PIK3CA and breast cancer: BM MSCs also induce dormancy in metastatic BC cells [134] through FGF-2-mediated inhibition of cell cycle progression through TGFβ1 [135], activation of cyclin-dependent kinase inhibitors p21Waf1 [136], p15INK4b [135], and p27Kip1 [135], inhibit motility through stromal FGF-2- and integrin α5β1-mediated RhoA inhibition and actin-rearrangement in the cancer cells [137,138] and induce cytotoxic therapy resistance through phophatidylinositol-3 kinase (PI3K)/AKT [134,139].