PURPOSE: Cyclin G2 has been reported to be a negative cell-cycle regulator in various cancer tissues. However, the pattern of cyclin G2 expression in gastric cancer is relatively unknown. We investigated the expression of cyclin G2 in gastric cancer tissues and evaluated the clinical significance of its expression. MATERIALS AND METHODS: Well-preserved gastric cancer tissues were consecutively obtained from 172 patients who underwent gastric cancer operations at Samsung Medical Center between November 1994 and December 1997. Cyclin G2 expression in the tissues was examined immunohistochemically, and the clinicopathological features and prognostic significance according to the expression were analyzed. RESULTS: Of the 172 gastric cancer tissues, cyclin G2 expression was positive in 43 tissues (25.0%). According to the stage, cyclin G2 expression was lower in more advanced stages (P<0.001). Negative expression of cyclin G2 was positively correlated with more advanced depth of tumor invasion (P<0.05), presence of lymph-node metastasis (P<0.05) and presence of lymphatic invasion (P<0.05). The prognosis of the cyclin G2 (+) group was significantly better than that of the cyclin G2 (-) group (P<0.001). Multivariate analysis revealed that T stage, lymph-node metastasis, distant metastasis, and lymphatic invasion were independent prognostic factors, but the expression of cyclin G2 was not. CONCLUSION: Cyclin G2 was expressed in 25% of the gastric cancer tissues, and negative expression of cyclin G2 was associated with more advanced tumor progression. Cyclin G2 may be a negative cell-cycle regulator in gastric cancer, and further studies are necessary to elucidate its exact role in the mechanism of carcinogenesis.
Carcinogenesis ; Cyclin G2* ; Cyclins* ; Humans ; Multivariate Analysis ; Neoplasm Metastasis ; Prognosis ; Stomach Neoplasms

PURPOSE: Cyclin G2 has been reported to be a negative cell-cycle regulator in various cancer tissues. However, the pattern of cyclin G2 expression in gastric cancer is relatively unknown. We investigated the expression of cyclin G2 in gastric cancer tissues and evaluated the clinical significance of its expression. MATERIALS AND METHODS: Well-preserved gastric cancer tissues were consecutively obtained from 172 patients who underwent gastric cancer operations at Samsung Medical Center between November 1994 and December 1997. Cyclin G2 expression in the tissues was examined immunohistochemically, and the clinicopathological features and prognostic significance according to the expression were analyzed. RESULTS: Of the 172 gastric cancer tissues, cyclin G2 expression was positive in 43 tissues (25.0%). According to the stage, cyclin G2 expression was lower in more advanced stages (P<0.001). Negative expression of cyclin G2 was positively correlated with more advanced depth of tumor invasion (P<0.05), presence of lymph-node metastasis (P<0.05) and presence of lymphatic invasion (P<0.05). The prognosis of the cyclin G2 (+) group was significantly better than that of the cyclin G2 (-) group (P<0.001). Multivariate analysis revealed that T stage, lymph-node metastasis, distant metastasis, and lymphatic invasion were independent prognostic factors, but the expression of cyclin G2 was not. CONCLUSION: Cyclin G2 was expressed in 25% of the gastric cancer tissues, and negative expression of cyclin G2 was associated with more advanced tumor progression. Cyclin G2 may be a negative cell-cycle regulator in gastric cancer, and further studies are necessary to elucidate its exact role in the mechanism of carcinogenesis.
Carcinogenesis ; Cyclin G2* ; Cyclins* ; Humans ; Multivariate Analysis ; Neoplasm Metastasis ; Prognosis ; Stomach Neoplasms

This study is to examine the effects of NNIspm-mediated cellular senescence of HepG2 cells and elucidate its potential molecular mechanism. Cellular senescence was detected with senescence-associated beta-galactosidase staining. Cell cycle distribution, intracellular fluorescence intensity and accumulation of intracellular reactive oxygen species (ROS) were detected by high content screening (HCS). Protein expression was detected by Western blotting. Polyamines content was analyzed by high performance liquid chromatography (HPLC). The results demonstrated that NNIspm significantly induced HepG2 cells senescence. This effect was due to the decrease of intracellular polyamines, the arrest at G0/G1 phase and an increase of ROS level. The molecular senescence marker p21 increased significantly after NNIspm treatment. In contrast, the protein expressions of Cyclin E and CDK2 were obvious down-regulation. The results indicated that cellular senescence induced by NNIspm was one of its antitumor mechanisms.
Antineoplastic Agents ; metabolism ; pharmacology ; Cellular Senescence ; drug effects ; Cyclin E ; metabolism ; Cyclin-Dependent Kinase 2 ; metabolism ; Cyclin-Dependent Kinase Inhibitor p21 ; metabolism ; G1 Phase ; Hep G2 Cells ; Humans ; Oncogene Proteins ; metabolism ; Polyamines ; metabolism ; pharmacology ; Reactive Oxygen Species ; metabolism

PURPOSE: In our previous study, we have shown the main cell death pattern induced by irradiation or protein tyrosine kinase (PTK) inhibitors in K562 human myelogenous leukemic cell line. Death of the cells treated with irradiation alone was characterized by mitotic catastrophe and typical radiation-induced apoptosis was accelerated by herbimycin A (HMA). Both types of cell death were inhibited by genistein. In this study, we investigated the effects of HMA and genistein on cell cycle regulation and its correlation with the alterations of radiation-induced cell death. MATERIALS AND METHODS: K562 cells in exponential growth phase were used for this study. The cells were irradiated with 10 Gy using 6 MeV Linac (200-300 cGy/min). Immediately after irradiation, cells were treated with 250 nM of HMA or 25 microM of genistein. The distributions of cell cycle, the expressions of cell cycle-related protein, the activities of cyclin-dependent kinase, and the yield of senescence and differentiation were analyzed. RESULTS: X-irradiated cells were arrested in the G2 phase of the cell cycle but unlike the p53-positive cells, they were not able to sustain the cell cycle arrest. An accumulation of cells in G2 phase of first cell-cycle post-treatment and an increase of cyclin B1 were correlated with spontaneous, premature, chromosome condensation and mitotic catastrophe. HMA induced rapid G2 checkpoint abrogation and concomitant p53-independent G1 accumulation. HMA-induced cell cycle modifications correlated with the increase of cdc2 kinase activity, the decrease of the expressions of cyclins E and A and of CDK2 kinase activity, and the enhancement of radiation-induced apoptosis. Genistein maintained cells that were arrested in the G2-phase, decreased the expressions of cyclin B1 and cdc25C and cdc2 kinase activity, increased the expression of p16, and sustained senescence and megakaryocytic differentiation. CONCLUSION: The effects of HMA and genistein on the radiation-induced cell death of K562 cells were closely related to the cell cycle regulatory activities. In this study, we present a unique and reproducible model in which for investigating the mechanisms of various, radiation-induced, cancer cell death patterns. Further evaluation by using this model will provide a potent target for a new strategy of radiotherapy.
Aging ; Apoptosis ; Cell Cycle Checkpoints ; Cell Cycle* ; Cell Death* ; Cell Line ; Cyclin B1 ; Cyclins ; G2 Phase ; Genistein ; Humans ; K562 Cells ; Neoplasms, Radiation-Induced* ; Phosphotransferases ; Protein-Tyrosine Kinases ; Radiotherapy

OBJECTIVETo investigate the effects of simvastatin on the proliferation, cell cycle and expression of cyclin-dependent kinase inhibitor p21 protein in human hepatocellular carcinoma (HepG2) cells in vitro.

METHODSHepG2 cells were administrated with simvastatin. Proliferation of the cells was detected by MTT assay, cell cycle was measured by flowcytometry and the cyclin-dependent kinase inhibitor p21 protein expression was detected by immunocytochemistry. The results were evaluated by factorial design and one-way analysis of variance.

RESULTSSimvastatin inhibited HepG2 cells growth in vitro (F(concentration) = 1264, P value less than 0.001; F(time) = 17.466, P value less than 0.001; F(concentration*time) = 35.053, P value less than 0.001) and could arrest HepG2 cells in G0/G1 phase of cell cycle. However, apoptosis of HepG2 cells was not obvious. Simvastatin could also increase cyclin-dependent kinase inhibitor p21 protein expression (F = 512.133, P value less than 0.001).

CONCLUSIONSimvastatin can inhibit the growth of HepG2 cells in vitro, which may be explained by its effects of enhancing cyclin-dependent kinase inhibitor p21 protein expression and arresting HepG2 cells at G0/G1 phase of cell cycle.

Carcinoma, Hepatocellular ; metabolism ; pathology ; Cell Cycle ; drug effects ; Cell Proliferation ; drug effects ; Cyclin-Dependent Kinase Inhibitor p21 ; metabolism ; Hep G2 Cells ; Humans ; Liver Neoplasms ; metabolism ; pathology ; Simvastatin ; pharmacology

OBJECTIVESTo investigate the inhibitory effect of macrophage migration inhibitory factor (MIF) antibody on the proliferation of HepG-2 cells and its mechanism.

METHODSHepG-2 cells were stimulated by different concentrations of MIF antibody (50, 100, 200 and 400 microg/L). The cell survival rates were evaluated by MTT assay. The cell cycles were assessed by flow cytometry (FCM) analysis. Cyclin D1 protein expression was examined by immunohistochemical methods. Vascular endothelial growth factor (VEGF) protein expression was examined by Western blot. ELISA was applied to detect the influence of MIF antibody on the production of IL-6 of HepG-2 cells.

RESULTSHepG-2 cells were inhibited by MIF antibody in a dose and time dependent manner. FCM analysis showed the cell cycles of HepG-2 cells were blocked at G0/G1 phase. With concentrations of MIF antibody of 0, 50, 100, 200, 400 microg/L, the percentages of cells in G0/G1 phase at 48 h were 61.34%+/-1.08%, 65.08%+/-2.71%, 71.19%+/-1.19%, 78.39%+/-1.00%, 83.92%+/-0.51%. With concentrations of MIF antibody of 50, 100, 200, 400 microg/L, the expressions of cyclin D1 protein were 26.06%+/-0.47%, 22.34%+/-0.75%, 18.06%+/-1.16%, 14.03%+/-0.59%, significantly lower than those of the control group (29.51%+/-1.28%). When HepG-2 cells were treated with different concentrations of MIF antibodies of 50, 100, 200, 400 microg/L the expressions of VEGF protein were 21.22%+/-0.68%, 19.64%+/-0.54%, 18.04%+/-0.42%, 16.59%+/-0.66%, significantly lower than those of the control group (23.23%+/-0.51%). With MIF antibody concentrations of 0, 50, 100, 200, 400 microg/L, the exudation amount of IL-6 were correspondingly lower [(210.67+/-9.31) pg/ml, (181.67+/-10.05) pg/ml, (160.50+/-6.60) pg/ml, (143.67+/-10.56) pg/ml, (118.01+/-7.48) pg/m].

CONCLUSIONThe proliferation of HepG-2 cells was inhibited after treatment with MIF antibody. The inhibiting effect is caused by blocking cell cycle progression at G0/G1 phase, decreasing cyclin D1 protein expression, decreasing VEGF protein expression and decreasing the exudation amount of IL-6.

Antibodies ; pharmacology ; Cell Cycle ; Cell Proliferation ; drug effects ; Cyclin D1 ; metabolism ; Hep G2 Cells ; Humans ; Interleukin-6 ; metabolism ; Macrophage Migration-Inhibitory Factors ; immunology ; Vascular Endothelial Growth Factor A ; metabolism

This paper focuses on the effect of the venom of the spider Macrothele raveni on the proliferation of human hepatocelluar carcinoma cell line HepG2 and the related molecular mechanism. XTT test showed that the proliferation of HepG2 cells in vitro was inhibited by the spider venom (P<0.05) in a concentration-dependent manner. By using flow cytometry, it was found that the spider venom caused selective G(2)/M cell cycle arrest in HepG2 cells. RT-PCR and Western blot indicated the expressions of p21 mRNA and protein in HepG2 cells were obviously up-regulated by the spider venom. The venom of the spider Macrothele raveni inhibited the proliferation of HepG2 cells. These results suggest that the possible mechanism of the spider venom is to activate the expressions of p21 gene and protein and to cause selective cell cycle arrest at G(2)/M phase, leading to HepG2 cell apoptosis.
Cell Cycle ; drug effects ; Cell Proliferation ; drug effects ; Cyclin-Dependent Kinase Inhibitor p21 ; genetics ; metabolism ; Hep G2 Cells ; Humans ; RNA, Messenger ; genetics ; metabolism ; Spider Venoms ; pharmacology

OBJECTIVETo assess the ability of tetrandrine (Tet) to enhance the sensitivity to irradiation and its mechanism in cell lines of human breast cancer p53-mutant MCF-7/ADR, p53-wild-type MCF-7 and human colon carcinoma p53-mutant HT-29 as well as in C26 colorectal carcinoma-bearing BALB/c mice.

METHODSMCF-7/ADR, HT-29 and MCF-7 cells were exposed to irradiation in the absence or presence of tetrandrine. The effect of Tet on the cytotoxicity of X-irradiation in these three cells was determined and the effect of tetrandrine on cell cycle arrest induced by irradiation in its absence or presence was studied by flow cytometry. Moreover, mitotic index measurement determined mitosis of cells to enter mitosis. Western blotting was employed to detect cyclin B 1 and Cdc2 proteins in extracts from irradiated or non-irradiated cells of MCF-7/ADR, HT-29 and MCF-7 treated with tetrandrine at various concentrations. Tumor growth delay assay was conducted to determine the radio-sensitization of tetrandrine in vivo.

RESULTSClonogenic assay showed that tetrandrine markedly enhanced the lethal effect of X-rays on p53-mutant MCF-7/ADR and HT-29 cells and the sensitization enhancement ratio (SER) of tetrandrine was 1.51 and 1.63, but its SER was only 1.1 in p53-wt MCF-7 cells. Irradiated p53-mutant MCF-7/ADR and HT-29 cells were only arrested in G2/M phase while MCF-7 cells were arrested in G1 and G2/M phases. Radiation-induced G2 phase arrests were abrogated by tetrandrine in a concentration-dependent manner in MCF-7/ADR and HT-29 cells, whereas redistribution within MCF-7 cell cycle changed slightly. The proportion of cells in M phase increased from 1.3% to 14.7% in MCF-7/ADR cells, and from 1.5% to 13.2% in HT-29 cells, but 2.4% to 7.1% in MCF-7 cells. Furthermore, the levels of cyclin B 1 and Cdc2 expression decreased after X-irradiation in MCF-7/ADR and HT-29 cells, and the mitotic index was also lower. Tet could reverse the decrease and induce the irradiated cells to enter mitosis (M phase). Endosomatic experiment showed that tetrandrine caused tumor growth delay in irradiated mice.

CONCLUSIONTetrandrine boosts the cell killing activity of irradiation both in vitro and in vivo. Tetrandrine is a potent abrogator for G2 checkpoint control and can sensitize the cells to radiation.

Animals ; Benzylisoquinolines ; pharmacology ; CDC2-CDC28 Kinases ; metabolism ; Cell Line, Tumor ; Cyclin B ; metabolism ; Cyclin B1 ; Drug Screening Assays, Antitumor ; G2 Phase ; drug effects ; Humans ; Male ; Mice ; Mice, Inbred BALB C ; Radiation Tolerance

AIMTo investigate the radiosensitizing effect and mechanism of action of staurosporine (STP) in human colon carcinoma HT-29 and breast cancer MCF-7/ADR cells.

METHODSThe effect of STP on the cytotoxicity of X-ray was determined by clonogenic assay. The effect of STP on cell cycle arrest induced by X irradiation was studied in two cell lines by using flow cytometry, Western Blotting was performed to indicate the changes of cyclin B1 and cdc2 protein levels.

RESULTSSTP sensitized the two cell lines to X-ray by clonogenic assay. STP potentiated the cytotoxicity of X-ray by 2.10- and 2.09-fold in HT-29 and MCF-7/ADR cells. Flow cytometry assay showed that exposure of HT-29 and MCF-7/ADR cells to X-ray caused cells arrest in G2 phase. The percentage of arrest G2 phase cells were 56% and 52.7%, respectively. The addition of STP after irradiation resulted in a dose-dependent reduction of G2 phase arrest induced by X-ray. Furthermore, the results showed that STP blocked decrease of cyclin B1 expression induced by X-ray, while mitotic index measurement indicated that X-ray-irradiated cells treated with STP entered mitosis. The data suggested that the potentiation of cytotoxicity of X-ray by STP is associated with the suppression of cyclin B1 expression, which result in the abrogation of G2 arrest, before the cells entered into M phase, they had not enough time to repair.

CONCLUSIONSTP is a potent G2 checkpoint abrogator and markedly enhanced the cytotoxicity of X irradiation in the p53 mutant cancer cells.

Breast Neoplasms ; pathology ; Cyclin B ; biosynthesis ; Cyclin B1 ; Enzyme Inhibitors ; pharmacology ; Female ; G2 Phase ; drug effects ; HT29 Cells ; Humans ; Mitotic Index ; Particle Accelerators ; Radiation Tolerance ; drug effects ; Radiation-Sensitizing Agents ; pharmacology ; Staurosporine ; pharmacology ; Tumor Cells, Cultured

OBJECTIVECellular senescence as one of the important steps against tumor is observed in many cancer patients receiving chemotherapy and is related to chemotherapeutic response. To investigate the effect of cisplatin on hepatocellular carcinoma, we treated HepG2 cells exhibiting wild-type TP53 with gradient concentrations of cisplatin.

METHODSThe inhibitory effects of cisplatin on human hepatoma HepG2 cells were detected by MTT assay and colony formation test. The changes in cell cycle were analyzed by flow cytometry, and cellular senescence was detected with senescence associated β-galactosidase (SA β-gal) staining. The relative mRNA expression levels of TP53, P21 and P19 was estimated using semi-quantitative real-time RT-PCR, and the protein expressions of P53 and P21 were detected using Western blotting.

RESULTSCisplatin induced irreversible proliferation inhibition and G1 phase arrest of HepG2 cells. Elevated levels of senescence-associated β-galactosidase was observed in HepG2 cells exposed to low doses of cisplatin. P19 expression immediately increased following cisplatin exposure and reached the maximum level at 48 h, followed then by a rapid decrease to the baseline level, whereas the expressions levels of TP53 and P21 mRNA increased continuously. Western blotting confirmed P53 and P21 expression changes similar to their mRNA expressions during cisplatin-induced cellular senescence in HepG2 cells.

CONCLUSIONOur results revealed a functional link between cisplatin and hepatocellular senescence. Cellular senescence induced by cisplatin as a stabile senescent cellular model can be used for further research.

Cell Cycle ; drug effects ; Cell Cycle Checkpoints ; drug effects ; Cellular Senescence ; Cisplatin ; pharmacology ; Cyclin-Dependent Kinase Inhibitor p19 ; metabolism ; Cyclin-Dependent Kinase Inhibitor p21 ; metabolism ; Hep G2 Cells ; Humans ; Tumor Suppressor Protein p53 ; metabolism ; Up-Regulation