Abstract
Intracellular processes are cascades of biochemical reactions, triggered in response to various types of stimuli. Mathematical models describing their dynamics have become increasingly popular in recent years, as tools supporting experimental work in analysis of pathways and regulatory networks. Not only do they provide insights into general properties of these systems, but also help in specific tasks, such as search for drug molecular targets or treatment protocols. Different tools and methods are used to model complex biological systems. In this work, we focus on ordinary differential equations (ODEs) and Petri nets. We consider specific methods of analysis of such models, i.e., sensitivity analysis (SA) and significance analysis. So far, they have been applied separately, with different goals. In this paper, we show that they can complement each other, combining the sensitivity of ODE models and the significance analysis of Petri nets. The former is used to find parameters, whose change results in the greatest quantitative and qualitative changes in the model response, while the latter is a structural analysis and allows indicating the most important subprocesses in terms of information flow in Petri net. Ultimately, both methods facilitate finding the essential processes in a given signaling pathway or regulatory network and may be used to support medical therapy development. In the paper, the use of dual modeling is illustrated with an example of ATM/p53/NF-kappaB pathway. Each method was applied to analyze this system, resulting in finding different subsets of important processes that might be prospective targets for changing this system behavior. While some of the processes were indicated in each of the approaches, others were found by one method only and would be missed if only that method was applied. This leads to the conclusion about the complementarity of the methods under investigation. The dual modeling approach of comprehensive structural and parametric analysis yields results that would not be possible if these two modeling approaches were applied separately. The combined approach, proposed in this paper, facilitates finding not only key processes, with which significant parameters are associated, but also significant modules, corresponding to subsystems of regulatory networks. The results provide broader insight into therapy targets in diseases in which the natural control of intracellular processes is disturbed, leading to the development of more effective therapies in medicine.
Highlights
Intracellular processes are cascades of biochemical reactions, triggered in response to various types of stimuli
The ordinary differential equations (ODEs) model describing the mechanism of the DNA damage response system based on the Ataxia telangiectasia mutated (ATM)/p53/Nuclear Factor κ B (NF-κ B) pathways[12] was used as the basis for manual developing a corresponding model based on the Petri nets
Diagrams depicting biochemical reaction networks, whose kinetics is the basis for creation of ODE models, resemble, to some extent, Petri net model representation
Summary
Intracellular processes are cascades of biochemical reactions, triggered in response to various types of stimuli. The former is used to find parameters, whose change results in the greatest quantitative and qualitative changes in the model response, while the latter is a structural analysis and allows indicating the most important subprocesses in terms of information flow in Petri net Both methods facilitate finding the essential processes in a given signaling pathway or regulatory network and may be used to support medical therapy development. Petri nets and ODEs-based approaches were used to perform a comprehensive analysis of that model, aimed at finding those processes, and kinetic parameters associated with them, that are the most important for system behavior Once found, they should become the focus of much deeper experimental investigation as the best prospective targets in new drugs development. It has been shown that about half of the cancer types have mutations in the p53 gene, while in many others malfunctions of other proteins involved in the p53 signalling pathway are o bserved[16]
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