(From EurekAlert). An accurate and easily measured biomarker for the aging process would be an important step forward, and researchers may have found one: "As cells and tissues age, the expression of two proteins called p16INK4a and ARF dramatically increases. This increase in expression, more than a hundredfold in some tissues, suggests a strong link between cellular aging and the upregulation, or increased production, of p16INK4a and ARF. ... Both p16INK4a and ARF are known potent tumor suppressors, or proteins that halt tumor cell growth. The study suggests that the important anti-cancer function of these proteins to limit cellular growth might in turn cause aging. ... the increase in p16INK4a and ARF can be substantially inhibited by decreasing caloric intake, a known retardant of aging."