Clinical study of relative biological effectiveness for cervical carcinoma treated by 252Cf neutrons and assessed by histological tumour eradication

Clinical data of the University of Kentucky trial using californium (252Cf), or caesium (137Cs), are reviewed for dose-response based on the endpoint of tumour eradication estimated from hysterectomy specimens obtained 4-6 weeks after preoperative irradiation. These data are used to assess the relative biological effectiveness (RBE) for 252Cf neutrons compared with 137Cs gamma radiation. Tumours treated were of common stage but were of bulky or barrel shape suitable for "radiosurgical" therapy. Dose-response curves were constructed, and additional data from the literature used to analyse the curve shape. The photon dose-response curve is complex on a logarithmic plot, whereas the 252Cf neutron curve is exponential. This indicates that the RBE can be different depending on the number of implants, schedule and size of dose delivered per session. The RBE values were approximately 8.0 at low doses or for multiple implants but they may rise to approximately 16 at larger doses or for single 252Cf implants.     

Use of 252Cf in environmental and radioecological laboratory experiments

The prompt photons accompanying spontaneous fission decay of ²⁵²Cf are useful for in vivo and other environmental and radioecological laboratory experiments. Detection of > 2.6 MeV photons by a NaI(Tl) detector eliminates most natural background γ radiation and successful experiments can be carried out with nCi levels of ²⁵²Cf.     

Cure of cervical cancer using 252Cf neutron brachytherapy

252Cf neutron brachytherapy was tested in a feasibility trial for efficacy for cervix cancer therapy vs. high stage radioresistant and subsequently for all stages of disease. Actuarial survival curves were analyzed for 218 patients treated between 1976 and 1983 and followed five to 14 years to the present time. A variety of doses, schedules and methods for brachytherapy was tested during this period, and a dose-response relationship for tumor eradication studied. All treatments were combined with whole-pelvis photon radiotherapy to approximately 45 to 60 Gy. This combination was found effective, particularly if an early implant schedule was used for the Cf implant, followed by whole-pelvis photon radiotherapy. For bulky/barrel shaped low-stage disease in medically fit patients, 252Cf implants were combined with surgery, i.e., extrafascial hysterectomy and was readily usable for treatment without complications and with high cure rates (92% five-year survival). All survivals and outcomes to 13 years match the best results of conventional photon radiotherapy. For all stages better results were observed for bulky, barrel, and advanced-stage tumors, especially for local tumor control, if optimal schedules, doses and implant numbers were used. Knowledge about neutron dose, dose per implant, number of implants and combination with photon beam therapy evolved during the trials. 252Cf represents a new quick acting effective radioisotope for human cancer therapy especially for treatment of radioresistant, bulky and high stage cancers.     

吩噻嗪衍生物协同放射对HeLa细胞增殖的抑制效应比较研究

目的 探讨吩噻嗪衍生物对人宫颈癌HeLa细胞增殖的抑制作用及与放射联合应用抑制肿瘤的协同效应。方法 采用MTT法和细胞克隆形成法检测细胞的增殖活性和细胞辐射敏感性。结果 比较了6种吩噻嗪衍生物对HeLa细胞增殖的抑制效应，发现化合物α-氯-N-二甲胺基乙基吩噻嗪（PTZD2）、α-三氟甲基-N-二甲胺基乙基吩噻嗪（PTZD3）和α-氯-N-二乙胺基乙基吩噻嗪（PTZD5）的作用比较明显，在10μmol／L浓度能产生出显著抑制效应，40-50μmol／L浓度作用3和4d，细胞增殖完全被抑制而死亡。PTZD2或PTZD3与放射联合应用，显示出明显抗HeLa细胞增殖的协同效应，10μmol／L PTZD3对2和4Gy照射细胞的增殖抑制的增强比分别为3．5和1．8。实验结果还表明，在照射前18h用药的协同作用更加显著。结论 吩噻嗪衍生物具有程度不同的抑制HeLa细胞增殖的作用，与放射联合应用具有抗肿瘤的协同效应，而且照射前18h用药的效应最佳。     

Californium-252 (252Cf) versus Conventional Gamma Radiation in the Brachytherapy of Advanced Cervical Carcinoma

BACKGROUND: When photon radiotherapy is applied to cervical carcinoma, it has been observed that, despite important progress in radiotherapy technique and quality assurance, no significant increase in curative rates has resulted. Among the reasons for this is the varying radiosensitivity of different tumor subpopulations. Treatment with californium-252 ((252)Cf), as a source of gamma/neutron radiation in brachytherapy, provides properties and new treatment modalities that help to overcome this factor. PATIENTS AND METHODS: From January 1985 to June 1993, 227 women with stage IIB and IIIB cervical carcinoma were treated in a randomized brachytherapy study as follows: (1) 117 patients (55 with stage IIB, 62 with stage IIIB) were treated with (252)Cf during the 1st week of therapy by 6 Gy (40 Gy-eq) of the neutron component in point A. Supplementation by a 16-Gy dose with (226)Ra or (137)Cs was done in the 5th week. (2) 110 patients (50 with stage IIB, 60 with stage IIIB) were treated solely by gamma radiation ((226)Ra or (137)Cs). A dose of 56 Gy in point A was applied in two fractions at the 3rd and 5th week, respectively. The dose of 56 Gy-equivalents was completed by external radiation with 40 Gy. The total radiation doses at points A and B amounted to 85 Gy and 59 Gy, respectively. The treatment results were compared. RESULTS: The overall 5-year survival rate for all stages IIB and IIIB was better by 18.9% for (252)Cf patients than for patients receiving conventional treatment (75.2% vs. 56.3%, respectively; p < 0.001). In the stage IIIB (252)Cf group, it was significantly better by 22.8% than for the conventional group (66.1% vs. 43.3%, respectively; p < 0.003). The higher survival rate in (252)Cf patients was the result of significantly less local relapses compared with patients treated conventionally (12,8% vs. 31.8%; p < 0.0009). CONCLUSION: The importance of neutron source (252)Cf in the brachytherapy of cervical carcinoma by overcoming the tumor resistance to conventional photon irradiation has been confirmed.     

Lethal and Mutagenic Effects of 252Cf Radiation in Cultured Human Cells

Summary

HeLa MR cells were exposed to radiation emitted from a man-made spontaneously fissioning isotope, californium-252. The neutron to gamma-ray ratio in the radiation dose was measured to be 2·0. The extrapolation number of the dose-survival curve was 1·3 and the Do was 200 cGy. A dose-dependent increase in mutation to 6-TG^r (6-thioguanine resistant) was observed. The relative biological effectiveness (r.b.e.) for cell killing of the neutrons from ²⁵²Cf, calculated relative to high-dose-rate X-rays, was 2·6 at 50 per cent survival. The r.b.e. for mutation induction was 2·7 at a mutation frequency of 5 × 10^?5 per surviving cell.     

Work in progress: 252Cf neutron brachytherapy for hemispheric malignant glioma

It has been shown that 252Cf neutron brachytherapy of hemispheric malignant glioma can be readily carried out and may be combined with external, whole brain photon beam therapy of 6,000 rad (60 Gy) administered over a five-week to seven-week period. The ten patients who were studied tolerated both procedures well. There was improvement in performance status, and a decrease in tumor size was observed upon computed tomographic scanning.     

沉默Krüppel样因子5对电离辐射后大鼠小肠上皮IEC-6细胞生物学功能的影响

目的 探讨沉默Krüppel样因子5（KLF5）对电离辐射后体外培养的大鼠小肠上皮IEC-6细胞生物学功能的影响。方法 给予大鼠小肠上皮IEC-6细胞12 Gy照射,分别在照后0、0.5、1、2、3、5、7、24 h,检测KLF5的表达。给予IEC-6细胞0、2、4、8、12和16 Gy X射线照射,照后3 h收集细胞蛋白,采用Western blot法检测IEC-6细胞中KLF5的表达。设计并合成特异性针对大鼠KLF5基因的shRNA靶序列,构建到慢病毒载体中,通过感染人胚肾293T细胞,对慢病毒进行包装和滴度测定。使用包装好的慢病毒感染IEC-6细胞,荧光显微镜下观察转染效率,转染72 h后分别采用实时-PCR和Western blot方法检测感染后细胞中KLF5 mRNA及蛋白的表达。后续实验分为阴性对照组、shKLF5组、单纯照射组、照射+shKLF5组4组。采用CCK-8法观察8 Gy照射后KLF5沉默细胞的增殖活性,流式细胞术检测8 Gy照射后KLF5沉默细胞的周期分布和凋亡,免疫荧光染色观察2 Gy照射后KLF5沉默细胞中γ-H2AX焦点数量。结果 不同剂量射线照射后KLF5表达逐渐增加,呈现明显的剂量效应关系。12 Gy照射后KLF5表达呈现先升高后降低的趋势,照后5 h表达量最高。KLF5 shRNA慢病毒载体构建成功,感染的IEC-6细胞中KLF5 mRNA及蛋白水平均在转染72 h明显降低。照射+shKLF5组细胞在照射后24 h阻滞在G₂/M期现象显著（t=11.56,P<0.05）,细胞增殖明显受到抑制,其细胞凋亡率（12.49±0.63）%,明显高于单纯照射组（7.42±0.49）%,两组比较差异有统计学意义（t=10.98,P<0.05）,照射+shkLF5组细胞核中各时间点的γ-H2AX焦点数量明显多于同一时间点阴性对照组（t=22.07、23.89、11.24、59.97、20.85,P<0.05）。结论 成功构建KLF5 shRNA慢病毒载体,并建立KLF5敲低小肠上皮细胞株。下调细胞内KLF5表达,能够使细胞周期阻滞在G₂/M期,抑制照射后细胞的增殖,促进细胞的凋亡,DNA双链断裂水平增加,修复延迟。