TIMP1 and cancer: The expression of Timp1, an inhibitor of matrix metalloproteinases that promotes mitogenesis and angiogenesis, and previously found up-regulated in thyroid cancer [28] and of Steap1, a cell surface protein found over-expressed in various cancers [29] was already increased (although at a lower level) in Ptenthyr−/− mice, suggesting a direct role of PI3K signaling in their regulation.