TUBB3 and chronic obstructive pulmonary disease: In contrast to previous results, we found increased expression of biomarker genes for club cells (Secretoglobin Family 1A Member 1, CC10; SCGB1), ciliated cells (Forkhead Box J1; FOXJ1), and pulmonary neuroendocrine cells (tubulin beta 3 class III; TUBB3) in COPD airway epithelium, while no differences were observed for the mucus cell marker MUC5B at the mRNA level (Figure 4B).