To investigate which portion of ICOSL is required for responsiveness to OPN-induced migration, OPN pro-migratory activity was assessed in not expressing ICOSL-HeLa cells (cervical cancer cell line), in comparison with HeLa transfected for full-length ICOSL (ICOSLWT), or an intracellular tailless mutant (ICOSLTL), or a mutant composed of the transmembrane and intracellular portions plus a poly-histidine sequence substituting the extracellular portion (ICOSLIC) (Fig. 1f). This evidence concerns the gene SPP1 and cervical carcinoma.