Colon carcinoma cell lines are used widely as screening models for intestinal absorption of drugs. However, the expression of important transport systems and of metabolic enzymes is not completely characterized yet. The expression and inducibility of multidrug resistance gene 1 (MDR1) and cytochrome P450 isoform 3A4 (CYP3A4) was investigated in Caco-2 parental, Caco-2 TC-7 (TC-7) and LS180 cell lines. In the same three cell lines, we investigated the expression of isoforms of the multidrug resistance associated protein family (MRP1-MRP5) and the human pregnane X receptor (hPXR), which may be important for MDR1 and CYP3A4 induction. Cells were treated with rifampicin or 1alpha,25-dihydroxycholecalciferol (1,25(OH)(2)D(3)) for 72 h and the total RNA was extracted. Afterwards reverse transcription real-time polymerase chain reaction (TaqMan) assay was performed to determine the mRNA expression level. We have shown that in LS180 cells, MDR1 and CYP3A4 were inducible with both inducers. In Caco-2 parental and TC-7 cells, CYP3A4 was only inducible with 1,25(OH)(2)D(3). Furthermore, differences were shown in gene expression of several transport proteins (MDR1 and MRP1-MRP5) and CYP3A4 in different human colon carcinoma derived cell lines. hPXR mRNA was expressed in all three cell lines but the amount of mRNA detected was significantly higher in LS180 cells than in Caco-2 and TC-7 cells. We concluded that LS180 cells were a suitable model to study MDR1 and CYP3A4 induction, but for drug transport studies Caco-2 parental and TC-7 cells would be preferred as the more physiological model.