In addition, studies in HER2-positive BC mouse models have uncovered a novel premalignant mechanism, that is, in precancerous lesions, monocyte chemotactic protein-1 (CCL2) produced by cancer cells and myeloid cells attracts CD206+/Tie2+ macrophages and induces the upregulation of WNT-1 to stimulate Wnt signaling. This evidence concerns the gene ERBB2 and breast cancer.