Three independent cell lines from each group were randomly CP-358774 EGFR/HER2 inhibitor chosen and subjected to microarray analysis using Affymetrix Human Gene 1.0 ST Array containing 28,869 well-annotated genes. Parental BEAS-2B cells were also included in this study. First, we explored the microarray results by comparing gene FTY720 162359-56-0 expression profiles among Cr_large, Cr_small and untreated control groups. As shown in Figure 4A, a total of 1289 genes in the Cr_small group and 1216 genes in the Cr_large group displayed a greater than 1.5-fold difference as compared with the control group. When the cut-off threshold was increased to a 5.0-fold difference, the numbers decreased to 40 and 47 respectively. Interestingly, when the Cr_small group and the Cr_large group were compared, only 21 genes whose expression changed more than 1.5-fold showed a statistically significant difference between the two groups, but none of these genes exhibited more than a 2.0-fold change, suggesting that cells from the Cr_large and the Cr_small group shared a very similar gene expression pattern. Principal Components Analysis of the microarray data revealed a clear separation among samples from the control group and those from both Cr transformed groups, but not between the Cr_large and the Cr_small groups. The size of the small colonies derived from the Cr treated cells were specifically selected to match the size of the control colonies, indicating that it is the Cr treatment and not the colony size that contributed to the observed differences in gene expression. Since the gene expression pattern from the Cr_large group and the Cr-small group were quite similar, a combined gene list from two groups was generated for further comparison with the untreated control. After elimination of the probe sets that represented unannotated genes, there were a total of 45 genes that changed more than 5-fold in 1 out of 2 groups in the Cr transformed cells compared with the control group, including 23 down-regulated and 22 up-regulated genes. The gene names and fold change of these two groups are listed in Table 1. Among genes up-regulated in chromate transformed cells, there were two major sub-groups. The first group was related to female reproduction, including 5 pregnancy specific beta-1-glycoproteins that were clustered on human chromosome 19. The second group contained three genes required for the assembly of the desmosome complex, a cellto- cell junction important for maintaining the structural integrity of the epithelia. In contrast to the up-regulated genes, the down-regulated gene exhibited more diversification in functional categories. Most of down-regulated genes encoded proteins that were either localized in the plasma membrane or in the extracellular space. For example, a major sub-group of the down-regulated genes encoded proteins associated with a cell surface receptor that mediated cell signaling, including CD24, DDX3Y, BGN, CPE, DNER, HHIP, LPHN 2, and TLR4.