ATF4 and idiopathic interstitial pneumonia: For ER stress gene ATF4, as far as we know, no association with survival was investigated before in other studies, although it was found that ATF4 expression was increased in IPF lung tissue and colocalized with apoptosis markers CHOP and cleaved caspase 3, and encoded by DDIT3 and CASP3, respectively, in alveolar epithelial cells overlying fibroblast foci [9].