低剂量全身照射增强荷瘤小鼠局部大剂量照射的抑瘤作用

本实验采用Ｃ５７ＢＬ／６小鼠皮下接种Ｌｅｗｉｓ肺癌细胞为实验肿瘤模型。当荷瘤小鼠肿瘤局部１０ｍＧｙＸ射线照射前２４ｈ接受７５ｍＧｙ全身照射时，发现对肿瘤生长的抑制作用比单纯局部照射时增强。将７５ｍＧｙ全身照射或假照射的荷瘤小鼠脾细胞与Ｌｅｗｉｓ肺癌细胞混合接种于正常小鼠皮下进行Ｗｉｎｎ试验，观察到照射小鼠脾细胞与癌细胞混合接种的小鼠肿瘤发生率低于假照射小鼠脾细胞与癌细胞混合接种的小鼠，后者肿瘤出现的时间亦较早。这些差别在接种效靶细胞比５０：１的小鼠中更为明显。提示这种抑瘤作用的增强可能是由于低剂量Ｘ射线全身照射后促进荷瘤机体免疫反应所致。＊Ｐ＜０．００１ｖｓ１０Ｇｙｉｒｒａｄ．１６．７％，后者８０％。Ｆｉｇ．２Ｅｆｆｅｃｔｓｏｆｓｐｌｅｎｉｃｃｅｌｌｓｏｆｔｕｍｏｒ─ｂｅａｒ－ｉｎｇｍｉｃｅｆｏｌｌｏｗｉｎｇ７５ｍＧｙＷＢＩｏｎｔｕ－ｍｏｒｉｎｃｉｄｅｎｃｅｉｎａＷｉｎｎａｓｓａｙｔｕｍｏｒｃｅｌｌｏｎｌｙＳｐｌｅｎｏｃｙｔｅｆｒｏｍＴＢＭＳｐｌｅｎｏｃｙｔｅｆｒｏｍＴＢＭＩＴＢＭＴｕｍｏｒ─ｂｅａｒｉｎｇｍｉｃｅＴＢＭＩ：Ｔｍｕｏｒ─ｂｅａｒｉｎｇｍｉｃｅｉｒｒａｄ．＊Ｎｏｔｕ－ｍｏｒｄｅｖｃｌｏｐｉｎｇ?

Whole──body low dose irradiation enhances the tumor suppressive effect of high dose local irradiation given to the tumor site

C57BL/6 mice implanted subcutaneously with Lewis lung carcinoma cells were uscd asa model in the present report. When the tumor bearing mice were given whole body irradiation(WBI) with 75 mGy X rays 24 h before a local irradiation with 10 Gy X rays to the tumor site,thesuppressive effect on tumor growth was found to be greater than that following local irradiation with10 Gy alone. A Winn assay was performed with subcutaneous implantation into normal mice of a mix-ture of Lewis lung cancer cells and splenocytes from tumor bearing mice with or without WBI with75 mGy. It was observed that the tumor growth rate was lower in the animals implanted with a mix-ture of cancer cells with splenocytes from low dose irradiated tumor bearing mice than in those im-planted with a mixture of cancer cells with splenocytes from sham irradiated tumor bearing miceand the time of appearance of the tumor was found to be earlier in the latter group,the difference be-ing more marked at an E:T ratio of 50:1.These results implicate that the increased tumor suppres-sive effect miglit be due to a potentiation of immunological reactions after WBI with low dose X rays.