Individualization of Radiotherapy by Micronucleus Test

肿瘤细胞放射敏感性的微小差异对肿瘤的最终控制率有很大影响。因此，理想的做法是在放疗开始前检查肿瘤细胞和正常组织的放射敏感性，并改变每个患者的剂量分数和总剂量。我们检测了14例不同类型食管癌手术标本的放射敏感性。肿瘤细胞悬液培养数天后，用50KVPX射线照射。然后加入细胞松弛素B继续培养48或72小时，以鉴定照射后进入有丝分裂相的细胞。细胞松弛素B在不干扰核分裂的情况下抑制细胞质分裂。因此，这种细胞很容易被识别出来。固定肿瘤细胞，制备微核试验用微载玻片。用碘化丙啶染色后在荧光显微镜下观察微核，用线性-二次模型分析微核的剂量效应曲线。14例食道癌的α/β值从1.5到无限大。与贝塔值相比，不同肿瘤的阿尔法值差异更大。氧增强比(OERs)也有很大的范围(1.3-2.7)，特别是在低辐射剂量范围(0-2Gy.为了检测个体患者正常组织放射敏感性的差异，我们研究了3种不同品系的小鼠(Balb/C，A/J，C3H/He)的放射敏感性差异。微核试验测定淋巴细胞辐射敏感性与成纤维细胞、肠腺细胞辐射敏感性的相关性3种不同品系小鼠的淋巴细胞对辐射的敏感性顺序与成纤维细胞和肠腺细胞的顺序一致。

A small difference of the radiosensitivity of tumor cells asserts great influence on the final control rate of tumors. Therefore, it is ideal that radiosensitivities of tumor cells and normal tissues could be examined before the start of radiotherapy, and dose fraction, total dose could be changed on each patient. We have examined the radiosensitivity in 14 different esophageal cancers cultured from surgical specimens The tumor cell suspensions were cultured and several days after, 50 KVp xrays were irradiated. Thereafter the culture was continued for 48 or 72 hours with cytochalasin B. This agent was added to identify the cells passed through mitotic phase after irradiation. Cytochalasin B inhibits cytoplasmic cleavage without interfering nuclear division. Therefore, such cells could be easily identified. The tumor cells were fixed and microslides for micronucleus assay were prepared. The micronuclei were observed by fluorescence microscope after staining with propidium iodide.The dose response curves of micronuclei were analyzed according to linear-quadratic model. The alpha/beta values among 14 esophageal cancers ranged from 1.5 to unlimited size. Alpha values differed more largely from tumor to tumor compared with beta values. Oxygen enhancement ratios (OERs) also ha wide range (1.3-2.7) especially in low radiation dose range (0-2 Gy). The differences in tumor cell radiosensitivity were clearly demonstrated.To examine the difference of normal tissue radiosensitivity in individual patient, we have studied that in 3 different strain of mice (Balb/C, A/J, C3H/He). The correlation between the radiosensitivity of lymphocytes determined by micronucleus assay and those of fibroblasts and intestinal crypt cells. The order of radiosensitiity of lymphocytes obtained in 3 different strain of mice was accurately repeated in those of fibroblasts and intestinal crypt cells.