Troglitazone Stimulates Cancer Cell Uptake of 18F-FDG by Suppressing Mitochondrial Respiration and Augments Sensitivity to Glucose Restriction.

Abstract

We evaluated how troglitazone influences cancer cell glucose metabolism and uptake of (18)F-FDG, and we investigated its molecular mechanism and relation to the drug's anticancer effect. Human T47D breast and HCT116 colon cancer cells that had been treated with troglitazone were measured for (18)F-FDG uptake, lactate release, oxygen consumption rate, mitochondrial membrane potential, and intracellular reactive oxygen species. Viable cell content was measured by sulforhodamine-B assays. Treatment with 20 μM troglitazone for 1 h acutely increased (18)F-FDG uptake in multiple breast cancer cell lines, whereas HCT116 cells showed a delayed reaction. In T47D cells, the response occurred in a dose-dependent (threefold increase by 40 μΜ) manner independent of peroxisome proliferator-activated receptor-γ and was accompanied by a twofold increase of lactate production, consistent with enhanced glycolytic flux. Troglitazone-treated cells showed severe reductions of the oxygen consumption rate, indicating suppression of mitochondrial respiration, which was accompanied by significantly decreased mitochondrial membrane potential and increased concentration of reactive oxygen species. Troglitazone dose-dependently reduced T47D and HCT116 cell content, which was significantly potentiated by restriction of glucose availability. In T47D cells, cell reduction closely correlated with the magnitude of increase in relative (18)F-FDG uptake (r = 0.821, P = 0.001). Troglitazone stimulates cancer cell uptake of (18)F-FDG through a shift of metabolism toward glycolytic flux, likely as an adaptive response to impaired mitochondrial oxidative respiration.