Generation of IgE-based immunotherapies against HER-2 overexpressing tumours

Ergänzend zu Chemotherapie und Strahlentherapie ist die passive Immuntherapie mit monoklonalen Antikörpern eine moderne Behandlungsmethode in der Krebstherapie. Zwei Eigenschaften von Antikörpern werden dabei genutzt: i) über das Fab Fragment binden sie spezifisch Tumorantigene und ii) über den Fc Teil rekrutieren sie Effektorzellen und aktivieren das Komplementsystem. Einer dieser Antikörper ist Trastuzumab (Herceptin®), ein wachstumshemmender, humanisierter, monoklonaler IgG1 Antikörper. Trastuzumab ist gegen das Tumorantigen HER-2 gerichtet, welches in 30% aller Brusttumore überexprimiert wird. Alle Antikörper, die bis jetzt in Form von passiver Immuntherapie in der Klinik eingesetzt werden, sind ausschließlich der IgG Subklasse zu zuordnen. Antikörper der IgE Subklasse sind hingegen bekannt für ihre schädliche Funktion in der Typ I Allergie. Es ist jedoch kaum bekannt, dass IgE Antikörper eine anti-Tumor Wirkung haben und diese Eigenschaft für Immuntherapien in der Onkologie ausgenutzt werden könnte. Das Ziel dieser Doktorarbeit war es daher alternative Strategien zur Behandlung von Krebserkrankungen basierend auf IgE Antikörper zu untersuchen, sowie deren Wirksamkeit mit der von IgG zu vergleichen. Die orale Immunisierungsroute eignet sich sehr gut zur Induktion einer Th2 Immunantwort mit hoch affinen IgE Antikörpern, die gegen das applizierte Antigen gerichtet sind. Daher wird die Etablierung eines IgE-abhängiges Nahrungsmittelallergiemodells in Mäusen beschrieben. Dieses Modell haben wir anschließend für unsere Krebsstudien adaptiert. Mäuse wurden mit unterschiedlichen Konzentrationen von Ovalbumin unter gleichzeitiger Säuresuppression gefüttert. Dies führte zu einer Induktion von antigen-spezifischen IgE in einem Th2 Milieu. Dieses orale Immunisierungsschema wurde auch mit HER-2 Mimotopen, d.h. Peptide, die das Trastuzumab-Epitop imitieren, angewendet. Die durch das Mimotop induzierten IgE Antikörper erkannten spezifisch das Tumorantigen auf HER-2 überexprimierende Brustkrebszellen und führten zur Lyse der Tumorzellen. Ergänzend zu diesem aktiven immuntherapeutischen Ansatz wurde ein Trastuzumab IgE Antikörper für passive Immuntherapie konstruiert. Wir konnten zeigen, dass Trastuzumab IgE die gleiche Spezifität wie Trastuzumab IgG besitzt. In einem Three-Colour Flow Cytometric Assay zeigte sich, dass beide Antikörper Tumorzellen erfolgreich zerstören, dies aber durch unterschiedliche Mechanismen tun: Trastuzumab IgG führte zu „antibody-dependent cellmediated phagocytosis“ (ADCP), während Trastuzumab IgE „antibody-dependent cellmediated cytotoxicity“ (ADCC) auslöste. Ausgehend von den hier präsentierten Daten schließen wir, dass tumor-spezifisches IgE, aktiv induziert oder passiv verabreicht, eine vielversprechende Alternative zu Immuntherapien mit IgG gegen Krebs darstellt.In combination with chemotherapy or radiation, passive immunotherapy with monoclonal antibodies is state of the art in cancer therapy. For this purpose, two properties of antibodies are harnessed: i) via the Fab fragment they bind a specific tumour antigen and ii) via the Fc portion they recruit effector cells and activate the complement system. One of these antibodies is trastuzumab (Herceptin®), a growth-inhibitory humanized monoclonal IgG1 antibody recognizing the tumour antigen HER-2, which is overexpressed in 30% of human breast cancers. Interestingly, all antibodies applied for passive immunotherapy are so far exclusively of the IgG subclass. In contrast, antibodies of the IgE subclass are best-known for their detrimental function in type I hypersensitivity. It is little-known that IgE has anti-tumour capacity which could be exploited for immunotherapy of cancer. Thus, the aim of this doctoral thesis was to examine alternative strategies for cancer treatment based on IgE antibodies, and to compare their efficacy with that of IgG. The oral immunization route is well suited for the induction of a Th2 immunity including high affine IgE responses to administered antigens. Therefore, the establishment of an IgEdependent food allergy model in mice is described, which we applied also for our cancer studies. When mice were fed with different concentrations of ovalbumin under concomitant anti-acid medication, an antigen-specific IgE induction in a Th2 environment could be achieved. This oral vaccination regimen was also used for feeding HER-2 mimotopes, i.e. epitope-mimics of the anti-HER-2 IgG antibody trastuzumab. Indeed, these mimotopes induced IgE antibodies recognizing the tumour antigen which were able to bind HER-2 overexpressing breast cancer cells and led to tumour cell lysis. Complementary to this active immunotherapeutic approach a trastuzumab-like IgE antibody for passive immunotherapy was constructed. We could show that this trastuzumab IgE exhibited the same specificity as the original trastuzumab IgG. Moreover, a three-colour flow cytometric assay indicated that even though both antibodies were able to induce tumour cell killing, they used different mechanisms: trastuzumab IgG acted via antibody-dependent cell-mediated phagocytosis (ADCP), whereas trastuzumab IgE elicited mostly antibody-dependent cell-mediated cytotoxicity (ADCC). Based on the presented data we conclude that tumour-specific IgE, induced actively or applied in a passive manner, represents a potent alternative to IgG-based immunotherapies against cancer

Enhanced membrane protein expression by engineering increased intracellular membrane production

Background: Membrane protein research is frequently hampered by the low natural abundance of these proteins in cells and typically relies on recombinant gene expression. Different expression systems, like mammalian cells, insect cells, bacteria and yeast are being used, but very few research efforts have been directed towards specific host cell customization for enhanced expression of membrane proteins. Here we show that by increasing the intracellular membrane production by interfering with a key enzymatic step of lipid synthesis, enhanced expression of membrane proteins in yeast is achieved. Results: We engineered the oleotrophic yeast, Yarrowia lipolytica, by deleting the phosphatidic acid phosphatase, PAH1, which led to massive proliferation of endoplasmic reticulum (ER) membranes. For all eight tested representatives of different integral membrane protein families, we obtained enhanced protein accumulation levels and in some cases enhanced proteolytic integrity in the Delta pah1 strain. We analysed the adenosine A2AR G-protein coupled receptor case in more detail and found that concomitant induction of the unfolded protein response in the Delta pah1 strain enhanced the specific ligand binding activity of the receptor. These data indicate an improved quality control mechanism for membrane proteins accumulating in yeast cells with proliferated ER. Conclusions: We conclude that redirecting the metabolic flux of fatty acids away from triacylglycerol-and sterylester-storage towards membrane phospholipid synthesis by PAH1 gene inactivation, provides a valuable approach to enhance eukaryotic membrane protein production. Complementary to this improvement in membrane protein quantity, UPR co-induction further enhances the quality of the membrane protein in terms of its proper folding and biological activity. Importantly, since these pathways are conserved in all eukaryotes, it will be of interest to investigate similar engineering approaches in other cell types of biotechnological interest, such as insect cells and mammalian cells

Impact of the Specific Mutation in KRAS Codon 12 Mutated Tumors on Treatment Efficacy in Patients with Metastatic Colorectal Cancer Receiving Cetuximab-Based First-Line Therapy: A Pooled Analysis of Three Trials

Purpose: This study investigated the impact of specific mutations in codon 12 of the Kirsten-ras (KRAS) gene on treatment efficacy in patients with metastatic colorectal cancer (mCRC). Patients: Overall, 119 patients bearing a KRAS mutation in codon 12 were evaluated. All patients received cetuximab-based first-line chemotherapy within the Central European Cooperative Oncology Group (CECOG), AIO KRK-0104 or AIO KRK-0306 trials. Results: Patients with KRAS codon 12 mutant mCRC showed a broad range of outcome when treated with cetuximab-based first-line regimens. Patients with tumors bearing a KRAS p.G12D mutation showed a strong trend to a more favorable outcome compared to other mutations (overall survival 23.3 vs. 14-18 months; hazard ratio 0.66, range 0.43-1.03). An interaction model illustrated that KRAS p.G12C was associated with unfavorable outcome when treated with oxaliplatin plus cetuximab. Conclusion: The present analysis suggests that KRAS codon 12 mutation may not represent a homogeneous entity in mCRC when treated with cetuximab-based first-line therapy. Copyright (C) 2012 S. Karger AG, Base

Adiponutrin Functions as a Nutritionally Regulated Lysophosphatidic Acid Acyltransferase

SummaryNumerous studies in humans link a nonsynonymous genetic polymorphism (I148M) in adiponutrin (ADPN) to various forms of fatty liver disease and liver cirrhosis. Despite its high clinical relevance, the molecular function of ADPN and the mechanism by which I148M variant affects hepatic metabolism are unclear. Here we show that ADPN promotes cellular lipid synthesis by converting lysophosphatidic acid (LPA) into phosphatidic acid. The ADPN-catalyzed LPA acyltransferase (LPAAT) reaction is specific for LPA and long-chain acyl-CoAs. Wild-type mice receiving a high-sucrose diet exhibit substantial upregulation of Adpn in the liver and a concomitant increase in LPAAT activity. In Adpn-deficient mice, this diet-induced increase in hepatic LPAAT activity is reduced. Notably, the I148M variant of human ADPN exhibits increased LPAAT activity leading to increased cellular lipid accumulation. This gain of function provides a plausible biochemical mechanism for the development of liver steatosis in subjects carrying the I148M variant

Porin 1 Modulates Autophagy in Yeast

Autophagy is a cellular recycling program which efficiently reduces the cellular burden of ageing. Autophagy is characterised by nucleation of isolation membranes, which grow in size and further expand to form autophagosomes, engulfing cellular material to be degraded by fusion with lysosomes (vacuole in yeast). Autophagosomal membranes do not bud from a single cell organelle, but are generated de novo. Several lipid sources for autophagosomal membranes have been identified, but the whole process of their generation is complex and not entirely understood. In this study, we investigated how the mitochondrial outer membrane protein porin 1 (Por1), the yeast orthologue of mammalian voltage-dependent anion channel (VDAC), affects autophagy in yeast. We show that POR1 deficiency reduces the autophagic capacity and leads to changes in vacuole and lipid homeostasis. We further investigated whether limited phosphatidylethanolamine (PE) availability in por1∆ was causative for reduced autophagy by overexpression of the PE-generating phosphatidylserine decarboxylase 1 (Psd1). Altogether, our results show that POR1 deficiency is associated with reduced autophagy, which can be circumvented by additional PSD1 overexpression. This suggests a role for Por1 in Psd1-mediated autophagy regulation

MimoDB 2.0: a mimotope database and beyond

Mimotopes are peptides with affinities to given targets. They are readily obtained through biopanning against combinatorial peptide libraries constructed by phage display and other display technologies such as mRNA display, ribosome display, bacterial display and yeast display. Mimotopes have been used to infer the protein interaction sites and networks; they are also ideal candidates for developing new diagnostics, therapeutics and vaccines. However, such valuable peptides are not collected in the central data resources such as UniProt and NCBI GenPept due to their ‘unnatural’ short sequences. The MimoDB database is an information portal to biopanning results of random libraries. In version 2.0, it has 15 633 peptides collected from 849 papers and grouped into 1818 sets. Besides the core data on panning experiments and their results, broad background information on target, template, library and structure is included. An accompanied benchmark has also been compiled for bioinformaticians to develop and evaluate their new models, algorithms and programs. In addition, the MimoDB database provides tools for simple and advanced searches, structure visualization, BLAST and alignment view on the fly. The experimental biologists can easily use the database as a virtual control to exclude possible target-unrelated peptides. The MimoDB database is freely available at http://immunet.cn/mimodb

Mimotope ELISA for Detection of Broad Spectrum Antibody against Avian H5N1 Influenza Virus

Science and Technology Foundation of Fujian Province [2009YZ0002]; National Natural Science Foundation of China [30901077]; National High Technology Research and Development Program [2010AA022801]Background: We have raised a panel of broad spectrum neutralizing monoclonal antibodies against the highly pathogenic H5N1 avian influenza virus, which neutralize the infectivity of, and afford protection against infection by, most of the major genetic groups of the virus evolved since 1997. Peptide mimics reactive with one of these broad spectrum H5N1 neutralizing antibodies, 8H5, were identified from random phage display libraries. Method: The amino acid residues of the most reactive 12mer peptide, p125 (DTPLTTAALRLV), were randomly substituted to improve its mimicry of the natural 8H5 epitope. Result: 133 reactive peptides with unique amino acid sequences were identified from 5 sub-libraries of p125. Four residues (2,4,5.9) of the parental peptide were preserved among all the derived peptides and probably essential for 8H5 binding. These are interspersed among four other residues (1,3,8,10), which exhibit restricted substitution and probably could contribute to binding, and another four (6,7,11,12) which could be randomly substituted and probably are not essential for binding. One peptide, V-1b, derived by substituting 5 of the latter residues is the most reactive and has a binding constant of 3.16x10(-9) M, which is 38 fold higher than the affinity of the parental p125. Immunoassay produced with this peptide is specifically reactive with 8H5 but not also the other related broad spectrum H5N1 avian influenza virus neutralizing antibodies. Serum samples from 29 chickens infected with H5N1 avian influenza virus gave a positive result by this assay and those from 12 uninfected animals gave a negative test result. Conclusion: The immunoassay produced with the 12 mer peptide, V1-b, is specific for the natural 8H5 epitope and can be used for detection of antibody against the broad spectrum neutralization site of H5N1 avian influenza virus

A dynamic actin cytoskeleton is required to prevent constitutive VDAC-dependent MAPK-signalling and aberrant lipid homeostasis.

The dynamic nature of the actin cytoskeleton is required to coordinate many cellular processes and a loss of its plasticity has been linked to accelerated cell ageing and attenuation of adaptive response mechanisms. Cofilin is an actin-binding protein that controls actin dynamics and has been linked to mitochondrial signalling pathways that control drug resistance and cell death. Here we show that cofilin-driven chronic depolarisation of the actin cytoskeleton activates cell wall integrity MAPK-signalling and disrupts lipid homeostasis in a VDAC-dependent manner. Expression of the cof1-5 mutation, which reduces the dynamic nature of actin, triggers loss of cell wall integrity, vacuole fragmentation, disruption of lipid homeostasis, lipid droplet (LD) accumulation and the promotion of cell death. The integrity of the actin cytoskeleton is therefore essential to maintain the fidelity of MAPK signalling, lipid homeostasis and cell health in S. cerevisiae. Graphical abstrac