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Biomedical subjects

Yan Zhao

Publications and source records attributed to Yan Zhao.

At least 127 records · Page 7Linked to original sources
PubMed2005

[Roles of mitochondria in vitamin E succinate-induced apoptosis in human gastric cancer SGC-7901 cells].

OBJECTIVE: In order to investigate the roles of mitochondria in vitamin E succinate (VES)-induced apoptosis in human gastric cancer SGC-7901 cells. METHODS: Mitochondrial transmembrane potential (deltapsi(m)) was observed by confocal laser scanning microscopy, while the expression of cytochrome c in cytosol and caspase-3 was measured by western blotting after the cells were treated with VES at 5, 10, 20 microg/ml. RESULTS: VES obviously decreased deltapsi(m) with dose- and time-dependent relationship, increased the expression of cytochrome c in cytosol and caspase-3 and activated caspase-3 as well. CONCLUSION: VES-induced apoptosis in SGC-7901 cells might involve mitochondrial permeability transition, release of cytochrome c and activation of caspase-3 downstream.

Apoptosis↗
PubMed2005

[The effect of short hairpin RNA on hTERT expression].

AIM: To study the effect of short hairpin RNA (shRNA) on hTERT expression. METHODS: Oligonucleotides encoding shRNA against hTERT was cloned into a mammalian shRNA expression vector pUC18U6 to form pUC18U6ht which was transfected into HepG2 cells by using liposome. HepG2 cells transfected by pUC18U6 and pUC18U6GFPsir which expressed shRNA against green fluorescent protein were used as controls. hTERT mRNA in the transfected cells was quantified by using real-time fluorescent RT-PCR. RESULTS: Compared with the controls, the short hairpin RNA against hTERT decreased the hTERT mRNA level by 49% (P<0.05). CONCLUSION: hTERT expression was reduced by the shRNA.

Animals↗
PubMed2005

[Changes in the immune function of dendritic cells (DC) derived from HBV-related hepatocellular carcinoma (HCC) patient's peripheral blood monocytes (PBMC) pulsed with tumor antigen].

OBJECTIVE: To identify the phenotype and immune function of dendritic cells derived from HBV-related HCC patients's peripheral blood monocytes pulsed with soluble tumor antigen, and their relation to immune escape. METHODS: Peripheral blood monocytes were isolated from 18 HBV-related hepatocellular carcinoma (HCC) patients, 11 HBV-related liver cirrhosis patients (LC) and 10 health blood donors; DCs were induced in the completed medium containing GM-CSF and IL-4. The morphology of DCs was studied using a confocal microscope and scanning electronic microscope, and the phenotype of DCs were detected by flow cytometric analysis. The mixed leucocyte reaction test was employed to determine the stimulatory capacity of DCs before and after being pulsed with soluble tumor antigen (prepared from HCCLM6 cell line). IL-12 ELISA kit was used to investigate IL-12 secretion of DCs in the supernate of MLR. RESULTS: The amount of PBMC and DCs was significantly lower in LC and HCC compare to those in the healthy subjects; the expression levels of HLA-DR, CD1a, CD80 and CD86 on DC surfaces were lower in LC and HCC patients than those of the healthy group; the stimulating capacity of DC in MLR and levels of IL-12 in supernate of MLR were also lower in LC and HCC, but were enhanced after tumor antigen pulsed in all three groups, particularly in the LC group; the secretion of IL-12 in MLR supernate was still lower than that of the healthy group. CONCLUSION: The phenotype and function defects of DC derived from PBMC of LC and HCC patients might play a key role in immune escape in HBV infection and HCC. The function of DC of LC patients can be enhanced after the tumor was antigen-pulsed.

Antigens, Neoplasm↗
PubMed2005

[Relationship between DLC-1 expressions and metastasis in hepatocellular carcinoma].

OBJECTIVES: To study the relationship between the expression level of DLC-1 mRNA (located in 8p) and the invasion/metastasis of human hepatocellular carcinoma (HCC). METHODS: Fifty-one surgical specimens of human HCC were divided into high-invasive and low invasive groups according to their clinicopathological features. DLC-1 mRNA expression was studied in the 51 HCC specimens as well as 5 different metastasis potential cell lines using real-time quantitative PCR (RQ-PCR). RESULTS: The expression level of DLC-1 mRNA in HCC specimens with high invasiveness was significantly lower than that with low invasiveness (P < 0.05). The expression levels of DLC-1 mRNA were significantly different between non-metastatic (Hep3B and HepG2) and metastatic (MHCC97-H, MHCC97-L and HCCLM3) cell lines (P < 0.05). From MHCC97-L to HCCLM3, with an increase of invasiveness and metastatic potentials, the expression level of DLC-1 decreased correspondingly, and its expression level in HCCLM3 was significantly lower than that in MHCC97-L (P < 0.01). CONCLUSION: The expression of DLC-1 mRNA may play an important role in inhibiting the invasiveness and metastasis of HCC.

Carcinoma, Hepatocellular↗
PubMed2005

[Effect of hepatocyte growth factor on oxygen-glucose deprived injury of astrocytes].

OBJECTIVE: To explore the effect of hepatocyte growth factor (HGF) on oxygen-glucose deprived injury and apoptosis of astrocytes. METHODS: The injury of primary cultured rat cerebral cortical astrocytes was induced by oxygen-glucose deprivation. Astrocytes were treated with HGF at various final concentrations of 20 - 100 ng/mL. The cell damage and viability were evaluated by the lactate dehydrogenase (LDH) released rate and the 3- (4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) conversion method. Detection of apoptotic cells was determined by the flow cytometry, and the ultrastructure was observed by the transmission electron microscope. RESULTS: Oxygen-glucose deprivation increased the LDH release rate, decreased the cell viability and increased the number of apoptotic astrocytes. While exposed to HGF at the same condition, the LDH release rate decreased, the cell viability increased, and the percentage of apoptotic cells decreased (P <0.05). The maximum protective effect of HGF was observed at 60 ng/mL. CONCLUSION: HGF can protect cultured astrocytes from oxygen-glucose deprived injury, and attenuate the apoptosis of astrocytes in a dose-dependent manner.

Animals↗
PubMed2005

[Inheritance analysis and molecular marker selection of genes for wheat spindle streak mosaic disease resistance].

Three wheat spindle streak mosaic viruses (WSSMV) resistant cultivars ('Yining Xiaomai', 'Xu87-633', and 'Xifeng') and one susceptible cultivar ('Zhen9523') were used as parents of 3 crosses in this experiment. WSSMV resistance of the parents, F1, and F2 was evaluated under field condition. Based on the segregation ratios of resistant and susceptible plants in F, and F2 populations, it was deduced that the resistance to WSSMV was dominant and the inheritable factors controlling WSSMV resistance were encoded by the nuclear genome. WSSMV resistances in 'Yining Xiaomai' and 'Xifeng' were controlled by two pairs of alleles, which showed complementary effects. However the resistance in 'Xu-87633' was controlled by a single dominant gene. 266 pairs of SSR primers located on 21 wheat chromosomes were used for polymorphic analysis of the two resistant and the susceptible parents 'Yining Xiaomai' and 'Zhen9523', and 108 of them amplified polymorphic DNA products. By Bulk Segregant Analysis of resistant and susceptible pools, one pair of primer located on chromosome arm 2DS, Xgwm261, were found being linked to WSSMV resistance. The 224 F2 individuals were then amplified with marker Xgwm261. The statistic genetic distance between Xgwm261 and the resistance locus was calculated to be 22.9 cM using the software Mapmaker 3.0.

Chromosomes, Plant↗
PubMed2005

[Clinical management and prognostic analysis of primary peritoneal neoplasms].

OBJECTIVE: To investigate the clinical management strategies and prognostic factors of primary peritoneal neoplasms. METHODS: We retrospectively reviewed the clinical and pathological records of 24 cases with primary peritoneal neoplasms treated in the People's Hospital, Peking University during May 1995 and April 2004. RESULTS: Among 24 cases, 15 patients were diagnosed as serous papillary adenocarcinoma (9 highly and intermediately differentiated, and 6 lowly differentiated), 6 as mixed epithelial carcinoma and 3 as mixed malignant Mullerian tumor (MMMT). All patients underwent cytoreductive surgery, 21 cases having, suboptimal debulking one. Then they received a platinum-based chemotherapy. Thirteen cases received paclitaxel + cisplatin (TP) and 9 received cisplatin + doxorubicin + cyclophosphamide (PAC) combination chemotherapy. The primary response reached 80% (complete response 55% and partial response 25%). The median survival of all patients was 42 months (95% CI = 22-62 months). Survival for patients with primary peritoneal serous papillary carcinoma (PPSPC), mixed epithelial carcinoma and MMMT was 44, 19 and 13 months respectively, with a significant difference between PPSPC and MMMT (P < 0.05). Patients receiving TP combination also exhibited longer survival than those receiving PAC regimen (mean survival 75 vs 28 months, P < 0.05). CONCLUSIONS: Patients with primary peritoneal neoplasms should be treated with appropriate cytoreductive surgery. A primary surgical protocol is bilateral salpingo-oophorectomy and omentectomy. Overestimating an optimal debulking surgery may have no benefit on the survival. TP combination therapy may bring longer survival than PAC regimen. Histopathologic types and chemotherapy regimens are the essential factors of the prognosis.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

[Determination of trace cadmium in environment water samples by flame atomic absorption spectrometry using flow injection on-line preconcentration with double microcolumns].

A rapid and sensitive methed for the determination of trace cadmium in environment water samples based on flowinjection on-line preconcentration on two-microcolumn system-flame atomic absorption spectrometry has been developed. The cadmium in samples was sequentially retained on two microcolumns with cation exchange resin and was eluted directly in the nebulizer by 1.5 mol x L(-1) HCl solution. The characteristic concentration (preconcentration time 1 min) for cadmium was 0.931 microg x L(-1). The relative standard deviation at the 5 microg x L(-1) level was 2.69% and the corresponding detection limit (3sigma) was 0.808 microg x L(-1). The method has been successfully applied to the determination of cadmium in water reference material GBW08608 and other water samples.

Cadmium↗
PubMed2005

[Local injection of alpha, beta-methylene ATP induces excitation of primary afferent fibers in rats].

OBJECTIVE: To observe the excitation and sensitization of dorsal cutaneous primary afferent fibers induced by P2X agonist alpha, beta-methylene ATP (alphabetame-ATP) in rats. METHODS: By means of single fiber electrophysiological recordings on the nerve filaments isolated from the dorsal cutaneous branches of the T(9)-T(13) spinal nerves, the effects of alphabetame-ATP (100 micromol/L, 10 microl) injection into the cutaneous receptive field on the mechanical threshold and spontaneous discharge of rat primary sensory afferent units were observed. RESULTS: The mean mechanical threshold of Adelta and C fibers prior to alphabetame-ATP injection were 0.384+/-0.018 and 0.943+/-0.102 mN, and lowered to 0.304+/-0.013 and 0.659+/-0.071 mN after the injection, respectively (P<0.05, P<0.01). The mechanical threshold of the Abeta fibers before alphabetame-ATP injection was 0.301+/-0.019 mN, and slightly lowered to 0.288+/-0.018 mN after the injection (P>0.05). Injection of alphabetame-ATP (10 microl) into the receptive fields evoked spontaneous discharge in 7.7% of the Abeta fibers, 66.7% of Adelta fibers and 75.0% of C fibres, respectively, and the proportions of Adelta and C fibers with spontaneous discharge evoked by alphabetame-ATP were significantly greater than that of Abeta fibers (P<0.05). In the control experiments, injection of saline did not significantly affect spontaneous discharge or excite the nerve fibers. The mean discharge frequency of Adelta and C fibers increased from 0.73+/-0.24 and 0.54+/-0.21 impulses/min before injection to 3.05+/-0.65 and 8.53+/-2.04 impulses/min during the injection, with subsequent reduction to 2.40+/-0.60 and 6.68+/-1.68 impulses/min in the following 5 min (P<0.05). In contrast to Adelta and C fibers, Abeta fibers exhibited no significant changes in the mean discharge frequency in response to alphabetame-ATP (0.23+/-0.09 impulses/min before injection, 0.28+/-0.09 impulses/min during injection and 0.22+/-0.14 impulses/min after injection, P>0.05). The excitatory effects of alphabetame-ATP on the discharge rate in Adelta and C primary afferent terminal could be observed in the entire course of experiment. CONCLUSION: Peripheral application of alphabetame-ATP, an ATP analogue, excites and sensitizes a subpopulation of Adelta and C fibers but not Abeta fibers of rat dorsal cutaneous primary afferent fibers.

Adenosine Triphosphate↗
PubMed2005

A pilot trial for severe, refractory systemic autoimmune disease with stem cell transplantation.

OBJECTIVE: To evaluate the feasibility, efficacy, and safety of high dose immunosuppressive therapy (HDIT) and autologous hemopoietic stem cell transplantation (HSCT) with CD34+ cell selection in patients with severe, refractory autoimmune diseases. METHODS: Twenty-six patients with persistent systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), primary Sjögren's syndrome (pSS), or systemic sclerosis (SSc) who had been treated unsuccessfully with conventional treatment were enrolled in the trial in Peking Union Medical College Hospital from September 1999 to June 2004. The patients received HDIT with 200 mg/kg cyclophosphamide followed by an infusion of autologous stem cells that were CD34 selected. Disease activity, adverse effect, hemopoietic and immune reconstitution, and time to recurrence of disease were monitored. RESULTS: Overall treatment related mortality was 7.7% (2/26) with 1 patient died of cytomegalovirus infection and another of severe pneumonia. Relapse occurred in 3 SLE patients (17.6%) in 37, 26, and 19 months posttransplantation respectively, and 1 RA patient in 15 months posttransplantation. SLE Disease Activity Index (SLEDAI) scores of SLE survivors decreased significantly (P < 0.01). RA patients recorded a drop of Disease Activity Score 28 (DAS 28). The pSS patient remained symptoms free up to now, more than 50 months after the transplantation. CONCLUSION: HSCT can be performed relative safely in patients with severe autoimmune disease. Short-term effect of HSCT is promising. However treatment related mortality and relapse were observed in a subset of patients.

Adolescent↗
PubMed2005

Evaluation of international classification criteria (2002) for primary Sjögren's syndrome in Chinese patients.

OBJECTIVE: To evaluate the sensitivity and specificity of international classification criteria (2002) for primary Sjögren's syndrome (pSS) and the role of lower lip biopsy in diagnosis of pSS in Chinese patients. METHODS: Patients who were diagnosed by the experts/rheumatologists as pSS during 1990-2002 from the Department of Rheumatology, Peking Union Medical College Hospital were retrospectively collected as experimental group. Patients who were diagnosed as non-pSS connective tissue diseases or non-connective tissue diseases served as control group. Those with a history of head-neck radiation, hepatitis C virus infection, AIDS, lymphoma, sarcoidosis, graft versus host disease (GVHD), and anti-acetylcholine drug use were exempted. Both groups were required to complete questionnaires about symptoms such as dry eyes and dry mouth, and complete the objective tests of keratoconjunctivitis and xerostomia including Schirmer test, corneal staining, unstimulated salivary flow, sialography, lower lip biopsy, and antinuclear antibodies (including anti-SSA/SSB antibodies) test. RESULTS: A total of 330 pSS patients were included in experimental group and 185 non-pSS patients in control group. The mean age of both groups matched (47.8 +/- 10.9 years vs. 46.2 +/- 13.6 years, P > 0.05). The sensitivities of the criteria in pSS patients with lower lip biopsy and in pSS patients without lower lip biopsy were 89.2% and 87.2%, respectively; the overall sensitivity was 88.5%. The specificity was 97.3%. A total of 11.3% pSS patients with negative anti-SSA/SSB anti- bodies were diagnosed as pSS by lower lip biopsy. CONCLUSION: The international classification criteria (2002) for pSS is feasible in Chinese patients. It has high sensitivity and specificity, and may serve as diagnosis criteria in routine clinical practice.

Adolescent↗
PubMed2005

[Study on mechanism of infertility or sterility caused by uterine septa and reproductive prognosis after hysteroscopic metroplasty].

OBJECTIVE: To study the mechanism of infertility/sterility caused by uterine septa and the reproductive prognosis after transcervical resection of septum (TCRS). METHODS: One hundred and eleven patients with uterine septum including 34 patients of infertility and 77 patients of sterility were performed on TCRS. The patients were followed up of the reproductive outcomes. The process of pregnancies and deliveries were compared with those of 1548 normal uterine pregnancies. We also studied and compared the pathomorphologic and the micro-structure features between the septum and uterine wall in 30 cases (8 cases with infertility and 22 cases with sterility). RESULTS: (1) The amount of the endometrium glands on septum was less than that on the uterine wall or endometrium un-synchronous growth between septum and uterine wall was shown in 7 cases of infertility and 13 cases of sterility. The positive index level of estrogen and progestogen receptors on septum was weaker than that on uterine wall. The densities of the smooth muscle cells were thicker and the collagenous fibers were sparser in the base and middle of septum compared with uterine wall (P < 0.05). The amounts of the small arteries in septum were rarer than in uterine wall (P < 0.05). Ultrastructure characters showed glandular epithelium cells distributed irregularly and poor pili on septum in the sterility patients. (2) Sixteen infertility patients became pregnant (47.1%, 16/34) postoperation, which was much higher than pregnancy rate of preoperation (8.8%, 3/34, P < 0.01). In sterility group, the spontaneous abortion rate decreased from 84.1% (180/214) to 29.0% (18/62, P < 0.01), and the mature delivery rate and live birth rate rose from 3.3% (7/214), 0.9% (2/214) to 56.4% (35/62) and 64.5% (40/62) respectively (P < 0.01). (3) There were no differences between TCRS patients and normal uterine pregnant women in complications, and the mortality of perinatal (P > 0.05). The rate of cesarean section in post-TCRS patients was higher than in normal control group (P < 0.01). CONCLUSIONS: The differences of pathomorphology and ultra-structure between septum and uterine wall are the causation of infertility/sterility in the uterine septum patients. The reproductive prognosis can be improved remarkably by performing TCRS, which does not increase pregnant complications or affect fetus growth. Cesarean section should not be a standard way for delivery.

Adult↗
PubMed2005

[A study of antiendothelial cell antibodies in Behcet's disease].

OBJECTIVE: To investigate the clinical significant of antiendothelial cell antibodies (AECA) in Behcet's disease. METHODS: With human umbilical vein endothelial cell as substrate cell, sera from 59 Behcet's disease patients were detected for the presence of AECA by using fixed cell-ELISA. The associations of AECA to clinical disease activity were analyzed. In addition, Sera from other 70 systemic vasculitis (including 28 Takayasu arteritis, 20 Wegener's granulomatosis, 8 polyarteritis nodosa, 9 microscopic polyangiitis, 5 Churg-Strauss syndrome), 57 systemic lupus erythematosus (SLE), 25 rheumatoid arthritis and 85 healthy donors were screened for AECA. The associations of AECA to clinical disease activity were analyzed. RESULTS: The prevalence of AECA by human umbilical vein endothelial cell cell-ELISA was 47.5% in Behcet's disease. Compared with patients with rheumatoid arthritis (4.0%) and normal group (1.2%), AECA were more frequently found in patients with Behcet's disease, other systemic vasculitis (68.6%) and SLE (45.7%) (P < 0.01). The positive result on pathergy testing was more frequently found in AECA-positive patient with Behcet's disease (P < 0.05). After the treatment, patients with active disease entering remission showed a decrease in both AECA titers and the mean level of ESR (P < 0.05). CONCLUSIONS: AECA could be found more frequently in patients with Behcet's disease, associated closely with disease activity, which suggest that AECA may be used as an index in monitoring disease activity and effect of therapy in Behcet's disease. But AECA could also be found in other systemic vasculitis and SLE.

Adolescent↗
PubMed2005

[Triple-phase helical CT in the differential diagnosis between small hepatocellular carcinoma and small hepatic cavernous hemangioma].

OBJECTIVE: To scrutinize the enhancement pattern at hepatic arterial phase (HAP), portal venous phase (PVP) and delayed phase (DP) by helical CT examination in order to differentiate small hepatocellular carcinoma (SHCC) from small hepatic cavernous hemangioma (SHCH). METHODS: In 38 patients (41 lesions) with SHCC and 35 patients (45 lesions) with SHCH, the images at HAP, PVP and DP were recorded as to the characteristic of enhancements with the average CT value at the HAP monitored and compared. RESULTS: The enhancement patterns of SHCC at the HAP, PVP, and DP were assessed as hyper-hypo-hypodense in 20 lesions, hyper-iso-hypodense in 6 lesions, hyper-hyper-hypodense in 3 lesions, hyper-iso-isodense in 5 lesions, iso-hypo-hypodense in 3 lesions, and hypo-hypo-hypodense in 4 lesions. The enhancement patterns of the SHCH were assessed as a peripheral hyperdense nodular at HAP, then progressively enlarged at PVP and turned into a isodense or homogeneous hyperdense nodular at DP in 27 lesions, hyper-hyper-iso or hyperdense in 9 lesions, hyper-iso-isodense in 3 lesions, hypo-hypo-hypodense in 6 lesions. The enhancement CT values at the HAP of homogeneous hyperdense SHCC and SHCH were (40.4 +/- 15.5) Hounsfield Unit (HU) and (102.8 +/- 18.9) HU respectively (P < 0.01). CONCLUSION: Most of the small hepatocellular carcinoma and small hepatic cavernous hemangioma have typical appearance by triple-phase helical CT examination, and can easily and properly be diagnosed. But it is difficult to distinguish SHCC from SHCH with atypical appearance in isolated cases. Hence differentiation may be difficult. Therefore, further examinations such as MRI, ultra-sonography or isotope scintigraphy are helpful in the differential diagnosis.

Adult↗
PubMed2004

[Treatment of severe systemic autoimmune diseases with autologous peripheral blood stem cell transplantation].

OBJECTIVE: To investigate the feasibility, efficacy and safety of high dose immunosuppressive therapy (HDIT) and autologous peripheral blood stem cell transplantation (PBSCT) with CD(34)(+) cell selection in patients with refractory and severe autoimmune diseases. METHODS: Twenty-one patients with SLE, RA, pSS, SSc or MCTD were enrolled in the study from 1999. Autologous haemopoietic stem cells were mobilized with CTX 3 approximately 4 g/m(2) and granulocyte colony stimulating factor (G-CSF). CD(34)(+) cells were selected by CliniMACS. After conditioning with CTX (200 mg/kg) and pig antithymocyte globulin (ATG, 90 mg/kg) or CTX (150 mg/kg) and total body irradiation (TBI, 4 approximately 6 Gy), the enriched CD(34)(+) cells were reinfused. RESULTS: All patients completed the mobilization and leukapheresis procedures successfully, and proceeded to receive conditioning and transplantation. Two patients died of complication related to transplantation, one is CMV infection, the other is severe pneumonia during the course of granulocyte deficiency. A MCTD patient completed the stem cell mobilization and died of severe pulmonary hypertension and heart failure before CD(34)(+) cells reinfusing. Two SLE patients relapsed in 26, 37 months respectively and a RA patient relapsed in 15 months after transplantation. Other patients got improved, with SLE-DAI score decreasing from 17 to 4 score and proteinuria decreasing from 6.7 g to 2.3 g in SLE patients; DAS28 score from 7.9 to 2.1 in RA patient; Symptom improved and lab results recovered in SS. CONCLUSION: High dose immunosuppressive therapy followed by autologous peripheral blood stem cell transplantation with CD(34)(+) cell selection is feasible and relative safe. Patients remain free from disease active and improved continuously. Some patients could relapse after transplantation. Long-term effect need to be further observed.

Arthritis, Rheumatoid↗
PubMed2004

Prenatal stress causes gender-dependent neuronal loss and oxidative stress in rat hippocampus.

Our purpose was to investigate the effects of prenatal stress on neuronal changes in the hippocampus and the possible involvement of oxidative stress in female and male rats. Female and male offspring (1-month-old), whose dams were restrained in middle or later pregnant stage (MS or LS), were studied to observe changes in the number of hippocampal neurons and the expression of neuronal nitric oxide synthase (nNOS) in the hippocampus. Both MS and LS induced an increase in the number of nNOS-positive expression in female and male offspring in the hippocampus; however, both MS and LS caused a significant decrease in the number of hippocampal neurons in the female, but not in the male offspring. In addition, significant increases in calcium content and oxidant generation were induced by LS in the hippocampal CA3 region in female rats. These data suggest that prenatal stress can cause oxidative stress and consequent damage to neurons, leading to neuronal loss in the brain of offspring during development.

Animals↗
PubMed2004

Identification and characterization of a novel and specific inhibitor of the ataxia-telangiectasia mutated kinase ATM.

The serine/threonine protein kinase ATM signals to cell cycle and DNA repair components by phosphorylating downstream targets such as p53, CHK2, NBS1, and BRCA1. Mutation of ATM occurs in the human autosomal recessive disorder ataxia-telangiectasia, which is characterized by hypersensitivity to ionizing radiation and a failure of cells to arrest the cell cycle after the induction of DNA double-strand breaks. It has thus been proposed that ATM inhibition would cause cellular radio- and chemosensitization. Through screening a small molecule compound library developed for the phosphatidylinositol 3'-kinase-like kinase family, we identified an ATP-competitive inhibitor, 2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one (KU-55933), that inhibits ATM with an IC(50) of 13 nmol/L and a Ki of 2.2 nmol/L. KU-55933 shows specificity with respect to inhibition of other phosphatidylinositol 3'-kinase-like kinases. Cellular inhibition of ATM by KU-55933 was demonstrated by the ablation of ionizing radiation-dependent phosphorylation of a range of ATM targets, including p53, gammaH2AX, NBS1, and SMC1. KU-55933 did not show inhibition of UV light DNA damage induced cellular phosphorylation events. Exposure of cells to KU-55933 resulted in a significant sensitization to the cytotoxic effects of ionizing radiation and to the DNA double-strand break-inducing chemotherapeutic agents, etoposide, doxorubicin, and camptothecin. Inhibition of ATM by KU-55933 also caused a loss of ionizing radiation-induced cell cycle arrest. By contrast, KU-55933 did not potentiate the cytotoxic effects of ionizing radiation on ataxia-telangiectasia cells, nor did it affect their cell cycle profile after DNA damage. We conclude that KU-55933 is a novel, specific, and potent inhibitor of the ATM kinase.

Ataxia Telangiectasia Mutated Proteins↗