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Targeted inhibition of PI3 kinase/mTOR specifically in fibrotic lung fibroblasts suppresses pulmonary fibrosis in experimental models.

Science translational medicine (2020-10-30)
Suraj U Hettiarachchi, Yen-Hsing Li, Jyoti Roy, Fenghua Zhang, Estela Puchulu-Campanella, Spencer D Lindeman, Madduri Srinivasarao, Konstantin Tsoyi, Xiaoliang Liang, Ehab A Ayaub, Cheryl Nickerson-Nutter, Ivan O Rosas, Philip S Low
ABSTRACT

Idiopathic pulmonary fibrosis (IPF) is a lethal disease with an average life expectancy of 3 to 5 years. IPF is characterized by progressive stiffening of the lung parenchyma due to excessive deposition of collagen, leading to gradual failure of gas exchange. Although two therapeutic agents have been approved from the FDA for IPF, they only slow disease progression with little impact on outcome. To develop a more effective therapy, we have exploited the fact that collagen-producing myofibroblasts express a membrane-spanning protein, fibroblast activation protein (FAP), that exhibits limited if any expression on other cell types. Because collagen-producing myofibroblasts are only found in fibrotic tissues, solid tumors, and healing wounds, FAP constitutes an excellent marker for targeted delivery of drugs to tissues undergoing pathologic fibrosis. We demonstrate here that a low-molecular weight FAP ligand can be used to deliver imaging and therapeutic agents selectively to FAP-expressing cells. Because induction of collagen synthesis is associated with phosphatidylinositol 3-kinase (PI3K) activation, we designed a FAP-targeted PI3K inhibitor that selectively targets FAP-expressing human IPF lung fibroblasts and potently inhibited collagen synthesis. Moreover, we showed that administration of the inhibitor in a mouse model of IPF inhibited PI3K activation in fibrotic lungs, suppressed production of hydroxyproline (major building block of collagen), reduced collagen deposition, and increased mouse survival. Collectively, these studies suggest that a FAP-targeted PI3K inhibitor might be promising for treating IPF.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
MTT Formazan, powder
Sigma-Aldrich
Agarose, low gelling temperature, Type VII-A
Sigma-Aldrich
Monoclonal Anti-Collagen Type I antibody produced in mouse, clone COL-1, purified from hybridoma cell culture