CLDN2 and breast carcinoma: To verify the effectiveness of our leaf-vein microfluidic multi-organ tropism model, based on reported molecular mechanisms regulating breast cancer metastasis, we constructed three overexpressed MDA-MB-231 cell lines: CXCR4 OE 231, claudin-2 OE 231, and Linc-ZNF469–3 OE 231.