ABSTRACT
To explore the role of the Chk2 protein expression and DNA double strand breaks (DSBs) repair in low dose hyper-radiosensitivity (HRS)/increased radioresistance (IRR) of non-small cell lung cancer, A549 cells were subjected to irradiation at the dosage ranging from 0.05-2 Gy. Clonogenic survival was measured by using fluorescence-activated cell sorting (FACS) plating technique. Percentage of cells in M-phase after low doses of X-irradiation was evaluated by phospho-histone H3-FITC/PI and Western blotting was used to detect protein expression of Chk2 and phospo-Chk2. DNA DSBs repair efficiency was also measured by induction and persistence of γ-H2AX. The results showed that the killing ability of irradiation with A549 cells increased at low conditioning dose below 0.3 Gy. Within the dose of 0.3 to 0.5 Gy, A549 cells showed a certain extent of radiation resistance. And when the dose was more than 0.5 Gy, survival fraction exhibited a negative correlation with the dosage. There was no difference between the 0.1 or 0.2 Gy dosage groups and the un-irradiated group in terms of the percentage of cells in M phase. But in the high dosage group (0.3-1.0 Gy), the percentage of cells in M phase was decreased markedly. In addition, the percentage of cells in M phase began to decrease two hours after irradiation. One hour after irradiation, there was no conspicuous activation of Chk2 kinase in 0.1 or 0.2 Gy group, but when the irradiation dose reached 0.3 Gy or higher, Chk2 kinase started to be activated and the activation level showed no significant difference among high dosage groups (0.4, 0.5, 1.0 Gy). Within 1 to 6 h, the DNA DSBs repair efficiency was decreased at 0.2 Gy but increased at 0.5 Gy and 1.0 Gy, which was in line with Chk2 activation. We are led to conclude that the mechanism of HRS/IRR in A549 cell line was probably due to early G(2)/M checkpoint arrest and enhanced DNA DSBs repair. In this regard, Chk2 activation plays a key role in G(2)/M checkpoint activation.
ABSTRACT
To explore the role of the Chk2 protein expression and DNA double strand breaks (DSBs) repair in low dose hyper-radiosensitivity (HRS)/increased radioresistance (IRR) of non-small cell lung cancer, A549 cells were subjected to irradiation at the dosage ranging from 0.05-2 Gy. Clonogenic survival was measured by using fluorescence-activated cell sorting (FACS) plating technique. Percentage of cells in M-phase after low doses of X-irradiation was evaluated by phospho-histone H3-FITC/PI and Western blotting was used to detect protein expression of Chk2 and phospo-Chk2. DNA DSBs repair efficiency was also measured by induction and persistence of γ-H2AX. The results showed that the killing ability of irradiation with A549 cells increased at low conditioning dose below 0.3 Gy. Within the dose of 0.3 to 0.5 Gy, A549 cells showed a certain extent of radiation resistance. And when the dose was more than 0.5 Gy, survival fraction exhibited a negative correlation with the dosage. There was no difference between the 0.1 or 0.2 Gy dosage groups and the un-irradiated group in terms of the percentage of cells in M phase. But in the high dosage group (0.3-1.0 Gy), the percentage of cells in M phase was decreased markedly. In addition, the percentage of cells in M phase began to decrease two hours after irradiation. One hour after irradiation, there was no conspicuous activation of Chk2 kinase in 0.1 or 0.2 Gy group, but when the irradiation dose reached 0.3 Gy or higher, Chk2 kinase started to be activated and the activation level showed no significant difference among high dosage groups (0.4, 0.5, 1.0 Gy). Within 1 to 6 h, the DNA DSBs repair efficiency was decreased at 0.2 Gy but increased at 0.5 Gy and 1.0 Gy, which was in line with Chk2 activation. We are led to conclude that the mechanism of HRS/IRR in A549 cell line was probably due to early G(2)/M checkpoint arrest and enhanced DNA DSBs repair. In this regard, Chk2 activation plays a key role in G(2)/M checkpoint activation.
Subject(s)
Humans , Adenocarcinoma , Genetics , Metabolism , Cell Line, Tumor , Checkpoint Kinase 2 , Genetics , Metabolism , DNA Damage , Genetics , DNA Repair , Genetics , Lung Neoplasms , Genetics , Metabolism , Radiation Tolerance , GeneticsABSTRACT
The low dose hyper-radiosensitivity (HRS) in human lung cancer cell line A549 was investigated, the changes of ATM kinase, cell cycle and apoptosis of cells at different doses of radiation were observed, and the possible mechanisms were discussed. A549 cells in logarithmic growth phase were irradiated with (60)Co gamma-rays at doses of 0-2 Gy. Together with flow cytometry for precise cell sorting, cell survival fraction was measured by means of conventional colony-formation assay. The expression of ATM1981Ser-P protein was examined by Western blot 1 h after radiation. Apoptosis was detected by Hoechst 33258 fluorescent staining, and Annexin V-FITC/PI staining flow cytometry 24 h after radiation. Cell cycle distribution was observed by flow cytometry 6, 12 and 24 h after radiation. The results showed that the expression of ATM1981Ser-P protein was observed at 0.2 Gy, followed by an increase at >0.2 Gy, and reached the peak at 0.5 Gy, with little further increase as the dose exceeded 0.5 Gy. Twenty-four h after radiation, partial cells presented the characteristic morphological changes of apoptosis, and the cell apoptosis curve was coincident with the survival curve. As compared with control group, the cell cycle almost had no changes after exposure to 0.1 and 0.2 Gy radiation (P>0.05). After exposure to 0.3, 0.4 and 0.5 Gy radiation, G(2)/M phase arrest occurred 6 and 12 h after radiation (P<0.05), and the ratio of G(2)/M phase cells was decreased 24 h after radiation (P<0.05). It was concluded that A549 cells displayed the phenomenon of HRS/IRR. The mode of cell death was mainly apoptosis. The activity of ATM and cell cycle change may take an important role in HRS/IRR.
Subject(s)
Cell Cycle Proteins/genetics , Cell Cycle Proteins/metabolism , Cell Cycle Proteins/physiology , Cell Line, Tumor , DNA-Binding Proteins/antagonists & inhibitors , DNA-Binding Proteins/metabolism , DNA-Binding Proteins/physiology , Dose-Response Relationship, Radiation , Lung Neoplasms/pathology , Protein Serine-Threonine Kinases/metabolism , Radiation Dosage , Radiation Tolerance/physiology , Tumor Suppressor Proteins/metabolismABSTRACT
Objective To study the low dose hyper-radiosensitivity in human lung cancer cell line A549,and its possible mechanisms.Methods Exponentially growing A549 cells were irradiated with 60Co γ-rays at doses of 0-2 Gy.Together with flow cytometry for precise cell sorting,cell survival fraction was measured by mean of conventional colony-formation assay.ATM1981 Ser-P protein expression was examined by Western blot.Apoptosis was identified by Hoechst 33258 fluorescent staining,and Annexin V-FITC and propidium iodide staining flow cytometry.Cell cycle distribution was observed by flow cytometry.Results There was an excessive cell killing per unit dose when the doses were below about 0.3 Gy,and the cells exhibited more resistant response at the doses between 0.3 and 0.5 Gy,the cell survival fraction was decreased as the doses over 0.5 Gy.The expression of ATM1981Ser-P protein was first observed at 0.2 Gy,followed by an increase over 0.2 Gy,and reached the peak at 0.5 Gy(compared with 0.2 Gy group,t=7.96,P＜0.05),with no further increase as the doses at 1.0 and 2.0 Gy(t=0.69,0.55,P＞0.05).24 hours after irradiation,part cells presented the characteristic morpholos4cal change of apoptosis,and the apoptosis curve was coincident with the dose-survival curve.Compared with the control group,the cell cycle had no change post-irradiation to 0.1 and 0.2 Gy.G2/M phase arrest was manifested at 6 and 12 hours post-irradiation to 0.3,0.4 and 0.5 Gy(t=2.87,2.88,4.92 and 3.70,3.12,8.11,P＜0.05),and the ratio of G2/M phase was decreased at 24 hours post-irradiation(t=3.87,4.77,3.01,P＜0.05).Conclusions A549 cells displays the phenomenon of hyper-radiosensitivity(HRS)/induced radioresistance(IRR).The model of cell death induced by low dose irradiation is mainly apoptosis.The activity of ATM and cell cycle change might play an important role in HRS/IRR.
ABSTRACT
<p><b>BACKGROUND</b>To evaluate the clinical effect of gemcitabine and concurrent three-dimensional conformal radiation therapy (3D-CRT) for locally advanced non-small cell lung cancer (NSCLC).</p><p><b>METHODS</b>From April 2002 to June 2003, 28 patients with inoperable stage III NSCLC were treated with gemcitabine and 3D-CRT simultaneously. Chemotherapy consisted of intravenously gemcitabine 350 mg/m 2 on days 1, 8, 15, 22, 29, 36. 3D-CRT was delivered up to a total dose of 60-64 Gy with a 2.0 Gy dose fraction per day, 5 days per week.</p><p><b>RESULTS</b>The overall response rates of primary tumor and mediastinum metastatic node were 89.3%(25/28) and 96.0%(24/25) respectively, and 94.7%(18/19) and 77.8%(7/9) for squamous cell carcinoma and adenocarcinoma respectively. The acute side effects of patients were mostly myelosuppression, nausea, vomiting, radiation-induced esophagitis and pneumonitis (RTOGI/II), however, all of them were cured.</p><p><b>CONCLUSIONS</b>Concurrent application of gemcitabine and 3D-CRT can improve the overall response rate for locally advanced NSCLC without aggravating the side effects.</p>
ABSTRACT
The clinical implication of microvessel density (MVD) and vascular endothelial growth factor (VEGF) expression in breast cancer and the relationship between them were studied. Specimens of 53 cases of breast cancer were examined for MVD in tumor and VEGF expression by using immunohistochemical staining. The results showed that the mean MVD in node-positive breast cancers and in the patients with postoperative distant metastasis was higher than that in node-negative breast cancers and those without metastasis, respectively (both P<0.01). The expression rate of VEGF in breast cancer was 67.92 % and was closely relative to MVD. It was suggested that MVD was closely correlated with metastasis of the tumors and might be a useful prognostic indicator for breast cancer. VEGF might be an important factor responsible for the induction of angiogenesis in breast cancer.