Cryptobiosis, aging, and cancer: yin-yang balancing of signaling networks.

Some organisms adapt to persistent and severe stress by reversibly adjusting life-death balance to a new equilibrium, e.g., anhydrobiosis ("life without water") enables survival in a quiescent state on extreme desiccation. Aging is characterized by declining response and increasing vulnerability to stress, and the balance slowly, and irreversibly, tilts toward death. Although tumorigenesis tips the balance of cells to prolonged life, paradoxically it can cause organismal death. At the molecular level, all these phenomena involve complex signaling pathways, but it is highly likely that the overall balance of signaling outcomes, rather than individual signals themselves, plays the pivotal role in life-death decisions.