CD44 and breast carcinoma: Using polyacrylamide (PA) substrates to mimic the stiff (4020 pa) and soft (120 pa) microenvironments of breast tumors and normal tissues, respectively; in the stiffer matrix, 4T1 and MDA-MB-231 cells expressed higher CSC markers, including CD44, Nanog, CD49, and ALDH and in regions of human breast cancer with low collagen levels (soft region), only 4% of tumor cells expressed CD44 and Integrin-linked kinase (ILK), a crucial mediator used by cells to sense their surroundings as opposed to the regions of BC with high collagen levels, where more than 25% of cells expressed CD44 and ILK.