In conclusion, we show that the PPARα/HIF1α interplay, triggered in breast CSCs by the tumor associated fibroblast secreted TGFβ, engenders the expression of two acknowledged breast CSCs regulatory genes (IL6 and SLUG), as well as up-regulates two less characterized regulators of breast CSCs, namely CAIX and ApoE (Figure 9). This evidence concerns the gene APOE and neoplasm.