The spectrum of stem cell-like transcriptional state. The stem cell signature genes stratify a phenotypically diverse database according to pluripotentiality. Each panel shows the entire expression database plotted on the principal coordinates defined by the stem cell signature genes. PC1 is represented on the x-axis of each plot, while PC2 is on the y-axis. In each plot, the pluripotent stem cells (induced pluripotent stem and ES cells) are clustered on the extreme right-hand side (magenta), followed by mesenchymal stem cells (cyan) and immortalized cell lines (blue). Taken together, the panels demonstrate that, across tissue types, this stem cell signature draws a coherent picture of pluripotentiality and differentiation. While the distinction between the pluripotent stem cells and normal tissues represents the predominant signal (PC1) in the data, the contrast in the expression profiles of hematopoietic and neural tissues apparently defines the second strongest signal (PC2). Even so, both tissues' respective malignancies show a common tendency to exhibit greater stem-like activity, as demonstrated by their closer proximity to the pluripotent stem cell cluster. (a-d) Blood (a), breast (b), neural (c) and colon (d) all demonstrate the same enhanced stem-like expression activity among their respective malignancies.