A route to RNA with an alkylating group at the 5'-triphosphate residue

Expression of human organic cation transporter 3 in kidney carcinoma cell lines increases chemosensitivity to melphalan, irinotecan, and vincristine

Renal cell carcinoma (RCC) is usually chemoresistant. This chemoresistance could be overcome if specific cytostatics are applied for which the RCC expresses an uptake transporter. In the present study, we investigated the expression of solute carrier (SLC) transporters in different RCC lines and their ability to interact with chemotherapeutics. We tested five RCC lines for the expression of different SLCs by reverse transcription-PCR and TaqMan real-time PCR. In two of five RCC lines, A498 and 7860, we observed a highly significant expression of SLC22A3 (hOCT3). Uptake of the organic cation [(3)H]MPP (4-methyl-pyridinium iodide) into these cells and also into hOCT3 stably transfected Chinese hamster ovary (CHO) cells was inhibited by irinotecan, vincristine, and melphalan. The K(i) values [determined from Dixon plots] for irinotecan, vincristine, and melphalan were 1.72 +/- 0.45 micromol/L, 17 +/- 4.81 micromol/L, and 366 +/- 51 micromol/L, respectively. Cytotoxic activities of the selected drugs were tested by [(3)H]thymidine incorporation and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays on CHO-hOCT3, A498 (high expression of hOCT3), and ACHN cell lines (low expression of hOCT3). The growth of CHO-hOCT3 was inhibited by 20% more with irinotecan and by 50% more with vincristine compared with nontransfected CHO cells. Melphalan produced 20% to 30% more inhibition in hOCT3-expressing cells compared with nonexpressing control cells. Similar results were obtained for A498 and ACHN cells. Thus, our data support the hypothesis that the sensitivity of tumor cells to chemotherapeutic treatment depends on the expression of transporter proteins mediating specific drug accumulation into target cells.