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 ]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.

Background: A mutation (R298S) in NBCe1 induces a transport defect and causes proximal renal tubular acidosis. Results: The equivalent mutation (R283S) in AE1 disrupted an H-bonding network without affecting functional expression. Conclusion: Arg 283 stabilizes the cytosolic domain but is not essential for transport. Significance: A substrate tunnel in the cytosolic domain is not an essential feature of the SLC4 family of bicarbonate transporters.

Chronic lymphatic leukemia (CLL) is often associated with nephritic syndrome. Effective treatment of CLL by chlorambucil and bendamustine leads to the restoration of renal function. In this contribution, we sought to elucidate the impact of organic anion transporters (OATs) on the uptake of bendamustine and chlorambucil as a probable reason for the superior efficacy of bendamustine over chlorambucil in the treatment of CLL. We examined the effects of structural analogs of p-aminohippurate (PAH), melphalan, chlorambucil, and bendamustine, on OAT1-mediated [(3)H]PAH uptake and OAT3- and OAT4-mediated [(3)H]estrone sulfate (ES) uptake in stably transfected human embryonic kidney-293 cells. Melphalan had no significant inhibitory effect on any OAT, whereas chlorambucil reduced OAT1-, OAT3-, and OAT4-mediated uptake of PAH or ES down to 14.6%, 16.3%, and 66.0% of control, respectively. Bendamustine inhibited only OAT3-mediated ES uptake, which was reduced down to 14.3% of control cells, suggesting that it interacts exclusively with OAT3. The IC50 value for OAT3 was calculated to be 0.8 μM. Real-time PCR experiments demonstrated a high expression of OAT3 in lymphoma cell lines as well as primary CLL cells. OAT3-mediated accumulation of bendamustine was associated with reduced cell proliferation and an increased rate of apoptosis. We conclude that the high efficacy of bendamustine in treating CLL might be partly contributed to the expression of OAT3 in lymphoma cells and the high affinity of bendamustine for this transporter.

fructose-6-phosphate (F6P). To directly determine whether PFK1 is a control point for slow metabolic oscillations, we experimentally manipulated the flux through PFK1 by altering the activity of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB). This bifunctional enzyme, which contains an N-terminal kinase domain (PFK2) and C-terminal phosphatase domain (FBPase2), strongly activates PFK1 activity via conversion of F6P to fructose-2,6-bisphosphate, a potent allosteric activator of PFK1. PFKFB has also been proposed to bind and directly activate glucokinase, further accelerating glycolytic flux. Using optical measurements of NAD(P)H and Ca 2þ , we found that increasing the level of PFK2, but not FBPase2, in islets strongly decreased both the period and amplitude of slow oscillations by ~40%. In many of the PFK2-expressing islets slow oscillations (period >120s) were either converted to fast oscillations (period <120s) or were abolished. These data are consistent with the predictions of the DOM after modification of the model to include regulation of PFK1 by PFKFB, and furthermore support the hypothesis that slow oscillations are driven by oscillations in glycolysis.

Renal cancer cell (RCC) carcinoma is usually chemoresistant. This chemoresistance would be overcome when a cytostatic is applied for which the RCC possess an uptake transporter. Therefore, in the present study we investigated the expression of solute carrier (SLC) transporters in different RCC samples and their ability to interact with chemotherapeutical drugs. We tested five RCC cancer lines as well as normal and tumor tissue for expression of 30 different SLC by RT‐PCR and TaqMan real‐time PCR. In two of five RCC lines, A498 and 7860, we observed a highly significant expression of SLC22A3 (hOCT3). The uptake of organic cation [3H] MPP (4‐methyl‐pyridinium iodide) into these cells and also into hOCT3 stably transfected CHO cells was highly inhibited by irinotekan and vincristine. The Ki values calculated from Dixon plots for irinotekan and vincristine are 1.72±0.45 μM and 17±4.81 μM, respectively. Cytotoxic activities of the selected drugs were tested by the MTT assay on CHO‐OCT3, A498 and ACHN cell lines. The growth of CHO‐OCT3 was inhibited by 20% more with irinotekan and by 50% more with vincristine compared to non transfected CHO cells. Similar results were obtained for A498 and ACHN cells. Thus, our data support the hypothesis that the sensitivity of tumor cells to chemotherapeutical treatment depends on the expression of transporter proteins mediating specific drug accumulation into the target cell.