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- MRB Forschungszentrum für Magnet-Resonanz-Bayern e.V., Am Hubland, D-97074 Würzburg (1)
- Rudolf-Virchow-Zentrum DFG-Forschungszentrum für Experimentelle Biomedizin der Universität Würzburg (1)
Engineering non-linear hybrid light-matter states in tailored lattices is a central research strategy for the simulation of complex Hamiltonians. Excitons in atomically thin crystals are an ideal active medium for such purposes, since they couple strongly with light and bear the potential to harness giant non-linearities and interactions while presenting a simple sample-processing and room temperature operability. We demonstrate lattice polaritons, based on an open, high-quality optical cavity, with an imprinted photonic lattice strongly coupled to excitons in a WS2 monolayer. We experimentally observe the emergence of the canonical band-structure of particles in a one-dimensional lattice at room temperature, and demonstrate frequency reconfigurability over a spectral window exceeding 85 meV, as well as the systematic variation of the nearest-neighbour coupling, reflected by a tunability in the bandwidth of the p-band polaritons by 7 meV. The technology presented in this work is a critical demonstration towards reconfigurable photonic emulators operated with non-linear photonic fluids, offering a simple experimental implementation and working at ambient conditions.
p97 uses the energy of ATP hydrolysis to unfold and thereby segregate proteins. It is involved in various cellular processes such as proteasomal degradation, DNA damage repair, autophagy, and endo-lysosomal trafficking. The specificity for these processes is controlled by more than 30 regulatory cofactors.
Interactions of p97 with cofactors and target proteins are known to be highly dynamic and transient. To identify new interaction partners and to uncover novel cellular functions of p97, the interactome of endogenous p97 was determined by using in cellulo crosslinking followed by immunoprecipitation and mass spectrometry. Myoferlin (MYOF) was identified as a novel interactor of p97 and the interaction was validated in reciprocal immunoprecipitation experiments for different cell lines.
The ferlin family member MYOF is a tail-anchored membrane protein containing multiple C2 domains. MYOF is involved in various membrane repair and trafficking processes such as the endocytic recycling of cell surface receptors. The MYOF interactome was determined by mass spectrometry. Among others, the p97 cofactor PLAA, CD71 and Rab14 were identified as common interactors of p97 and MYOF. Immunoprecipitation experiments with PLAA KO cells revealed that the interaction between MYOF and p97 depends on PLAA. Immunofluorescence microscopy showed a co-localization of MYOF with Rab14 and Rab11, which are both involved in endocytic recycling pathways. Furthermore, immunofluoroscence experiments revealed that MYOF and the p97 cofactor PLAA are localized to Rab14- and Rab5-positive endosomal compartments.
Using p97 inhibitors and p97 trapping mutants, the presence of p97 at MYOF-positive and Rab14-positive structures could be demonstrated. Consistent with this finding, the endocytic recycling of transferrin was delayed upon inhibition of p97. Taken together, this work identified MYOF as a novel interactor of p97 and suggests a role for p97 in the recycling of endocytic cargo.
Background
Deregulated expression of MYC is a driver of colorectal carcinogenesis, suggesting that decreasing MYC expression may have significant therapeutic value. CIP2A is an oncogenic factor that regulates MYC expression. CIP2A is overexpressed in colorectal cancer (CRC), and its expression levels are an independent marker for long-term outcome of CRC. Previous studies suggested that CIP2A controls MYC protein expression on a post-transcriptional level.
Methods
To determine the mechanism by which CIP2A regulates MYC in CRC, we dissected MYC translation and stability dependent on CIP2A in CRC cell lines.
Results
Knockdown of CIP2A reduced MYC protein levels without influencing MYC stability in CRC cell lines. Interfering with proteasomal degradation of MYC by usage of FBXW7-deficient cells or treatment with the proteasome inhibitor MG132 did not rescue the effect of CIP2A depletion on MYC protein levels. Whereas CIP2A knockdown had marginal influence on global protein synthesis, we could demonstrate that, by using different reporter constructs and cells expressing MYC mRNA with or without flanking UTR, CIP2A regulates MYC translation. This interaction is mainly conducted by the MYC 5′UTR.
Conclusions
Thus, instead of targeting MYC protein stability as reported for other tissue types before, CIP2A specifically regulates MYC mRNA translation in CRC but has only slight effects on global mRNA translation. In conclusion, we propose as novel mechanism that CIP2A regulates MYC on a translational level rather than affecting MYC protein stability in CRC.
Herpesviruses have mastered host cell modulation and immune evasion to augment productive infection, life-long latency and reactivation thereof 1,2. A long appreciated, yet elusively defined relationship exists between the lytic-latent switch and viral non-coding RNAs 3,4. Here, we identify miRNA-mediated inhibition of miRNA processing as a thus far unknown cellular mechanism that human herpesvirus 6A (HHV-6A) exploits to disrupt mitochondrial architecture, evade intrinsic host defense and drive the lytic-latent switch. We demonstrate that virus-encoded miR-aU14 selectively inhibits the processing of multiple miR-30 family members by direct interaction with the respective pri-miRNA hairpin loops. Subsequent loss of miR-30 and activation of the miR-30/p53/Drp1 axis triggers a profound disruption of mitochondrial architecture. This impairs induction of type I interferons and is necessary for both productive infection and virus reactivation. Ectopic expression of miR-aU14 triggered virus reactivation from latency, identifying viral miR-aU14 as a readily drugable master regulator of the herpesvirus lytic-latent switch. Our results show that miRNA-mediated inhibition of miRNA processing represents a generalized cellular mechanism that can be exploited to selectively target individual members of miRNA families. We anticipate that targeting miR-aU14 provides exciting therapeutic options for preventing herpesvirus reactivations in HHV-6-associated disorders.
Sharks occupy diverse ecological niches and play critical roles in marine ecosystems, often acting as apex predators. They are considered a slow-evolving lineage and have been suggested to exhibit exceptionally low cancer rates. These two features could be explained by a low nuclear mutation rate. Here, we provide a direct estimate of the nuclear mutation rate in the epaulette shark (Hemiscyllium ocellatum). We generate a high-quality reference genome, and resequence the whole genomes of parents and nine offspring to detect de novo mutations. Using stringent criteria, we estimate a mutation rate of 7×10\(^{−10}\) per base pair, per generation. This represents one of the lowest directly estimated mutation rates for any vertebrate clade, indicating that this basal vertebrate group is indeed a slowly evolving lineage whose ability to restore genetic diversity following a sustained population bottleneck may be hampered by a low mutation rate.
The ATPase p97 (also known as VCP, Cdc48) has crucial functions in a variety of important cellular processes such as protein quality control, organellar homeostasis, and DNA damage repair, and its de-regulation is linked to neuromuscular diseases and cancer. p97 is tightly controlled by numerous regulatory cofactors, but the full range and function of the p97–cofactor network is unknown. Here, we identify the hitherto uncharacterized FAM104 proteins as a conserved family of p97 interactors. The two human family members VCP nuclear cofactor family member 1 and 2 (VCF1/2) bind p97 directly via a novel, alpha-helical motif and associate with p97-UFD1-NPL4 and p97-UBXN2B complexes in cells. VCF1/2 localize to the nucleus and promote the nuclear import of p97. Loss of VCF1/2 results in reduced nuclear p97 levels, slow growth, and hypersensitivity to chemical inhibition of p97 in the absence and presence of DNA damage, suggesting that FAM104 proteins are critical regulators of nuclear p97 functions.
YAP, the key protein effector of the Hippo pathway, is a transcriptional co-activator that controls the expression of cell cycle genes, promotes cell growth and proliferation and regulates organ size. YAP modulates gene transcription by binding to distal enhancers, but the mechanisms of gene regulation by YAP-bound enhancers remain poorly understood. Here we show that constitutive active YAP5SA leads to widespread changes in chromatin accessibility in untransformed MCF10A cells. Newly accessible regions include YAP-bound enhancers that mediate activation of cycle genes regulated by the Myb-MuvB (MMB) complex. By CRISPR-interference we identify a role for YAP-bound enhancers in phosphorylation of Pol II at Ser5 at MMB-regulated promoters, extending previously published studies that suggested YAP primarily regulates the pause-release step and transcriptional elongation. YAP5SA also leads to less accessible ‘closed’ chromatin regions, which are not directly YAP-bound but which contain binding motifs for the p53 family of transcription factors. Diminished accessibility at these regions is, at least in part, a consequence of reduced expression and chromatin-binding of the p53 family member ΔNp63 resulting in downregulation of ΔNp63-target genes and promoting YAP-mediated cell migration. In summary, our studies uncover changes in chromatin accessibility and activity that contribute to the oncogenic activities of YAP.
Peroxisomes are ubiquitous organelles with essential functions in numerous cellular processes such as lipid metabolism, detoxification of reactive oxygen species and signaling. Knowledge of the peroxisomal proteome including multi-localized proteins and, most importantly, changes of its composition induced by altering cellular conditions or impaired peroxisome biogenesis and function is of paramount importance for a holistic view on peroxisomes and their diverse functions in a cellular context. In this chapter, we provide a spatial proteomics protocol specifically tailored to the analysis of the peroxisomal proteome of baker's yeast that enables the definition of the peroxisomal proteome under distinct conditions and to monitor dynamic changes of the proteome including the relocation of individual proteins to a different cellular compartment. The protocol comprises subcellular fractionation by differential centrifugation followed by Nycodenz density gradient centrifugation of a crude peroxisomal fraction, quantitative mass spectrometric measurements of subcellular and density gradient fractions and advanced computational data analysis, resulting in the establishment of organellar maps on a global scale.
RNA helicases are key players in the regulation of gene expression. They act by remodeling local RNA secondary structures as well as RNA-protein interactions to enable the dynamic association of RNA binding proteins to their targets. The putative RNA helicase DHX30 is a member of the family of DEAH-box helicases with a putative role in the ATP-dependent unwinding of RNA secondary structures. Mutations in the DHX30 gene causes the autosomal dominant neuronal disease “Neurodevelopmental Disorder with severe Motor Impairment and Absent Language” (NEDMIAL;OMIM#617804). In this thesis, a strategy was established that enabled the large-scale purification of enzymatically active DHX30. Through enzymatic studies performed in vitro, DHX30 was shown to act as an ATP-dependent 3’ → 5’ RNA helicase that catalyzes the unwinding of RNA:RNA and RNA:DNA substrates. Using recombinant DHX30, it could be shown that disease-causing missense mutations in the conserved helicase core caused the disruption of its ATPase and helicase activity. The protein interactome of DHX30 however, was unchanged indicating that the pathogenic missense-mutations do not cause misfolding of DHX30, but rather specifically affect its catalytic activity. DHX30 localizes predominantly in the cytoplasm where it forms a complex with ribosomes and polysomes. Using a cross-linking mass spectrometry approach, a direct interaction of the N-terminal double strand RNA binding domain of DHX30 with sites next to the ribosome’s mRNA entry channel and the subunit interface was uncovered. RNA sequencing of DHX30 knockout cells revealed a strong de-regulation of mRNAs involved in neurogenesis and nervous system development, which is in line with the NEDMIAL disease phenotype. The knockdown of DHX30 results in a decreased 80S peak in polysome gradients, indicating that DHX30 has an effect on the translation machinery. Sequencing of the pool of active translating mRNAs revealed that upon DHX30 knockout mainly 5’TOP mRNAs are downregulated. These mRNAs are coding for proteins of the translational machinery and translation initiation factors. This study identified DHX30 as a factor of the translation machinery that selectively impacts the expression of a subset of proteins and provides insight on the etiology of NEDMIAL.
Oncogenic transformation of lung epithelial cells is a multistep process, frequently starting with the inactivation of tumour suppressors and subsequent development of activating mutations in proto-oncogenes, such as members of the PI3K or MAPK families. Cells undergoing transformation have to adjust to changes, including altered metabolic requirements. This is achieved, in part, by modulating the protein abundance of transcription factors. Here, we report that the ubiquitin carboxyl-terminal hydrolase 28 (USP28) enables oncogenic reprogramming by regulating the protein abundance of proto-oncogenes such as c-JUN, c-MYC, NOTCH and ∆NP63 at early stages of malignant transformation. USP28 levels are increased in cancer compared with in normal cells due to a feed-forward loop, driven by increased amounts of oncogenic transcription factors such as c-MYC and c-JUN. Irrespective of oncogenic driver, interference with USP28 abundance or activity suppresses growth and survival of transformed lung cells. Furthermore, inhibition of USP28 via a small-molecule inhibitor resets the proteome of transformed cells towards a ‘premalignant’ state, and its inhibition synergizes with clinically established compounds used to target EGFR\(^{L858R}\)-, BRAF\(^{V600E}\)- or PI3K\(^{H1047R}\)-driven tumour cells. Targeting USP28 protein abundance at an early stage via inhibition of its activity is therefore a feasible strategy for the treatment of early-stage lung tumours, and the observed synergism with current standard-of-care inhibitors holds the potential for improved targeting of established tumours.
Eukaryotic cells react to various stress conditions with the rapid formation of membrane-less organelles called stress granules (SGs). SGs form by multivalent interactions between RNAs and RNA-binding proteins and are believed to protect stalled translation initiation complexes from stress-induced degradation. SGs contain hundreds of different mRNAs and proteins, and their assembly and disassembly are tightly controlled by post-translational modifications. The ubiquitin system, which mediates the covalent modification of target proteins with the small protein ubiquitin (‘ubiquitylation’), has been implicated in different aspects of SG metabolism, but specific functions in SG turnover have only recently emerged. Here, we summarize the evidence for the presence of ubiquitylated proteins at SGs, review the functions of different components of the ubiquitin system in SG formation and clearance, and discuss the link between perturbed SG clearance and the pathogenesis of neurodegenerative disorders. We conclude that the ubiquitin system plays an important, medically relevant role in SG biology.
Background
ACAM2000, a thymidine kinase (TK)-positive strain of vaccinia virus, is the current smallpox vaccine in the US. Preclinical testing demonstrated potent oncolytic activity of ACAM2000 against several tumor types. This Phase I clinical trial of ACAM2000 delivered by autologous adipose stromal vascular fraction (SVF) cells was conducted to determine the safety and feasibility of such a treatment in patients with advanced solid tumors or acute myeloid leukemia (AML).
Methods
Twenty-four patients with solid tumors and two patients with AML participated in this open-label, non-randomized dose-escalation trial. All patients were treated with SVF derived from autologous fat and incubated for 15 min to 1 h with ACAM2000 before application. Six patients received systemic intravenous application only, one patient received intra-tumoral application only, 15 patients received combination intravenous with intra-tumoral deployment, 3 patients received intravenous and intra-peritoneal injection and 1 patient received intravenous, intra-tumoral and intra-peritoneal injections. Safety at each dose level of ACAM2000 (1.4 × 106 plaque-forming units (PFU) to 1.8 × 107 PFU) was evaluated. Blood samples for PK assessments, flow cytometry and cytokine analysis were collected at baseline and 1 min, 1 h, 1 day, 1 week, 1 month, 3 months and 6 months following treatment.
Results
No serious toxicities (> grade 2) were reported. Seven patients reported an adverse event (AE) in this study: self-limiting skin rashes, lasting 7 to 18 days—an expected adverse reaction to ACAM2000. No AEs leading to study discontinuation were reported. Viral DNA was detected in all patients’ blood samples immediately following treatment. Interestingly, in 8 patients viral DNA disappeared 1 day and re-appeared 1 week post treatment, suggesting active viral replication at tumor sites, and correlating with longer survival of these patients. No major increase in cytokine levels or correlation between cytokine levels and skin rashes was noted. We were able to assess some initial efficacy signals, especially when the ACAM2000/SVF treatment was combined with checkpoint inhibition.
Conclusions
Treatment with ACAM2000/SVF in patients with advanced solid tumors or AML is safe and well tolerated, and several patients had signals of an anticancer effect. These promising initial clinical results merit further investigation of therapeutic utility.
Trial registration Retrospectively registered (ISRCTN#10201650) on October 22, 2018.
Background
Previous studies have identified IFNγ as an important early barrier to oncolytic viruses including vaccinia. The existing innate and adaptive immune barriers restricting oncolytic virotherapy, however, can be overcome using autologous or allogeneic mesenchymal stem cells as carrier cells with unique immunosuppressive properties.
Methods
To test the ability of mesenchymal stem cells to overcome innate and adaptive immune barriers and to successfully deliver oncolytic vaccinia virus to tumor cells, we performed flow cytometry and virus plaque assay analysis of ex vivo co-cultures of stem cells infected with vaccinia virus in the presence of peripheral blood mononuclear cells from healthy donors. Comparative analysis was performed to establish statistically significant correlations and to evaluate the effect of stem cells on the activity of key immune cell populations.
Results
Here, we demonstrate that adipose-derived stem cells (ADSCs) have the potential to eradicate resistant tumor cells through a combination of potent virus amplification and sensitization of the tumor cells to virus infection. Moreover, the ADSCs demonstrate ability to function as a virus-amplifying Trojan horse in the presence of both autologous and allogeneic human PBMCs, which can be linked to the intrinsic immunosuppressive properties of stem cells and their unique potential to overcome innate and adaptive immune barriers. The clinical application of ready-to-use ex vivo expanded allogeneic stem cell lines, however, appears significantly restricted by patient-specific allogeneic differences associated with the induction of potent anti-stem cell cytotoxic and IFNγ responses. These allogeneic responses originate from both innate (NK)- and adaptive (T)- immune cells and might compromise therapeutic efficacy through direct elimination of the stem cells or the induction of an anti-viral state, which can block the potential of the Trojan horse to amplify and deliver vaccinia virus to the tumor.
Conclusions
Overall, our findings and data indicate the feasibility to establish simple and informative assays that capture critically important patient-specific differences in the immune responses to the virus and stem cells, which allows for proper patient-stem cell matching and enables the effective use of off-the-shelf allogeneic cell-based delivery platforms, thus providing a more practical and commercially viable alternative to the autologous stem cell approach.
Interleukin 2 (IL-2) was the first cytokine applied for cancer treatment in human history. It has been approved as monotherapy for renal cell carcinoma and melanoma by the FDA and does mediate the regression of the tumors in patients. One of the possible mechanisms is that the administration of IL-2 led to T lymphocytes expansion, including CD4+ and CD8+ T cells. In addition, a recent study demonstrated that antigen-specific T cells could also be expanded through the induction of IL-2, which plays a crucial role in mediating tumor regression. However, despite the long-term and extensive use of IL-2 in the clinic, the ratio of patients who get a complete response was still low, and only about one-fifth of patients showed objective tumor regression. Therefore, the function of IL-2 in cancer treatment should continue to be optimized and investigated. A study by Franz O. Smith et al. has shown that the combination treatment of IL-2 and tumor-associated antigen vaccine has a strong trend to increased objective responses compared to patients with melanoma receiving IL-2 alone. Peptide vaccines are anti-cancer vaccines able to induce a powerful tumor antigenspecific immune response capable of eradicating the tumors. According to the type of antigens, peptide vaccines can be classified into two distinct categories: Tumor-associated antigens (TAA) vaccine and tumor-specific neoantigens (TSA) vaccine. Currently, Peptide vaccines are mainly investigated in phase I and phase II clinical trials of human cancer patients with various advanced cancers such as lung cancer, gastrointestinal tumors, and breast cancers. Vaccinia virus (VACV) is one of the safest viral vectors, which has been wildly used in cancer treatment and pathogen prevention. As an oncolytic vector, VACV can carry multiple large foreign genes, which enable the virus to introduce diagnostic and therapeutic agents without dramatically reducing the viral replication. Meanwhile, the recombinant vaccinia virus (rVACV) can be easily generated by homologous recombination. Here, we used the vaccinia virus as the therapeutic cancer vector, expressing mouse Interleukin 2 (IL-2) and tumor-associated antigens simultaneously to investigate the combined effect of anti-tumor immune response in the 4T1 mouse tumor model. As expected, the VACV driven mIL-2 expression remarkably increased both CD4+ and CD8+ populations in vivo, and the virus-expressed tumor-associated peptides successfully elicited theantigen-specific T cell response to inhibit the growth of tumors. Furthermore, the experiments with tumor-bearing animals showed that the mIL-2 plus tumor antigens expressing VACV vector gave a better anti-cancer response than the mIL-2 alone expressing vector. The combinations did significantly more inhibit tumor growth than mIL-2 treatment alone. Moreover, the results confirmed our previous unpublished data that the mIL-2 expression driven by synthetic early/late promoter in the Lister strain VACV could enhance the tumor regression in the 4T1 mouse model.
Im Zellkern eukaryotischer Zellen werden Gene in mRNAs transkribiert, welche umfangreich prozessiert und aus dem Zellkern exportiert werden. Im Zytoplasma erfolgt die Translation der mRNAs in Proteine, ein Prozess, welcher viel Energie benötigt und daher mittels vielfältiger Mechanismen streng reguliert wird. Ein Beispiel hierfür stellt die Klasse der TOP-mRNAs dar, eine RNA-Spezies, welche hauptsächlich Transkripte von Genen umfasst, die selbst in die Translation involviert sind. Die prominentesten Vertreter dieser Klasse sind die Proteine der kleinen und großen ribosomalen Untereinheiten. TOP-mRNAs zeichnen sich durch ein gemeinsames Sequenz-Motiv am Anfang Ihrer 5’-UTR aus, welches aus einem Pyrimidinstrang besteht und unmittelbar nach dem Cap mit einem Cytosin beginnt. Dieses allen TOP-RNAs gemeinsame Motiv ermöglicht die zeitgleiche Translationskontrolle dieser RNA-Klasse. So kann die Translation der TOP-mRNAs unter Stressbedingungen wie z.B. Nährstoffmangel koordiniert inhibiert werden, wodurch Energie eingespart wird.
Bereits lange wird nach einem Regulator gesucht, der an dieses TOP-Motiv bindet und die koordinierte Regulation ermöglicht. Man kann sich hier einen Inhibitor oder auch einen Aktivator vorstellen. Verschiedene Proteine wurden bereits in Erwägung gezogen. In dieser Arbeit wurde das Protein TIAR mittels Massenspektrometrie als TOP-interagierender Faktor identifiziert und dessen Bindungseigenschaften mit dem TOP-Motiv durch Shift Assays untersucht. Hierbei konnten Minimalkonstrukte verschiedener Organismen sowie RNA-TOP – Sequenzen identifiziert werden, welche sich für Strukturanalysen eignen würden. Als weiterer TOP-interagierender Faktor wurde über verschiedene sequenzielle Reinigungsschritte das Protein 14-3-3ε identifiziert.
Weiterhin wurden die TOP-Motiv-bindenden Proteine LARP1 und LARP7 auf Ihre Bindungseigenschaften mit Ihren Zielsequenzen untersucht. Während gezeigt werden konnte, dass LARP1 einen inhibierenden Einfluss auf TOP-RNAs hat, wurde in weiteren Shift-Assays die Bindungseigenschaften von LARP7 mit 7SK untersucht, wobei ebenfalls ein minimales LARP7–Konstrukt sowie 7SK-Konstrukte für Strukturanalysen identifiziert werden konnten. Weiterhin konnte gezeigt werden, dass verschiedene Substanzen wie tRNA und Arginin einen starken Einfluss auf die LARP7-7SK – Interaktion ausüben, welcher in weiteren Studien berücksichtigt werden sollte.
Das kolorektale Karzinom ist eines der häufigsten beim Menschen vorkommenden
Karzinome [2]. Diesem liegen unterschiedliche Mutationen zugrunde, die in knapp 100%
der kolorektalen Karzinome zu einer Überexpression von MYC führen, welches als
Transkriptionsfaktor maßgeblich den Zellzyklus, Proliferation und Vaskularisierung
beeinflusst [10,16]. Damit stellt MYC ein potenzielles Therapieziel in der Behandlung des
Kolorektalen Karzinoms dar. Zusätzlich konnte in den letzten Jahren ein Onkoprotein
namens CIP2A identifiziert werden, welches nach Depletion mit einem Verlust von MYC
Protein einhergeht [69]. Zusätzlich ist CIP2A ein unabhängiger prognostischer Faktor im
Kolorektalen Karzinom [70].
Diese Arbeit konnte zeigen, dass CIP2A-depletierte Zellen einen deutlichen
Wachstumsnachteil gegenüber unbehandelten Zellen zeigen. Dieser Unterschied kann nicht
durch eine gesteigerte Apoptose, sondern vielmehr durch einen verlängerten Zellzyklus
erklärt werden. Weiterhin konnte eine neue Zelllinie mit DOX-induzierbarer shCIP2A
hergestellt werden, die für weitere Experimente genutzt werden kann. Entgegen der
Wirkweise im Zervixkarzinom [69], konnte im kolorektalen Karzinom kein Einfluss auf die
Stabilität von MYC Protein durch CIP2A nachgewiesen werden. Auch konnte der Verlust
von MYC nach CIP2A Knockdown nicht durch gleichzeitige Inhibierung des Abbaus, durch
Okadasäure, MG132 oder in den FBWX7-defizienten Zellen, verhindert werden. Stattdessen
resultiert die Herunterregulation von CIP2A in einem leichten Rückgang der MYC-mRNA
Menge und einem deutlichen Verlust an MYC-Protein. In Zellen mit verschiedenen
Konstrukten der MYC Transkripte kann dieser Verlust an MYC Protein auf eine
translationelle Regulation in der 5’UTR zurückgeführt werden, was eine bisher nicht
beschriebene Wirkweise von CIP2A darstellt. Da CIP2A in normalen Zellen praktisch nicht
exprimiert ist [78], könnte dies ein mögliches Ziel in der Tumortherapie darstellen. Dieses
gilt es in weiteren Experimenten noch genauer zu untersuchen.
Die Krebstherapie und Behandlung von Tumoren stellt für die moderne Medizin auch in Zukunft eine enorme Herausforderung dar. Trotz intensiver Forschung konnten in den letzten Jahrzehnten zwar zunehmend Fortschritte erzielt werden, allerdings muss das Spektrum an neuen Therapieformen und Möglichkeiten kontinuierlich erweitert werden. In den letzten Jahren haben die Kalorienrestriktion sowie die Aminosäuren- und Proteinrestriktion zunehmend an Bedeutung gewonnen, da sie einen erheblichen positiven Einfluss auf die Entstehung von altersassoziierten Erkrankungen wie z.B. Krebs haben. Allen Formen gemeinsam ist die Induktion eines Low-Energy-Metabolismus, der die Zellen in einen antiproliferativen und selbst-regenerierenden Zustand versetzt. In dieser Arbeit sollte untersucht werden, ob die Methionin-Restriktion als eine Form der Aminosäurerestriktion sich grundsätzlich als Therapieform im Plattenepithelkarzinom (HNSCC) eignet. Zusätzlich sollte ein einfaches zelluläres Modellsystem etabliert werden, das auf metaboler Ebene die Charakterisierung und Analyse des Low-Energy-Metabolismus ermöglicht. Es konnte aufgezeigt werden, dass die Methionin-Restriktion eine effektive Methode ist, um die Proliferation ausgesuchter Zelllinien des HNSCC zu inhibieren. Des Weiteren konnte aufgezeigt werden, dass der Einsatz von Aminosäure-Analoga eine weitere Möglichkeit darstellt, auf die Proliferation von Tumorzellen Einfluss zu nehmen. Die massenspektrometrische Analyse der murinen Zelllinie L929 mittels LC/MS lieferte über einen Zeitraum von 5 Tagen ein detailliertes Bild des Stoffwechsels von mehr als 150 Metaboliten unter Methionin-Restriktion. Durch die Definition eines charakteristischen Fingerabdrucks nach 48 h und eines nur wenige Metabolite umfassenden Fußabdrucks konnte ein murines Modellsystem etabliert werden, dass die Analyse von potentiellen Wirkstoffen, u.a. sogenannten caloric restriction mimetics, ermöglicht.
∆Np63 is a master regulator of squamous cell identity and regulates several signaling pathways that crucially
contribute to the development of squamous cell carcinoma (SCC) tumors. Its contribution to coordinating the
expression of genes involved in oncogenesis, epithelial identity, DNA repair, and genome stability has been
extensively studied and characterized. For SCC, the expression of ∆Np63 is an essential requirement to
maintain the malignant phenotype. Additionally, ∆Np63 functionally contributes to the development of cancer
resistance toward therapies inducing DNA damage.
SCC patients are currently treated with the same conventional Cisplatin therapy as they would have been
treated 30 years ago. In contrast to patients with other tumor entities, the survival of SCC patients is limited,
and the efficacy of the current therapies is rather low. Considering the rising incidences of these tumor entities,
the development of novel SCC therapies is urgently required. Targeting ∆Np63, the transcription factor, is a
potential alternative to improve the therapeutic response and clinical outcomes of SCC patients.
However, ∆Np63 is considered “undruggable.” As is commonly observed in transcription factors, ∆Np63 does
not provide any suitable domains for the binding of small molecule inhibitors. ∆Np63 regulates a plethora of
different pathways and cellular processes, making it difficult to counteract its function by targeting
downstream effectors. As ∆Np63 is strongly regulated by the ubiquitin–proteasome system (UPS), the
development of deubiquitinating enzyme inhibitors has emerged as a promising therapeutic strategy to target
∆Np63 in SCC treatment.
This work involved identifying the first deubiquitinating enzyme that regulates ∆Np63 protein stability. Stateof-the-art SCC models were used to prove that USP28 deubiquitinates ∆Np63, regulates its protein stability,
and affects squamous transcriptional profiles in vivo and ex vivo. Accordingly, SCC depends on USP28 to
maintain essential levels of ∆Np63 protein abundance in tumor formation and maintenance. For the first time,
∆Np63, the transcription factor, was targeted in vivo using a small molecule inhibitor targeting the activity of
USP28. The pharmacological inhibition of USP28 was sufficient to hinder the growth of SCC tumors in
preclinical mouse models.
Finally, this work demonstrated that the combination of Cisplatin with USP28 inhibitors as a novel therapeutic
alternative could expand the limited available portfolio of SCC therapeutics. Collectively, the data presented
within this dissertation demonstrates that the inhibition of USP28 in SCC decreases ∆Np63 protein abundance,
thus downregulating the Fanconi anemia (FA) pathway and recombinational DNA repair. Accordingly, USP28
inhibition reduces the DNA damage response, thereby sensitizing SCC tumors to DNA damage therapies, such
as Cisplatin.
Cancer is one of the major causes of mortality in developed countries. In 2020, there were more than 19.3 million new cases of tumor malignancies worldwide, with more than 10 million deaths. The high rates of cancer cases and mortality necessitate extensive research and the development of novel cancer treatments and antitumor agents. In most cases, conventional treatment strategies for tumor therapy are based on chemotherapeutic treatment, which is supplemented with radiotherapy and/or surgical resection of solid tumors [1]. The use of chemotherapy for the treatment of cancer has significant side effects, the most dangerous of which is toxicity [2] [3].
Modern methods of treating tumors focus on specific drug delivery to the tumor site, actively targeting the tumor cells, as well as the reduction of side effects. One of the most promising current approaches is based on oncolytic viruses. Antitumor properties of viruses were documented at the beginning of the 20th century when some cancer patients recovered after acute viral infections, particularly influenza [4]. Vaccinia virus (VACV) is a member of the Poxviridae family, has natural antitumor properties, and provides a good basis for generating efficient recombinant oncolytic strains. Furthermore, VACV has never been shown to integrate into the host genome [5]. VACV is likely one of the safest and well-studied viruses due to extensive research being done in molecular biology and pathophysiology to investigate its potential as a vaccine for smallpox eradication programs. It has been administered to over 200 million people worldwide. VACV antitumor therapeutic effectiveness has been established in xenograft models with a variety of tumor types for human and canine cancers. Furthermore, recombinant oncolytic VACVs expressing genes encoding light-emitting proteins are a big improvement in a treatment strategy that combines tumor-specific therapies and diagnostics.
Oncolytic virus treatments are effective in xenograft cancer models in mice, however, the significant improvements found in mice do not always translate to human cancer patients. These therapies should be tested in dogs with spontaneous cancer not only to offer well translatable information regarding the possible efficiency of viral therapy for human cancers but also to improve the health of our household pets as well. Spontaneous canine tumors are starting to be regarded as an essential model of human cancers that can reproduce the tumor microenvironment and immune response of cancer patients [6]. Just as data obtained in dog experiments can improve cancer therapy for human patients, these findings can also be used to improve treatment protocols in canine patients.
Hundreds of studies and dozens of reviews have been published regarding the antitumor effects of various recombinants of VACV, but information on the anticancer features of initial, genetically-unmodified “naïve” VACV is still limited. In the first studies, we compared different wild-type, non-modified strains of VACV and tested their oncolytic properties on a panel of various cancer cells derived from different organs. In addition, we also tested a protection system based on the “Trojan horse” concept - using a combination of human Adipose tissue-derived Stem Cells (hADSC) and three different wild-type single plaque purified Vaccinia virus strains: W1, L1, and T1. We showed that all tested human cell lines (FaDu, MDA MB 231, HNT-13, HNT-35, and PC-3) are permissive to L0, W0, T0, L1, W1, and L1 infection. Furthermore, we tested the cytotoxicity of VACV in different cancer cell lines (A549, PC-3, MDA-MB 231, FaDu, HNT-13, HNT-25, and HNT-35). All strains lysed the cells, which was most visible at 96 hpi. We also showed that all tested strains could efficiently infect and multiply in hADSC at a high level. In our in vivo study, we tested the therapeutic efficacy of the wild-type Vaccinia viruses L1, W1, and T1 alone or in combination with hADSC. Wild-type VACV strains were tested for their oncolytic efficiency in human lung adenocarcinoma (A549) in a xenograft model. Treatment of A549 tumors with different doses of L1 and W1 as well as with a L1/ADSC or W1/ADSC combination led to significant tumor regression compared to the PBS control. Additionally, the treatment with L1 and W1 and the combination of L1/ADSC and W1/ADSC was well tolerated by the animals. In the case of the wild-type Tian Tan strain, results were not obtained due to the high cytotoxicity of this strain. Therefore, it should be attenuated for further studies.
In the second part of the current study, we investigated the oncolytic effect of C1-opt1, W1 opt1, and L3-opt1 strains based on the wild-type Copenhagen, Wyeth, and Lister vaccines with additional expression of turboFP635. Replication and cytotoxicity assays demonstrated that all 3 viruses were able to infect, replicate in and kill canine tumor cell lines STSA-1 and CT1258 in a virus dose- and time- dependent fashion. Cytotoxicity and replication assays were also performed on cultured canine Adipose-derived Mesenchymal Stem Cells (cAdMSC). The results showed that the cells were lysed much slower than the tumor cells. It suggests that these cells can harbour the virus for a long-term period, allowing the virus to spread into the body and there is enough time to reach the primary tumor or metastases before the cell carrier is destroyed. The viral replication in cAdMSC in our study was lower than in canine cancer cells (STSA-1 and CT1258) at the same MOI. After being studied in cell culture, C1 opt1 and their combination with cAdMSC (C1-opt1/cAdMSC) were used in canine STSA 1 tumor bearing nude mice. We tested the oncolytic effect of the C1-opt1 virus alone and in combination with cAdMSC in the canine STSA-1 xenograft mouse model. Altogether, our findings have shown that both C1-opt1 and cAdMSC/C1-opt1 significantly reduced tumor size or eliminated the tumor. There was no significant difference between C1-opt1 alone and cAdMSC/C1-opt1. The virus particles were mostly found within the tumor after 24 dpi, some amount of virus particles were found in the lungs of mice injected with a combination of cAdMSC/C1-opt1 but not in the group injected with virus alone (cAdMSC might get stuck in the lungs and cause virus propagation there).
Taken together, this study provided a proof-of-concept that hADSC/cAdMSC can be used as a carrier system for the “Trojan horse” concept. However, it should be confirmed in another experimental model system, such as canine patients. Moreover, these findings suggest that wild-type, non-modified strains of Vaccinia virus isolates can be considered promising candidates for oncolytic virotherapy, especially in combination with mesenchymal stem cells.
The macromolecular SMN complex facilitates the formation of Sm-class ribonucleoproteins involved in mRNA processing (UsnRNPs). While biochemical studies have revealed key activities of the SMN complex, its structural investigation is lagging behind. Here we report on the identification and structural determination of the SMN complex from the lower eukaryote Schizosaccharomyces pombe, consisting of SMN, Gemin2, 6, 7, 8 and Sm proteins. The core of the SMN complex is formed by several copies of SMN tethered through its C-terminal alpha-helices arranged with alternating polarity. This creates a central platform onto which Gemin8 binds and recruits Gemins 6 and 7. The N-terminal parts of the SMN molecules extrude via flexible linkers from the core and enable binding of Gemin2 and Sm proteins. Our data identify the SMN complex as a multivalent hub where Sm proteins are collected in its periphery to allow their joining with UsnRNA.