The actual role of Vav1 in modulating malignant properties of breast tumor-derived cells was investigated in both BT-474 and MDA-MB-231 cells that were transiently transfected with siRNAs specific for Vav1 (Supplementary Figure 1A) or with a construct expressing the entire human Vav1 protein (Supplementary Figure 1B) and subjected to analysis of their invasion kinetics. The gene discussed is VAV1; the disease is breast neoplasm.