p16INK4a

p16INK4a is a cyclin-dependent kinase inhibitor encoded by the CDKN2A locus that blocks CDK4/6, halting cell cycle progression and enforcing cellular senescence. Its expression rises markedly with chronological age across many tissues, making it a widely used biomarker of senescent cell burden and biological aging. Selective elimination of p16-positive senescent cells (senolysis) extends healthspan in mice, motivating ongoing senolytic drug development for age-related disease.