Tax induces the expression of genes related to cell cycle progression and apoptosis It was hypothesized that changes in gene expression may provide valuable information about the dysregulation of cell cycle progression induced by Tax and about how Tax might affect the genes relevant to this process. As shown Gefitinib FDA in Figure 2A, of 17 genes related to cell cycle progression that were regulated by Tax, five were down regulated and 12 were upregulated. Genes associated with mitosis, including the mitotic cell cycle checkpoint and mitotic centrosome separation, were repressed by Tax. By contrast, genes upregulated by Tax were functionally classified as genes related to the cell cycle. Many of these genes are also involved in other processes, such as the response to stress, the response to DNA damage, MAP kinase activity, cell proliferation, and negative regulation of the cell cycle.

Genes such as SMAD3, GADD45B, and DUSP1 were also identified as having a role in apoptosis, and IL8 is additionally involved in inflammation and the immune response. The microarray results for genes related to cell cycle progression were validated by performing real time quantitative reverse transcription polymerase chain reac tion on five upregulated genes. The results of the qRT PCR agreed with those obtained by microarray analysis. Next, Tax regulated genes related to apoptosis were identified. The microarray results revealed that 21 pro or anti apoptotic genes were regulated by Tax. Two genes associated with the induction of apoptosis, CARD10 and BCLAF1, were downregulated by Tax.

The majority of the genes upregulated by Tax were involved in apoptosis. Further more, several of these genes also function in the immune response. Interestingly, several highly upregulated genes, such as IER3, TNFAIP3, BIRC3 and IL6, have both pro and anti apoptotic functions. In contrast, the highly upregulated GSK-3 gene, TNFRSF9, is pro apoptotic only. TNF and TNF receptor family genes were also found to be upregulated by Tax in this study. To confirm and extend the results of the microarray experiments, expression of the pro apoptotic and anti apoptotic genes regulated by Tax was measured by qRT PCR using specific primers. Genes upregulated in the microarray were also upregulated in qRT PCR, although there were small differences in the levels measured by the two methods. For example, the expression levels of BIRC3 and IL6 measured by qRT PCR were almost twice that measured by microarray analysis, and the expression level of the apoptosis in ductor TNFRSF9 was more than three times higher by qRT PCR than by microarray. Despite these minor differences, overall gene expression levels measured by qRT PCR were similar to those measured by microarray analysis.