TP53 and Keratoconjunctivitis sicca: Our results are also consistent with a number of reports that demonstrated that the p53/p21 pathway is stimulated by ROS.(29–31) Up-regulation of p53 and p21 is known to induce apoptosis, cell cycle arrest and senescence-associated secretory phenotype (SASP) in several cell types,(16,29–31) and may contribute to the development of dry eye.