RECK: A novel suppressor of malignancy linking oncogenic signaling to extracellular matrix remodeling

RECK was first isolated as a transformation suppressor gene by cDNA expression cloning in a mouse fibroblast cell line transformed by an activated RAS oncogene. Subsequently, reduced expression of RECK in transformed cells and cancer cells were demonstrated. Moreover, in several types of tumors, positive correlation between RECK expression and survival of patients have been noted. RECK encodes a GPI-anchored glycoprotein harboring three protease inhibitor-like domains. The RECK protein regulates at least three members of the matrix metalloproteinase (MMP) family, MMP-2, MMP-9, and MT1-MMP, in vitro or in cultured cells. Restored expression of RECK in cancer cell lines results in strong suppression of invasion, metastasis, and tumor angiogenesis. Mice lacking RECK die in utero with reduced integrity of blood vessels, the neural tube, and mesenchymal tissues. In these mice, MMP activity is elevated, and the amount of collagen type I greatly reduced. The RECK null phenotype is partially rescued (half day delay of death and marked recovery of tissue integrity) by MMP-2 null mutation, demonstrating functional interaction between RECK and MMP-2 in vivo and involvement of other target(s) for RECK in the lethal phenotype. These findings indicate that (i) RECK is an important regulator of extracellular matrix remodeling and that (ii) down-regulation of RECK by oncogenic signaling leads to the excessive activation of MMPs thereby promoting malignant behavior of cancer cells such as invasion, metastasis, and angiogenesis.