Interestingly, PBC serum IgG also recognized caspase substrates in cells undergoing apoptosis induced by staurosporine or TRAIL (TNF-related apoptosis inducing ligand). In addition to intracellular antigens, serum IgG from PBC patients detected caspase-dependent antigens in the supernatants of apoptotic (secondary necrotic) cells and antigens on the surface of apoptotic Jurkat cells. Among the caspase substrates recognized by PBC serum IgG we could identify the components PDC-E2 and -E1β of the known autoantigen PDC (pyruvate dehydrogenase complex). Thus, caspase-mediated processing of intracellular proteins might generate de novo autoantigens that upon release contribute to the generation of autoantibodies and autoimmune diseases as PBC.

Hepatitis C virus core protein induces apoptosis-like caspase independent cell death

BackgroundHepatitis C virus (HCV) associated liver diseases may be related to apoptotic processes. Thus, we investigated the role of different HCV proteins in apoptosis induction as well as their potency to interact with different apoptosis inducing agents.Methods and ResultsThe use of a tightly adjustable tetracycline (Tet)-dependent HCV protein expression cell system with the founder osteosarcoma cell line U-2 OS allowed switch-off and on of the endogenous production of HCV proteins. Analyzed were cell lines expressing the HCV polyprotein, the core protein, protein complexes of the core, envelope proteins E1, E2 and p7, and non-structural proteins NS3 and NS4A, NS4B or NS5A and NS5B. Apoptosis was measured mainly by the detection of hypodiploid apoptotic nuclei in the absence or presence of mitomycin C, etoposide, TRAIL and an agonistic anti-CD95 antibody. To further characterize cell death induction, a variety of different methods like fluorescence microscopy, TUNEL (terminal deoxynucleotidyl transferase (TdT)-catalyzed deoxyuridinephosphate (dUTP)-nick end labeling) assay, Annexin V staining, Western blot and caspase activation assays were included into our analysis.Two cell lines expressing the core protein but not the total polyprotein exerted a strong apoptotic effect, while the other cell lines did not induce any or only a slight effect by measuring the hypodiploid nuclei. Cell death induction was caspase-independent since it could not be blocked by zVAD-fmk. Moreover, caspase activity was absent in Western blot analysis and fluorometric assays while typical apoptosis-associated morphological features like the membrane blebbing and nuclei condensation and fragmentation could be clearly observed by microscopy. None of the HCV proteins influenced the apoptotic effect mediated via the mitochondrial apoptosis pathway while only the core protein enhanced death-receptor-mediated apoptosis.ConclusionOur data showed a caspase-independent apoptosis-like effect of the core protein, which seems to be inhibited in the presence of further HCV proteins like the non structural (NS) proteins. This observation could be of relevance for the viral spread since induction of an apoptosis-like cell death by the core protein may have some impact on the release of the HCV particles from the host cell.

Treatment of Recurrent Genotype 1 Hepatitis C Post-Liver Transplantation: Single Center Experience with Telaprevir-Based Triple Therapy

Recurrent HCV infection post-liver transplantation (post-LT) is still a major challenge in the treatment of hepatitis C virus (HCV) infection. In this retrospective analysis we gathered data about treatment response and safety of all 14 post-LT patients who were treated between 2011 and 2013 at our centre with a telaprevir (TVR)-based triple therapy. Seven out of 14 patients completed the full treatment course of 48 weeks. Five patients achieved a SVR 24, while 3 additional HCV RNA-negative patients are still in follow-up (end of treatment, SVR 12 and 22). Four patients discontinued treatment prematurely due to side effects. A virological non-response at TW 4 was seen in 1 patient. Virological breakthrough was observed in 2 patients at TW 16 and 28, respectively; 1 patient displayed a virological relapse after the end of treatment (EOT). Patients with a complicated course post-LT accumulated most of the severe side effects, largely infections. One patient with cholestatic hepatitis died 11 weeks after discontinuation of treatment due to progressive graft failure. In conclusion, TVR-based triple therapy in post-LT patients reveals an acceptable antiviral efficacy. Unfortunately, severe side effects are frequent and often require therapeutic interventions. Therefore, with the approval of less straining DAA like sofosbuvir in sight, TVR-based triple therapy in post-LT patients should be, if possible avoided.