MUC1 extracellular domain contains the KL6 epitope domain, which can be shed into the lumen by proteolytic cleavage [14] and it has been observed increased in serum, broncho-alveolar lavage fluid (BALF) and lung tissue of IPF patients [13], serving as a potential biomarker in IPF disease [15]. The gene discussed is MUC1; the disease is idiopathic pulmonary fibrosis.