ELN and idiopathic pulmonary fibrosis: Central to this cluster are collagen genes, as well as other key ECM components such as lumican (LUM; a keratan sulfate proteoglycan which is normally diffusely present in peripheral lung tissue, mainly in vessel walls [21]), tenascin C (TNC; a proteoglycan expressed in the lung parenchyma in disease states such as asthma, idiopathic pulmonary fibrosis and acute lung injury [22], where it may play a role in modulating the influx of inflammatory cells) and elastin (ELN).