The senescent cells, which are unable to proliferate as a result of aging, are considered one of the significant etiological factors for IPF, and it has been reported that IPF can be characterized by an increase of alveolar epithelial type II cells (AECII) which are p53 and p21WAF (senescent cell markers) positive [80]. The gene discussed is TP53; the disease is idiopathic pulmonary fibrosis.