Levels of a well-known tumor suppressor protein, p16INK4a, increase sharply with age in most mammalian tissues, and these increases contribute to an age-induced functional decline of certain self-renewing compartments. Researchers at the University of North Carolina have now shown that p16INK4 can be detected in peripheral blood T-lymphocytes (PBTL) and that its expression levels are strongly correlated with an individual's chronological age and, in fact, increase exponentially with age. In addition, increased expression levels of p16INK4a were independently associated with certain behaviors (tobacco use and physical inactivity) known to accelerate human aging. p16INK4a levels were also associated with a biomarker of human frailty. The authors said that the data suggest that p16INK4 expression in PBTL is an easily measured, peripheral blood biomarker of molecular age. "This is a major step toward a practical tool to clinically determine a person's actual molecular, as opposed to just their chronological, age," said Dr. Norman Sharpless, the senior author of the study. "Although we don't know whether this test is a good reflection of cellular age in all types of human tissues, we believe it is a first step toward a better understanding of issues like the suitability of organs for transplantation, how well patients are likely to recover after surgery, or the future toxicity of chemotherapy for cancer patients," he added. This work was published online ahead of pring in Aging Cell. [Press release] [Aging Cell abstract]
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