For ER stress marker GRP78/BiP encoded by HSPA5, conflicting results have been found; in one study elevated GRP94 and CHOP, encoded by HSP90B1 and DDIT3, respectively, and reduced expression of GRP78 were observed in alveolar epithelial cells type 2 (AEC2s) from IPF lung tissue compared to AEC2s from normal donors [36], whereas in another study increased GRP78/BiP expression was observed in IPF lung tissue compared to control lung tissue. Here, DDIT3 is linked to idiopathic pulmonary fibrosis.