Integrins are known to function as cell-adhesion receptors that mediate interactions of cells with the extracellular matrix.[32] Several β-integrins including β1, β3, β4, and β5 have been linked to invasion, EMT, and cancer stem cell biology.[33], [34], [35] Their downstream pathways or molecules are different and include FAK, Src kinase, integrin-linked kinase, PI3K/Akt, and mitogen activated protein kinase.[36] Integrins bind FAK and activate FAK phosphorylation at several Tyr residues including Y397, Y861, and Y925, thereby contributing to focal adhesion. This evidence concerns the gene PTK2 and cancer.