Fig 2: Principal component analysis (PCA) discriminates tumor-initiating cells (TICs) from cancer cells based on gene expression of the selected iron metabolism-related genes (Aco1, Abcb10, Cybrd1, Epas1, Glrx5, Heph, Hfe, Ireb2, Qsox1 and Tfrc)Principal component analysis (PCA) based on selected iron metabolism-related genes was run on malignant breast MCF-7, BT-474, T-47D, ZR-75-30 and malignant prostate DU-145 as well as LNCaP cell lines using the GenEx software which was also used for plotting the PCA. White squares depict control conditions, grey show agar conditions, blue boxes show sphere conditions and red boxes show TAMR cells. Individual clusters were also highlighted with corresponding lines using identical colors.

Fig 3: Putative scheme depicting changes in iron metabolism of tumor-initiating cells (TICs)TICs show higher levels of labile iron pool (LIP) and subsequently higher reactive oxygen species (ROS) which in connection with lower Fes cluster biogenesis (lower expression of ABCB10 and GLRX5) leading to accumulation of iron in mitochondria and possibly affecting genome stability and increasing plasticity of these cells. Alterations in the FeS cluster assembly lead to reduced activity of ACO1/IRP1 as well as mitochondrial respiratory complex I. The IRP binding activity of ACO1 is elevated resulting in higher TFRC and lower ferritin levels. Furthermore, TICs show an increase in the protein level of of EPAS1/ HIF2A connected with higher iron uptake (CYBRD1, TFRC) as well as with the extracellular matrix remodelling and redox balance equilibrium via the expression of QSOX1. On the other hand, reduced glutathione (GSH) is lower in TICs and these cells seem to be in a more pro-oxidative state and contain lower protein levels of IREB2/IRP2 likely reflecting increased LIP.