TITLE:
A Dual-radiolabel Marker Quantifies Decrease in HT29 Xenograft Hypoxia Induced by Mild Temperature Hyperthermia
AUTHORS:
Mutian Zhang, Xiao-Feng Li, Makiko Suehiro, Zhihong Zhao, David Gagne, John Pizzonia, Zhigang Zhang, Gloria Li, C. Clifton Ling, John L. Humm
KEYWORDS:
Digital Autoradiography; IAZGP; Imaging Plate; Mild Temperature Hyperthermia; Tumor Hypoxi
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.1 No.2,
August
20,
2012
ABSTRACT: Purpose: In this project, we developed novel methods to quantify changes in tumor hypoxia following a mild tempera-ture hyperthermia (MTH) treatment in rat HT29 human colon adenocarcinoma xenograft. Materials and Methods: An exogenous hypoxia marker (IAZGP) was labeled with two radioisotopes of iodine (131I and 123I, respectively) to form two distinct tracers. The two tracers were injected into HT29-bearing nude rats 4-hour before and immediately following 41.5℃, 45-minute mild hyperthermia treatment. The distributions of the two hypoxia tracers were obtained by performing digital autoradiography on tumor sections, and image processing resulted in quantitative information at 50 μm pixel size. Results: Following the hyperthermia treatment, there was a remarkable decrease in hypoxia tracer binding. The average whole tumor hypoxia tracer targeted fraction in five animals changed from 30.3% ± 9.7% to 13.0% ± 5.3% after the hyperthermia treatment (P = 0.001). Detailed pixelby-pixel analysis of the image data revealed a decline in hypoxia tracer uptake after hyperthermia in most regions. However, there was concomitant emergence of some new regions of hypoxia identified by increased tracer uptake. In the control group, the overall hypoxia tracer targeted fraction remained almost constant, with some hypoxic tracer redistribution (putative acute hypoxia) observed. Conclusion: Reoxygenation occurred in the rat HT29 xenograft following MTH treatment. This was evident with preponderance of decreased hypoxia specific tracer uptake on tumor sections. Our methodology might be a useful tool in hypoxia study.