CDKN2A and atherosclerosis: Furthermore, macrophage removal reduces the p16ink4a signal in p16ink4a reporter mice,39 and expression of p16 and SAβG are reversible in macrophages,9 suggesting that p16 is another checkpoint in macrophage polarization, and that these markers do not necessarily indicate senescence.40 These studies and our findings suggest significant limitations in using p16, p16 reporters, or p16-linked suicide genes and SAβG to identify and/or remove senescent cells in atherosclerosis.