Using three different experimental systems, including three-dimensional (3D) mixed cell spheroid co-cultures of mammary epithelial and fibroblast cells, a 3D organotypic culture model of human skin tumors, and a mouse xenograft model of human breast cancer, we recently reported that Tiam1 deficiency in tumor-associated fibroblasts induces increased invasion of the associated epithelial or tumor cells and increased tumor metastasis [28]. This evidence concerns the gene TIAM1 and breast cancer.