Cytokines and growth factors, such as platelet-derived growth factor-B (PDGF-B), epidermal growth factor (EGF), and transforming growth factor-β (TGF-β), play a significant role in this remodeling, released from the sites of the airway wall (Remodeling in Asthma and Chronic Obstructive Lung Disease, n.d.). Here, EGF is linked to asthma.