Loss of E-cadherin-mediated cell–cell adhesion and expression of proteolytic enzymes characterize the transition from benign lesions to invasive, metastatic tumor, a rate-limiting step in the progression from adenoma to carcinoma in vivo. A soluble E-cadherin fragment found recently in the serum and urine of cancer patients has been shown to disrupt cell–cell adhe-sion and to drive cell invasion in a dominant-interfering manner.