We evaluated protein expression of the junctional proteins ZO-1, occludin, claudin, and JAM-A from hearts harvested from mice inoculated with BT474 breast cancer cells with or without DOX/TRZ treatment and found similar decreases in junctional protein expression as compared to control mice in the absence of cancer cells or the absence of DOX/TRZ treatment. This evidence concerns the gene TJP1 and breast cancer.