Edema-induced increase in tumour cell survival for 125I and 103Pd prostate permanent seed implants--a bio-mathematical model

Edema caused by the surgical procedure of prostate seed implantation expands the source-to-point distances within the prostate and hence decreases the dose coverage. The decrease of dose coverage results in an increase in tumour cell survival. To investigate the effects of edema on tumour cell survival, a bio-mathematical model of edema and the corresponding cell killing by continuous low dose rate irradiation (CLDRI) was developed so that tumour cell surviving fractions can be estimated in an edematous prostate for both 125I and 103Pd seed implants. The dynamic nature of edema and its resolution were modelled with an exponential function V(T) = V(p)(1 + M exp(-0.693T/ T(e))) where V(p) is the prostate volume before implantation, M is the edema magnitude and T(e) is edema half-life (EHL). The dose rate of a radioactive seed was calculated according to AAPM TG43, i.e. D = SkAg(r)phi(an)/r2, where r is the distance between a seed and a given point. The distance r is now a function of time because of edema. The g(r) was approximated as 1/r(0,4) and 1/r(0.8) for 125I and 103Pd, respectively. By expanding the mathematical expression of the resultant dose rate in a Taylor series of exponential functions of time, the dose rate was made equivalent to that produced from multiple fictitious radionuclides of different decay constants and strengths. The biologically effective dose (BED) for an edematous prostate implant was then calculated using a generalized Dale equation. The cell surviving fraction was computed as exp(-alphaBED), where alpha is the linear coefficient of the survival curve. The tumour cell survival was calculated for both 125I and 103Pd seed implants and for different tumour potential doubling time (TPDT) (from 5 days to 30 days) and for edemas of different magnitudes (from 0% to 95%) and edema half-lives (from 4 days to 30 days). Tumour cell survival increased with the increase of edema magnitude and EHL. For a typical edema of a half-life of 10 days and a magnitude of 50%. the edema increased tumour cell survival by about 1 and 2 orders of magnitude for 125I and 103Pd seed implants respectively. At the extreme (95% edema magnitude and an edema half-life of 30 days), the increase was more than 3 and 5 orders of magnitude for 125I and I03Pd seed implants respectively. The absolute increases were almost independent of TPDT and the prostate edema did not significantly change the effective treatment time. Tumour cell survival for prostate undergoing CLDRI using 125I or 103Pd seeds may be increased substantially due to the presence of edema caused by surgical trauma. This effect appears to be more pronounced for 103Pd than 125I because of the shorter half-life of 103Pd. If significant edema is observed post implantation, then a boost to the prostate using external beam radiotherapy may be considered as a part of the treatment strategy.     

A mathematical model of malignant tissue sterilization probability

Conclusions 1. A mathematical model for determining the PS of malignant tissue as a function of its volume and DF scheme was developed. It is assumed that malignant tissue consists both of typical cells and cells with enhanced radioresistance. The number of radioresistant malignant cells is proportional to the total number of cells in the tumor. The dependence of the survival rate of typical and radioresistant cell subpopulations on the radiation dose is described by LQ functions. 2. A software complex for determining the LQ function parameters and the relative number of radioresistant cells based on clinical data was developed. 3. The developed software complex calculates the PS of malignant tissue as a function of its volume, type, and DF scheme. 4. Four examples of practical use of the software complex for determining parameters of the mathematical model and calculating the PS of malignant tissue are presented. This work was supported by the Russian Foundation for Basic Research (project No. 980100057).     

Dose, dose-rate and field size effects on cell survival following exposure to non-uniform radiation fields

For the delivery of intensity-modulated radiation therapy (IMRT), highly modulated fields are used to achieve dose conformity across a target tumour volume. Recent in vitro evidence has demonstrated significant alterations in cell survival occurring out-of-field which cannot be accounted for on the basis of scattered dose. The radiobiological effect of area, dose and dose-rate on out-of-field cell survival responses following exposure to intensity-modulated radiation fields is presented in this study. Cell survival was determined by clonogenic assay in human prostate cancer (DU-145) and primary fibroblast (AG0-1522) cells following exposure to different modulated field configurations delivered using a X-Rad 225 kVp x-ray source. Uniform survival responses were compared to in- and out-of-field responses in which 25-99% of the cell population was shielded. Dose delivered to the out-of-field region was varied from 1.6-37.2% of that delivered to the in-field region using different levels of brass shielding. Dose rate effects were determined for 0.2-4 Gy min?1 for uniform and modulated exposures with no effect seen in- or out-of-field. Survival responses showed little dependence on dose rate and area in- and out-of-field with a trend towards increased survival with decreased in-field area. Out-of-field survival responses were shown to scale in proportion to dose delivered to the in-field region and also local dose delivered out-of-field. Mathematical modelling of these findings has shown survival response to be highly dependent on dose delivered in- and out-of-field but not on area or dose rate. These data provide further insight into the radiobiological parameters impacting on cell survival following exposure to modulated irradiation fields highlighting the need for refinement of existing radiobiological models to incorporate non-targeted effects and modulated dose distributions.     

Predictions of a stochastic model of bone marrow cell survival in high dose rate radiation fields with arbitrary neutron to gamma-ray absorbed dose rate ratios

In this paper, a stochastic model of cell survival, which was developed by Cotlet and Blue, based on the work of Jones, is extended to describe bone marrow cell survival in high dose rate radiation fields with arbitrary neutron to gamma-ray absorbed dose rate ratios. Mathematical formulas are obtained that describe the interaction of the neutron and gamma-ray components of the absorbed dose, for radiation fields with arbitrary neutron to gamma-ray dose rate ratios, for exposures of cells to various absorbed doses, at various high dose rates.     

应用OriginLab对调强放射治疗中剂量体积直方图的建模初步分析

目的以非小细胞肺癌调强放射治疗中剂量体积直方图（DVH）为研究对象,旨在建立数学模型,分析由呼吸运动所致靶区位移对剂量分布的影响。方法选取临床上采用调强放射治疗的非小细胞肺癌8例,通过在放射治疗计划系统中设置治疗床在单一方向上特定步长的位移,模拟呼吸运动造成的靶区位移,获取位移后的DVH曲线数据,采用数据分析软件OriginLab8.0对DVH曲线进行拟合,比较模型之间的拟合效果,并对位移前后的参数变化作初步分析。结果高斯模型和费米模型都能较好地拟合DVH曲线,但费米模型的残差平方和较高斯模型更小,AIC值相对更小;2个模型的参数计算结果经过转换后数值上一致;对于临床靶区或肿瘤靶区未移出计划靶区的位移时,剂量均值下降,方差增大,并未呈现出对称性变化。结论费米模型更适合应用于今后的DVH曲线建模研究。模型中的参数有助于在临床放射治疗计划系统中利用DVH曲线参数评价肿瘤靶区的剂量体积关系。     

An Experimental Study on the Anti-Ehrlich Ascites Carcinoma Effect of Purified Toad Venom Extract

The objective of this paper was to study the anti-Ehrlich ascites carcinoma effect of purified toad venom extract and its mechanism. Mouse model of Ehrlich ascites carcinoma was established with cisplatin as the control to observe the inhibitory effect of purified toad venom extract on malignant peritoneal effusion in mice. The results showed that compared with the control group, ascites volume, number of tumour cells and tumour cell viability decreased and ascites inhibition rate reached over 50% in each treatment group, and with the increase of the dose, incidence of ascites showed a downward trend. The number of tumour cells in ascites and tumour cell viability in the purified toad venom high-dose group were lower than those of the cisplatin group. Compared with the model group, survival time was prolonged in varying degrees in the purified toad venom groups and cisplatin group. The study concluded that purified extract of toad venom has an anti-Ehrlich ascites carcinoma effect.     

The immune response towards beta-adrenergic ligands and their receptors--VII. Equilibrium and kinetic binding studies of l-alprenolol to a monoclonal anti-alprenolol antibody

Binding of the catecholamine beta-adrenergic antagonist, l-alprenolol, by the IgGl anti-alprenolol monoclonal antibody 37A4 was examined using the radioligand 3H-dihydroalprenolol as an extrinsic signal and the increase in antibody fluorescence upon l-alprenolol binding as intrinsic signal. Equilibrium binding studies based on both signals indicated that the binding process was exothermic with a positive entropy change. The difference in the affinity constants obtained by radioligand binding studies and by fluorescence analysis could be ascribed to the higher affinity of the hydrogenated tritiated l-dihydroalprenolol compared to the unsaturated l-alprenolol. The association rate constants determined by both signals were 10(4)-10(5)/M/sec and showed a high activation enthalpy (8-10 kcal/mol), thus excluding a diffusion controlled reaction. At low temp (7 degrees C), the fluorescence stopped-flow studies showed non-linear pseudo first order kinetics, indicating the existence of a fast pre-equilibrium of low affinity, followed by a conformational change leading to the tight binding of the ligand. The dissociation rate constants determined using both signals were very similar. Thus, the differences in affinity between the hydrogenated and non-saturated l-alprenolol could be ascribed to the association rate constants. Affinity constants and thermodynamic parameters calculated from the kinetic data were in close agreement with those determined by equilibrium binding. The mechanisms of ligand binding are discussed in terms of the interactions of idiotypes and anti-idiotypes in the anti-catecholamine immune response.     

Relationship between the generalized equivalent uniform dose formulation and the Poisson statistics-based tumor control probability model

The generalized equivalent uniform dose (GEUD) model uses a power-law formalism, where the outcome is related to the dose via a power law. We herein investigate the mathematical compatibility between this GEUD model and the Poisson statistics based tumor control probability (TCP) model. The GEUD and TCP formulations are combined and subjected to a compatibility constraint equation. This compatibility constraint equates tumor control probability from the original heterogeneous target dose distribution to that from the homogeneous dose from the GEUD formalism. It is shown that this constraint equation possesses a unique, analytical closed-form solution which relates radiation dose to the tumor cell survival fraction. It is further demonstrated that, when there is no positive threshold or finite critical dose in the tumor response to radiation, this relationship is not bounded within the realistic cell survival limits of 0%-100%. Thus, the GEUD and TCP formalisms are, in general, mathematically inconsistent. However, when a threshold dose or finite critical dose exists in the tumor response to radiation, there is a unique mathematical solution for the tumor cell survival fraction that allows the GEUD and TCP formalisms to coexist, provided that all portions of the tumor are confined within certain specific dose ranges.     

红藻氨酸诱导PC12细胞凋亡及阿魏酸对神经元的保护作用

 目的： 探讨阿魏酸(ferulic acid, FA)对红藻氨酸(kainic acid, KA)诱导的PC12细胞凋亡的作用及其机制。方法：采用50 μmol/L KA诱导PC12细胞凋亡建立阿尔茨海默病神经细胞模型,然后将处理后的PC12细胞分为KA模型组和KA＋FA (25、50和100 μmol/L)处理的低、中、高剂量组,同时设立正常对照组。采用MTT比色法检测PC12细胞的存活率;采用免疫细胞化学法观察PC12细胞中凋亡蛋白Bcl-2、Bax和细胞色素C (Cyt C)的表达;annexin Ⅴ+PI双染流式细胞术检测PC12的细胞凋亡率;蛋白免疫印记技术检测PC12细胞中Bcl-2、Bax和Cyt C的表达水平。结果：MTT法和免疫细胞化学检测显示,与正常组相比,模型组PC12细胞的存活率明显下降,且细胞中Bcl-2表达减少(P<0.01),而Bax和Cyt C表达升高,Bcl-2/Bax比值下降(P<0.01),流式细胞术检测细胞的凋亡率显示,模型组细胞的凋亡率显著上升(P<0.01)。蛋白印迹术检测显示,模型组细胞中Bcl-2表达量减少,Bax和Cyt C表达量升高,与正常组比较差异显著(均P<0.01)。当采用FA干预后,与模型组相比,25、50和100 μmol/L组细胞的存活率明显上升,细胞凋亡率减少,而且能增加Bcl-2阳性百分率和表达水平,明显减少Bax和Cyt C阳性百分率和表达水平,使Bcl-2/Bax比值增加 (P<0.05或P<0.01)。结论：KA在50 μmol/L时可明显诱导PC12发生凋亡,FA在25～100 μmol/L时能显著抑制KA诱导的PC12细胞凋亡,其神经保护机制可能是通过抑制Bax和Cyt C的表达,升高Bcl-2表达和Bcl-2/Bax比值,从而阻断内源性细胞凋亡通路而提高神经细胞的存活率。     

Effect of dose rate on the radiation-induced bystander response

Radiation-induced biological bystander effects have become a well-established phenomenon associated with the interaction of radiation with cells. These so-called bystander effects have been seen across a variety of end points for both high and low linear energy transfer (LET) radiations, utilizing a variety of dose rates and radiation sources. In this study, the effect of dose rate and different low LET sources on the bystander cell survival fraction (SF) was examined. The cell line investigated was the human keratinocyte HPV-G. The bystander response was measured via clonogenic assay after medium transfer protocol. Cells were irradiated using (60)Co gamma-rays and 20 MeV electrons at doses of 0.5, 5 and 10 Gy with varying dose rates. Both gamma and electron irradiation decreased recipient SF at 0.5 Gy and 5 Gy, respectively. Subsequent recovery of the SF to control levels for 10 Gy was observed. There was no dose rate dependence for (60)Co irradiation. A significant difference in the survival fraction was observed for electron irradiation at 10 Gy and a high dose rate. Furthermore, survival fractions were compared between (60)Co and 20 MeV electron irradiations. This showed a significant increase in the survival fraction 'recovery' at 10 Gy for a (60)Co dose rate of 1.1 Gy min(-1) compared to 20 MeV electrons at 1.0 Gy min(-1). No such difference was observed when comparing at higher dose rates. Lastly, increases in survival fraction at 10 Gy were abolished and the SF decreased by the plating of increased numbers of recipient cells. Such evidence may help gain insight into the nature and mechanism(s) surrounding bystander signal production, how these phenomena are tested and their eventual application in a clinical setting.     

Infused CD34+ cell dose predicts long-term survival in acute myelogenous leukemia patients who received allogeneic bone marrow transplantation from matched sibling donors in first complete remission.

Allogeneic stem cell transplantation (ASCT) has improved the outcome of acute myelogenous leukemia (AML). To further improve the treatment outcome of ASCT in AML, finding a modifiable prognostic factor is mandatory. We evaluated the effect of CD34(+) cell dose on survival in allogeneic bone marrow transplantation (BMT) from HLA-matched sibling donors for AML patients in first complete remission (CR1). The 99 patients included in our analysis were classified into high CD34(+) cell dose group (CD34(+) cells > or = 2.5 x 10(6)/kg) and low CD34(+) cell dose group (CD34(+) cells < 2.5 x 10(6)/kg). The high CD34(+) cell dose patients had better overall survival (5-year overall survival rate, 75% +/- 6% vs 52% +/- 9%; P = .01) and leukemia-free survival (5-year leukemia-free survival rate, 70% +/- 6% vs 44% +/- 9%; P = .04). CD34(+) cell dose was the only independent prognostic factor in overall survival and leukemia-free survival. The high CD34(+) cell dose group had a lower relapse incidence with a borderline statistical significance (5-year relapse rate, 27% +/- 6% vs 50% +/- 10%; P = .09). There were no differences in the engraftment of neutrophil and platelet, grade II-IV acute graft-versus-host disease (GVHD), extensive-stage chronic GVHD, and transplant-related mortality between the high and low CD34(+) cell dose groups. We confirmed that high CD34(+) cell dose favorably affects the outcomes in allogeneic BMT for AML. The effort to attain a high CD34(+) cell dose should be pursued during bone marrow harvest in allogeneic BMT for AML in CR1.     

Activity of recombinant human interleukin-15 against tumor recurrence and metastasis in mice

Transplantable experimental tumor models were constructed to study the activities of recombinant human interleukin-15 （rhIL-15） against tumor recurrence and metastasis. The results showed that tumor nodule formation was retarded and tumor growth was inhibited in the subcutaneous tumor model of LA795 lung adenocarcinoma after treatment with rhIL-15, and the survival rate of T739 tumor-bearing mice treated with rhIL-15 was much higher than that of mice treated with either saline or with the same dose of rhIL-2. This indicats that rhIL-15 had better antitumor effect than rhIL-2 at the same dose level. In some rhIL-15 treated mice, the tumor cells inoculated subcutaneously were eradicated and there was no tumor formation even 138 days after tumor cell inoculation. The tumor-free mice were rechallenged with live tumor cells and no tumor reoccurred in the following two months in all of these mice, indicating that long-lasting antitumor systemic immunity developed. It was also shown that tumor recurrence and metastasis were inhibited markedly after treatment with rhIL-15, but not with the same dose of rhIL-2, in both subcutaneously and intravenously disseminated tumor models of LA795 lung adenocarcinoma. Simultaneously, the CTL and NK cell activities of the splenocytes obtained from tumor-bearing mice that had been treated with either rhIL-15 or rhIL-2 were both markedly enhanced. However, the enhancement of CTL and NK cell activities was more significant in rhIL-15 treated mice than that in rhIL-2 treated mice. This suggests that the anti-tumor effect of rhIL-15 in vivo was achieved by enhancing the CTL and NK cell activities in tumor immune response.     

The radiobiological effect of intra-fraction dose-rate modulation in intensity modulated radiation therapy (IMRT)

Intensity-modulated radiation therapy (IMRT) achieves optimal dose conformity to the tumor through the use of spatially and temporally modulated radiation fields. In particular, average dose rate and instantaneous dose rate (pulse amplitude) are highly variable within a single IMRT fraction. In this study we isolate these variables and determine their impact on cell survival. Survival was assessed using a clonogenic assay. Two cell lines of differing radiosensitivity were examined: melanoma (MM576) and non-small cell lung cancer (NCI-H460). The survival fraction was observed to be independent of instantaneous dose rate. A statistically significant trend to increased survival was observed as the average dose rate was decreased, for a constant total dose. The results are relevant to IMRT practice, where average treatment times can be significantly extended to allow for movement of the multi-leaf collimator (MLC). Our in vitro study adds to the pool of theoretical evidence for the consequences of protracted treatments. We find that extended delivery times can substantially increase the cell survival. This also suggests that regional variation in the dose-rate history across a tumor, which is inherent to IMRT, will affect radiation dose efficacy.     

The effect of stochastic fluctuation in radiation dose-rate on cell survival following fractionated radiation therapy

In radiobiological models, it is often assumed that the radiation dose rate remains constant during the course of radiation delivery. However, instantaneous radiation dose rate undergoes random (stochastic) temporal fluctuation. The effect of stochastic dose rate in fractionated radiation therapy is unknown and there has been no analytical formulation of stochastic dose-rate fluctuation effect in fractionated radiation therapy which we endeavor to pursue here. We have obtained the quantitative expression of cellular survival fraction considering stochastic temporal fluctuation or noise in dose rate. We have shown that the constant dose-rate approximation overestimates the survival fraction compared to that under stochastic dose rate in a fractionated radiation therapy situation and this overestimation effect increases appreciably with the increase in the fluctuation level in dose rate. However, for a given level of fluctuation in dose rate, overestimation of survival fraction also depends on the value of cellular radiation sensitivity parameter β and the repair rate of DNA lesion. This overestimation effect is higher for the cells which have a higher value of β parameter or have a lower repair rate. Our study draws attention to stochastic temporal fluctuation in the radiation dose rate and its potential contribution to cell survival following fractionated radiotherapy.     

临床计划评估的放射生物学模型研究进展

放射治疗计划评估方式主要是基于体积剂量,未能反映肿瘤以及正常组织接受剂量后的生物学效应,将生物学模 型应用到放疗计划评估中进一步反映其生物学效应和临床效果。本研究主要对细胞存活率模型、肿瘤控制率模型、正常 组织并发症模型以及次级肿瘤风险预测模型等不同生物学模型的发展进行简要概括。对于细胞存活模型简述其典型模 型线性二次模型,以及针对高剂量、高剂量率以及损伤修复等提出的其他修正模型。在肿瘤控制率以及正常组织并发症 模型简述基于泊松函数和逻辑关系的不同泊松模型、逻辑模型。对于次级肿瘤风险预测模型主要对基于线性二次模型以 及考虑细胞增殖等不同的预测模型发展进行简要概括。     

Self-consistent tumor control probability and normal tissue complication probability models based on generalized EUD

Traditional methods to compute the tumor control probability (TCP) or normal tissue complication probability (NTCP) typically require a heterogeneous radiation dose distribution to be converted into a simple uniform dose distribution with an equivalent biological effect. Several power-law type dose-volume-histogram reduction schemes, particularly Niemierko's generalized equivalent uniform dose model [Med. Phys. 26, 1000 (1999)], have been proposed to achieve this goal. In this study, we carefully examine the mathematical outcome of these schemes. We demonstrate that (1) for tumors, with each tumor cell independently responding to local radiation dose, a closed-form analytical solution for tumor survival fraction and TCP can be obtained; (2) for serial structured normal tissues, an exponential power-law form relating survival to functional sub-unit (FSU) radiation is required, and a closed-form analytical solution for the related NTCP is provided; (3) in the case of a parallel structured normal tissue, when NTCP is determined solely by the number of the surviving FSUs, a mathematical solution is available only when there is a non-zero threshold dose and/or a finite critical dose defining the radiotherapy response. Some discussion is offered for the partial irradiation effect on normal tissues in this category; (4) for normal tissues with alternative architectures, where the radiation response of FSU is inhomogeneous, there is no exact global mathematical solution for SF or NTCP within the available schemes. Finally, numerical fits of our models to some experimental data are also presented.     

Modeling dose response in the presence of spatial variations in dose rate

Nonuniform dose rates are an inevitability in treatments involving internal sources, arising from electronic disequilibrium effects as well as nonuniformity in activity distribution. These dose-rate nonuniformities are of consequence for protracted treatments (when dose-delivery times are of the order of cell-repair times). The influence of nonuniform dose rates on tumor control probability (TCP) has thus been considered. A model for TCP has been developed by merging established (linear-quadratic based) TCP models for dose nonuniformity, with dose-rate effects as influenced by cell repair and proliferation capacities. This model has been examined by considering treatment of spherical tumors of varying sizes filled with uniform distributions of several beta-emitting isotopes. Dose (or dose-rate) volume histograms (DVHs) were calculated for the combinations of tumor size and isotope, and applied to the developed TCP model. Comparison of the results identified several characteristics of the effect of nonuniform dose rate, including the balance between minimum dose and cell number as they vary with tumor size, the dominance of minimum dose (dose rate) on TCP, and the influence of cell-proliferation effects on effective delivered dose (and the effective DVH). The model was also used to determine TCPs for simulated 90Y-labeled microsphere treatments of liver metastases using both uniform and clustered-microsphere models for activity distributions, and for varying tumor size. Despite significantly higher doses being achieved via clustered (nonuniform) activity distributions, the minimum dose for clustered distributions is consistently lower than that of the corresponding uniform distributions, and TCP is always higher for the uniform distributions.     

Lactoferrin can protect mice against a lethal dose of Escherichia coli in experimental infection in vivo.

Experiments were undertaken to demonstrate and partially explain the protective effect of bovine lactoferrin (LB) when administered intravenously to mice 24 h before a challenge with a lethal dose of Escherichia coli. About 70% of mice pretreated with LB survived challenge. The survival rates in control mice treated with E. coli alone and pretreated with bovine serum albumin (BSA), were 4 and 8%, respectively. Human lactoferrin (LH) had almost the same protective effect as LB. Sufficient amounts of ferric ions were given to mice, in single and multiple doses, for full serum transferrin saturation 30 min before or after E. coli administration. The multiple dose of ferric ions did not change considerably the survival rate of mice pretreated with LB. In contrast, a single dose of ferric ions gradually decreased the survival rate of the mice after the first week of experiment. From day 14 this decrease was statistically significant in all groups of mice treated with a single dose of ferric ions when compared with mice pretreated only with LB, and the difference ranged from 25 to 35% on day 30. The possible mechanism(s) of protective effect of LB and role of iron ions are discussed.     

Lactoferrin can protect mice against a lethal dose of Escherichia coli in experimental infection in vivo

Experiments were undertaken to demonstrate and partially explain the protective effect of bovine lactoferrin (LB) when administered intravenously to mice 24 h before a challenge with a lethal dose of Escherichia coli. About 70% of mice pretreated with LB survived challenge. The survival rates in control mice treated with E. coli alone and pretreated with bovine serum albumin (BSA), were 4 and 8%, respectively. Human lactoferrin (LH) had almost the same protective effect as LB. Sufficient amounts of ferric ions were given to mice, in single and multiple doses, for full serum transferrin saturation 30 min before or after E. coli administration. The multiple dose of ferric ions did not change considerably the survival rate of mice pretreated with LB. In contrast, a single dose of ferric ions gradually decreased the survival rate of the mice after the first week of experiment. From day 14 this decrease was statistically significant in all groups of mice treated with a single dose of ferric ions when compared with mice pretreated only with LB, and the difference ranged from 25 to 35% on day 30. The possible mechanism(s) of protective effect of LB and role of iron ions are discussed.     

介质阻挡放电等离子体诱导白血病细胞凋亡及其机制研究

目的 探索介质阻挡放电(DBD)等离子体对肿瘤细胞的杀伤作用并分析其凋亡机制.方法 利用噻唑蓝(MTT)检测低温等离子体在不同作用时间下对正常脾脏白细胞和大鼠急性早幼粒白血病细胞(LT-12)细胞毒性的影响,检测等离子体处理后细胞内活性氧(ROS)含量的变化,利用Annexin V/PI双染法检测不同作用时间剂量下细胞凋亡情况,实时荧光定量PCR和Western Blot检测相关凋亡基因和蛋白的表达变化.结果 MTT结果表明,等离子体对细胞的杀伤呈作用时间剂量和时间依赖性,随着作用时间从30 s到240 s,处理8h后细胞的存活率从98％降至63％.在相同作用时间下,如240 s,细胞的存活率从2h的78％降至24 h的39％;Annexin V/PI双染法结果显示,等离子体作用可引起细胞凋亡,凋亡率不仅与等离子体作用时间剂量呈正相关,还与作用后的时间相关,等离子体处理后时间越长,其凋亡率越高,如处理12h后,细胞的凋亡率从60 s的48％增至120 s的55.3％;流式细胞仪检测的ROS的产生也显示了时间相关性,等离子体作用后其ROS立即增至1.24倍,至20 h急剧增高至5.39倍;qRT-PCR和Western Blot的实验结果表明,在等离子体处理后8～12 h Caspase家族和Bcl-2家族基因和蛋白表达非常活跃.结论 本研究表明低温等离子体能有效杀伤肿瘤细胞,凋亡是其主要的致死机制,并初步阐述了低温等离子体促进肿瘤细胞凋亡的分子机制.