Although many tetraspanins are regarded as key mediators of tumor development and progression, their actions have been connected to at least two classes of cell surface molecules: CD151-associated heterodimeric adhesion receptors for laminins, α3β1, α6β1, and α6β4 integrins, and the CD9/CD81/CD82-binding Ig-G-containing proteins such as EWI-2 and EWI-F. This evidence concerns the gene CD9 and neoplasm.