Results Parametric geneset enrichment analysis (PGSEA). Gene expression profiles derived from AK (n = 14) and SCC (n = 15) samples were compared with gene expression profiles derived from normal skin (NS, n = 13) samples and analyzed using PGSEA for the gene lists that contain genes responsive to oncogenes or for indicated pathways. The genes that show increased expression to NS for each pathway are indicated with ‘up’. List of genes that show decreased expression relative to control cells for each pathway are indicated with ‘down’ . The resulting t-statistic for each gene list was plotted (−10 < t < 10), p < 0.005); red squares represent significant number of genes in the list with increased expression in tumor samples (AK or SCC) relative to NS; blue squares represent a significant number of genes in each list with decreased expression.