Hypoxia-induced CTGF expression contributes to pulmonary fibrosis via the mitogen-activated kinase–MEK kinase 1–extracellular-signal-regulated kinase 1–GLI 1–GLI2 and activator protein-1 (MEKK1–MEK1–ERK1–GLI 1–GLI 2 and AP-1) signaling pathways [57]. Here, CCN2 is linked to pulmonary fibrosis.