Matrix stiffness regulated this effect by regulating the PI3K/Akt pathway rather than Smad to switch the effect of TGFβ, which induced breast cell apoptosis in the soft matrix but EMT in the stiff matrix.[9b] Breast cancer cells cultured on aligned fibers showed upregulated expression of metastasis‐related EMT genes, and elongated spindle‐like morphology rather than flat stellar shape in messy fibers. This evidence concerns the gene TGFB1 and breast cancer.