CDKN2A and neoplasm: However, it is important to acknowledge that no single, definitive biomarker of aging exists, such as the SASP, which can also be observed during chronic inflammation and immune system activation [52, 131]; markers like p21 and p16, which are intimately associated with tumorigenesis and tumor progression, are not exclusively indicative of senescence, as they are also implicated in cellular apoptosis [132, 133].