At-RA treatment blocks VLA-4-dependent cell adhesion. The effects of at-RA in VLA-4-dependent adhesion was estimated performing adhesion assays to VCAM-1. of K562-α4 treated with 50, 100 and 500 nM of at-RA during 24, 48 and 72 h. Cell adhesion was quantified in a fluorescence analyser previous labelling the cells with BCECF-AM. Data are presented as mean ± SD of triplicate of samples from three independent experiments. *P < 0.001 vs. non-treated K562-α4 cells.