OBJECTIVETo investigate the expressions of protein kinase C (PKC) isoforms in X-ray-exposed HepG2 cells and identify the PKC isoforms that induce radioresistance in HepG2 cells.

METHODSCultured HepG2 cells were divided into control group and 6 Gy radiation group for corresponding treatments. The fluorescence intensity (FI) and the percentage of positive cells were determined using flow cytometry.

RESULTSThe FI of PKCalpha and PKCdelta were 2.28 and 5.05 in the radiation group, respectively, significantly higher than those in the control group (P<0.05). The percentages of PKCalpha- and PKCdelta -positive cells were significantly higher in the radiation group than in the control group (P<0.05). The FI and the percentages of PKC zeta, gamma, epsilon, zeta positive cells were rather low and showed no significant differences between the two groups (P>0.05); PKCbeta expression was not detected in the two groups of cells. The apoptosis rates of the control and radiation groups were 1.73% and 20.90%, respectively.

CONCLUSIONPKCalpha and PKCdelta may be involved in protecting HepG2 cells from radiation-induced apoptosis.

Apoptosis ; physiology ; radiation effects ; Hep G2 Cells ; Humans ; Isoenzymes ; classification ; metabolism ; Protein Kinase C-alpha ; metabolism ; Protein Kinase C-delta ; metabolism ; Radiation Tolerance ; Signal Transduction ; drug effects ; physiology

When cells are exposed to a low dose of a mutagenic or clastogenic agent, they often become less sensitive to the effects of a higher dose administered subsequently. Such adaptive responses were first described in Escherichia coli. Studies on mammalian cells have been limited to human lymphocytes exposed to low doses of an alkylating agent. In this study, the adaptive response to 1 cGy of gamma rays was investigated in human tumor cells using two human hepatoma cell lines, Hep G2 and Hep 3B. Experiments were carried out by delivering 1 cGy followed by 50 cGy of gamma radiation and chromatid breaks were scored as an endpoint. The results of this study indicate that prior exposure to 1 cGy of gamma rays reduces the number of chromatid breaks induced by subsequent higher doses (50 cGy). The time necessary for the expression of the adaptive response was determined by varying the time interval between the two doses from 1 hour to 72 hours. In G2 chromatids, the adaptive response was observed both at short time intervals, as early as 1 hour, and at long time intervals. In S chromatids, however, the adaptive response was shown only at long time intervals. When 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, was added after 50 cGy, adaptive responses were abolished in all the experimental groups. Therefore, it is suggested that the adaptive response can be observed in human hepatoma cell lines, which is first documented through this study.
*Adaptation, Physiological ; Carcinoma, Hepatocellular/genetics ; Chromosome Aberrations ; *Gamma Ray ; Human ; Liver Neoplasms/genetics ; Radiation Tolerance/*physiology ; Support, Non-U.S. Gov't ; Tumor Cells, Cultured/*radiation effects

OBJECTIVETo seek for the appropriate concentration, at which IGF-II can exerts its strong effects on postirradiation proliferation, physiological function and differentiation of the rat's osteoblast-like cells (ROB).

METHODSThe osteoblast-like cells used were isolated from the calvariae of neonatal (one-day-old) SD rats by sequential enzymatic digestion. The third passages of the cells were irradiated with gamma-ray from a (60)Co source at the doses of 100, 400, 600, and 900 cGy. The medium was changed immediately after irradiation and 5 concentrations of IGF-II, i.e., 0, 0.1, 1.0, 10.0, and 100.0 microgram/L were added. 6 days after radiation (9 days in culture), the examination, or the measurement of relative cell number, was carried out.

RESULTSRadiation inhibited the ROB, even lethally. IGF-II completely counteracted the inhibitory effects when the cells were exposed to the radiation at lower dose (100 cGy), and partially when at higher dose (400 cGy). But after the radiation at much higher dose as 900 cGy, the damages were irreversible, even with the existence of this growth factor.

CONCLUSIONSAt least a portion of effective recovery of postirradiation damages may be due to IGF-II-induced radioresistance. Incubation with IGF-II can increase radioresistance or repair of radiation-induced cells damages. However, this effect depends on the dose of radiation.

Animals ; Cell Division ; drug effects ; radiation effects ; Cells, Cultured ; Dose-Response Relationship, Drug ; Dose-Response Relationship, Radiation ; Insulin-Like Growth Factor II ; pharmacology ; Osteoblasts ; drug effects ; physiology ; radiation effects ; Radiation Tolerance ; drug effects ; Rats ; Rats, Sprague-Dawley

BACKGROUNDThe second mitochondria-derived activator of caspases (Smac) is a novel proapoptotic gene, which plays an important role in the apoptosis-inducing effects of irradiation on tumor cells. The purpose of this study was to investigate the effects of extrinsic Smac gene transfer and its over-expression in radiotherapeutic sensitivities of cervical cancer cells.

METHODSAfter the Smac gene was transferred into the cervical cancer cell line HeLa, subcloned cells were obtained by persistent G418 selection. Cellular Smac gene expression was detected by RT-PCR and Western blot, while in vitro cell viabilities were detected by trypan blue staining assay. After treatment with X-ray irradiation, cellular radiotherapeutic sensitivities were investigated by tetrazolium bromide colorimetry. Cellular apoptosis and its rate were determined by electronic microscopy, annexin V-FITC and propidium iodide staining flow cytometry. The expression and activities of cellular caspase-3 were assayed by Western blot and colorimetry.

RESULTSSmac mRNA and protein levels in HeLa/Smac cells and the selected subclone cell line of cervical cancer were significantly higher than those of HeLa (P < 0.01). There was no significant difference in cellular viabilities between them (P > 0.05). However, after irradiation with 8 Gy X-ray, growth activities of HeLa/Smac were reduced by 22.42% (P < 0.01). When compared with those of HeLa, partial HeLa/Smac cells presented characteristic morphological changes of apoptosis under electronic microscope, with higher apoptosis rates (16.4% vs. 6.2%, P < 0.01); the caspase-3 expression levels in HeLa/Smac cells were improved significantly (P < 0.01), while its activities were increased by 3.42 times (P < 0.01).

CONCLUSIONSStable transfer of the extrinsic Smac gene and its over-expression in cervical cancer cell line could significantly enhance the expression and activities of cellular caspase-3 and ameliorate apoptosis-inducing effects of irradiation on cancer cells, which was a novel strategy to improve radiotherapeutic effects on cervical cancer.

Apoptosis ; radiation effects ; Carrier Proteins ; genetics ; physiology ; Caspase 3 ; Caspases ; metabolism ; Female ; Gene Transfer, Horizontal ; HeLa Cells ; Humans ; Intracellular Signaling Peptides and Proteins ; Mitochondrial Proteins ; genetics ; physiology ; Radiation Tolerance ; Uterine Cervical Neoplasms ; drug therapy ; enzymology ; pathology

The purpose of this study was to estimate predictive markers of intrinsic radiosensitivity in individuals who were exposed to occupational or environmental radiation. Throughout this process, the actual biohazard risks and base-line chromosome damage were evaluated in human population. Further studies were carried out to provide evidence for the existence of individual variations in age-dependent responses through micronuclei (MN) assay.Spontaneous frequencies not only vary greatly between individuals, but also working or living areas. It was shown that the increased level of spontaneous cell with MN was observed with increasing age. The relationship between radiosensitivity and the increased spontaneous level of MN may be in an inverse proportion. Ionizing radiation may be targeted mutagenic effects at the usual exposures of background levels that populations were exposed. Age and gender are the most important demographic variables in determining the MN index with frequencies in females, which were greater than those in males. The main life-style factors influencing the MN index in subjects were correlated significantly and positively with smoke. The results showed that an indicator of the genetic damaged rate in MN index in human populations significantly correlated with age, sex and life-style factors. So far, it is evident that with regard to the application of MN assay all future studies have to take into account the influence of age, gender, and life-style.In Conclusion, using micronuclei assay technique a large population can be easily monitored. This study illustrated that the MN assay may provide a high potential to ensure appropriate quality control and standard documentation protocol that can be used to monitor a large population exposed to radiation epidemiologically.
Adolescent ; Adult ; Age Factors ; Aged ; Background Radiation/*adverse effects ; Chromosomes, Human/radiation effects ; Environmental Exposure/*adverse effects ; Female ; Humans ; Korea ; Life Style ; Lymphocytes/*radiation effects/ultrastructure ; Male ; Micronuclei, Chromosome-Defective/*radiation effects ; *Micronucleus Tests ; Middle Aged ; Occupational Exposure/*adverse effects ; Radiation Tolerance/*physiology ; Sex Factors

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.
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/metabolism

Apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1), as a type of multifunctional protein, plays an essential role in the base excision repair (BER) pathway, which is responsible for the repair of DNA caused by oxidative and alkylation damage. As importantly, APE/Ref-1 also functions as a redox factor maintaining transcription factors in an active reduced state. APE/Ref-1 stimulates the DNA-binding activity of numerous transcription factors that are involved in cancer promotion and progression, such as AP-1 (Fos/Jun), NF-kappaB, HIF-1alpha, p53, and others. Based on the structures and functions of APE1/Ref-1, we will provide an overview of its activities and explore the budding clinical use of this protein as a target in cancer treatment, and propose that APE/Ref-1 has a great potential for application in clinical research.
Apoptosis ; DNA Repair ; genetics ; DNA-(Apurinic or Apyrimidinic Site) Lyase ; antagonists & inhibitors ; genetics ; metabolism ; physiology ; Drug Delivery Systems ; Drug Resistance, Neoplasm ; Humans ; Neoplasms ; drug therapy ; metabolism ; radiotherapy ; Oxidation-Reduction ; Polymorphism, Single Nucleotide ; Precancerous Conditions ; metabolism ; Radiation Tolerance

OBJECTIVETo assess the correlation of O6-methylguanine-DNA methyltransferase (MGMT) to radiation sensitivity of nasopharyngeal carcinoma (NPC).

METHODSEighty randomly selected NPC patients were divided into high (+/++, n=62) and low (-/+/+, n=18) MGMT groups according to the results of MGMT detection using immunohistochemistry. All the patients received irradiation with external beam radiotherapy, and the radiation sensitivity of NPC was analyzed after the irradiation.

RESULTSThe rates of high and low radiation sensitivity were 83.3% and 16.7% in low MGMT group, respectively, showing significant differences from those of the high MGMT group (45.2% and 54.8%, respectively, chi(2)=4.393, P=0.036).

CONCLUSIONThe content of MGMT correlates to the radiation sensitivity of NPC and may serve as valuable indicators for predicting the radiation sensitivity of NPC.

Adolescent ; Adult ; Aged ; Carcinoma, Squamous Cell ; enzymology ; radiotherapy ; DNA Modification Methylases ; blood ; DNA Repair Enzymes ; blood ; Female ; Humans ; Male ; Middle Aged ; Nasopharyngeal Neoplasms ; enzymology ; radiotherapy ; Radiation Tolerance ; physiology ; Tumor Suppressor Proteins ; blood ; Young Adult

AC133 Antigen ; Animals ; Antigens, CD ; metabolism ; Cell Differentiation ; Cell Proliferation ; Drug Resistance, Neoplasm ; Glioma ; pathology ; Glycoproteins ; metabolism ; Humans ; Neoplastic Stem Cells ; metabolism ; pathology ; physiology ; Neovascularization, Pathologic ; etiology ; pathology ; Peptides ; metabolism ; Radiation Tolerance

Glioblastomas (GBMs) are highly lethal primary brain tumors. Despite current therapeutic advances in other solid cancers, the treatment of these malignant gliomas remains essentially palliative. GBMs are extremely resistant to conventional radiation and chemotherapies. We and others have demonstrated that a highly tumorigenic subpopulation of cancer cells called GBM stem cells (GSCs) promotes therapeutic resistance. We also found that GSCs stimulate tumor angiogenesis by expressing elevated levels of VEGF and contribute to tumor growth, which has been translated into a useful therapeutic strategy in the treatment of recurrent or progressive GBMs. Furthermore, stem cell-like cancer cells (cancer stem cells) have been shown to promote metastasis. Although GBMs rarely metastasize beyond the central nervous system, these highly infiltrative cancers often invade into normal brain tissues preventing surgical resection, and GSCs display an aggressive invasive phenotype. These studies suggest that targeting GSCs may effectively reduce tumor recurrence and significantly improve GBM treatment. Recent studies indicate that cancer stem cells share core signaling pathways with normal somatic or embryonic stem cells, but also display critical distinctions that provide important clues into useful therapeutic targets. In this review, we summarize the current understanding and advances in glioma stem cell research, and discuss potential targeting strategies for future development of anti-GSC therapies.
Biomarkers, Tumor ; metabolism ; Brain Neoplasms ; metabolism ; pathology ; therapy ; Cell Differentiation ; Cell Hypoxia ; Drug Resistance, Neoplasm ; Gene Expression Regulation ; Glioblastoma ; metabolism ; pathology ; therapy ; Humans ; MicroRNAs ; physiology ; Neoplastic Stem Cells ; metabolism ; pathology ; Neovascularization, Pathologic ; Radiation Tolerance ; Signal Transduction ; Transcription Factors ; metabolism