Mosaic Overgrowth with Fibroadipose Hyperplasia is Caused by Somatic Activating Mutations in PIK3CA

摘要

The phosphatidylinositol-3-kinase (PI3K)/AKT signaling pathway is critical for cellular growth and metabolism. Correspondingly, loss of function of PTEN, a negative regulator of PI3K, or activating mutations in AKT1, AKT2, or AKT3 have been found in distinct disorders featuring overgrowth or hypoglycemia. We performed exome sequencing of DNA from unaffected and affected cells of a patient with an unclassified syndrome of congenital, progressive segmental overgrowth of fibrous and adipose tissue and bone and identified the cancer-associated p.His1047Leu mutation in PIK3CA, which encodes the p110α catalytic subunit of PI3K, only in affected cells. Sequencing of PIK3CA in 10 further patients with overlapping syndromes identified either p.His1047Leu or a second cancer-associated mutation, p.His1047Arg, in 9 cases. Affected dermal fibroblasts showed enhanced basal and EGF-stimulated phosphatidylinositol-3,4,5-trisphosphate (PIP3) generation and concomitant activation of downstream signaling. Our findings characterize a distinct overgrowth syndrome, biochemically demonstrate activation of PI3K signaling and thereby identify a rational therapeutic target.