MTOR and idiopathic pulmonary fibrosis: During maturation of type I collagen, soluble pro-collagen is processed to its insoluble form by carboxy and amino terminal endopeptidase cleavage, generating peptide fragments such as the N-terminal P1NP which can be monitored as a sensitive biomarker of collagen formation.25 Our studies revealed that P1NP was released from ex-vivo IPF precision-cut lung slices for up to 5 days in culture and further that PI3K/mTOR inhibition attenuated this process.