Role of PTK7 in cell survival. (A) Effect of growth factor deprivation evaluated in the Baf3 model. After 24 hours of incubation, most of the Baf3 cells transfected with the empty vector (Baf3-vector) are dead, whereas a percentage of Baf3-PTK7 remains alive (Trypan blue dye exclusion assay and luminometric cell viability assay). (B) Western blot using anti-PTK7 antibody. Down-regulation of PTK7 expression in TF1 cells by 2 different shRNAs (shPTK7a and shPTK7c). (C) Reduced cell survival of TF1 cells expressing low amounts of PTK7 in a growth factor deprivation assay. (D-E) Induction of apoptosis by anthracyclines. After 24 hours of incubation, the number of surviving cells was evaluated by a cell viability luminometric assay in the Baf3 (D) and TF1 (E) cell systems. Student t test was used for statistics; all P values < .05.