SPARC is a mediator for fenretinide inhibiting cell invasion but not cell motility. (A) Cell motility was analyzed by in vitro wound assay. 4T1 cells were grown on 24-well culture plates overnight and were then left untreated or pretreated with 2.5 μM or 5.0 μM fenretinide for 6 hrs. The confluent cell monolayers were gently scratched with a pipette tip to produce a wound. After wash, the cells were cultured in medium containing different combinations of fenretinide with anti-SPARC antibodies. Quantitative analysis was performed 18 hrs later, as described in the Materials and Methods section. Data shown are means ± SEM. *P < 0.01. (B) In vitro invasion assay was performed using 24-well trans-well units with polycarbonate filters (pore size 8 μm) coated on the upper side with ECMatrix™. Cells pretreated or untreated with fenretinide for 6 hrs were collected, and 5 × 104 cells in 0.3 ml of serum-free medium with different combinations of fenretinide with anti-SPARC antibodies were placed in the upper part of the trans-well unit and allowed to invade for 24 hrs. The lower chamber of the plate was filled with medium containing 10% FBS. The relative invasion of cells cultured in medium without fenretinide and anti-SPARC antibodies was considered as 100%. Results from three independent experiments were expressed as mean ± SEM. *P < 0.01, compared with untreated cells. **P < 0.01, compared with cells treated with fenretinide alone.