Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) plays an essential role in angiogenesis and development. It is differentially expressed in tumor cell lines, but its role in carcinogenesis is largely unknown. We demonstrate here that noninvasive human lung cancer cells become invasive when COUP-TFII was expressed. The expression of extracellular matrix degrading proteinases, such as matrix metalloproteinase 2 and urokinase-type plasminogen activator, was up-regulated in these cells. This finding was confirmed by transduction of different human lung cancer cell lines with COUP-TFII protein and also by using antisense expression. We observed disorganization of actin filaments and focal adhesion kinase phosphorylation in COUP-TFII-transfected human lung cancer cells in addition to the increase in extracellular metalloproteinase activity. These results suggest that COUP-TFII may be considered as a new target for anticancer therapies.