不同剂量全脑放疗胶质瘤模型对血脑屏障紧密连接影响的研究

目的:观察C6脑胶质瘤单次全脑放疗后早期血脑屏障(BBB)通透性的变化、超微结构特征及紧密连接蛋白Claudin-5的表达变化。方法:荷瘤鼠50只,随机分为假照射组和5、10、15、20Gy组各10只,行相应剂量全脑放射线单次照射,并于照射后24h处死,各5只分别行硝酸镧透射电镜示踪法观察肿瘤临近处(BAT)BBB通透性,免疫组化法测定Claudin-5的变化。结果:硝酸镧示踪电镜观察:假照射组、5Gy组荷瘤鼠BAT处见La3+渗出至局部基底膜,大部分分布在血管腔内;10Gy组BAT处可见La3+渗出至广泛基底膜及脑组织间隙,紧密连接开放;15、20Gy组BAT处均可见La3+渗出至基底膜、血管腔外、脑组织间隙内及细胞内。统计学分析硝酸镧渗出显示,20、15Gy>10Gy>5、0Gy,P<0.05。Clau-din-5表达变化:假照射组、5Gy组荷瘤鼠BAT处脑组织表达下降,仍呈中度表达;10Gy组BAT处可见较假照射组脑组织表达下降,呈轻中度表达,血管扭曲、变形与间断表达状态并存;15、20Gy组BAT处均可见较假照射组脑组织表达下降,呈轻度表达,沿血管间断表达,并见碎片状。统计学分析显示,20、15Gy>...     

Influence of radiation on the blood-brain barrier and optimum time of chemotherapy

A pilot study of the destructive effects of radiation on the blood-brain barrier (BBB) was made on 14 patients with localized and limited brain tumors by 99MTc-GH imaging from August 1988 to November 1989. Count/pixel data were obtained from the unirradiated, irradiated, and tumor areas before and after radiotherapy of 30-40 Gy. It was observed that, a) the BBB in the unirradiated area outside the radiation portal was not changed, b) the degree of destructive effect on the BBB in the irradiated normal area was directly proportional to the radiation dose. For 30-40 Gy, the count/pixel change enhances to average 24.7% [(147.6-118.4)/118.4], and c) the BBB in the tumor area is partially destroyed on an average of 22.1% [(206.8-169.4)/169.4] by the tumor. The radiotherapy further enhances this effect to an average of 74.7% [(206.8-118.4)/118.4]. Case 3 showed that before radiation, the degree of destructive effect on the BBB in the tumor area was 22% [(167-137)/137] higher than normal brain tissue. After a dose of 30 Gy of irradiation, it increased to 76.7% [(242-137)/137]; 8 months later it decreased to 17% [(160.3-137)/137]. It has been proven that the BBB can recover at least partially. Based on these observations, the authors believe that in the combined treatment of operated brain tumors, radiotherapy should precede chemotherapy so as to enhance the destruction of the BBB, facilitating the incorporation of drugs into the tumor. The dose at which to start chemotherapy is 20-30 Gy.     

Successful receptor-mediated radiation therapy of xenografted human midgut carcinoid tumour

Somatostatin receptor (sstr)-mediated radiation therapy is a new therapeutic modality for neuroendocrine (NE) tumours. High expression of sstr in NE tumours leads to tumour-specific uptake of radiolabelled somatostatin analogues and high absorbed doses. In this study, we present the first optimised radiation therapy via sstr using [(177)Lu-DOTA(0)-Tyr(3)]-octreotate given to nude mice xenografted with the human midgut carcinoid GOT1. The tumours in 22 out of 23 animals given therapeutic amounts showed dose-dependent, rapid complete remission. The diagnostic amount (0.5 MBq [(177)Lu-DOTA(0)-Tyr(3)]-octreotate) did not influence tumour growth and was rapidly excreted. In contrast, the therapeutic amount (30 MBq [(177)Lu-DOTA(0)-Tyr(3)]-octreotate) induced rapid tumour regression and entrapment of (177)Lu so that the activity concentration of (177)Lu remained high, 7 and 13 days after injection. The entrapment phenomenon increased the absorbed dose to tumours from 1.6 to 4.0 Gy MBq(-1) and the tumours in animals treated with 30 MBq received 120 Gy. Therapeutic amounts of [(177)Lu-DOTA(0)-Tyr(3)]-octreotate rapidly induced apoptosis and gradual development of fibrosis in grafted tumours. In conclusion, human midgut carcinoid xenografts can be cured by receptor-mediated radiation therapy by optimising the uptake of radioligand and taking advantage of the favourable change in biokinetics induced by entrapment of radionuclide in the tumours.     

Monitoring HSVtk suicide gene therapy: the role of [(18)F]FHPG membrane transport

Favourable pharmacokinetics of the prodrug are essential for successful HSVtk/ganciclovir (GCV) suicide gene therapy. [(18)F]FHPG PET might be a suitable technique to assess the pharmacokinetics of the prodrug GCV noninvasively, provided that [(18)F]FHPG mimics the behaviour of GCV. Since membrane transport is an important aspect of the pharmacokinetics of the prodrug, we investigated the cellular uptake mechanism of [(18)F]FHPG in an HSVtk expressing C6 rat glioma cell line and in tumour-bearing rats. The nucleoside transport inhibitors dipyridamol, NBMPR and 2-chloroadenosine did not significantly affect the [(18)F]FHPG uptake in vitro. Thymidine and uridine significantly decreased [(18)F]FHPG uptake by 84 and 58%, respectively, but an enzyme assay revealed that this decline was due to inhibition of the HSVtk enzyme rather than membrane transport. Nucleobase transport inhibitors, thymine and adenine, caused a 58 and 55% decline in tracer uptake, respectively. In vivo, the ratio of [(18)F]FHPG uptake in C6tk and C6 tumours decreased from 3.0+/-0.5 to 1.0+/-0.2 after infusion of adenine. Thus, in our tumour model, [(18)F]FHPG transport exclusively occurred via purine nucleobase transport. In this respect, FHPG does not resemble GCV, which is predominantly taken up via the nucleoside transporter, but rather acyclovir, which is also taken up via the purine nucleobase carrier.     

Examination of blood–brain barrier (BBB) integrity in a mouse brain tumor model

The present study evaluates, both functionally and biochemically, brain tumor-induced alterations in brain capillary endothelial cells. Brain tumors were induced in Balb/c mice via intracranial injection of Lewis Lung carcinoma cells into the right hemisphere of the mouse brain using stereotaxic apparatus. Blood–brain barrier (BBB) permeability was assessed at various stages of tumor development, using both radiolabeled tracer permeability and magnetic resonance imaging with gadolinium diethylene-triamine-pentaacetate contrast enhancement (Gad-DTPA). The expression of the drug efflux transporter, P-glycoprotein (P-gp), in the BBB at various stages of tumor development was also evaluated by Western blot and immunohistochemistry. Median mouse survival following tumor cell injection was 17 days. The permeability of the BBB to ³H-mannitol was similar in both brain hemispheres at 7 and 10 days post-injection. By day 15, there was a twofold increase in ³H-mannitol permeability in the tumor bearing hemispheres compared to the non-tumor hemispheres. Examination of BBB permeability with Gad-DTPA contrast enhanced MRI indicated cerebral vascular permeability changes were confined to the tumor area. The permeability increase observed at the later stages of tumor development correlated with an increase in cerebral vascular volume suggesting angiogenesis within the tumor bearing hemisphere. Furthermore, the Gad-DPTA enhancement observed within the tumor area was significantly less than Gad-DPTA enhancement within the circumventricular organs not protected by the BBB. Expression of P-gp in both the tumor bearing and non-tumor bearing portions of the brain appeared similar at all time points examined. These studies suggest that although BBB integrity is altered within the tumor site at later stages of development, the BBB is still functional and limiting in terms of solute and drug permeability in and around the tumor.     

The late effects of radiation on the blood brain barrier

Rats were irradiated with 60 to 20 Gy in a single dose focussed to a volume of 0.5 cc in the center of the left hemisphere. Breakdown of the BBB was detected by the presence of spikes on EEG after subcutaneous injection of Bicuculline methiodide, and the presence of staining following Evans Blue dye injection. Breakdown of the BBB (mean and standard deviation) occurred in 38/46 of the 60 Gy rats at 98 +/- 16 days, 7/11 of the 50 Gy rats at 128 +/- 25 days, 11/18 of the 40 Gy rats at 162 +/- 3 days, 5/11 of the 30 Gy rats at 178 +/- 5 days and, 7/12 of the 20 Gy rats at 217 +/- 7 days post irradiation. This study suggests that endothelial damage could be the principle mechanism mediating the late radiation syndrome.     

胶质瘤模型单剂量全脑放疗后血脑屏障开放的时间阈及紧密连接变化的研究

目的观察C6脑胶质瘤15 Gy单次全脑放射线照射后血-脑屏障(blood-brain barrier,BBB)通透性的动态变化及紧密连接蛋白claudin-5的表达变化,观察大鼠血-脑屏障(BBB)开放的时间阈。方法荷瘤鼠（建模后17天）60只,行15 Gy全脑放射线单次照射,并于照射后24 h、3 d、7 d、14 d、21 d、28 d各处死10只,各5只分别行硝酸镧（La+）透射电子显微镜示踪法观察肿瘤邻近处（brain adjacent to tumor,BAT）即距肿瘤边界2 mm以内BBB通透性及免疫组织化学法测定紧密连接蛋白claudin -5的变化研究。结果（1）照射后24 h、3 d硝酸镧渗出广泛,基底膜、血管腔外、脑组织间隙内及细胞内均可见;第7 d为La3+渗出减弱,基底膜及脑组织间隙内见细小的镧颗粒;第14 d为La3+渗出至局部基底膜,较前减少;第21 d、28 d均为La3+ 无渗出。统计学分析硝酸镧渗出程度显示：24 h和3 d>7 d>14 d>21 d和28 d（P<0.05）。（2）照射后24 h、3 d紧密连接蛋白claudin-5呈轻度表达,呈碎片状表达;照射后第7 d为轻中度表达,血管扭曲、变形;照射后第14 d为中度表达,血管扭曲、变形,但仍呈连续状态;照射后第21 d、28 d为中强度表达,出现连续与碎片表达并存。统计学分析claudin-5表达程度显示：24 h和3 d<7 d<14d<21 d和28 d（P<0.05）。结论荷瘤鼠单次15 Gy照射后BBB开放,且2周后BBB通透性逐渐消失,表现出时间依赖性。     

Evaluation of hypoxia in an experimental rat tumour model by [(18)F]fluoromisonidazole PET and immunohistochemistry

This study aimed to evaluate tumour hypoxia by comparing [(18)F]Fluoromisonidazole uptake measured using positron emission tomography ([(18)F]FMISO-PET) with immunohistochemical (IHC) staining techniques. Syngeneic rhabdomyosarcoma (R1) tumour pieces were transplanted subcutaneously in the flanks of WAG/Rij rats. Tumours were analysed at volumes between 0.9 and 7.3 cm(3). Hypoxic volumes were defined using a 3D region of interest on 2 h postinjection [(18)F]FMISO-PET images, applying different thresholds (1.2-3.0). Monoclonal antibodies to pimonidazole (PIMO) and carbonic anhydrase IX (CA IX), exogenous and endogenous markers of hypoxia, respectively, were used for IHC staining. Marker-positive fractions were microscopically measured for each tumour, and hypoxic volumes were calculated. A heterogeneous distribution of hypoxia was observed both with histology and [(18)F]FMISO autoradiography. A statistically significant correlation (P<0.05) was obtained between the hypoxic volumes defined with [(18)F]FMISO-PET and the volumes derived from the PIMO-stained tumour sections (r=0.9066; P=0.0001), regardless of the selected threshold between 1.4 and 2.2. A similar observation was made with the CA IX staining (r=0.8636; P=0.0006). The relationship found between [(18)F]FMISO-PET and PIMO- and additionally CA IX-derived hypoxic volumes in rat rhabdomyosarcomas indicates the value of the noninvasive imaging method to measure hypoxia in whole tumours.     

Optimum dose range for the amelioration of long term radiation-induced hyposalivation using prophylactic pilocarpine treatment.

BACKGROUND: To determine dose and time dependency of pilocarpine pre-treatment protection from late damage after unilateral irradiation of the rat parotid gland. METHODS AND MATERIALS: The right parotid gland of saline (1mg/ml) or pilocarpine (4 mg/kg) pre-treated rats was irradiated with 10, 15 and 20 Gy. Saliva was collected from the irradiated and shielded parotid before, 30, 60, 120 and 240 days after irradiation. The number of acinar cells/gland was determined 30, 120 and 240 days after irradiation by histological examination. RESULTS: Pilocarpine pre-treated rats, protection of parotid gland function was seen in the early-intermediate phase (0-120 days) after 15 Gy and in the late phase (>120 days) after 10 and 15 Gy. Although no protection was observed after 20 Gy, a stimulatory effect of pilocarpine on the non-irradiated gland resulted in a significant increase in total saliva secretion. The increase in function after pilocarpine treatment was paralleled by a significant increase in the number of acinar cells in both the irradiated and shielded glands. CONCLUSIONS: Pre-irradiation treatment with pilocarpine induces compensatory response, at lower doses, in the irradiated and at higher doses in the non-irradiated gland reducing late damage, due to stimulation of unirradiated or surviving cells to divide.     

PET identifies transitional metabolic change in the spinal cord following a subthreshold dose of irradiation

Positron emission tomographic (PET) investigations were performed to obtainin vivo information on symptomless radiation-induced pathological changes in the human spinal cord. PET investigations were carried out prior to radiotherapy and during the regular follow-up in an early hypopharyngeal cancer patient (the spinal cord was irradiated with a biologically effective dose of 80 Gy₂), with [¹⁸F]fluorodeoxyglucose (FDG), [¹¹C]methionine and [¹⁵O]butanol as tracers; radiosensitivity and electroneuronographic (ENG) studies were also performed. A very low background FDG accumulation (mean standardized uptake values, i.e. SUV: 0.84) was observed in the spinal cord before the initiation of radiotherapy. An increased FDG uptake was measured 2 months after the completion of radiotherapy (mean SUV: 1.69), followed by a fall-off, as measured 7 months later (mean SUV: 1.21). By 44 months after completion of irradiation, the FDG accumulation in the irradiated segments of the spinal cord had decreased to a level very close to the initial value (mean SUV: 1.11). The simultaneous [¹⁵O]butanol uptake results demonstrated a set of perfusion changes similar to those observed in connection with the FDG accumulation. The patient exhibited an extremely low [¹¹C]methionine uptake within the irradiated and the nonirradiated spinal cord during the clinical course. She has not had any neurological symptoms, and the results of central ENG measurements before radiotherapy and 2 months following its completion proved normal. Radiobiological investigations did not reveal unequivocal signs of an increased radiosensitivity. A transitory increased spinal cord FDG uptake following radiotherapy may be related to the posttherapeutic mild inflammatory and regenerative processes. The normal [¹¹C]methionine accumulation observed is strong evidence against intensive cell proliferation. The high degree of normalization of the temporarily increased FDG uptake of the irradiated spinal cord segments by 44 months is in good agreement with the results of monkey studies, which demonstrated a nearly complete recovery from radiation-induced spinal cord injury. This work was supported in part by grants from the Hungarian Research Fund (OTKA T-032499 and T-046128), ETT 395/KO/2003, 37/2003 and the Ministry of Education „Széchenyi” (OM 1/008/2001).     

In vivo evaluation of [18F]fluoroetanidazole as a new marker for imaging tumour hypoxia with positron emission tomography

Development of hypoxia-targeted therapies has stimulated the search for clinically applicable noninvasive markers of tumour hypoxia. Here, we describe the validation of [(18)F]fluoroetanidazole ([(18)F]FETA) as a tumour hypoxia marker by positron emission tomography (PET). Cellular transport and retention of [(18)F]FETA were determined in vitro under air vs nitrogen. Biodistribution and metabolism of the radiotracer were determined in mice bearing MCF-7, RIF-1, EMT6, HT1080/26.6, and HT1080/1-3C xenografts. Dynamic PET imaging was performed on a dedicated small animal scanner. [(18)F]FETA, with an octanol-water partition coefficient of 0.16+/-0.01, was selectively retained by RIF-1 cells under hypoxia compared to air (3.4- to 4.3-fold at 60-120 min). The radiotracer was stable in the plasma and distributed well to all the tissues studied. The 60-min tumour/muscle ratios positively correlated with the percentage of pO(2) values <5 mmHg (r=0.805, P=0.027) and carbogen breathing decreased [(18)F]FETA-derived radioactivity levels (P=0.028). In contrast, nitroreductase activity did not influence accumulation. Tumours were sufficiently visualised by PET imaging within 30-60 min. Higher fractional retention of [(18)F]FETA in HT1080/1-3C vs HT1080/26.6 tumours determined by dynamic PET imaging (P=0.05) reflected higher percentage of pO(2) values <1 mmHg (P=0.023), lower vessel density (P=0.026), and higher radiobiological hypoxic fraction (P=0.008) of the HT1080/1-3C tumours. In conclusion, [(18)F]FETA shows hypoxia-dependent tumour retention and is, thus, a promising PET marker that warrants clinical evaluation.     

Drug binding to P-glycoprotein is inhibited in normal tissues following SDZ-PSC 833 treatment

Rats were treated with daily injections of SDZ-PSC 833 (PSC) to study the interaction of this potent modulator of multidrug resistance (MDR) with P-glycoprotein (P-gp) expressed in normal tissues. After 2 days of treatment, the level of P-gp expression, detected by Western blot analysis, was not modified in renal brush border membranes (BBMs) and brain capillaries. However, the amount of P-gp detected with the photoaffinity probe [¹²⁵I]-arylazidoprazosin (IAAP) was decreased in both tissues, suggesting that the drug binding properties of P-gp were altered by PSC treatment. This effect was further characterized by treating rats with PSC for 10 days. Following these treatments, the amount of immunodetected P-gp was increased in renal BBMs and brain capillaries. However, no increase in P-gp expression was observed in photolabeling experiments, suggesting that induced P-gp was not functional. In vitro experiments performed with renal BBMs showed that the inhibition of P-gp photolabeling by cyclosporin A (CsA), verapamil and vinblastine could be reversed by performing washing steps to remove these drugs before incubating the samples with IAAP. However, the inhibition mediated by PSC was less reversible since photolabeling of P-gp remained inhibited following the washing steps. Pre-incubation of intact CH^RC5 cells with PSC, CsA and verapamil also inhibited P-gp photolabeling and increased rhodamine 123 accumulation. For PSC pre-treated samples, these effects were not completely reversed following washing, but were abolished for CsA and Ver pre-treated samples. Our results suggest that PSC could block P-gp function by a different mechanism from that of CsA and verapamil, involving modification of the drug binding sites. Int. J. Cancer 76:00–00, 1998.© 1998 Wiley-Liss, Inc.     

食管癌细胞照射后细胞周期及相关蛋白表达的变化

目的：探讨食管癌细胞照射后细胞周期、细胞凋亡及其相关蛋白表达的变化。方法：食管癌细胞株TE-1和TE-13照射2、5、10、15Gy后，应用流武细胞仪分别检测照射后6、24和48h细胞周期和凋亡指数变化、Western blot检测细胞周期相关蛋白的表达。结果：2、5、10、15Gy照射0～48h，TE-1和TE-13细胞均出现明显剂量依赖性的G2／M期阻滞和解除变化；5～15Gy照射后48h，TE-13细胞在G2／M期阻滞逐渐解除时伴随着细胞凋亡的明显增加，而TE-1细胞凋亡不增加。2株细胞胞浆CHK2-p68磷酸化水平均呈随照射后时间延长而出现时相性变化，但与照射剂量无关；而CHK1、CHK2、CHK1-p345和CDK1蛋白表达均无明显变化。15Gy照射后24h，TE-13细胞胞浆中eyelin B1表达下降而TE1细胞中无明显变化。结论：病理不同分化的食管癌细胞照射后细胞周期、细胞凋亡以及细胞周期相关蛋白表达变化不尽相同。     

A cyclin-dependent kinase inhibitor (p21(WAF1/CIP1)) affects thymidine incorporation in human liver cancer cells

p21(WAF1/CIP1) is a universal cyclin-dependent kinase inhibitor. To investigate the role of p21(WAF1/CIP1) in proliferation of human liver cancer cells, we examined the expression of p53, p21(WAF1/CIP1), cdk2 and cdk4 expression in two human liver cancer cell lines (HepG2 and PLC/PRF/5 cells). The effects of p21(WAF1/CIP1) on [(3)H]thymidine incorporation and cdks were also examined in these cells. HepG2 cells expressed all these proteins with lower level of cdk4. PLC/PRF/5 cells expressed the other proteins except p21(WAF1/CIP1). Transfection of p21(WAF1/CIP1) gene inhibited [(3)H]thymidine incorporation of both cells with different extent. Although the transfection of p21(WAF1/CIP1) did not affect cdk2 and cdk4 expression, it did reduce cdk2 kinase activity by 20%. These results suggest that: (a) p21(WAF1/CIP1) involved in DNA synthesis of human liver cancer cells; (b) p21(WAF1/CIP1) could be a target gene for the treatment of human hepatocellular carcinoma.     

大鼠全脑照射后脑内一氧化氮含量的变化

[目的]观察大鼠全脑照射后脑组织中一氧化氮（NO）含量的变化，探讨放射性脑损伤中NO所起的作用。[方法]对SD大鼠用4MeV电子线单次全脑5Gy、15Gy和30Gy照射后，于照射后6h、1d、2d和3d检测大大脑皮层中NO的含量．[结果]5Gy、15Gy和30Gy照射后1d、2d．脑内NO随照射剂量递增而增加（P〈0．05）．在6h和3d各剂量组无差异。各剂量组在1d时脑内NO达峰值，2d时逐渐下降．3d时恢复对照组水平。[结论]大鼠全脑照射后脑组织中NO升高，它在放射性脑损伤的发病机制中可能有重要的作用。     

Radiation sterilisation of cultured human brain tumour cells for clinical immune tumour therapy

The aim is to investigate the radiosensitivity of noninfected cultured human glioma cells to ascertain that intracutaneously administered cells are viable enough to produce interferon-gamma but not able to proliferate. Cell cultures were established from five patients undergoing brain tumour surgery. By karyotyping, we found four malignant (three glioblastoma multiforme (GBM), one giant cell glioma) and one normal. The cells were irradiated with (137)Cs-gamma rays at absorbed dose levels of 0, 20, 40, 60, 80, 100 and 120 Gy. The fraction of viable cells was examined by MTT incorporation assay. The average of the data obtained from three GBM cell cultures was fitted to an exponential model. The parameters were: extrapolation number n=0.85+/-0.10, mean lethal dose D(0)=12.4+/-3.2 Gy and an additional uncertainty parameter deltaS=0.14+/-0.03. By setting deltaS=0, the corresponding values of the parameters were n=0.86+/-0.16 and D(0)=30.0+/-8.1 Gy. The rate of proliferation was examined by (3)H-thymidine incorporation. The average of the proliferation data obtained from three GBM cell cultures was fitted to an exponential model yielding n=0.943+/-0.005 and D(0)=5.8+/-0.5 Gy for deltaS=0.057+/-0.005, and by setting deltaS=0, n=1.00+/-0.02 and D(0)=8.4+/-1.6 Gy. No outgrowth of plated cells was observed after 4 weeks at an absorbed dose of 100 Gy. This absorbed dose is recommended for irradiation of 2 x 10(6) glioma cells used for clinical immunisation.     

Intracranial ependymomas: results of treatment with partial or whole brain irradiation without spinal irradiation

Twenty patients with intracranial ependymoma (16) or anaplastic ependymoma (4) received post-operative radiation therapy at the University of California, San Francisco from 1959 through 1981. No patient received prophylactic spinal irradiation. The actuarial survival at 5, 10, and 15 years for 15 patients with ependymoma who received greater than 45 Gy was 67, 57, and 46%, respectively. Only one patient (7%) developed clinically recognized spinal metastases; this patient was eventually shown to have tumor at the primary site, within the irradiated volume. Six of 11 patients treated with partial brain irradiation had an intracranial recurrence, versus 1 of 4 patients treated with whole brain irradiation. Three patients were autopsied after failing partial brain irradiation for an ependymoma and the site of failure was within the irradiated volume of each patient. Partial brain irradiation was used to treat 4 patients with anaplastic ependymoma. One developed a local recurrence within the irradiated volume. The other three survived longer than 10 years. At UCSF, most patients with low grade ependymomas are presently treated with partial brain irradiation, but whole brain plus spinal irradiation is used for anaplastic tumors.     

阿帕替尼对胃癌HGC-27细胞放射敏感性的影响及其作用机制

目的 探讨阿帕替尼对胃癌HGC-27细胞放射敏感性的影响及可能的作用机制。方法 以不同浓度阿帕替尼（5 μmol/L、10 μmol/L、15 μmol/L、20 μmol/L）以及不同照射剂量（2 Gy、4 Gy、6 Gy、10 Gy、20 Gy）分别处理HGC-27细胞,再选取2 Gy和6 Gy单独照射或联合10 μmol/L阿帕替尼处理HGC-27细胞;采用ELISA法检测细胞中血管内皮生长因子（vascular endothelial growth factor,VEGF）的表达情况,CCK-8法检测细胞增殖能力,流式细胞术检测细胞凋亡和细胞周期,免疫荧光染色技术检测γ-H2AX的表达情况。结果 阿帕替尼呈浓度及时间依赖性抑制胃癌HGC-27细胞增殖（均P<0.05）;不同剂量照射可促进细胞VEGF表达释放,且呈时间及剂量依赖性（均P<0.01）。10 μmol/L阿帕替尼分别联合2 Gy和6 Gy照射后,HGC-27细胞增殖抑制作用、细胞凋亡率及G2/M期的细胞比例均较单照组升高（均P<0.01）,且6 Gy联合组的作用强度大于2 Gy联合组（均P<0.01）。6 Gy联合组细胞核内γ-H2AX焦点淬灭较6 Gy单照组延迟。结论 阿帕替尼通过抑制细胞增殖,促进细胞凋亡并诱导细胞周期再分布增强胃癌HGC-27细胞放射敏感性,其作用机制可能与延迟γ-H2AX表达而干扰DNA双链断裂修复有关。     

The blood-brain barrier and oncology: new insights into function and modulation

The efficacy of chemotherapy for malignant primary or metastatic brain tumours is still poor. This is at least partly due to the presence of the blood-brain barrier (BBB). The functionality of the BBB can be explained by physicochemical features and efflux pump mechanisms. An overview of the literature is presented with emphasis on oncology.The BBB consists of capillary endothelial cells that lack fenestrations and are connected together with continuous tight junctions, with a high electrical resistance. Permeability of tight junctions can be increased in vitro by contraction of the cytoskeleton, caused by bradykinin agonists. Different efflux pumps are present in the BBB. Examples are P-glycoprotein (P-gp), organic anion transporters, (OAT) and multidrug-resistance-associated proteins (MRP)(1 and 3). These pumps act as a multi-specific efflux pump for various chemotherapeutic drugs. Experiments have shown that P-gp can be inhibited by different non-chemotherapeutic substrates such as cyclosporin A. The functionality in vivo of P-gp can be measured with positron emission tomography and [(11)C]-verapamil or with single photon emission computer tomography and(99m)Tc-sestamibi. MRP(1)and MRP(3)act as organic anion transporters that in vitro act as efflux pumps for substances that are conjugated or co-transported with glutathione and glucuronide, respectively. Methotrexate has been recently demonstrated to be transported by MRP(1)and MRP(3). Results of studies which demonstrate the clinical relevance and applicability of BBB modulators are eagerly awaited.