Canine hemangiosarcoma cells segregate from non-malignant splenic hematoma cells via their gene expression profile. (A) Hierarchical clustering and heat map of differentially expressed genes in 10 hemangiosarcoma samples versus three splenic hematoma samples. Increasing red intensity indicates increased gene expression and increasing green intensity indicates decreased gene expression as shown in the scale bar. The scale (-1 to +1) reflects variation in intensity from the mean (0) and not fold-change. Fold-change differences are shown in Table S2. (B) Quantitative expression and graphical representation of 2 genes shown in Figure 2A (TIMP-1 and PLZF) and 1 additional gene (FN-1) that were differentially expressed between hemangiosarcoma and splenic hematoma cells. Samples were evaluated for gene expression changes by RT-qPCR, normalized to the endogenous 18 S gene. One sample originating from a dog with splenic hematoma was set to the unitary value (1.0) and used as the calibrator; gene expression is presented as the log fold-change compared to the calibrator. (C) Genes whose expression was significantly different (p <0.05) between hemangiosarcomas and splenic hematomas based on analysis of variance of the complete filtered lists were plotted according to their cytogenetic location on the 38 canine autosomes and the X chromosome. The color intensity for each chromosome (red-over represented to gray to blue-under represented) represents the sum of all changes.