MAPK8 and pulmonary fibrosis: IGF2 is highly expressed in systemic sclerosis and idiopathic pulmonary fibrosis and promotes extracellular matrix deposition by promoting fibronectin and Col1 expression in lung fibroblasts via phosphoinositide 3-kinase (PI3K) and c-Jun N-terminal kinase (JNK) pathways and disrupting the balance between matrix metalloproteinase 3 (MMP3) and tissue inhibitor of metalloproteinase 1/4 (TIMP1/4) 9, 10.