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KMID : 0350519960490010445
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Journal of Catholic Medical College
1996 Volume.49 No. 1 p.445 ~ p.452
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The Effects of Low-Dose Whole Body Irradiation on the Growth of Sarcoma- 180 Solid Tumor in Mouse
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Abstract
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Radiation hormesis (i. e. the possible beneficial effect of low dose radiation) has attracted the attention of many researchers. Should radiation hormesis exist at all, it would not only the very interesting academically, but also very important
practically because it would be in contradictio to the fundamental philosophy of present radiation protection policies. A variety of mechanism has been proposed to explain this apparent paradox. Whatever the mechanism, However, the end result was
that
the host appears to be resistant, or partially resistant to the tumor by low dose irradiation. Recently, much evidence is presented to show the potentiation of anti-tumor response by exposing them to single or multiple low dose of ionizing
radiation.
Although it has been known for over 100 years the mechanism responsible for that phenomenon was not clarified.
The purpose of this paper was to show the augmented growth inhibitory effect by low dose whole body irradiation to the radioresistant mouse sarcoma-180 solid tumor and then to discuss possible mechanisms that might explain the enhanced anti-tumor
effects.
One hundred ICR mice weighing 29-30g and aged 6-9 weeks were used for the study. The experiment was designed to include to include groups of normal, tumor control, total body irradiation (TBI) alone, local irradiation (RT) alone and combination
with TBI
and local RT. Malignant tumor was produced in the right thigh of mice by the inoculation of mouse sarcoma-180 tumor cells. Ten cGy of total body irradiation from a 6-MV linear accelerator was administered 3 times per week starting on the day of
inoculation up to total dose of 130 cGy for 30 days. In the groups of local RT alone and combination with TBI and local RT, total 2800 cGy of local RT was delivered to the inoculation site with daily 400 cGy, 3 times per week, starting on the 7th
post-inoculation day. For the evaluation of tumor growth, the longest transverse diameter of right thigh was measured 3 times per week with the perpendicular to the long axis of femur. Complete blood count was performed weekly in each group.
@ES The results obtained were summarized as follows.
@EN 1. Changes of the transverse diameter of right thigh by mouse sarcoma-180 tumor growth in the groups of tumor control, TBI alone, local RT alone and combination of TBI and local RT at the 20th, 30th, 40th post-inoculation day were 1.30±o.26
cm,
1.15±0.33cm, 1.24±0.27 cm, 0.87±0.26cm/ 1.32±0.3cm, 1.19±0.34cm, 1.24±0.34cm, 1.24±0.34cm, o.74±0.24cm/ 1.39±0.34cm, 1.18±0.37cm, 1.31±o.42cm, 0.63±0.14cm respectively.
2. The combination group of TBI and local RT showed prominent growth inhibitory effect on the tumor than other experimental groups (P<0.05) after the cumulative TBI dose of 90 cGy (on the 20th post-inoculation day) and lasted for 20 days
3. 10 cGy of TBI totally up to 130 cGy did not induce changes of peripheral blood profile (hemoglobin, hematocrit, red blood cell, white blood cell, platelet count through the experiment.
In the present experiment, 10 cGy TBI, totally up to 130 cGy, apparently resulted I growth inhibitory effect on the radioresistant mouse sarcoma-180 solid tumor and especially this effect was augmented in case of combination with local RT. This
investigation should be followed further extensive studies before clinical application.
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