Masato Ito, Presenter: Nothing to Disclose

Chikao Sugie, Abstract Co-Author: Nothing to Disclose

Hiroyuki Ogino MD, Abstract Co-Author: Nothing to Disclose

Yuta Shibamoto MD, Abstract Co-Author: Nothing to Disclose

Whole-body irradiation at doses higher than 200 mGy may impair host immunity, but low doses of radiation such as those used in diagnostic radiology may activate immune system of the host. The purpose of this study was to investigate the effect of pretreatment with various doses of whole-body irradiation on the tumor cell transplantability in syngeneic mice.

Two murine tumor systems, SCCVII in C3H/He mice and EMT6 in Balb/c mice, were used. Mice were divided into six groups according to pre-irradiation doses: 0, 50, 100, 200, 500, and 1,500 mGy. Whole-body irradiation was carried out using a 210 kVp X-ray machine 6 h before tumor cell inoculation. Control groups were sham-irradiated. Exponentially-growing SCCVII and EMT6 cells were harvested from in vitro culture, and 100 or 1000 cells were inoculated subcutaneously into both hind legs of 8-week-old male C3H/He or Balb/c mice. All mice were observed for 50 days after transplantation. Tumors were judged as grown when palpable nodules exceeded 8 mm.

Following inoculation of 100 SCCVII cells, the tumors grew in 6% of the mice in the control 0-Gy group, 6% in the 50-mGy group, 22% in the 100-mGy group, 16% in the 200-mGy group, 13% in the 500-mGy group, and 47% in the 1,500-mGy group. The transplantability rate in the 1,500-mGy group was significantly higher than the rates in the control 0-Gy group and the 50-mGy one (P < 0.01), but there was no significant difference between the control group and the groups pre-irradiated with 50-500 mGy. Following inoculation of 1,000 SCCVII cells, the transplantability was 38%, 28%, 41%, 38%, 25%, and 69% in the groups receiving 0, 50, 100, 200, 500, and 1,500 Gy, respectively. There was a difference between the 1,500-mGy group and the other groups (P < 0.01), but there was no significant difference between the control group and the groups pre-irradiated with 50-500 mGy. Experiments with EMT6 tumors are still ongoing, but similar results have been obtained so far.

To date, our results have not suggested the positive effect of low-dose irradiation against murine immune system, but up to 500-mGy doses, no deteriorating effects of whole-body irradiation have been observed.

Ito, M, Sugie, C, Ogino, H, Shibamoto, Y, The Effect of Low-dose Whole-body Irradiation on the Tumor Cell Transplantability in Syngeneic Mice.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4413611.html