ATF6B and chronic obstructive pulmonary disease: ATF6B was implicated in the unfolded protein response (UPR) pathway during endoplasmic reticulum (ER) stress following cigarette smoke, and may contribute to lung inflammation in patients with COPD [49], while integrins were found to be involved in COPD through the mitogen-activated protein kinase (MAPK) pathway [50, 51].