Additionally, the low phosphatase activity of PTEN results in inhibition of downstream transcription factor forkhead box O3a (FoxO3a) via phosphorylation at Ser253, which reduces the expression levels of CDK inhibitor p27 and promoted cell cycle arrest in IPF-derived fibroblasts cultured on polymerized collagen [107]. Here, FOXO3 is linked to idiopathic pulmonary fibrosis.