Class comparison and principal components analysis (PCA) among the cell populations. A. Class comparisons show the numbers of differentially expressed genes with > 2 fold change on each comparison. B. PCA mapping for the microarray data. The gene expression data (> 2 fold change) for each cell population are represented by different colors: normal basal cell (NB) gene expression = red; normal differential cell (ND) gene expression = blue; and tumor cell (T) gene expression = green.