TRPM2- und TRPM8-vermittelte Radioresistenz in malignen Tumoren

Die Strahlentherapie stellt eine der wichtigsten Säulen dar, auf die sich die moderne Behandlung von Krebserkrankungen stützt. Die Resistenz der Tumorzellen gegenüber dieser Behandlung stellt hierbei trotz immer fortschrittlicherer Behandlungsstrategien ein großes Problem dar. Insbesondere die durch Bestrahlung veränderte Regulation des zellulären Ca2+-Signalosoms scheint hier von großer Bedeutung zu sein. Ca2+-Signale werden unter anderem von in der Plasmamembran lokalisierten Kationenkanälen generiert. Dabei konnte bereits mehrfach gezeigt werden, dass Kationenkanäle der Melastatin-Familie (TRPM) insbesondere die Resistenz und Malignizität von Tumoren beeinflussen, weshalb sie immer weiter in den Fokus der Krebsforschung rücken. Welche Rolle zwei ausgewählten Mitgliedern der TRPM-Familie bei der Radioresistenz maligner Tumore zukommt und wie sich diese Erkenntnis auf eine Strahlentherapie auswirken könnte, wurde in dieser Arbeit näher analysiert. Im ersten Teil dieser Arbeit wurde die Interaktion von TRPM2 mit dem anti-apoptotischen Protein Bcl-2 in T-Zell Leukämiezellen untersucht. Insbesondere Bcl-2 ist nachweislich an der Therapieresistenz verschiedener Tumorentitäten beteiligt. Um dieses Zusammenspiel näher zu charakterisieren, wurden Jurkatzellen mit ionisierender Strahlung behandelt und anschließend der Zellzyklus sowie das TRPM2-vermittelte Ca2+-Signaling analysiert. Hierbei konnte gezeigt werden, dass Bestrahlung vor allem in Bcl-2 überexprimierenden Zellen einen Ca2+-Einstrom induzierte, der nach pharmakologischer Inhibition von TRPM2 stark vermindert war. In Kontrollzellen führte dieser erhöhte Ca2+-Einstrom zur Produktion von reaktiven Sauerstoffspezies. Bcl-2 überexprimierende Jurkatzellen waren jedoch in der Lage, im Gegensatz zu Kontrollzellen, diese letale Ca2+-Dosis zu tolerieren. Weiter führte der TRPM2-vermittelte Einstrom zu einem G2/M-Arrest, der durch Inhibition der TRPM2-Kanäle verhindert wurde, was zu einer erhöhten Apoptoserate führte. Im zweiten Teil dieser Arbeit wurde die Strahlenresistenz von Glioblastomen untersucht. Im Gegensatz zu benignem Hirngewebe ist der Kälterezeptor TRPM8 im Glioblastom stark überexprimiert. Der retrospektive Vergleich von mRNA-Daten zeigte, dass eine erhöhte Expression von TRPM8 im low-grade Gliom mit einer geringeren Lebenserwartung korreliert. In nachfolgenden in vitro Experimenten konnte diese Erkenntnis bestätigt werden: Eine siRNA-vermittelte Inhibition von TRPM8 führte zu einem geringeren klonogenen Überleben. Die Kombination von Bestrahlung und Inhibition zeigte weiter sowohl eine erhöhte Caspasen-Aktivität als auch eine gestörte Proliferation. Zusammenfassend legen diese Ergebnisse nahe, dass die beiden Kanäle TRPM2 und TRPM8 in den untersuchten Tumorentitäten eine wichtige Rolle in der Radioresistenz spielen. Weiter zeigen die Untersuchungen, dass diese beiden Kationenkanäle als mögliche Targets, einzeln oder in Kombination, zukünftiger Behandlungen in Frage kommen und somit neue Strategien in der Krebstherapie eröffnet werden

Petrification: Software Model Checking for Programs with Dynamic Thread Management (Extended Version)

We address the verification problem for concurrent program that dynamically create (fork) new threads or destroy (join) existing threads. We present a reduction to the verification problem for concurrent programs with a fixed number of threads. More precisely, we present petrification, a transformation from programs with dynamic thread management to an existing, Petri net-based formalism for programs with a fixed number of threads. Our approach is implemented in a software model checking tool for C programs that use the pthreads API.Comment: 32 pages, 8 figures, 2 tables, extended version of the paper which is to appear at VMCAI 202

Quantification of Volatile Acetone Oligomers Using Ion-Mobility Spectrometry

Background. Volatile acetone is a potential biomarker that is elevated in various disease states. Measuring acetone in exhaled breath is complicated by the fact that the molecule might be present as both monomers and dimers, but in inconsistent ratios. Ignoring the molecular form leads to incorrect measured concentrations. Our first goal was to evaluate the monomer-dimer ratio in ambient air, critically ill patients, and rats. Our second goal was to confirm the accuracy of the combined (monomer and dimer) analysis by comparison to a reference calibration system. Methods. Volatile acetone intensities from exhaled air of ten intubated, critically ill patients, and ten ventilated Sprague-Dawley rats were recorded using ion-mobility spectrometry. Acetone concentrations in ambient air in an intensive care unit and in a laboratory were determined over 24 hours. )e calibration reference was pure acetone vaporized by a gas generator at concentrations from 5 to 45 ppbv (parts per billion by volume). Results. Acetone concentrations in ambient laboratory air were only slightly greater (5.6 ppbv; 95% CI 5.1–6.2) than in ambient air in an intensive care unit (5.1 ppbv; 95% CI 4.4–5.5; p < 0.001). Exhaled acetone concentrations were only slightly greater in rats (10.3 ppbv; 95% CI 9.7–10.9) than in critically ill patients (9.5 ppbv; 95% CI 7.9–11.1; p < 0.001). Vaporization yielded acetone monomers (1.3–5.3 mV) and dimers (1.4–621 mV). Acetone concentrations (ppbv) and corresponding acetone monomer and dimer intensities (mV) revealed a high coefficient of determination (R2 � 0.96). )e calibration curve for acetone concentration (ppbv) and total acetone (monomers added to twice the dimers; mV) was described by the exponential growth 3-parameter model, with an R2 � 0.98. Conclusion. )e ratio of acetone monomer and dimer is inconsistent and varies in ambient air from place-to-place and across individual humans and rats. Monomers and dimers must therefore be considered when quantifying acetone. Combining the two accurately assesses total volatile acetone

Walking the tightrope between expressiveness and uncomputability: AGM contraction beyond the finitary realm

Although there has been significant interest in extending the AGM paradigm of belief change beyond finitary logics, the computational aspects of AGM have remained almost untouched. We investigate the computability of AGM contraction on non-finitary logics, and show an intriguing negative result: there are infinitely many uncomputable AGM contraction functions in such logics. Drastically, even if we restrict the theories used to represent epistemic states, in all non-trivial cases, the uncomputability remains. On the positive side, we use Büchi automata to construct computable AGM contraction functions on Linear Temporal Logic (LTL)

Targeting TRPM2 Channels Impairs Radiation-Induced Cell Cycle Arrest and Fosters Cell Death of T Cell Leukemia Cells in a Bcl-2-Dependent Manner

Messenger RNA data of lymphohematopoietic cancer lines suggest a correlation between expression of the cation channel TRPM2 and the antiapoptotic protein Bcl-2. The latter is overexpressed in various tumor entities and mediates therapy resistance. Here, we analyzed the crosstalk between Bcl-2 and TRPM2 channels in T cell leukemia cells during oxidative stress as conferred by ionizing radiation (IR). To this end, the effects of TRPM2 inhibition or knock-down on plasma membrane currents, Ca2+ signaling, mitochondrial superoxide anion formation, and cell cycle progression were compared between irradiated (0–10 Gy) Bcl-2-overexpressing and empty vector-transfected Jurkat cells. As a result, IR stimulated a TRPM2-mediated Ca2+-entry, which was higher in Bcl-2-overexpressing than in control cells and which contributed to IR-induced G2/M cell cycle arrest. TRPM2 inhibition induced a release from G2/M arrest resulting in cell death. Collectively, this data suggests a pivotal function of TRPM2 in the DNA damage response of T cell leukemia cells. Apoptosis-resistant Bcl-2-overexpressing cells even can afford higher TRPM2 activity without risking a hazardous Ca2+-overload-induced mitochondrial superoxide anion formation

Simulating the impact of digitalization on retail logistics efficiency

Purpose: The study uses the results of an efficiency analysis for digitalization within a retail logistics blue-collar work system of professional truck drivers and aims to elaborate an ex-ante efficiency simulation approach for digitalization scenarios. Methodology: The simulation method combines the efficiency scores of Data Envelopment Analysis (DEA), statistical bootstrapping, and regression analysis. By increas-ing the original sample size of n=30 truck drivers up to 60,000 samples through 2,000 bootstrap iterations, it is possible to gain a highly significant regression function. Findings: The mathematical simulation approach can be transferred to alternate scenarios in terms of forecasting efficiency development based on the experience distribution of the workforce. Originality: As the impact of digitalization on the efficiency of blue-collar work systems is often unknown, this methodology could provide insights for logistics researchers and managers when estimating the efficiency impact of digitalization

Stratified commutativity in verification algorithms for concurrent programs

The importance of exploiting commutativity relations in verification algorithms for concurrent programs is well-known. They can help simplify the proof and improve the time and space efficiency. This paper studies commutativity relations as a first-class object in the setting of verification algorithms for concurrent programs. A first contribution is a general framework for abstract commutativity relations. We introduce a general soundness condition for commutativity relations, and present a method to automatically derive sound abstract commutativity relations from a given proof. The method can be used in a verification algorithm based on abstraction refinement to compute a new commutativity relation in each iteration of the abstraction refinement loop. A second result is a general proof rule that allows one to combine multiple commutativity relations, with incomparable power, in a stratified way that preserves soundness and allows one to profit from the full power of the combined relations. We present an algorithm for the stratified proof rule that performs an optimal combination (in a sense made formal), enabling usage of stratified commutativity in algorithmic verification. We empirically evaluate the impact of abstract commutativity and stratified combination of commutativity relations on verification algorithms for concurrent programs

Commutativity simplifies proofs of parameterized programs

Commutativity has proven to be a powerful tool in reasoning about concurrent programs. Recent work has shown that a commutativity-based reduction of a program may admit simpler proofs than the program itself. The framework of lexicographical program reductions was introduced to formalize a broad class of reductions which accommodate sequential (thread-local) reasoning as well as synchronous programs. Approaches based on this framework, however, were fundamentally limited to program models with a fixed/bounded number of threads. In this paper, we show that it is possible to define an effective parametric family of program reductions that can be used to find simple proofs for parameterized programs, i.e., for programs with an unbounded number of threads. We show that reductions are indeed useful for the simplification of proofs for parameterized programs, in a sense that can be made precise: A reduction of a parameterized program may admit a proof which uses fewer or less sophisticated ghost variables. The reduction may therefore be within reach of an automated verification technique, even when the original parameterized program is not. As our first technical contribution, we introduce a notion of reductions for parameterized programs such that the reduction R of a parameterized program P is again a parameterized program (the thread template of R is obtained by source-to-source transformation of the thread template of P). Consequently, existing techniques for the verification of parameterized programs can be directly applied to R instead of P. Our second technical contribution is that we define an appropriate family of pairwise preference orders which can be effectively used as a parameter to produce different lexicographical reductions. To determine whether this theoretical foundation amounts to a usable solution in practice, we have implemented the approach, based on a recently proposed framework for parameterized program verification. The results of our preliminary experiments on a representative set of examples are encouraging