Moreover, suppression of Stat3 activation by the small molecular inhibitor WP1066 inhibited the activation of brain endothelial cells and brain metastasis of breast cancer cells in an animal model, presumably by inhibition of the transcription of Stat3-target genes including VEGFR2 and MMP-9 in both endothelial cells and tumor cells (Fig. 6E). This evidence concerns the gene MMP9 and breast cancer.