CTSK and idiopathic pulmonary fibrosis: It was found that COL1A1, CTSK, MMP1, MMP7, and SPP1 could be potential biomarkers for poor prognosis of IPF patients because the survival rate of IPF patients with high expression levels of COL1A1, CTSK, MMP1, MMP7, and SPP1 was lower than that of those with low expression levels of the abovementioned genes.