Hierarchical Levels of Biological Systems and their Integration as a Principal Cause for Tumour Occurrence.

The development of new theories, mathematical methods and models for effective control of complex systems is one of the main problems for modern science. Biological systems are complex and hierarchically organized, with the behaviour of higher levels influencing the dynamics of the lower ones and vice versa. Hierarchical organization can be observed from subcellular to supercellular levels. When biological systems are far from their steady states, then nonlinear dependences take place, and a slight external impact can cause unexpected and unpredictable (chaotic, irregular) behaviour in these systems, resulting in fractal hierarchical structures. By examining tumours as strange (chaotic) attractors, we define in this article the hypothesis that the cause of their occurrence, development and spread (metastasis) is due to disorders in the hierarchical structure and integration of cell signalling pathways in tumour cells. An essential point in this article is the thesis (contrary to the view that the only causality in hierarchical systems is physical causality, i.e. there is no "top-down,' "holistic causality,' "intelligent causality,' etc.) that hierarchical systems are built on the principle of communication. Intelligent systems (in particular biological) that do not interact as mechanical objects, but on the basis of different meanings of biochemical signals obtained after their interpretation, participate in this communication.