Screening of antibiotics that interact with organic anion-transporting polypeptides 1B1 and 1B3 using fluorescent probes.

Hepatic organic anion transporters OATP1B1 and OATP1B3 are expressed at the sinusoidal membrane of hepatocytes and contribute to the hepatic uptake of a wide variety of clinically used drugs. To identify the antibiotics that interact with the human organic anion transporters OATP1B1 and OATP1B3, we applied a screening system using fluorescent probes. Twenty-six antibiotics with a variety of mechanisms of action were examined. The screening demonstrated that four antibiotics inhibited OATP1B1-mediated transport and 11 antibiotics inhibited OATP1B3-mediated transport in a concentration-dependent manner. Antibiotics that inhibited OATP1B3-mediated transport tended to exhibit higher affinity than those that inhibited OATP1B1-mediated transport. To clarify whether the antibiotics that interacted with OATP1B1 and/or OATP1B3 were substrates for these transporters, an uptake study was performed. Rifampicin and penicillin were transported by both OATP1B1 and OATP1B3. Moreover, OATP1B3 was involved in the transport of ceftriaxone, cefmetazole, cefoperazone, and cefotaxime. Macrolides were not significantly transported by either transporter. In conclusion, the results demonstrated that our system is a useful method for the rapid screening of transporter-antibiotic interaction, and we found novel substrates. Our results indicate that OATP1B1 and/or OATP1B3 contribute to the transport process of some antibiotics, and that drug-drug interactions associated with these transporters could occur after the administration of antibiotics.

Gene expression profiles of colorectal carcinoma in response to neo-adjuvant chemotherapy.

The combination of irinotecan and a fluoropyrimidine has been widely accepted as a treatment for advanced colorectal carcinoma. However, there have been no evaluable data on the feasibility of these combinations. To assess the significance of such combinations, we attempted to identify gene expression patterns in response to irinotecan and two different types of fluoropyrimidines. In 12 patients dispositioned to receive preoperative chemotherapy for colorectal carcinoma, pre-therapy tumor biopsies and final resected specimens were available for analysis. Patients were randomly assigned to receive one of the following four regimens: (I), oral doxifluridine; (II), intravenous infusion of 5-FU; (III), intravenous infusion of irinotecan; (IV), combination of doxifluridine and irinotecan (I+III). To identify genes whose expressions changed, we analyzed the gene expression profiles prior to and after these therapies using an oligonucleotide microarray consisting of 12,000 genes. Next, we focused on the genes that demonstrated similar kinetics of altered expression in all patients in each of the regimens. We identified two proto-oncogenes, nuclear receptor of T-cells (NOT) and c-fos, that were up-regulated in doxifluridine- and irinotecan-related regimens but unchanged in the 5-FU-related regimen. Moreover, group IV tumors showed the highest apoptotic rate and lowest proliferation activity following the combined chemotherapy. These results suggest that doxifluridine has a synergistic impact on the therapeutic effect of irinotecan by up-regulating proto-oncogenes such as NOT and c-fos, and thus justify the use of one of the irinotecan and fluoropyrimidine combinations.