VEGFA and breast cancer: Previous studies reported other examples of stiffness-activated paracrine signaling in several types of cell combinations such as endothelial cell proliferation via cardiomyocyte-derived VEGF (49), osteogenic differentiation of bone marrow-derived mesenchymal stem cells by macrophages (50), macrophage migration and polarization via breast cancer cell-derived colony stimulating factor 1 (38), and inflammatory reaction of macrophages via mesenchymal stem cell-derived tumor necrosis factor-α-stimulated protein 6 (51).