@phdthesis{Wendlinger2023,
  author    = {Wendlinger, Simone Alice},
  title     = {Function of Peripheral Blood Eosinophils in Melanoma},
  publisher = {Cancers (Basel)},
  doi       = {10.25972/OPUS-30119},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301194},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Despite accounting for only a small proportion of all skin cancers, malignant melanoma displays a serious health risk with increasing incidence and high mortality rate. Fortunately, advances in the treatment of malignant melanoma now prolong survival and enhance response and treatment efficacy. Established biomarkers help evaluate disease progression and facilitate choosing appropriate and individual treatment options. However, the need for easily accessible and reliable biomarkers is rising to predict patient-specific clinical outcome. Eosinophil infiltration into the tumor and high peripheral eosinophil counts prior and during treatment have been associated with better response in patients for various cancer entities, including melanoma. An analysis of a heterogeneous study cohort reported high serum ECP levels in non-responders. Hence, eosinophil frequency and serum ECP as a soluble eosinophil-secreted mediator were suggested as prognostic biomarkers in melanoma. We examined whether melanoma patients treated with first-line targeted therapy could also benefit from the effects of eosinophils. In total, 243 blood and serum samples from patients with advanced melanoma were prospectively and retrospectively collected before and after drug initiation. To link eosinophil function to improved clinical outcome, soluble serum markers and peripheral blood counts were used for correlative studies using a homogeneous study cohort. In addition, functional and phenotypical characterizations provided insights into the expression profile and activity of freshly isolated eosinophils, including comparisons between patients and healthy donors. Our data showed a significant correlation between high pre-treatment blood eosinophil counts and improved response to targeted therapy and by trend to combinatorial immunotherapy in patients with metastatic melanoma. In accordance with previous studies our results links eosinophil blood counts to better response in melanoma patients. High pre-treatment ECP serum concentration correlated with response to immunotherapy but not to targeted therapy. Eosinophils from healthy donors and patients showed functional and phenotypical similarities. Functional assays revealed a strong cytotoxic potential of blood eosinophils towards melanoma cells in vitro, inducing apoptosis and necrosis. In addition, in vitro cytotoxicity was an active process of peripheral eosinophils and melanoma cells with bidirectional features and required close cell-cell interaction. The extent of cytotoxicity was dose-dependent and showed susceptibility to changes in physical factors like adherence. Importantly, we provide evidence of an additive tumoricidal function of eosinophils and combinatorial targeted therapy in vitro. In summary, we give valuable insights into the complex and treatment-dependent role of eosinophils in melanoma. As a result, our data support the suggestion of eosinophils and their secreted mediators as potential prognostic biomarkers. It will take additional studies to examine the molecular mechanisms that underlie our findings.},
  subject      = {Melanom},
  language  = {en}
}
@phdthesis{Baur2019,
  author    = {Baur, Florentin Philipp},
  title     = {Establishment of a 3D tumour model and targeted therapy of BRAF-mutant colorectal cancer},
  doi       = {10.25972/OPUS-17412},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-174129},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {Cancer remains after cardiovascular diseases the leading cause of death worldwide and an estimated 8.2 million people died of it in 2012. By 2030, 13 million cancer deaths are expected due to the growth and ageing of the population. Hereof, colorectal cancer (CRC) is the third most common cancer in men and the second in women with a wide geographical variation across the world. Usually, CRC begins as a non-cancerous growth leading to an adenomatous polyp, or adenoma, arising from glandular cells. Since research has brought about better understanding of the mechanisms of cancer development, novel treatments such as targeted therapy have emerged in the past decades. Despite that, up to 95\% of anticancer drugs tested in clinical phase I trials do not attain a market authorisation and hence these high attrition rates remain a key challenge for the pharmaceutical industry, making drug development processes enormously costly and inefficient. Therefore, new preclinical in vitro models which can predict drug responses in vivo more precisely are urgently needed. Tissue engineering not only provides the possibility of creating artificial three-dimensional (3D) in vitro tissues, such as functional organs, but also enables the investigation of drug responses in pathological tissue models, that is, in 3D cancer models which are superior to conventional two-dimensional (2D) cell cultures on petri dishes and can overcome the limitations of animal models, thereby reducing the need for preclinical in vivo models. In this thesis, novel 3D CRC models on the basis of a decellularised intestinal matrix were established. In the first part, it could be shown that the cell line SW480 exhibited different characteristics when grown in a 3D environment from those in conventional 2D culture. While the cells showed a mesenchymal phenotype in 2D culture, they displayed a more pronounced epithelial character in the 3D model. By adding stromal cells (fibroblasts), the cancer cells changed their growth pattern and built tumour-like structures together with the fibroblasts, thereby remodelling the natural mucosal structures of the scaffold. Additionally, the established 3D tumour model was used as a test system for treatment with standard chemotherapeutic 5-fluorouracil (5-FU). The second part of the thesis focused on the establishment of a 3D in vitro test system for targeted therapy. The US Food and Drug Administration has already approved of a number of drugs for targeted therapy of specific types of cancer. For instance, the small molecule vemurafenib (PLX4032, Zelboraf™) which demonstrated impressive response rates of 50-80\% in melanoma patients with a mutation of the rapidly accelerated fibrosarcoma oncogene type B (BRAF) kinase which belongs to the mitogen active protein kinase (MAPK) signalling pathway. However, only 5\% of CRC patients harbouring the same BRAF mutation respond to treatment with vemurafenib. An explanation for this unresponsiveness could be a feedback activation of the upstream EGFR, reactivating the MAPK pathway which sustains a proliferative signalling. To test this hypothesis, the two early passage cell lines HROC24 and HROC87, both presenting the mutation BRAF V600E but differing in other mutations, were used and their drug response to vemurafenib and/or gefitinib was assessed in conventional 2D cell culture and compared to the more advanced 3D model. Under 3D culture conditions, both cell lines showed a reduction of the proliferation rate only in the combination therapy approach. Furthermore, no significant differences between the various treatment approaches and the untreated control regarding apoptosis rate and viability for both cell lines could be found in the 3D tumour model which conferred an enhanced chemoresistance to the cancer cells. Because of the observed unresponsiveness to BRAF inhibition by vemurafenib as can be seen in the clinic for patients with BRAF mutations in CRC, the cell line HROC87 was used for further xenografting experiments and analysis of activation changes in the MAPK signalling pathway. It could be shown that the cells presented a reactivation of Akt in the 3D model when treated with both inhibitors, suggesting an escape mechanism for apoptosis which was not present in cells cultured under conventional 2D conditions. Moreover, the cells exhibited an activation of the hepatocyte growth factor receptor (HGFR, c-Met) in 2D and 3D culture, but this was not detectable in the xenograft model. This shows the limitations of in vivo models. The results suggest another feedback activation loop than that to the EGFR which might not primarily be involved in the resistance mechanism. This reflects the before mentioned high attrition rates in the preclinical drug testing.},
  subject      = {Dickdarmtumor},
  language  = {en}
}
@phdthesis{FirdessaFite2015,
  author    = {Firdessa Fite, Rebuma},
  title     = {Use of polyhexanide and nanomedicine approach for effective treatments of cutaneous leishmaniasis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-115072},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {Despite huge suffering caused by cutaneous leishmaniasis (CL), there is no effective and affordable treatment strategy against CL and no licensed vaccines. The current treatments show limited efficacy and high toxicity. Improved therapies through discovery of novel drugs and/or an alternative treatment approaches are/is urgently needed. We aimed at identifying a novel antileishmanial agent and developing an innovative nanoparticle (NP) based platform for safe and effective treatments against CL. We discovered that polyhexanide (PHMB), a widely used antimicrobial polymer and wound antisepsis, shows an inherent antileishmanial activity at submicromolar concentrations. PHMB appears to kill L. major parasites via a dual mechanism involving disruption of membrane integrity and selective chromosome condensation. However, host chromosomes binding appear to be limited by exclusion from mammalian cell nuclei. Moreover, we attempted to establish effective drug delivery systems that overcome the various shortcomings in the present treatment of CL. In this scenario, we initially studied the cellular interactions of NPs and their uptake mechanisms into mammalian cells before applying them in drug delivery system. We obtained clear evidence for the involvement of multiple endocytic routes to internalize NPs. Physicochemical properties of NPs, cell type, temperature and pathogenesis of the target diseases were shown to be determinant factors. Thereafter, a mechanism based host- and pathogen-directed combination therapy comprising PHMB and CpG ODN immunomodulator was established for overall synergistic effect against CL. It simultaneously targets the pathogen and the host immunity with effective delivery system. The results show that PHMB binds to CpG ODN and form stable nanopolyplexes for efficient cell entry and therapy. The nanopolyplexes displayed enhanced cellular uptake and antileishmanial potency while drastically reducing the toxicity against mammalian cells. In conclusion, our findings clearly indicate that PHMB can be used as effective candidate drug against CL and as non-viral delivery of immunomodulatorynucleic acids. Moreover, our proof-of concept study showed nanomedicine approaches are effective strategy to challenge CL and other human diseases.},
  subject      = {Leishmaniose},
  language  = {en}
}
@phdthesis{Junker2015,
  author    = {Junker, Markus},
  title     = {Development and characterization of monoclonal antibodies to GDF-15 for potential use in cancer therapy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-132424},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {Background GDF-15 is a divergent member of the TGF-superfamily, which was first described as macrophage inhibitory cytokine-1 (MIC-1), revealing an immune modulatory function. GDF-15 is a soluble protein which is, under physiological conditions, highly expressed in the placenta and found in elevated levels in blood sera of pregnant women. Apart from the placenta, GDF-15 is expressed in healthy tissue, albeit to a lower extent and overexpressed in many solid tumors. A variety of different functions are attributed to GDF-15 in healthy as well as diseased humans. On the one hand, GDF-15 is required for successful pregnancy and low GDF-15 serum levels during pregnancy correlate with fetal abortion. On the other hand, overexpression of GDF-15, which can be observed in several malignancies is correlated with a poor prognosis. Furthermore, tumor derived GDF-15 leads to cancer associated anorexia-cachexia syndrome in mice. The aim of my PhD thesis was to further investigate the role of GDF-15 as an immune modulatory factor in cancer, in particular, by inhibiting the target molecule in vitro and in vivo. Therefore, the main focus was placed on the generation and characterization of monoclonal GDF-15 specific blocking antibodies, which were tested in vitro and in vivo, which represents a substantial part of my work. Results Here, GDF-15 was shown to be highly expressed in human gynecological cancer and brain tumors. We could then demonstrate that GDF-15 modulates effector immune cells in vitro. GDF-15 mediated a slight downregulation of the activating NKG2D receptor on NK and CD8+ T cells, which is crucial for proper anti-tumoral immune responses. Furthermore, we could demonstrate that GDF-15 reduces the adhesion of CD4+ and CD8+ T cells on endothelial cells in vitro. A negatively affected trans-endothelial migration of leukocytes into inflamed tissue could explain the low T cell infiltration in GDF-15 expressing tumors, which were observed in vivo, where mice bearing (shRNA mediated) GDF-15 deficient glioma cells revealed enhanced immune cell infiltrates in the tumor microenvironment, compared with the GDF-15 expressing control group. Those animals further exhibited a decreased tumor growth and prolonged survival. GDF-15 is a soluble protein, secreted by more than 50 \% of solid tumors and associated with grade of malignancy. Therefore a neutralizing monoclonal antibody to GDF-15 was assumed to be an auspicious therapeutically anti-cancer tool. Such an antibody was thus generated in GDF-15 knock out mice against human GFD-15. Amongst many clones, the GDF-15 antibody clone B1-23 was found to be applicable in Western Blot as well as in ELISA techniques, detecting a three-dimensional epitope of the mature GDF-15 dimer with high affinity and specificity. To enable the humanization for a later administration in humans, the variable regions of antibody B1-23 were identified by a special PCR method using degenerate primers and cloned into a sequencing vector. The sequence obtained thereby enabled the generation of chimeric and humanized B1-23 variants. After further comprehensive characterization, the original mouse antibody B1-23 as well as the chimeric antibody (ChimB1-23) and the humanized B1-23 antibody (H1L5) were applied in a melanoma xenograft study in vivo. None of the antibodies could significantly inhibit tumor growth. .However of utmost importance, body weight loss mediated by tumor derived GDF-15 could be significantly prevented upon administration of all three GDF-15 specific antibodies, which confirmed the antagonizing functionality of the immunoglobulin. Conclusion GDF-15 is a promising cancer target, involved in tumor progression and cancer related cachexia. A monoclonal GDF-15 antibody was generated, which served on one hand as a tool for molecular biological applications (Western Blot, ELISA, etc.) and on the other hand was applied as an antagonizing antibody in vitro and in vivo. Even though tumor growth inhibition by GDF-15 depletion in T cell deficient athymic mice failed using B1-23, the same antibody and derivates thereof (chimeric and humanized) impressively prevented tumor associated cachexia in UACC-257 melanoma bearing nude mice. The missing anti-tumor effect in our own melanoma model in nude mice can only partially be explained by the missing secondary immunity, in particular cytotoxic T cells, in the athymic animals, since in a similar melanoma model, performed by an external company, a tumor reduction in immunocompromised animals was observed, when B1-23 was administered. These findings support the idea that T cells are substantial for an effective tumor immunity and are in line with the results of the syngeneic, T cell comprising, mouse glioma model, where silencing of tumor expressed GDF-15 led to an enhanced intratumoral T cell infiltration and a prolonged survival. Taken together our data allow for the conclusion that tumor associated cachexia can be combatted with the GDF-15 antibody B1-23. Further, B1-23 might elicit direct anti-tumor effects in immune competent models, which contain T cells, rather than in an athymic, T cell deficient nude mouse model.},
  subject      = {Growth-differentiation Factor 15},
  language  = {en}
}
@phdthesis{Huang2013,
  author    = {Huang, Ting},
  title     = {Vaccinia Virus-mediated Therapy of Solid Tumor Xenografts: Intra-tumoral Delivery of Therapeutic Antibodies},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-91327},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {Over the past 30 years, much effort and financial support have been invested in the fight against cancer, yet cancer still represents the leading cause of death in the world. Conventional therapies for treatment of cancer are predominantly directed against tumor cells. Recently however, new treatments options have paid more attention to exploiting the advantage of targeting the tumor stroma instead. Vaccinia virus (VACV) has played an important role in human medicine since the 18th century as a vaccination against smallpox. In our laboratory, the recombinant, replication-competent vaccinia virus, GLV-1h68, was shown to enter, colonize and destroy cancer cells both in cell culture, and in vivo, in xenograft models (Zhang, Yu et al. 2007). In addition, combined therapy of GLV-1h68 and anti-VEGF immunotherapy significantly enhanced antitumor therapy in vivo (Frentzen, Yu et al. 2009). In this study, we constructed several new recombinant VACVs carrying genes encoding different antibodies against fibroblast activation protein (FAP) in stroma (GLV-1h282), nanobody against the extracellular domain of epidermal growth factor receptor (EGFR, GLV-1h442) or antibodies targeting both vascular endothelial growth factor (VEGF) and EGFR (GLV-1h444) or targeting both VEGF and FAP (GLV-1h446). The expression of the recombinant proteins was first verified using protein analytical methods, SDS-gel electrophoresis, Western blot analysis, immunoprecipitation (IP) assays and ELISA assays. The proteins were detected after infection of the cells with the different VACVs and the recombinant proteins purified by affinity adsorption. The purified antibodies were shown to specifically bind to their respective antigens. Secondly, the infection and replication capability of all the virus strains was analyzed in cell culture using several human tumor cell lines (A549, FaDu or DU145), revealing that all the new recombinant VACVs were able to infect cancer cells with comparable efficiency to the parental viruses from which they were derived. Thirdly, the antitumor efficacy of the new recombinant VACVs was evaluated in vivo using several human cancer xenograft models in mice. In A549 and DU145 xenografts, the new recombinant VACVs exhibited an enhanced therapeutic efficacy compared to GLV-1h68 with no change in toxicity in mice. In the FaDu xenograft, treatment with GLV-1h282 (anti-FAP) significantly slowed down the speed of tumor growth compared to GLV-1h68. Additionally, treatment with the recombinant VACVs expressed the various antibodies achieved comparable or superior therapeutic effects compared to treatment with a combination of GLV-1h68 and the commercial therapeutic antibodies, Avastin, Erbitux or both. Next, the virus distribution in tumors and organs of treated mice was evaluated. For most of the viruses, the virus titer in tumors was not signficantly diffferent than GLV-1h68. However, for animals treated with GLV-1h282, the virus titer in tumors was significantly higher than with GLV-1h68. This may be the reason for enhanced antitumor efficacy of GLV-1h282 in vivo. Lastly, the underlying mechanisms of therapeutic antibody-enhanced antitumor effects were investigated by immunohistochemistry. Blood vessels density and cell proliferation in tumors were suppressed after treatment with the antibody-encoded VACVs. The results indicated that the suppression of angiogenesis or cell proliferation in tumors may cause the observed therapeutic effect. In conclusion, the results of the studies presented here support the hypothesis that the treatment of solid tumors with a combination of oncolytic virotherapy and immunotherapy has an additive effect over each treatment alone. Moreover, expression of the immunotherapeutic antibody by the oncolytic VACV locally in the tumor enhances the antitumor effect over systemic treatment with the same antibody. Combined, these results indicate that therapy with oncolytic VACVs expressing-therapeutic antibodies may be a promising approach for the treatment of cancer.},
  subject      = {Vaccinia-Virus},
  language  = {en}
}
@phdthesis{Cook2012,
  author    = {Cook, Vanessa Janine},
  title     = {Protection of healthy tissues from infection with systemically administered vaccinia virus strains},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-69654},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Oncolytic virotherapy using recombinant vaccinia virus strains is a promising approach for the treatment of cancer. To further improve the safety of oncolytic vaccinia viruses, the cellular microRNA machinery can be applied as the host's own security mechanism to avoid unwanted viral replication in healthy tissues. MicroRNAs are a class of small single-stranded RNAs which due to their ability to mediate post-transcriptional gene-silencing, play a crucial role in almost every regulatory process in cellular metabolism. Different cancers display unique microRNA expression patterns, showing significant up- or downregulation of endogenously expressed microRNAs. Furthermore, the behavior of cancer cells can be altered by either adding microRNAs known to inhibit cancer cell spread and proliferation or suppressing cancer promoting microRNAs (oncomirs) making microRNAs promising targets for cancer gene therapy. The cell's own RNAi machinery can also be utilized to control viral replication due to the virus dependence on the host cell replication machinery, a process controlled by microRNAs. GLV-1h68 is a replication-competent recombinant oncolytic vaccinia virus constructed and generated by Genelux Corp., San Diego, CA, USA which carries insertions of three reporter gene cassettes for detection and attenuation purposes and is currently being evaluated for cancer treatment in clinical trials. Though there are hardly any side effects found in GLV-1h68 mediated oncolytic therapy an increased tropism for replication exclusively in cancer cells is desirable. Therefore it was investigated whether or not further cancer cell specificity of a recombinant vaccinia virus strain could be obtained without compromising its oncolytic activity using microRNA interference. Let-7a is a well characterized microRNA known to be expressed in high levels in healthy tissues and strongly downregulated in most cancers. To control vaccinia virus replication rates, four copies of the mature human microRNA let-7a target sequence were cloned behind the stop codon in the 3'end of the vaccinia virus D4R gene, using a GLV-1h68 derivative, GLV-1h190, as parental strain yielding the new recombinant virus strain GLV-1h250. The D4R gene belongs to the group of early transcribed vaccinia genes and encodes an essential enzyme, uracil DNA glycosylase, which catalyzes the removal of uracil residues from double-stranded DNA. A defect in D4R prevents vaccinia virus from entering into the intermediate and late phase of replication, leading to an aborted virus replication. After expression of the microRNA target sequence from the vaccinia virus genome, the endogenously expressed microRNA-let-7a should recognize its target structure within the viral mRNA transcript, thereby binding and degrading the viral mRNA which should lead to a strong inhibition of the virus replication in healthy cells. GLV-1h250 replication rates in cancerous A549 lung adenocarcinoma cells, which show a strong down-regulation of microRNA let-7a, was comparable to the replication rates of its parental strain GLV-1h190 and the control strain GLV-1h68. In contrast, GLV-1h250 displayed a 10-fold decrease in viral replication in non-cancerous ERC cells when compared to GLV-1h190 and GLV-1h68. In A549 tumor bearing nude mice GLV-1h250 replicated exclusively in the tumorous tissue and resulted in efficient tumor regression without adverse effects leading to the conclusion that GLV-1h250 replicates preferentially in cancerous cells and tissues, which display low endogenous let-7a expression levels.},
  subject      = {Vaccinia-Virus},
  language  = {en}
}
@phdthesis{Heisig2010,
  author    = {Heisig, Martin},
  title     = {Development of novel Listeria monocytogenes strains as therapeutic agents for targeted tumor therapy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48628},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {Despite marked progress in development and improvement of cancer therapies the rate of cancer related death remained stable over the last years. Especially in treating metastases alternative approaches supporting current therapies are required. Bacterial and viral vectors have been advanced from crude tools into highly sophisticated therapeutic agents detecting and treating neoplastic leasions. They might be potent enough to fill in this therapeutic demand. In this thesis Listeria monocytogenes was investigated as carrier for targeted bacterial cancer therapy. One part of the study focussed on modification of a functional bacterial mRNA delivery system. Genomic integration of T7 RNA polymerase driving mRNA production allowed reduction to an one-plasmid-system and thereby partially relieved the growth retardation exerted by mRNA delivery. Importantly the integration allowed metabolic attenuation of the mRNA delivery mutant potentially enabling in vivo applications. Further expansion of the bacterial RNA delivery system for transfer of shRNAs was examined. Bacterial mutants producing high amounts of RNA containing shRNA sequences were constructed, however a functional proof of gene silencing on delivery in eukaryotic cell lines was not achieved. The second part of this thesis focussed on increasing tumor colonization by Listeria monocytogenes in vivo. Coating bacteria with antibodies against receptors overexpressed on distinct tumor cell lines enabled specific bacterial internalization into these cells in vitro. Optimization of the bacterial antibody coating process resulted in an up to 104-fold increase of intracellular bacteria. Combination of this antibody-mediated targeting with the delivery of prodrug-converting enzymes showed a cytotoxic effect in cell lines treated with the corresponding prodrug. Since incubation in murine serum completely abrogated antibodymediated bacterial internalization the antibodies were covalently linked to the bacteria for application in xenografted tumor mice. Bacteria coated and crosslinked in this manner showed enhanced tumor targeting in a murine tumor model demonstrating antibodymediated bacterial tumor targeting in vivo. Independent of antibody-mediated tumor targeting the intrinsic tumor colonization of different Listeria monocytogenes mutants was examined. Listeria monocytogenes \&\#916;aroA \&\#916;inlGHE colonized murine melanoma xenografts highly efficient, reaching up to 108 CFU per gram of tumor mass 7 days post infection. Taken together the presented data shows highly promising aspects for potential bacterial application in future tumor therapies. Combination of the delivery systems with antibodymediated- and intrinsic bacterial tumor targeting might open novel dimensions utilizing Listeria monocytogenes as therapeutic vector in targeted tumor therapy.},
  subject      = {Krebs <Medizin>},
  language  = {en}
}
@phdthesis{Hauff2009,
  author    = {Hauff, Cornelia},
  title     = {Aspects of the mode of action of bispecific T cell engager (BiTE) antibodies},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48369},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {Bispecific T cell engager (BiTE) display a novel design among the class of bispecific antibodies and hold great promise to fight diverse cancers. BiTE molecules consist of two different binding entities derived from two human IgG antibodies connected by a short peptide linker. Their binding arms are directed against the CD3e chain of the T cell receptor on T cells and against an antigen that is specific for (e.g., CD19 for lymphoma in MT103) or over-expressed on (e.g., EpCAM for epithelial cancer in MT110) tumor cells. Without requirement for pre- or co-stimulation, BiTE molecules efficiently redirect CD3+ T cells towards tumor cells expressing the relevant target antigen. Only a BiTE molecule simultaneously bound to both tumor cell and T cell activates the T cell to exert its cytolytic function resulting in tumor cell death. In T cells stimulated with both BiTE and target cells, elevated levels of caspase activation and increased expression of cytotoxic and signaling proteins are observed. These include cytolytic proteins granzyme B and perforin, activation markers CD69 and CD25 and adhesion molecules CD2 and LFA-1. Activated T cells secrete the usual mix of cytokines, among them pro-inflammatory cytokines IFN-g and TNF-a. The membrane of tumor cells expressing the relevant target antigen is perforated during the attack of BiTE-stimulated effector cells as can be concluded from adenylate kinase release from the cytosol of tumor cells. Ca2+-chelator EGTA completely blocked BiTE-mediated activation of caspases and tumor cell lysis. As perforin is strictly Ca2+-dependent, a major role for this pore-forming protein is assumed for the elimination of tumor cells via BiTE-stimulated T cells. Granzyme B and caspases are main players in BiTE-mediated elimination of tumor cells. Inhibitors of granzyme B or caspases reduce or block, respectively the activation of caspases. However, other signals of apoptosis (cleavage of PARP and fragmentation of DNA) were only reduced by granzyme B inhibitor or caspase inhibitor. Most interestingly, the lytic capacity of BiTE molecules was not impaired by granzyme B inhibitor or caspase inhibitor. It seems that there is no requirement for granzyme B and caspases to be present simultaneously. Instead the data presented provide evidence that they can be replaced one at a time by related proteins. Pre-incubation of effector cells with the glucocorticoids dexamethasone or methylprednisolone resulted in markedly decreased secretion of cytokines by T cells yet only a small reduction in the expression of activation markers and adhesion molecules on T cells and specific lysis of tumor cells upon BiTE stimulation. Soluble factors secreted in an undirected manner by BiTE-stimulated T cells do not mediate tumor cell death by themselves. Bystander cells negative for the antigen that is recognized by the BiTE molecule will not be compromised by BiTE activity. The cytokine TGF-b reduced proliferation as well as granzyme B and perforin expression of BiTE-stimulated T cells. Redirected lysis by BiTE-activated T cells was also decreased under the influence of TGF-b, however lysis was still performed at a reasonable rate (72 \% of target cells). TGF-b does not exert a deleterious effect on lytic potential of BiTE-stimulated T cells. The minimal anticipated biological effect level for the BiTE MT110 was determined for the entry of MT110 into phase I clinical studies. Experiments analyzing redirected lysis of tumor cells, expression of activation marker CD25 and cytokine release by T cells revealed a MABEL value of 50 pg/ml for MT110.},
  subject      = {Antik{\"o}rper},
  language  = {en}
}