Institutes
Refine
Year of publication
Document Type
- Doctoral Thesis (311)
- Article (281)
- Preprint (38)
- Contribution to a Periodical (25)
- Book (18)
- Report (2)
Language
- English (520)
- German (154)
- Multiple languages (1)
Has Fulltext
- yes (675)
Is part of the Bibliography
- no (675)
Keywords
- RNA (12)
- SARS-CoV-2 (10)
- NMR spectroscopy (9)
- inflammation (9)
- photochemistry (9)
- NMR (8)
- Biochemistry (7)
- Cell biology (7)
- E2 enzyme (6)
- TRACT (6)
Institute
- Biochemie, Chemie und Pharmazie (675)
- Präsidium (43)
- Medizin (35)
- Buchmann Institut für Molekulare Lebenswissenschaften (BMLS) (30)
- Zentrum für Biomolekulare Magnetische Resonanz (BMRZ) (30)
- Biowissenschaften (23)
- MPI für Biophysik (15)
- Physik (12)
- Zentrum für Arzneimittelforschung, Entwicklung und Sicherheit (ZAFES) (5)
- Geowissenschaften / Geographie (4)
- Exzellenzcluster Makromolekulare Komplexe (3)
- Frankfurt Institute for Advanced Studies (FIAS) (3)
- Psychologie und Sportwissenschaften (3)
- Gesellschaftswissenschaften (2)
- MPI für Hirnforschung (2)
- Wirtschaftswissenschaften (2)
- Georg-Speyer-Haus (1)
- Pharmazie (1)
In der vorgelegten kumulativen Arbeit wurden strukturelle und funktionale Untersuchungen an Nukleinsäuren durchgeführt, hauptsächlich, aber nicht ausschließlich unter Verwendung von NMR-Spektroskopie (Kernspin Resonanzspektroskopie) als Analysemethode. Die untersuchten Biomoleküle umfassten kleinere und größere biologisch relevante RNAs sowie einen artifiziellen DNA G-Quadruplex. Hierbei konnten Ergebnisse im Bereich der Bestimmung der molekularen Struktur, der Aufklärung der biologischen Funktion und der Wirkstoffentwicklung gewonnen werden, die in sechs verschiedenen Publikationen dargelegt sind, an deren Erstellung der Autor maßgeblich oder hauptverantwortlich beteiligt war. Des Weiteren wird in einem mehrgliedrigen Einleitungssegment auf den Stand der aktuellen Forschung in den jeweiligen Teilgebieten eingegangen.
Hepatocyte nuclear factor 4α (HNF4α) is a ligand-sensing transcription factor and presents as a potential drug target in metabolic diseases and cancer. In humans, mutations in the HNF4α gene cause maturity-onset diabetes of the young (MODY), and the elevated activity of this protein has been associated with gastrointestinal cancers. Despite the high therapeutic potential, available ligands and structure–activity relationship knowledge for this nuclear receptor are scarce. Here, we disclose a chemically diverse collection of orthogonally validated fragment-like activators as well as inverse agonists, which modulate HNF4α activity in a low micromolar range. These compounds demonstrate the druggability of HNF4α and thus provide a starting point for medicinal chemistry as well as an early tool for chemogenomics.
In dieser Arbeit werden die Ergebnisse quantenchemischer Untersuchungen von verschiedenen Siliciumverbindungsklassen vorgestellt, die in weiten Teilen als Begleitung zu experimentellen Arbeiten durchgeführt wurden. Das erste Hauptkapitel befasst sich mit den Chloridkomplexen von Perchlorsilanen, zu denen die inversen Sandwichkomplexe und die Silafullerane mit endohedralem Gast gehören. Der Fokus liegt dabei auf den Bindungseigenschaften zwischen Ligand und Silan. Weiterhin werden thermodynamische Untersuchungen zu Aufbaureaktionen und Eigenschaften der Verbindungen vorgestellt. Mit den durchgeführten Rechnungen kann gezeigt werden, dass durch Wahl geeigneter Substituenten am Siliciumatom ein Wechsel in den Chloridkomplexen von einem hyperkoordinierten Siliciumatom hin zu einem Siliciumatom mit ausgebildeter Tetrelbindung erreicht werden kann. Bei den inversen Sandwichkomplexen sind beide Bindungsmodi möglich, von denen die Tetrelbindung die stärkere darstellt. Neben Chloridionen können hier auch Nitrile und Chlorsubstituenten am eigenen Silangerüst als Liganden fungieren. Die stärksten Tetrelbindungen können bei den endohedral funktionalisierten Silafullerankomplexen gefunden werden. Hier stellt das experimentell isolierte Strukturmotiv mit zwölf äußeren Trichlorsilylsubstituenten das thermodynamisch stabilste Substitutionsmuster dar. Im folgenden Kapitel werden die generellen physikalischen Ursachen für die beobachteten thermodynamischen Trends zwischen Perchlorsilanisomeren sowie Disproportionierungsreaktionen behandelt und ein direkter Vergleich mit Alkanhomologen angestellt. Bei den Perchlorsilanen und den meisten Homologen ist bei den untersuchten Systemen eine energetische Präferenz von verzweigteren Strukturen zu erkennen. Die Ursache hierfür liegt hauptsächlich bei stärkeren attraktiven Wechselwirkungen durch Korrelationseffekte, Hyperkonjugation sowie elektrostatische Effekte, welche stärkere repulsive Wechselwirkungen wie die Pauli-Repulsion überkompensieren. Im letzten Kapitel kommen zu den bisher behandelten Reaktionen unter Si-Cl- und Si-Si-Bindungsbeteiligung noch Reaktionen unter Si-C-Bindungsbeteiligungen hinzu. Dort werden die auch wegen ihrer Elektronentransporteigenschaften interessanten Silacyclopentadiene (Silole) hinsichtlich ihrer Isomerisierung, Dimerisierung und weiteren pericyclischen Reaktivität untersucht. Gegenüber dem verwandten Cyclopentadien zeigen diese eine deutlich erhöhte Reaktivität, was zu verschiedenen Dimerisierungsreaktionen führt, solange keine Abfangreagenzien im Überschuss zugegen sind.
Protein ubiquitination is a post-translational modification that typically involves the conjugation of ubiquitin to substrate proteins via a three-enzyme cascade and regulates a wide variety of cellular processes. Recent studies have revealed that SidE family of Legionella effectors such as SdeA catalyzes novel phosphoribosyl-linked ubiquitination (PR-ubiquitination) of serines in host substrate proteins utilizing NAD+, without the need of E2, E3. The catalytic core of SdeA comprises a mono-ADP-ribosyltransferase (mART) domain that functions to ADP-ribosylate ubiquitin, and a phosphodiesterase (PDE) domain that processes ADP-ribosylated ubiquitin and transfers the resulting phosphoribosylated ubiquitin to serines of substrates.
To date, extensive efforts have been made to study the function of SdeA and mechanism of SdeA mediated PR-ubiquitination, however, the cellular effects of this novel ubiquitination and phosphoribosylation of ubiquitin remained poorly understood. In our study, using biochemical and cell biological approaches, we explored the biological effect of phosphoribosylation of ubiquitin caused by SdeA in cells. We found that phosphoribosylated ubiquitin is not available for conventional ubiquitination, thereby phosphoribosylation of ubiquitin impairs numerous classical ubiquitination related cellular processes including mitophagy, TNF-α signaling and proteasomal degradation.
The precise temporal regulation of the functions of bacterial effectors during Legionella infection by other effectors with antagonizing activities has been well studied so far. Not surprisingly, PR-ubiquitination catalyzed by SidE family effecters is tightly controlled as well, it has been long known that effector SidJ counteracts the toxicity of SdeA to yeast cells. Interestingly, in an experiment for verifying the activity of SidJ, we found that Legionella lysate lacking SidJ was still able to remove ubiquitin from PR-ubiquitinated substrates. Using biochemical approach we identified DupA and DupB, two Legionella bacterial effectors that specifically reverse the novel serine PR-ubiquitination catalyzed by SdeA. We found that DupA and DupB possess a highly homologous PDE domain that removes ubiquitin from PR-ubiquitinated substrates by cleaving the phosphodiester bond between the phosphoribosylated-ubiquitin and serines of substrates. Catalytically deficient mutant DupA H67A strongly binds to PR-ubiquitinated proteins but not capable of cleaving PR-ubiquitin, using it as a trapping bait we identified over 180 substrates of PR-ubiquitination, including a number of ER and Golgi proteins.
In particular, we found that exogenously expressed SdeA localizes to the Golgi apparatus via its C-terminal region and disrupts the Golgi. We validated the identified potential substrates of SidE effectors and found that SdeA modifies Golgi tethering proteins GRASP55 and GRASP65. Using mass spectrometry analyses we identified four serine targets (S3, S408, S409, S449) of GRASP55 PR-ubiquitinated by SdeA in vitro. Ubiquitination of GRASP55 serine mutant in cells co-expressing SdeA or infected with Legionella was markedly decreased, compared with that of the wild-type GRASP55. In addition, with co-immunoprecipitation analyses we found that SdeA-catalyzed ubiquitination regulates the function of GRASP55. PR-ubiquitinated GRASP55 exhibited reduced self-interaction compared to unmodified GRASP55, expression of GRASP55 serine mutant in cells in part rescued Golgi damage caused by SdeA. Furthermore, our study reveals that Golgi structure disruption caused by SdeA does not result in the recruitment of Golgi membranes to the Legionella-containing vacuoles. Instead, it affects cellular secretory pathway including cytokine secretion in cells.
Taken all together, this work expands the understanding of this unconventional PR-ubiquitination catalyzed by Legionella effectors and sheds light on the functions of PR-ubiquitination by which Legionella regulates the Golgi function and secretion pathway during bacterial infection.
H/ACA-RNPs are involved in RNA guided pseudouridylation of rRNAs and snRNAs. In this thesis I reconstituted active and labeled archaeal as well as eukaryotic H/ACA-RNPs and studied the structural dynamics of complex assembly and pseudouridine formation. Single molecule FRET spectroscopy was used as method of analysis to study structure, assembly and dynamics of these important complexes.
Inhibitoren der Apoptose (IAP, inhibitor of apoptosis) Proteine spielen eine wichtige Rolle in Bezug auf Zelltodregulation und es ist anzunehmen, dass eine Dysregulation dieser Proteine zu einer Tumorentwicklung und Tumorprogression beiträgt. Erhöhte Expressionslevel von IAP Proteinen verhindern die Aktivierbarkeit des Zelltodprogrammes von Tumorzellen und eine Reihe von Studien konnte bereits erhöhte IAP Level in Tumorzelllinien sowie in primären Tumorproben nachweisen. Des Weiteren korrelieren erhöhte Expressionslevel von IAPs in Tumoren mit Behandlungsresistenzen und schlechten Prognosen für die Patienten.
Das diffuse großzellige B-Zell Lymphom (DLBCL, diffuse large B-cell lymphoma) zählt zu den häufigsten Subtypen der Non-Hodgkin Lymphome (NHL) mit 40 % aller neu diagnostizierten NHL Fälle. DLBCL ist eine sehr heterogene Erkrankung die in drei verschiedene Gruppen klassifiziert wurde: aktivierter B-Zell Typ (ABC, activated B-cell), Keimzentrum B-Zell Typ (GCB, germinal center B-Cell) und Mediastinaler großzelliger B-Zell Typ (PMBL, primary mediastinal B-cell lymphoma). Erhöhte Expressionslevel von zellulärem IAP1 (cIAP, cellular IAP) und cIAP2 wurden ebenfalls in primären Tumorproben von DLBCL Patienten nachgewiesen. Smac mimetics wurden entwickelt, um IAPs zu antagonisieren und stellen damit eine Behandlungsstrategie für DLBCL Patienten dar, denn ca. 40 % aller DLBCL Patienten entwickeln ein Rezidiv oder erreichen gar keine Remission unter Standardtherapie. Jedoch ist der Effekt von Smac mimetics in einer Einzelbehandlung limitiert, weswegen Kombinationstherapien mit Smac mimetics eine vielversprechende Strategie für ihren klinischen Einsatz darstellen. Aus diesem Grund haben wir in dieser Arbeit den Effekt von Smac mimetic in Kombination mit Proteasom-Inhibitoren analysiert und einen speziellen Fokus auf den molekularen Mechanismus des ausgelösten Zelltodsignalweges gelegt.
Die Kombination verschiedener Konzentrationen des Smac mimetics BV6 mit dem Proteasom-Inhibitor carfilzomib (CFZ) löst in allen drei getesteten DLBCL Subtypen (ABC, GCB und PMBL) Zelltod aus. Die Kalkulation des Kombinationsindexes (CI, combination index) sowie des Bliss Scores, zwei quantitative Parameter zur Bestimmung eines Synergismus, zeigen, dass fast alle getesteten Kombinationen einen Synergismus aufweisen. Dies verdeutlicht, dass eine Co-Behandlung von BV6 und CFZ eine wirksame Kombination ist um Zelltod in DLBCL Zelllinien auszulösen. Außerdem zeigt eine Kombination von BV6 mit anderen Proteasom-Inhibitoren wie ixazomib (IXA) oder oprozomib (OPR), ebenfalls eine synergistische Reduktion der Zellviabilität. Diese Ergebnisse deuten darauf hin, dass der detektierte Effekt nicht auf eine Substanz limitiert ist, sondern, dass ein genereller Effekt von Smac mimetic und Proteasom-Inhibitoren vorliegt, um Zellviabilität in DLBCL zu reduzieren. BV6 und CFZ induzieren einen apoptotischen Zelltod, da sie die Spaltung und Aktivierung von Initiator- und Effektorcaspasen (Caspasen-3, -7, -8 und -9) initiieren und sich der induzierte Zelltod mit Hilfe des Caspasen-Inhibitors zVAD.fmk verhindern lässt. Die Behandlung mit BV6 und CFZ führt zu einer Akkumulation von NIK, ein Protein welches zur Aktivierung des non-kanonischen NF-kB Signalweges benötigt wird. Weitere Untersuchungen zeigen jedoch, dass NIK nicht an der Zelltodinduktion beteiligt ist, da eine siRNA-basierte Herunterregulierung des NIK Proteins keinen Einfluss auf die Zelltodinduktion nimmt. Ebenfalls ist der Zelltod unabhängig von dem TNFa Signalweg, da weder eine Behandlung mit dem TNFa Inhibitor Enbrel den Zelltod verringern kann noch eine zusätzliche Gabe von TNFa den Zelltod erhöht. Weitere mechanistische Studien zeigen eine kritische Rolle der mitochondrialen Apoptose für den BV6/CFZ-vermittelten Zelltod. Unter Behandlung mit BV6/CFZ wurde eine Aktivierung von BAX und BAK nachgewiesen, welche beide mit verantwortlich für die Porenbildung in der mitochondrialen Membran sind. Eine Herunterregulation dieser beiden Proteine mittels siRNA reduziert signifikant den durch BV6/CFZ-induzierten Zelltod auf ein Minimum. Gleichzeitig löst eine Co-Behandlung mit BV6/CFZ einen Verlust des mitochondrialen Membranpotentials (LOMMP, loss of mitochondrial membrane potential) aus. In Übereinstimmung mit den vorherigen Experimenten, zeigen wir eine Akkumulation von mitochondrialen reaktiven Sauerstoffspezies (ROS; reactive oxygen species), sowie einen generellen Anstieg des allgemeinen ROS Levels. Eine Behandlung mit BV6/CFZ zeigt eine deutliche Akkumulation des pro-apoptotischen Proteins NOXA. Um dessen funktionelle Relevanz zu überprüfen, wurde die Proteinmenge von NOXA mittels siRNA stark reduziert. Eine Behandlung mit der Kombination aus BV6 und CFZ zeigt daraufhin eine signifikant reduzierte Zelltodinduktion, was die funktionelle Relevanz von NOXA für den BV6/CFZ-vermittelten Zelltod unterstreicht. Immunopräzipitationsstudien zeigen, dass in RIVA und U2932 Zellen NOXA konstitutiv an seinen anti-apoptotischen Bindungspartner MCL-1 gebunden ist, was die Zellen bereits darauf vorbereitet Apoptose zu durchlaufen. Dieses sogenannte „primen“ für Apoptose wird durch die Behandlung mit BV6 und CFZ weiter verstärkt, da es die Bindung zwischen NOXA und MCL-1 weiter erhöht. Dadurch wird die Balance zwischen pro- und anti-apoptotischen Proteinen zu Gunsten der pro-apoptotischen Proteine verschoben und die Induktion von Apoptose begünstigt.
Insgesamt zeigen die Ergebnisse, dass DLBCL Zelllinien sensitiv auf eine Behandlung mit Smac mimetic und Proteasom-Inhibitor reagieren und damit eine mögliche neue Behandlungsstrategie für diese heterogene Tumorerkrankung darstellt.
An overexpression of the E3 ubiquitin ligase TRIM25 is implicated in several human cancers and frequently correlates with a poor prognosis and occurrence of therapy resistance in patients. Previous studies of our group have identified the mRNA encoding the pro-apoptotic caspase-2 as a direct target of the ubiquitous RNA binding protein human antigen R (HuR). The constitutive HuR binding observed in colon carcinoma cells negatively interferes with the translation of caspase-2 mainly through binding to the 5' untranslated region (UTR) of caspase-2 and thereby confers an increased survival of tumor cells. The main objective of this thesis was to unravel novel regulatory proteins critically involved in the control of caspase-2 translation and their impact on therapeutic drug resistance of human colon carcinoma cells. By employing RNA affinity chromatography in combination with mass-spectrometry, among several putative caspase-2 mRNA binding proteins, we have identified the tripartite motif-containing protein 25 (TRIM25) as novel caspase-2 translation regulatory protein in colon carcinoma cells. The constitutive TRIM25 binding to caspase-2 mRNA in two different human colorectal carcinoma cell lines was validated by ribonucleoprotein (RNP)-immunoprecipitation (RIP)-RT-PCR assay and by means of biotin-labeled RNA-pull-down assay. Since caspase-2 is a caspase which is particularly involved in the DNA-damage-induced apoptosis, I tested the functional relevance of negative caspase-2 regulation by TRIM25 for chemotherapeutic drug-induced cell death of different adenocarcinoma cells by RNA interference (RNAi)- mediated loss-of-function and gain-of-function approaches. In the first part of the thesis, I could demonstrate that transient silencing of TRIM25 caused a significant increase in caspase-2 protein levels without affecting the amount of corresponding mRNAs. Mechanistically, the TRIM25 silencing-triggered increase in caspase-2 was totally impaired by cycloheximide, indicating that the stimulatory effects on caspase-2 levels depend on protein synthesis. This finding was corroborated by RNP/polysomal fractionation, which revealed that the transient knockdown of TRIM25 caused a significant redistribution of caspase-2 transcripts from the fraction of RNP particles to that from translationally active polyribosomes.
The second part of my thesis aimed at the elucidation of the functional consequences of the negative caspase-2 regulation by TRIM25 for enhanced tumor cell survival. Thereby, I found that the siRNA-mediated knockdown of TRIM25 caused a significant increase in the chemotherapeutic drug-induced cleavage of caspase-3 and to elevations in cytoplasmic cytochrome c levels implicating that TRIM25 depletion did mainly affect the intrinsic apoptotic pathway. Concordantly, the ectopic expression of TRIM25 caused a reduction in caspase-2 protein levels, concomitant with an attenuated sensitivity of tumor cells to doxorubicin.
To test the functional impact of caspase-2 in the TRIM25 depletion-dependent sensitization to drug-induced apoptosis, I employed a siRNA-mediated knockdown of caspase-2. Interestingly, the strong induction of caspase-3 and -7 cleavage after doxorubicin treatment was fully impaired after the additional knockdown of caspase-2, indicating the sensitizing effects by TRIM25 knockdown depend on caspase-2.
Data from this thesis identified the TRIM25 as a novel RNA-binding protein of caspase-2 mRNA, which negatively interferes with the translation of caspase-2 and which functionally contributes to chemotherapeutic drug resistance of colon carcinoma cells. Interfering with the negative TRIM25-caspase-2 axis may represent a promising therapeutic avenue for sensitizing colorectal cancers to conventional anti-tumor therapies.
Persistent and, in particular, neuropathic pain is a major healthcare problem with still insufficient pharmacological treatment options. This triggered research activities aimed at finding analgesics with a novel mechanism of action. Results of these efforts will need to pass through the phases of drug development, in which experimental human pain models are established components e.g. implemented as chemical hyperalgesia induced by capsaicin. We aimed at ranking the various readouts of a human capsaicin–based pain model with respect to the most relevant information about the effects of a potential reference analgesic. In a placebo‐controlled, randomized cross‐over study, seven different pain‐related readouts were acquired in 16 healthy individuals before and after oral administration of 300 mg pregabalin. The sizes of the effect on pain induced by intradermal injection of capsaicin were quantified by calculating Cohen's d. While in four of the seven pain‐related parameters, pregabalin provided a small effect judged by values of Cohen's d exceeding 0.2, an item categorization technique implemented as computed ABC analysis identified the pain intensities in the area of secondary hyperalgesia and of allodynia as the most suitable parameters to quantify the analgesic effects of pregabalin. Results of this study provide further support for the ability of the intradermal capsaicin pain model to show analgesic effects of pregabalin. Results can serve as a basis for the designs of studies where the inclusion of this particular pain model and pregabalin is planned.
Investigating the inhibition of anti-apoptotic BCL-2 family proteins in pediatric cancer cells
(2020)
Cancer is amongst the leading causes of death in childhood. Rhabdomyosarcoma (RMS) is the most frequently occurring soft tissue sarcoma in children and adolescents. It presumably arises from mesenchymal progenitors of skeletal muscle cells and presents with different subtypes that differ both histologically and genetically. Osteosarcoma (OS) and Ewing sarcoma (ES) are the most frequently diagnosed pediatric bone tumors. Even though the prognosis of these cancer entities improved significantly during recent decades, the survival rates are currently stagnating. Especially, dismal prognosis of relapsed and metastasizing cases of these malignancies urgently call for novel treatment options. BCL-2 proteins are vital guardians that control intrinsic apoptosis. Furthermore, it was shown that BCL-2 proteins critically regulate apoptosis in pediatric solid tumors. BH3 mimetics are small molecules that bind and inhibit anti-apoptotic BCL-2 proteins. They have already been investigated as cancer therapeutics for several years and show first encouraging clinical results. Therefore, we hypothesized that targeting BCL-2, MCL-1 and BCL-XL might be a promising approach to treat RMS, OS and ES.
In this study, we aimed to comprehensively evaluate the potential of anti-apoptotic BCL-2 family proteins as therapeutic targets for pediatric solid tumors such as RMS, OS and ES.
Notably, RMS, OS and ES cells largely expressed the most relevant BCL-2 family protein members. However, cells were widely insensitive to single pharmacological inhibition of either BCL-XL, BCL-2 or MCL-1 by A-1331852, ABT-199 and S63845, respectively. This finding was independent of their BCL-2 family protein expression levels. Significantly, co-administration of A-1331852 and S63845 induced cell death in RMS, OS and ES cell lines in a highly synergistic manner. Transient silencing of MCL-1 and/or BCL-XL verified the co-dependency of RMS cells on these proteins for survival. Importantly, A-1331852/S63845 co-treatment was more efficient in causing cell death in RMS, OS and ES cells than either inhibitor combined with ABT-199. Efficacy of A-1331852/S63845 co-treatment could be additionally demonstrated in a primary sample of pediatric malignant epithelioid mesothelioma.
Mechanistically, concomitant A-1331852/S63845 treatment mediated rapid intrinsic apoptosis involving swift loss of the mitochondrial outer membrane potential as well as activation of caspases-3, -8 and -9. An observed caspase dependent loss of MCL-1 might further amplify the A-1331852/S63845 triggered pro-death signaling. Furthermore, we identified BAX and BAK as key mediators of apoptosis caused by dual inhibition of MCL-1 and BCL-XL. A-1331852/S63845 induced cell death was relying on BAX and/or BAK in a cell line dependent manner. Interestingly, treatment with A-1331852 and S63845 liberated BAK from its interaction with MCL-1 and BCL-XL. Moreover, BAX and BAK were activated and interacted with each other to form a pore in the outer mitochondrial membrane. Further, in RD cells BIM and NOXA partially contributed to A-1331852/S63845 mediated cell death. Consistently, in this cell line BIM and NOXA were disrupted from their binding to BCL-XL and MCL-1 by A-1331852 and S63845, respectively. However, BH3 only proteins were not involved in A-1331852/S63845 induced cell death in Kym-1 cells. Therefore, we concluded that BH3 only proteins played only a marginal and cell line dependent role in mediating cell death caused by MCL-1 and BCL-XL co-repression.
Notably, A-1331852/S63845 co-treatment spared non-malignant fibroblasts, myoblasts and peripheral blood mononuclear cells, which suggests a therapeutic window for its application in vivo. Besides, we could demonstrate that sequential BH3 mimetic treatment still significantly induced cell death, albeit to minor extents compared to its dual administration. Importantly, we successfully evaluated concomitant treatment with A-1331852 and S63845 in multicellular RMS spheroids and in an in vivo embryonic chicken model of RMS. These findings stress the high transcriptional relevance of A-1331852/S63845 as an emerging novel cancer regimen.
Collectively, the thesis at hand explored the great potential of co-treatment with A-1331852 and S63845 in pediatric solid tumors and unveiled the underlying molecular mechanisms of cell death in RMS. Together, the current investigations support further preclinical and clinical studies to evaluate the effect of dual MCL-1 and BCL-XL targeting in pediatric solid tumors.
Paul Ehrlich's concept of the magic bullet, by which a single drug induces pharmacological effects by interacting with a single receptor has been a strong driving force in pharmacology for a century. It is continually thwarted, though, by the fact that the treated organism is highly dynamic and the target molecule(s) is (are) never static. In this article, we address some of the factors that modify and cause the mobility and plasticity of drug targets and their interactions with ligands and discuss how these can lead to unexpected (lack of) effects of drugs. These factors include genetic, epigenetic, and phenotypic variability, cellular plasticity, chronobiological rhythms, time, age and disease resolution, sex, drug metabolism, and distribution. We emphasize four existing approaches that can be taken, either singly or in combination, to try to minimize effects of pharmacological plasticity. These are firstly, to enhance specificity using target conditions close to those in diseases, secondly, by simultaneously or thirdly, sequentially aiming at multiple targets, and fourthly, in synchronization with concurrent dietary, psychological, training, and biorhythm‐synchronizing procedures to optimize drug therapy.