Chiho Komoto

Gene expression profiles of ABC transporters and cytochrome P450 3A in Caco-2 and human colorectal cancer cell lines.

AbstractPurpose. The mRNA levels of MDR1 (P-glycoprotein), multidrug resistance-associated proteins (MRP1, MRP2), cytochrome P450 3A (CYP3A) and villin in human colorectal cell lines (HCT-15, LoVo, DLD-1, HCT-116 and SW620) were quantitatively compared with those in Caco-2 cells. Methods. The mRNA levels were determined by real time quantitative polymerase chain reaction and expressed as the relative concentrations of MDR1 mRNA to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA. Results. MDR1 mRNA was expressed in HCT-15 LoVo and DLD-1 cells at similar or lower level to Caco-2. The expression of MRP1 mRNA in the cell lines tested was comparable with Caco-2. MRP2 mRNA was detected only in HCT-116 and SW620 at significantly lower level than Caco-2. CYP3A mRNA was detected in HCT-15, LoVo, DLD-1 and SW620 at similar level to Caco-2. Conclusions. HCT-15 LoVo and DLD-1 cells express proteins important for regulating the intestinal absorption of drugs, i.e., MDR1, MRP1 and CYP3A, whereas HCT-116 and SW620 cells were not acceptable for evaluation of absorption properties of drug candidates.

Haloperidol is an inhibitor but not substrate for MDR1/P-glycoprotein

The involvement of the multidrug resistant transporter MDR1/P‐glycoprotein in the penetration of haloperidol into the brain and absorption in the intestine was investigated to examine its role in inter/intra‐individual variability, using the porcine kidney epithelial cell line LLC‐PK1 and its MDR1‐overexpressing transfectant, LLC‐GA5‐COL150. The inhibitory effect of haloperidol on other MDR1 substrates was also investigated in terms of the optimization of haloperidol‐based pharmacotherapy. The transepithelial transport of [3H]haloperidol did not differ between the two cell lines, and vinblastine, a typical MDR1 substrate, had no effect on the transport, suggesting that haloperidol is not a substrate for MDR1, and it is unlikely that MDR function affects haloperidol absorption and brain distribution, and thereby the response to haloperidol. However, haloperidol was found to have an inhibitory effect on the MDR1‐mediated transport of [3H]digoxin and [3H]vinblastine with an IC50 value of 7.84 ± 0.76 and 3.60 ± 0.64 μM, respectively, suggesting that the intestinal absorption, not distribution into the brain, of MDR1 substrate drugs could be altered by the co‐administration of haloperidol in the clinical setting, although further clinical studies are needed.