These cells represent a very useful model to study the regulation exerted by the tetraspanin CD9 on cell adhesion molecules of the integrin, immunoglobulin and ADAM families, which are relevant to cancer-related processes such as tumorigenesis and metastasis, because they lack endogenous expression of CD9 but abundantly express the integrin α5β1 [9,10,11,12,13,14]. The gene discussed is CD9; the disease is cancer.