| Budget Amount *help |
¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000)
Fiscal Year 2010: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2009: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2008: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
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| Research Abstract |
Induction of intestinal P-glycoprotein (gene name, MDR1) by rifampicin (RIF) is mediated by transcriptional activation of MDR1 gene by pregnane X receptor (PXR). In this study, we found that endogenous MDR1 mRNA was highly induced by RIF in colon carcinoma cell line (LS180) but not in hepatocarcinoma cell line (HepG2), although PXR is expressed in both cell lines. In addition, we identified cis- and trans-regulatory factors responsible for the intestine-specific induction of MDR1 gene by using these cell lines. Reporter activities of a distal regulatory cluster (-7970/-7011) were markedly increased by RIF in only LS180 cells. The reporter activities in LS180 cells were decreased to the level observed in HepG2 cells by deletion or mutation of the DR4 motifs in the distal regulatory cluster. Moreover, we cloned epithelial-specific ets factor (ESE-3) that was highly expressed in LS180 cells but not in HepG2 cells. Exogenous expression of ESE-3 into HepG2 cells resulted in the transcriptional activation of MDR1 gene by RIF. The reporter activities enhanced by ESE-3 were completely decreased by mutation of the DR4 motifs. A knock-down of ESE-3 by siRNA significantly attenuated the induction of endogenous MDR1 mRNA by RIF in LS180 cells. These results suggest that ESE-3 is a novel trans-regulatory factor responsible for the intestinal induction of MDR1 gene by RIF via the DR4 motifs of MDR1 gene. Moreover, there was a significant correlation between the induction of mRNA and reporter activity for MDR1 by 21 different compounds. Therefore, the induction of mRNA and reporter activity for MDR1 by test compounds in LS180 cells will be possible to predict an intestinal induction of P-glycoprotein.
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