Tumor Uptake of Copper-Diacetyl-Bis(N4- Methylthiosemicarbazone): Effect of Changes in Tissue Oxygenation

Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Journal of Nuclear Medicine (Impact Factor: 5.56). 05/2001; 42(4).

ABSTRACT We showed previously that, in vitro, copper-diacetyl-bis(N4- methylthiosemicarbazone) (Cu-ATSM) uptake is dependent on the oxygen concentration (pO2). We also showed that, in vivo, Cu-ATSM uptake is heterogeneous in animal tumors known to contain hypoxic fractions. This study was undertaken to confirm the pO2 dependence of this selective uptake in vivo by corre- lating Cu-ATSM uptake with measured tumor pO2. Methods: Experiments were performed with the 9L gliosarcoma rat model using a needle oxygen electrode to measure tissue pO2. Using PET and electronic autoradiography, Cu-ATSM uptake was measured in tumor tissue under various pO2 levels. The oxygen concentration within implanted tumors was manipulated by chemical means or by altering the inhaled oxygen content. Results: A good correlation between low pO2 and high Cu- ATSM accumulation was observed. Hydralazine administration in animals caused a decrease in the average tumor pO2 from 28.61 6 8.74 mm Hg to 20.81 6 7.54 mm Hg in untreated control animals breathing atmospheric oxygen. It also caused the tumor uptake of Cu-ATSM to increase by 35%. Conversely, in animals breathing 100% oxygen, the average tumor pO2 increased to 45.88 615.9 mm Hg, and the tumor uptake of Cu-ATSM decreased to 48% of that of the control animals. PET of animals treated in a similar fashion yielded time-activity curves showing significantly higher retention of the tracer in hypoxic tissues than in oxygenated tissues. Conclusion: These data confirm that Cu-ATSM uptake in tissues in vivo is depen- dent on the tissue pO2, and that significantly greater uptake and retention occur in hypoxic tumor tissue. Therefore, the possible use of Cu-ATSM PET as a prognostic indicator in the manage- ment of cancer is further validated.

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