Total RNA was isolated from theses samples and used to prepare cRNA probes for hybridization with Affymetrix GeneChip Rat 230 2.0 arrays (Figure 3). The hybridized microarrays were then scanned and the signals acquired (Figure 4). At the 12th week, liver cirrhosis occurred in 10 of 10 rats, so we took the HM781-36B clinical trial pooled cirrhotic tissues from the 10 rats for the microarrays. At the 14th week, dysplastic nodules occurred only in the livers of 2/10 rats, so we took the pooled dysplastic nodules from the two rats for the microarrays. At the 16th week, early tumor nodules occurred

in the liver of 8/10 rats, so we took the pooled tumor nodules from the eight rats for the microarrays. At the 20th week, tumor nodules occurred in all of the ten HMPL-504 supplier rats(10/10), but lung metastasis only occurred in the two of them, so we took the pooled

tumor nodules in the liver from the two rats with lung metastasis for the microarrays. We used the pooled liver tissues from the control rats killed at the 12th, 14th, 16th and the 20th week for the microarrays. The decision to pool the mRNA from the rat livers was made in order to obtain a representative analysis of gene expression changes across more than one animal. Figure 3 Total RNA isolated from the liver tissues of the rats was identified by agar electrophoresis. (A) from normal rats; (B-E) from DEN-treated rats: cirrhosis tissue at 12th week (B), dysplastic nodules at the 14th week (C), early cancerous nodules at the 16th week (D), cancerous nodules with lung metastasis selleck at the 20th week (E). Figure 4 Scatter plot of gene expression comparisons between the normal rats and DEN-exposured rats. Each point represents a single gene or EST. x-axis:

control (from liver tissue of normal rat); y-axis: liver tissue from DEN- treated rat at 12th week (A); at 14th week (B); at 16th week (C); at 20th week (D). The red points represent Progesterone ‘present’ states both in control and DEN exposed; blue points represent ‘no present’ in either of control and DEN-exposed; yellow points represent ‘absent’ states both in control and DEN-exposed. Analysis of the differential expression genes The differential expression genes of cirrhotic tissue, dysplastic nodules, early tumors nodules and tumor nodules from rats with lung metastasis compared with the tissue from normal rats were screened and to determine the upregulated and downregulated DEGs. The results are shown in Table 1. Table 1 Number of differential expression genes (DEGs) of liver tissues from DEN-treated rats compared with control. DEGs 12th week 14th week 16th week 20th week Up-regulated DEGs 681 857 1223 999 Down-regulated DEGs 687 732 1016 906 Total 1368 1589 2239 1905 NOTE: The words ’12th week, 14th week, 16th week, 20th week’ in the table indicate the cirrhosis tissue, dysplastic nodules, early cancerous nodules and cancerous nodules with metastasis, respectively.