PTK2 and cancer: To test if VASP knockdown suppressed ECM-mediated β1-integrin activation thereby reducing p–FAK levels, we collected cancer spheroids and performed double immunofluorescence (IF) using anti–VASP and Huts-4 antibody selectively recognizing β1-integrin in an active conformation.25 In HCT116, KM12L4, and L3.6 cell lines, VASP and Huts-4 colocalized at the outer cellular layers of the spheroids (IF images of two cell lines are shown in Fig. 3a and another in Suppl.