IL-2 activates genes involved in inflammation in peripheral blood cells and in the tumor microenvironment. The profile of genes similarly expressed after 3 h stimulation with IL-2 in vitro and in vivo are shown. The 155 genes that were ≥ 3-fold up- or downregulated in the in vitro time course shown in Figure 2 were sorted. The expression pattern of these genes was compared between the 3-h sample in vitro (left-most column) and in vivo from five patients (one patient was sampled twice as described in Materials and methods). This data set was clustered according to gene-expression profile, and the nodes that demonstrated similar expression profiles in the in vitro and in vivo samples are shown. Fifty-two genes were included in the node that demonstrated upregulation in response to IL-2, and 28 in the node that demonstrated downregulation. The expression of these genes was also analyzed in subsets of leukocytes (orange bar) and FNA samples (blue bar). Leukocyte subsets were separated from PBMC exposed to IL-2 for 3 h and included monocytes (1), CD4 (2), CD8 (3), total lymphocytes (4) and neutrophils (5). The FNAs (10 samples) were obtained from six patients: the first four samples were taken after one dose of IL-2 (patients C.F.1, L.F.1, K.F.1, M.F.1) and the other six samples (G.F.a4, G.F.b4, H.F.4, K.F.4, L.F.4, M.F.4) after four doses of IL-2. Pre-IL-2 samples were labeled with Cy3. Samples obtained after IL-2 administration or exposure to supernatant were labeled with Cy5 and co-hybridized on the cDNA chip with their paired pre-IL-2 sample. Red exemplifies upregulation in test samples compared with the pre-IL-2 administration reference sample and green the opposite. The dendrogram on the left depicts similarity in gene expression between PBMC in vitro and in vivo. Individual genes are shown on the right along with suggested functional signatures.