Role of PTK7 in cell migration. (A) Measurement of chemotaxis (Transwell system) of Baf3 cells expressing (Baf3-PTK7) or not (Baf3-vector) PTK7 in the presence of SFM, 20% FCS, or SDF-1. After 4 hours, the cell migration ratio was evaluated using a luminometric assay. Expression of PTK7 increases cell migration in both SFM and FCS conditions. Cell migration induced by SDF-1 was not statistically different between the 2 cell lines. (B) Down-regulation of PTK7 by 2 different shRNAs (ie, shPTK7a and shPTK7c) in TF1 cells stimulated with SCF (250 ng/mL). Protein extracts were revealed by anti-PTK7 or antitubulin antibodies. (C) Decreased expression of PTK7 impairs cell migration. Reexpression of a PTK7 mutant resistant to shPTK7c restores cell migration (B-C). (D) Production of a soluble recombinant PTK7-Fc protein that is recognized by anti-IgG1 and anti-PTK7 antibodies by Western blot. As a control, recombinant Nectin4-Fc is only recognized by anti-IgG1 antibody. (E) Measurement of cell migration of a PTK7⁺ cell line (TF1) and PTK7⁺ (+) or PTK7⁻ (−) primary AML blasts isolated from patients. Cells were incubated in the presence of 5 μg/mL of soluble protein and stimulated by SCF as in panel B. Cell migration was measured in a Transwell system. Student t test was used for statistics; all P values < .05.