外源性p53对不同LET辐射诱导人黑色素瘤细胞系A375死亡途径的影响

目的 观察外源性P53蛋白对不同传能线密度(LET)射线辐照诱导肿瘤细胞凋亡和坏死的影响,并探讨其可能的机制。方法 人黑色素瘤细胞系A375(wild-type p53)经携带人野生型p53基因的腺病毒载体(AdCMV-p53)感染后分别给予X射线和碳离子束照射,采用克隆形成法测定细胞辐射敏感性,Hoechst 33258和吖啶橙-溴化乙锭双染荧光显微镜下观察细胞凋亡和坏死。结果1高LET辐照时,A375细胞和转导人野生型p53基因的A375细胞(A375/p53)的辐射敏感性没有明显差异;2虽然辐射诱导细胞凋亡比例的增加依赖于LET升高,但是无论高LET或低LET,外源性P53蛋白均可有效诱导细胞凋亡。3高LET辐照时,A375细胞的坏死细胞明显高于A375/p53细胞。结论 尽管高LET辐射对A375和A375/p53细胞的存活无明显影响,但是对细胞凋亡的诱导却部分依赖于P53蛋白的功能,P53蛋白可能在调节细胞死亡类型中发挥重要作用。这对临床应用高LET辐射联合p53基因治疗恶性黑色素瘤有一定参考意义。     

高传能线密度辐射对人眼晶状体的危害

眼晶状体是人体对辐射最敏感的组织之一,电离辐射的生物效应因其传能线密度（linear energy transfer, LET）的不同而不同,同等吸收剂量条件下,高LET辐射生物效应比低LET辐射更强,尽管目前辐射对眼晶状体的影响这一领域已经有了较多研究,但对于高LET对眼晶状体的影响知之甚少。本文简述人眼晶状体剂量限值的历史变化情况,综述各种高LET粒子的生物学实验,调查高LET辐射眼晶状体的流行病学,简要分析高原白内障高患病率的原因,并初步讨论未来研究高LET需要考虑的因素,旨在为国内今后开展高LET辐射对人眼晶状体的研究提供有价值的信息。     

Validation of 64Cu-ATSM damaging DNA via high-LET Auger electron emission

Radioactive copper (II) (diacetyl-bis N4-methylthiosemicarbazone) (Cu-ATSM) isotopes were originally developed for the imaging of hypoxia in tumors. Because the decay of a ⁶⁴Cu atom is emitting not only positrons but also Auger electrons, this radionuclide has great potential as a theranostic agent. However, the success of ⁶⁴Cu-ATSM internal radiation therapy would depend on the contribution of Auger electrons to tumor cell killing. Therefore, we designed a cell culture system to define the contributions to cell death from Auger electrons to support or refute our hypothesis that the majority of cell death from ⁶⁴Cu-ATSM is a result of high-LET Auger electrons and not positrons or other low-LET radiation. Chinese hamster ovary (CHO) wild type and DNA repair–deficient xrs5 cells were exposed to ⁶⁴Cu-ATSM during hypoxic conditions. Surviving fractions were compared with those surviving gamma-radiation, low-LET hadron radiation, and high-LET heavy ion exposure. The ratio of the D₁₀ values (doses required to achieve 10% cell survival) between CHO wild type and xrs5 cells suggested that ⁶⁴Cu-ATSM toxicity is similar to that of high-LET Carbon ion radiation (70 keV/μm). γH2AX foci assays confirmed DNA double-strand breaks and cluster damage by high-LET Auger electrons from ⁶⁴Cu decay, and complex types of chromosomal aberrations typical of high-LET radiation were observed after ⁶⁴Cu-ATSM exposure. The majority of cell death was caused by high-LET radiation. This work provides strong evidence that ⁶⁴Cu-ATSM damages DNA via high-LET Auger electrons, supporting further study and consideration of ⁶⁴Cu-ATSM as a cancer treatment modality for hypoxic tumors.     

Analysis of ionizing radiation‐induced DNA damage and repair in three‐dimensional human skin model system

Please cite this paper as: Analysis of ionizing radiation‐induced DNA damage and repair in three‐dimensional human skin model system. Experimental Dermatology 2010; 19 : e16–e22. Abstract: Knowledge of cellular responses in tissue microenvironment is crucial for the accurate prediction of human health risks following chronic or acute exposure to ionizing radiation (IR). With this objective, we investigated the radio responses for the first time in three‐dimensional (3D) artificial human skin tissue microenvironment after γ‐rays radiation. IR‐induced DNA damage/repair response was assessed by immunological analysis of well‐known DNA double strand break (DSB) repair proteins, i.e. 53BP1 and phosphorylated ataxia telangiectasia mutated^ser1981 (ATM^ser1981). Efficient 53BP1 and phosphorylated ATM foci formation was observed in human EpiDerm tissue constructs after low and high doses of γ‐rays. Interestingly, EpiDerm tissue constructs displayed less 53BP1 and ATM foci number at all radiation doses (0.1, 1, 2.5 and 5 Gy) than that observed for 2D human fibroblasts. DSB repair efficiency judged by the disappearance of 53BP1 foci declined with increasing doses of γ‐rays and tissue constructs irradiated with 2.5 and 5 Gy of γ‐rays displayed 53BP1 foci persisting up to 72 h of analysis. Pretreatment of EpiDerm tissue constructs with LY294002, [an inhibitor of phosphatidylinositol‐3 kinase and PI‐3 kinase like kinases (PIKK)] completely abolished IR‐induced 53BP1 foci formation and increased the apoptotic death. This observation indicates the importance of PIKK signalling pathway for efficient radiation responses in intact tissue constructs. In summary, we have successfully demonstrated the feasibility of monitoring the DNA damage response in human skin tissue microenvironment. In this system, 53BP1 can be used as a useful marker for monitoring the DSB repair efficiency.     

电离辐射诱发小鼠生殖细胞染色体畸变的规律及其影响因素

作者发现对低ＬＥＴ电离辐射（ｘ、γ射线）诱发小鼠生殖细胞染色体畸变的规律是大剂量照射呈现直线和线性平方两种模型：小剂量照射为直线模型。同时证明雄性生殖细胞畸变率最高；在减数分裂过程中受照次级精母细胞，染色体畸变率分别高于精原和初级精母细胞，其中细线期受照时，精母细胞染色体畸变率最低，终变期最高；全《照射诱发生殖细胞染色体畸变率明显高于睾丸局部照射；急性照射明显高于慢性照射的畸变率。     

Potential for therapeutic gain similar to pions by daily combinations of neutrons and low-LET radiations.

Biological studies with negative pi mesons (pions) at the Los Alamos Meson Physics Facility (LAMPF) have shown a relatively constant reduction of shoulder of the survival curve for single cell cultures and relatively constant reduction in the no response region for multicellular tumor spheroids (MTS) with little change in sensitivity (or slope), in both single dose and fractionated experiments. In clinical studies, a trend toward therapeutic gain for pions has been demonstrated in patients treated at LAMPF, with marked, rapid turmor regression for relatively mild acute normal tissue injury and no untoward effects observed over 7 to 24 months. Since the pion beams used therapeutically at LAMPF are characterized by a small amount of high-linear-energy-transfer (LET) radiation (in the range 10 to 20%), it is hypothesized that pion radiation as compared to x-rays increased the differential tolerance to sublethal injury in favor of normal tissues, resulting in therapeutic gain. It is further proposed that the near simultaneous application of high-LET radiation (such as neutrons) and low-LET radiation (such as x-rays) might create a bilogical situation similar to that of pion treatment, potentially resulting in therapeutic gain, although without the added benefit of dose localization obtainable with pions.     

Hypoxic cell sensitizers and heavy charged particle beams may play complementary roles in killing hypoxic tumor cells

The analysis of growth delay data of a rat rhabdomyosarcoma tumor system with and without misonidazole and irradiated with spread-peak heavy-ion radiation yields two conclusions that bear on the relative efficacy of the two modes of treatment and imply a complementary role of the two modes which enhances the effects of either given separately. 1. For both carbon and neon ion peak radiation given in four fractions, RBE values for tumor growth delay are significantly greater than the enhancement ratio for an X ray plus misonidazole fractionation scheme [2.0-2.3 (carbon) and 2.6-2.8 (neon) vs. 1.2-1.5 (X rays plus misonidazole)]. This implies that high LET killing is considerably more effective in this tumor system (hypoxic fraction of about 35%) than the hypoxic cell sensitization caused by misonidazole. 2. When misonidazole is given in conjunction with the heavy ion beam irradiations, an increased growth delay is seen, greater than when either heavy ions or misonidazole plus X rays are given separately. The product of the sensitizer enhancement ratio for heavy ions and the RBE for no sensitizer yields a measure of the overall enhancement of effect relative to an X ray treatment. The values of this product for the carbon beam (2.4-2.5) and neon beam (3.4) show high effectiveness for either beam plus misonidazole. The interpretation is that heavy ion beams reach and kill hypoxic cells not penetrated by the misonidazole, and some hypoxic cells not killed by the high LET component receive low LET damage which is made lethal by the drug. Thus, the net hypoxic cell killing is enhanced by the high LET beams and in a complementary way by the combination of the drug and the low LET portion of the radiation.     

Fast neutron irradiation of metastatic cervical adenopathy: the results of a randomized RTOG study

Between 1977 and 1982, 199 evaluable patients with measurable cervical adenopathy were entered on a prospective, randomized RTOG study evaluating the use of fast neutrons in treatment of advanced, inoperable squamous cell carcinomas of the head and neck region. One hundred-eleven patients were randomized to receive mixed beam radiation therapy, and 88 were randomized to the photon control treatment. The complete response rates were 86% for mixed beam vs 75% for photons for Stage N1 nodes, 62% for mixed beam vs 48% for photons for Stage N2 nodes, and 63% for mixed beam vs 53% for photons for N3 nodes. The percents of patients remaining free of their adenopathy for two years were 78% for mixed beam vs 55% for photons for Stage N1 nodes, 39% for both mixed beam and photons for N2 nodes and 24% for mixed beam vs 13% for photons for N3 nodes. The median disease-free status was 20.3 months for mixed beam treated patients and 6.4 months for photon-treated patients. Patients who had clearance of cervical adenopathy survived significantly longer than those who did not.     

Clinical Indications for Carbon Ion Radiotherapy

Compared with photon and proton therapy, carbon ion radiotherapy (CIRT) offers potentially superior dose distributions, which may permit dose escalation with the potential for improved sparing of adjacent normal tissues. CIRT has increased biological effectiveness leading to increased tumour killing compared with other radiation modalities. Here we review these biophysical properties and provide a comprehensive evaluation of the current clinical evidence available for different tumour types treated with CIRT. We suggest that patient selection for CIRT should move away from the traditional viewpoint, which confines use to deep-seated hypoxic tumours that are adjacent to radiosensitive structures. A more integrated translational approach is required for the future as densely ionising C-ions elicit a distinct signal response pathway compared with sparsely ionising X-rays. This makes CIRT a biologically distinct treatment compared with conventional radiotherapy.