Tumour growth activation by the central nervous system--An integrative theory of cancer.

The currently recognised mechanisms of the biology of cancer are not yet enough to explain the high incidence of the disease in industrialised countries. Survival and proliferation of cancer cells demand a well orchestrated combination of functional capabilities, or hallmarks, which requires complex signalling networks that often exceed the tumour boundaries. Based on latest research on environmental health, and aiming to provide cancer with a coherent set of organizing principles, we propose an integrative model of carcinogenesis founded on tumour growth activation by the central nervous system as an adaptive, allostatic response to both environmental and emotional challenges. In this way, chronicity of physical as well as psychological stressors may be directly involved in cancer genesis and progression, after an early inflammatory stage. The model also contemplates accidental activation of the tumour growth programme following direct DNA damage, but as a rare event that does not account for most cancers in humans. Bodily and cellular mechanisms designed to facilitate tumorigenesis may include exacerbation of the sympathetic activity, overexpression of membrane ion channels, promotion of selected mutations and methylations, degradation of the mitochondria, and reprogramming of adult stem cells.