fig2

Figure 2. Cytochrome P450 (CYP) activation of cyclophosphamide (CPA). Initial hydroxylation of CPA in the liver by CYP isoforms leads to generation of aldophosphamide, an intermediate which is a substrate for aldehyde dehydrogenases (ALDHs) metabolism. If aldophosphamide enters circulation it is very likely to be detoxified in ALDH-expressing cells including cancer stem cells (CSCs), but not in cancer cells with low or absent ALDH expression