p16 a biomarker of aging and tolerance for cancer therapy

There is great variability in life-expectancy, physical, cognitive, and functional domains in cancer patients of similar chronologic age. Nowhere is this more apparent than among middle-aged and older patients. However, even in younger patients of similar age, extensive exposure to environmental stressors can cause great variability in health status. A biomarker that would reflect biologic age and any and all health deficits in a cancer patient at a distinct point in time might help predict long term outcomes related to treatment, especially toxicity and overall survival. p16^INK4a (hereafter referred to as p16) expression represents an ideal biomarker that reflects both cellular senescence and biologic aging. In murine models, p16 expression reflects biologic aging in almost all organs. Preliminary findings in patients with cancer support p16 measurement as a marker of physiologic aging and predictor of toxicity in patients treated with chemotherapy. This review describes the role of p16 in cell senescence, the methodology of p16 measurement in humans, preliminary studies of p16 in humans, and the potential clinical utility of p16 in guiding treatment for cancer patients.