MR Characterization of the Tumor Microenvironment After Arsenic Trioxide Treatment: Evidence for an Effect on Oxygen Consumption That Radiosensitizes Solid Tumors

Caroline Diepart¹, Oussama Karroum, Julie Magat, Olivier Feron, Bndicte Jordan, Bernard Gallez

As2O3 inhibits mitochondrial respiratory function in human leukemia cells. We hypothesized that As2O3 could also be an important modulator of tumor oxygenation by affecting the oxygen consumption of solid tumors. We observed an increase in tumor pO2 in two tumor models after arsenic treatment using oximetry techniques based on EPR and 19F NMR relaxometry. This effect was explained by a decrease in oxygen consumption of the tumors. Finally, the irradiation of tumors showed a regrowth delay that was significantly increased in arsenic-treated mice. As2O3 is an important modulator of pO2 by decreasing oxygen consumption and enhances the response of tumors to radiotherapy.