Mirzaie-Joniani H, Eriksson D, Johansson A, Löfroth P-O, Johansson L, Ahlström K Riklund, Stigbrand T
Department of Immunology, Diagnostic Radiology, University of Umeå, 901 85 Umeå, Sweden.
Radiat Res. 2002 Nov;158(5):634-40. doi: 10.1667/0033-7587(2002)158[0634:aihhci]2.0.co;2.
Radioimmunotherapy with radiolabeled antibodies may cause inhibition of the growth of epithelial tumors, despite low total radiation doses and comparatively low radiosensitivity of epithelial tumor cells. The induction of apoptosis by low-dose radiation, such as delivered in radioimmunotherapy, was investigated in vitro in human HeLa Hep2 carcinoma cells. The cultured cells were exposed to defined radiation doses from a (60)Co radiation therapy source. The radiation source delivered 0.80 +/- 0.032 (mean +/- SD) Gy/min and the cells were given total doses of 1, 2, 5, 10 and 15 Gy. Using fluorescein-labeled Annexin V, followed by flow cytometry and DNA ladder analysis, apoptotic cells were detected and quantified. Radiation doses below 2 Gy did not cause any significant increase in apoptosis. Compared to control cells, apoptosis was pronounced after 5-10 Gy irradiation and was correlated to the radiation dose, with up to 42 +/- 3.5% of the cells examined displaying apoptosis. Clonogenic assays confirmed significantly decreased viability of the cells in the interval 2 to 10 Gy with low-dose-rate radiation, 60 +/- 2% compared to 2 +/- 2%. Lethal effects on the tumor cells were also evaluated by an assay of the cytotoxic effects of the release of (51)Cr. Significant cytotoxicity, with up to 64 +/- 6% dead cells, was observed at 5 Gy. Similar results were obtained when the dose rate was reduced to 0.072 +/- 0.003 Gy/min (mean +/- SD). In the case of the (137)Cs source, the dose rate could be reduced to 0.045 Gy/h, a level comparable to radioimmunotherapy, which induced significant apoptosis, and was most pronounced at 72-168 h postirradiation. It can be concluded that in vitro low-dose and low-dose-rate radiation induces apoptosis in epithelial HeLa Hep2 cells and thus may explain a mechanism by which pronounced inhibition of growth of HeLa Hep2 tumors at doses used in radioimmunotherapy has been obtained previously.
尽管总辐射剂量较低且上皮肿瘤细胞的放射敏感性相对较低，但用放射性标记抗体进行放射免疫治疗可能会抑制上皮肿瘤的生长。在体外对人HeLa Hep2癌细胞研究了低剂量辐射（如放射免疫治疗中所使用的）诱导细胞凋亡的情况。将培养的细胞暴露于来自钴 - 60放射治疗源的特定辐射剂量下。该辐射源的剂量率为0.80±0.032（平均值±标准差）Gy/分钟，细胞接受的总剂量分别为1、2、5、10和15 Gy。使用荧光素标记的膜联蛋白V，随后进行流式细胞术和DNA梯状分析，对凋亡细胞进行检测和定量。低于2 Gy的辐射剂量未导致凋亡有任何显著增加。与对照细胞相比，5 - 10 Gy照射后凋亡明显，且与辐射剂量相关，高达42±3.5%的检测细胞显示凋亡。克隆形成试验证实，在2至10 Gy的低剂量率辐射区间内，细胞活力显著降低，与2±2%相比为60±2%。还通过检测51铬释放的细胞毒性试验评估了对肿瘤细胞的致死效应。在5 Gy时观察到显著的细胞毒性，高达（64±6%）的细胞死亡。当剂量率降低至0.072±0.003 Gy/分钟（平均值±标准差）时，获得了类似结果。对于铯 - 137源，剂量率可降低至0.045 Gy/小时，这一水平与放射免疫治疗相当，其诱导了显著的凋亡，且在照射后72 - 168小时最为明显。可以得出结论，体外低剂量和低剂量率辐射可诱导上皮HeLa Hep2细胞凋亡，因此这可能解释了先前在放射免疫治疗中使用的剂量下HeLa Hep2肿瘤生长受到显著抑制的一种机制。
