CXCL12 induced the chemoinvasion of breast cancer cells. Cells were seeded into the upper compartments of Matrigel Invasion Chambers as described in Materials and Methods. Uncoated or Matrigel-coated membranes separated the upper from the lower compartment containing the indicated concentrations of CXCL12. Cells were treated with DETA NONOate with or without L-NAME, and two days later, cells that had migrated to the bottom of the membrane were stained and counted. The percentage of invasive cells (% Invasion) was calculated as the number of cells penetrating the Matrigel-coated membranes divided by the number penetrating the uncoated membranes. Determinations were performed in triplicate and expressed as the mean of three experiments ± SD. * indicates significant difference (p < 0.05) from L-NAME-treated cells.