Fig. 1

Microarray-based expression profiling. a Kinetics of hTERT expression in NB4-LR1 and NB4-LR1^SFD cells treated with ATRA (1 μM). b Volcano plot representation of the differentially expressed genes in a pair wise comparison of NB4-LR1 (left panel) and NB4-LR1^SFD (right panel) cells treated with ATRA (1 μM) for 7 days. The plot indicates -log₁₀ (p-value) for genome-wide genes (Y-axis) plotted against their respective log₂ (fold change) (X-axis). The significant cut-off was set to a p-value of 0.01 (−log₁₀ (p-value) ≥ − 2, horizontal line), the biological cut-off was set to a fold change of ±2 fold (log₂(fold change) < − 1 and > + 1, vertical lines). In ATRA-treated vs non-treated NB4-LR1 cells (left panel) biological and statistically insignificant genes are presented in black. A color was attributed to each gene whether it is significantly up-regulated (red) or down-regulated (blue). A star indicates hTERT and H19 genes in blue and red, respectively. Importantly, in the NB4-LR1^SFD right panel, all genes retained the color defined in the NB4-LR1 left panel. Therefore H19, in red in the NB4-LR1 Volcano panel, remained in red in the NB4-LR1^SFD Volcano panel, even though its expression was repressed. c Heat map of expression profiles of genes that were differentially expressed in NB4-LR1 compared to NB4-LR1^SFD ATRA-treated cells. Red indicates upregulated genes and green indicates downregulated genes d Venn diagrams showing the number of significantly differentially expressed genes (up-regulated and down-regulated) at 7 days of ATRA treatment (1 μM) in NB4-LR1 and NB4-LR1^SFD. Figures in the overlapping sections indicate the number of differentially expressed genes common to multiple pair-wise cell lines comparison. H19 is the only gene to be up-regulated in NB4-LR1 ATRA-treated cells but down-regulated in the NB4-LR1^SFD cells after ATRA treatment. Lists of corresponding genes are presented in Additional file 2 (Table S2)