Fig. 1.

Slit inhibits SDF1-induced chemotaxis of breast cancer cells. (A) Expression of CXCR4 and Robo1. Primary breast cancer samples (lanes 1–6) as well as cell lines (MDA231 and MDA435, lanes 7 and 8, respectively) were examined by RT-PCR with primers specific for CXCR4 or Robo1. Actin was used as a control. (B) Western blotting was used to detect Robo1 protein in MDA231 and MDA435 cells (lanes 1 and 2, respectively). A band of ≈210 kDa (the full-length Robo1 protein) and a lower band (a possible proteolytic product) were detected in these cells. (C and D) Slit2 inhibits cell migration in a Robo-dependent manner. In C, MDA231 and MDA435 cells were tested in a transwell migration assay in the presence of the vehicle control, SDF1 (10 nM), Slit2 (+, 30 pM; ++, 100 pM), or combinations. The cell migration index was measured as the ratio of cells that migrated into the lower well in the test group to those in the control group with only vehicle treatment. In D, similar transwell experiments were carried out by using MDA231 cells in the presence or absence of RoboN (10 nM). In C and D, data are presented as the mean ± SEM, representing the results from three independent experiments, and the differences between the marked groups are statistically significant (**, P < 0.01; ***, P < 0.001 by Mann–Whitney test).