Transformation of MSC induces transcriptional down-regulation of antioxidant genes. (A) The enrichment of genes involved in ROS metabolism was addressed by GSEA using gene expression microarray data from different paired cell lines (q values from different analysis are shown). The Y-axis plots the enrichment score and the X-axis is the rank of genes within the ROS list from up-regulated to down-regulated. The barcode below shows the rank position of individual ROS genes within the list. Arrow indicates ROS genes identified as the core-enriched genes by GSEA when MSC0 was compared with tMSC. Heatmap at the right panel shows relative expression of genes found within this core-enriched gene region from cell lines MSC0 and tMSC, where multiple probes per gene were averaged. Results were obtained by performing array experiments in triplicate (columns). Red indicates up-regulation, and blue down-regulation from the mean. Arrowhead indicates Nrf2 (NFE2L2). (B) GSEA shows the enrichment of ARE-containing genes for different MSC paired lines. (C) Relative mRNA expression of selected genes involved in antioxidant response measured by qRT-PCR. These genes include Nrf2, NAD(P)H dehydrogenase quinone 1 (NQO1), heme oxygenase 1 (HO-1), glutathione S-transferase M2 (GSTM2), glucose-6-phosphate dehydrogenase (G6PD), catalase (CAT), glutathione peroxidase 7 (GPX7) and peroxiredoxin 5 (PRDX5). (D) Relative mRNA expression of genes involved in glutathione biosynthesis (GCLC, GCLM, and GSS) and homeostasis (GSR). (E) Levels of intracellular reduced glutathione (GSH) presented as relative luciferase units per microgram of protein x105. The result shows the average of 2 experiments performed with at least 4 replicates each. P values are *P < 0.05, **P < 0.005 and ***P < 0.0005.