PTEN and breast cancer: Increased ECM stiffness mediates phenotypic transition of cancer stem into more metastatic forms in colorectal cancer (Tan et al., 2019) and breast cancer (Seewaldt, 2014) by reducing phosphatase and tensin homolog (PTEN) expression, thereby upregulating the phosphoinositide 3-kinase (PIP3)-AKT pathway (Mouw et al., 2014).