Fig. 2

The four main molecular pathways governing cellular senescence: DNA Damage Response, Mitochondrial Dysfunction, Oncogene Activation and Other Stressors. The expression of p53 is a key regulator of cellular senescence; p53 is upregulated by ATM/ATR, mTOR and p38MAPK. In contrast, ARF in the Other Stressors pathway can inhibit p53 expression. Two other key regulators of cellular senescence are p21 and p16 both of which are measurable and two of the probable indicators of cellular senescence. Key consequences of cellular senescence are beta-galactosidase expression (useful as a biomarker of cellular senescence), inflammatory cytokines and chemokines, reactive oxygen and nitrogen species (which characterize the SASP phenotype)