Home About us Contact
|
Home About us Contact | ||
|
|
||
Cycle Distribution (cycle + distribution)
Kinds of Cycle Distribution Selected AbstractsPX-478, an inhibitor of hypoxia-inducible factor-1,, enhances radiosensitivity of prostate carcinoma cells,INTERNATIONAL JOURNAL OF CANCER, Issue 10 2008Sanjeewani T. Palayoor Abstract Overexpression of hypoxia-inducible factor-1, (HIF-1,) in human tumors is associated with poor prognosis and poor outcome to radiation therapy. Inhibition of HIF-1, is considered as a promising approach in cancer therapy. The purpose of this study was to test the efficacy of a novel HIF-1, inhibitor PX-478 as a radiosensitizer under normoxic and hypoxic conditions in vitro. PC3 and DU 145 prostate carcinoma cells were treated with PX-478 for 20 hr, and HIF-1, protein level and clonogenic cell survival were determined under normoxia and hypoxia. Effects of PX-478 on cell cycle distribution and phosphorylation of H2AX histone were evaluated. PX-478 decreased HIF-1, protein in PC3 and DU 145 cells. PX-478 produced cytotoxicity in both cell lines with enhanced toxicity under hypoxia for DU-145. PX-478 (20 ,mol/L) enhanced the radiosensitivity of PC3 cells irradiated under normoxic and hypoxic condition with enhancement factor (EF) 1.4 and 1.56, respectively. The drug was less effective in inhibiting HIF-1, and enhancing radiosensitivity of DU 145 cells compared to PC3 cells with EF 1.13 (normoxia) and 1.25 (hypoxia) at 50 ,mol/L concentration. PX-478 induced S/G2M arrest in PC3 but not in DU 145 cells. Treatment of PC3 and DU 145 cells with the drug resulted in phosphorylation of H2AX histone and prolongation of ,H2AX expression in the irradiated cells. PX-478 is now undergoing Phase I clinical trials as an oral agent. Although the precise mechanism of enhancement of radiosensitivity remains to be identified, this study suggests a potential role for PX-478 as a clinical radiation enhancer. Published 2008 Wiley-Liss, Inc. [source] Inhibitors of the PI3-kinase/Akt pathway induce mitotic catastrophe in non-small cell lung cancer cellsINTERNATIONAL JOURNAL OF CANCER, Issue 5 2006Therese H Hemström Abstract Non-small cell lung cancer cells (NSCLC) are more resistant to anticancer treatment as compared with other types of cancer cells. Recently (Hemström et al., Exp Cell Res 2005;305:200,13) we showed that apoptosis of U1810 NSCLC cells induced by the staurosporine analog PKC 412 correlated with inhibition of Akt and ERK1/2, suggesting the involvement of these kinases in cell survival. Here we investigated the contribution of the PI3-kinase/Akt and MEK/ERK pathways to survival of NSCLC cells. The two signaling pathways were studied by using different combinations of the PI3-kinase inhibitors LY-294002 and wortmannin, the Akt activator Ro 31-8220, the MEK inhibitor PD 98059 and PKC 412. PI3-kinase inhibitors induced apoptosis-like death in U1810 cells. H157 cells in general were relatively resistant to PI3 kinase/Akt inhibitors yet these compounds sensitized cells to the DNA-damaging drug VP-16, while Ro 31-8220 could not. PD 98059 only had a sensitizing effect on H157 cells when combined with PI3-kinase inhibition and VP-16. Morphological data indicated that LY-294002 and PKC 412 induced cell death at anaphase and metaphase, respectively, suggesting death by mitotic catastrophe. Analyzes of cells blocked in G2/M-phase by nocodazol revealed that LY-294002 increased, while PKC 412 decreased histone H3 phosphorylation, suggesting that LY-294002 allowed, while PKC 412 inhibited cells to leave M-phase. Flow cytometric analysis of cell cycle distribution demonstrated that LY-294002 allowed cells to leave G2/M phase, while PKC 412 inhibited cytokinesis, resulting in formation of multinucleated cells. These results indicate that sensitization of NSCLC cells by PI3-kinase inhibition involves interplay between cell cycle regulation, mitotic catastrophe and apoptosis. © 2006 Wiley-Liss, Inc. [source] Topoisomerase inhibitor induced dephosphorylation of H1 and H3 histones as a consequence of cell cycle arrestJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2005Nicole Happel Abstract Posttranslational modifications of histones have an integral function in the structural and functional organization of chromatin. Several changes in the modification state of histones could be observed after induction of apoptosis with topoisomerase inhibitors and other inducers. Most of these studies include the analysis of the state of phosphorylation of histones, and the results are to some extent controversial, depending on cell lines and agents used. In the present study we compared the kinetics of the dephosphorylation of H1 and H3 histones with apoptosis markers after treatment of leukemic cell lines with topoisomerase inhibitors. In parallel, we determined cell cycle parameters in detail. Dephosphorylation of both histone classes started within 1 h of induction, and no direct correlation with timing and intensity of the investigated apoptotic features could be observed. In contrast, we show that the effect of topoisomerase inhibitors on the state of H1 and H3 phosphorylation is not directly related to apoptosis, but reflects the changes in the cell cycle distribution of cells treated with these inducers. © 2005 Wiley-Liss, Inc. [source] Epigenetics are involved in the regulation of the cell cycle and expression of tumor suppressor genes in human colon cancer cellsJOURNAL OF DIGESTIVE DISEASES, Issue 3 2003Ying Xuan CHEN OBJECTIVE: To investigate the effects of DNA methylation and histone acetylation on the cell cycle progression and expression of tumor suppressor genes in human colon cancer (HCC) cell lines. METHODS: Three HCC cell lines (HT-29, SW1116 and Colo-320) were treated with the DNA methylation inhibitor, 5-aza-2'-deoxycytidine (5-aza-dC) or/and histone deacetylase (HDAC) inhibitors, trichostatin A (TSA) or sodium butyrate. The methylation status of the promoter of the p16INK4A gene was assayed by methylation-specific PCR (MSP). The expression of p16INK4A and p21WAF1 was analyzed by RT-PCR. The cell cycle distribution was determined by flow cytometry. RESULTS: Before treatment, p16INK4A expression was slightly detected in the three cell lines (HT-29, SW1116 and Colo-320) and p21WAF1 expression was not detected in SW1116 and Colo-320 cells. The methylation level of the p16INK4A gene promoter significantly decreased and mRNA expression markedly increased in HT-29 cells after treatment with 1 µmol/L, but not 10 µmol/L, of 5-aza-dC for 24 h. In the SW1116 and Colo-320 cells, the expression of p16INK4A was markedly enhanced at 10 µmol/L or 5 µmol/L of 5-aza-dC for 24 h. However, p21WAF1 gene expression was not detected. Interestingly, after treatment with TSA or sodium butyrate, the transcription of p21WAF1 was significantly upregulated in these two cell lines. Furthermore, 5-aza-dC did not affect cell cycle distribution, but TSA or sodium butyrate blocked the cell cycle, mainly in the G1 phase. CONCLUSIONS: The expression of the p16INK4A gene is regulated by DNA methylation in three HCC cell lines. The expression of p21WAF1 gene is regulated by histone acetylation in SW1116 and Colo-320. In these two cell lines, histone hyperacetylation causes a G1 cell cycle arrest. [source] Bmi-1 is critical for the proliferation and invasiveness of gastric carcinoma cellsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 3 2010Wei Li Abstract Background and Aim:, Bmi-1 is a transcriptional repressor belonging to the Polycomb group and is associated with the cell proliferation and carcinogenesis of a variety of human cancers. The level of Bmi-1 expression correlates with the aggressiveness of many cancers, and is considered an important marker for cancer diagnosis. However, its role in gastric carcinoma is unknown. Methods:, We used lentiviral mediated interfering short hairpin RNA to knockdown Bmi-1 expression in gastric carcinoma human gastric cancer cell line (AGS cells), then tested the cell proliferation by MTT assay, rate of colony formation by colony formation assay, cell cycle distribution by fluorescence-activated cell sorting and cell invasiveness by cell invasion assay. To analyze the expression and localization of Bmi-1 in gastric tumor tissues, we further performed the immunohistochemistry analysis on a gastric cancer tissue array. Results:, We found that knocking down Bmi-1 led to slower cell growth, lesser cell invasiveness, decelerated colony formation, and altered cell cycle progression. In addition, a positive relationship between nuclear expression of Bmi-1 and gastric cancer was observed, suggesting that nucleus localization of Bmi-1 in the cells may be a novel marker of gastric cancer. Conclusions:, Our study highlights critical roles for Bmi-1 in gastric cancer, and suggests that Bmi-1 nuclear localization could be an important marker for the diagnosis of gastric cancer. [source] Hyalgan® has a dose-dependent differential effect on macrophage proliferation and cell deathJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2003Kyle M. Sheehan Abstract The intra-articular injection of high molecular weight hyaluronic acid (HA) has been reported to be an effective treatment for pain of osteoarthritis of the knee. However, the mechanism by which HA exerts its effect is unknown. To explore HA's influence on the growth of U937 human macrophages, cells were incubated for 168 h with three concentrations, 1, 0.1 and 0.01 mg/mL, of Hyalgan®, a high molecular weight HA preparation. At 24-h increments, the cells were examined for proliferation, cell cycle distribution as well as the number of apoptotic and dead cells. Exposing macrophages to 1 mg/mL Hyalgan® significantly reduced the rate of cellular proliferation and altered the cell cycle distribution to yield decreased proportions of G0/G1 cells but increased S and G2/M cells. Concomitantly, a 10-fold increase in apoptotic cells and a 12-fold increase in dead cells were observed. The population doubling time (PDT) for cells treated with 1.0 mg/mL Hyalgan® increased from 23.6 to 52.9 h. By contrast, the two lower Hyalgan® concentrations significantly promoted macrophage proliferation in a dose-dependent manner. They also increased the proportion of G2/M cells, but had no effect on the number of apoptotic or dead cells. The PDTs of 21.5 and 22.2 h were less than the control time of 23.6 h. These results demonstrate that Hyalgan® concentrations have a differential effect on macrophage growth dynamics and suggest an anti-inflammatory effect at high HA concentrations. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Monodemethylated polymethoxyflavones from sweet orange (Citrus sinensis) peel Inhibit growth of human lung cancer cells by apoptosisMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 3 2009Hang Xiao Abstract Polymethoxyflavones (PMFs) are almost exclusively found in the Citrus genus, particularly in the peels of sweet orange (Citrus sinensis L. Osbeck) and mandarin (C. reticulate Blanco). We studied the effects of two major PMFs, namely, nobiletin and 3,5,6,7,8,3,,4,-heptamethoxyflavone (HMF), and two major monodemethylated PMFs, namely 5-hydroxy-3,7,8,3,,4,-pentamethoxyflavone (5HPMF), and 5-hydroxy-3,6,7,8,3,,4,-hexamethoxyflavone (5HHMF), on the growth of human lung cancer H1299, H441, and H460 cells. Monodemethylated PMFs were much more potent in growth inhibition of lung cancer cells than their permethoxylated counterpart PMFs. In H1299 cells, cell cycle analyses further revealed that monodemethylated PMFs caused significant increase in sub-G0/G1 phase, suggesting possible role of apoptosis in the growth inhibition observed, whereas the permethoxylated counterpart PMFs did not affect cell cycle distribution at same concentrations tested. These results strongly suggested that the phenolic group is essential for the growth inhibitory activity of monodemethylated PMFs. Further studies in H1299 cells demonstrated that monodemethylated PMFs downregulated oncogenic proteins, such as iNOS, COX-2, Mcl-1, and K-ras, as well as induced apoptosis evidenced by activation of caspase-3 and cleavage of PARP. Our results provide rationale to develop orange peel extract enriched with monodemethylated PMFs into value-added nutraceutical products for cancer prevention. [source] Treponema denticola immunoinhibitory protein induces irreversible G1 arrest in activated human lymphocytesMOLECULAR ORAL MICROBIOLOGY, Issue 3 2004W. Lee Oral spirochetes may contribute to the pathogenesis of a number of disorders including periodontal and periradicular diseases; however, the mechanism (s) by which these organisms act to cause disease is unknown. We have previously shown that extracts of the oral spirochete, Treponema denticola, contain an immunosuppressive protein (Sip) which impairs human lymphocyte proliferation. The objective of this study was to determine the mechanism by which Sip alters the proliferative response of lymphocytes. Human T-cells were activated by PHA in the presence or absence of Sip and cell cycle progression was assessed by flow cytometry. Cell cycle distribution was based upon DNA, RNA and protein content as well as expression of the activation markers; CD69 and IL-2R. Seventy-two hours following activation with PHA, cells were found in the G0, G1, S and G2/M phases of the cell cycle. In contrast, pretreatment with Sip resulted in a significant reduction of cells in the S and G2/M phases and a concomitant increase in the G1 phase. Sip did not alter the expression of the early activation markers CD69 and CD25R. To determine if G1 arrest resulted in activation of the checkpoint and cell death, we also monitored Sip-treated cells for apoptosis. Indeed, treatment with Sip resulted in both DNA fragmentation and caspase activation after 96 h. Our results indicate that Sip induces G1 arrest in human T-cells and, furthermore, that the arrest is irreversible, culminating in activation of the apoptotic cascade. We propose that if cell cycle arrest occurs in vivo, it may result in local and/or systemic immunosuppression and thereby enhance the pathogenicity of spirochetes and/or that of other opportunistic organisms. [source] Ganoderma lucidum extract attenuates the proliferation of hepatic stellate cells by blocking the PDGF receptorPHYTOTHERAPY RESEARCH, Issue 6 2009Guei-Jane Wang Abstract Hepatic fibrosis is an outcome of chronic liver diseases. The activation and proliferation of hepatic stellate cells (HSCs) is a key event in liver injury. The fruiting body of Ganoderma lucidum has long been a popular oriental medicine for treating liver diseases. The aim of this present study was to investigate the antiproliferative effects of the triterpenoid-rich extract (GLT) of G. lucidum in a cell line of rat HSCs (HSC-T6) stimulated with platelet-derived growth factor (PDGF)-BB. DNA synthesis was investigated by bromodeoxyuridine (BrdU) incorporation. Flow cytometry using propidium iodide (PI) labeling was carried out to analyse the cell cycle distribution and apoptosis. , -Smooth muscle actin (, -SMA) was used to evaluate extracellular matrix deposition, and western blotting was performed to measure cyclins D1 and D2, and phosphorylation of the PDGF, -receptor (PDGF,R), Akt and JNK. The results indicated that the GLT attenuated BrdU incorporation in a concentration-dependent manner with an IC50 of 8.52 ± 0.33 µg/mL. The inhibitory effect of the GLT was associated with downregulation of cyclins D1 and D2, and PDGF,R and Akt phosphorylation, upregulation of JNK phosphorylation, and a reduction in , -SMA expression. These results indicated that G. lucidum inhibits PDGF-BB-activated HSC proliferation possibly through blocking PDGF,R phosphorylation, thereby indicating its efficacy for preventing and treating hepatic fibrosis. Copyright © 2008 John Wiley & Sons, Ltd. [source] Short cycle distribution in random regular graphs recursively generated by peggingRANDOM STRUCTURES AND ALGORITHMS, Issue 1 2009Pu Gao Abstract We introduce a new method of generating random d -regular graphs by repeatedly applying an operation called pegging. The pegging operation is abstracted from a type of basic operation applied in a type of peer-to-peer network called the SWAN network. We prove that for the resulting graphs, the limiting joint distribution of the numbers of short cycles is independent Poisson. We also use coupling to bound the rate at which the distribution approaches its limit. The coupling involves two different, though quite similar, Markov chains that are not time-homogeneous. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009 [source] The Aberrant Expressions of Nuclear Matrix Proteins During the Apoptosis of Human Osteosarcoma CellsTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 5 2010Zhen-Li Zhao Abstract The objective of this study was to investigate altered expressions of nuclear matrix proteins (NMPs) of human osteosarcoma (OS) MG-63 cells during curcumin-induced apoptosis of human OS MG-63 cells. MG-63 cells were cultured with curcumin (7.5 mg/L) for 72 hr. Morphological alterations of cells were captured using light microscopy and transmission electron microscopy, and cell cycle distribution was estimated by flow cytometry. NMPs were selectively extracted and subjected to two-dimensional gel electrophoresis (2-DE) analysis. Western blots were performed to determine changes in the expression levels of specific NMPs. The results demonstrated that typical characteristics of apoptosis were observed. Cellular chromatin agglutinated, cell nuclei condensed, and apoptotic bodies were formed after treatment with curcumin. The 2-DE results displayed 27 NMPs, 21 of which were identified to have change in expression levels significantly during apoptosis. The altered expressions of three of these NMPs (nucleophosmin, prohibitin, and vimentin) were further confirmed by immunoblotting. These findings indicated that the apoptosis of MG-63 cells was accompanied by the expression alteration of NMPs. Our results might help to reveal the relationship between NMPs and the regulation of gene expression in the process of apoptosis, as well as provide the basic concepts for future studies on the mechanisms of apoptosis and the therapy for bone diseases. Anat Rec, 2010. © 2010 Wiley-Liss, Inc. [source] Geminin predicts adverse clinical outcome in breast cancer by reflecting cell-cycle progressionTHE JOURNAL OF PATHOLOGY, Issue 2 2004Michael A Gonzalez Abstract Geminin inhibits DNA replication by preventing Cdt1 from loading minichromosome maintenance (MCM) proteins onto DNA. The present study has investigated whether the frequency of geminin expression predicts clinical outcome in breast cancer. Immunohistochemistry was used first to examine geminin expression in normal and malignant breast tissue (n = 67). Correlations with cell-cycle parameters, pathological features, and clinical outcome were then determined using an invasive breast carcinoma tissue microarray (n = 165). Breast carcinomas were scanned for mutations (n = 61) and copy number imbalances (n = 241) of the geminin gene. Finally, the cell cycle distribution of geminin in breast cancer cells was investigated in vivo and in vitro. Despite a putative tumour suppressor function, it was found that increased geminin expression is a powerful independent indicator of adverse prognosis in invasive breast cancer. Both poor overall survival (p = 0.0002) and the development of distant metastases (p = 0.005) are predicted by high geminin expression, which performs better in this patient cohort than traditional factors currently used to determine prognosis and appropriate therapy. No mutations or deletions of the geminin gene and no evidence that a high frequency of protein expression is related to gene amplification were found. It is shown that geminin is expressed from S to M phase in breast carcinoma tissue and cell lines, disappearing at the metaphase,anaphase transition. While MCM proteins identify all non-quiescent cells, geminin identifies the sub-fraction that have entered S phase, but not exited mitosis, thereby indicating the rate of cell-cycle progression. It is suggested that this explains its unexpected value as a prognostic marker in breast cancer. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Asperfuranone from Aspergillus nidulans Inhibits Proliferation of Human Non-Small Cell Lung Cancer A549 Cells via Blocking Cell Cycle Progression and Inducing ApoptosisBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 1 2010Clay C. C. Wang To identity the anti-cancer mechanism of asperfuranone, we assayed its effect on apoptosis, cell cycle distribution, and levels of p53, p21 Waf1/Cip1, Fas/APO-1 receptor and Fas ligand. Enzyme-linked immunosorbent assay showed that the G0/G1 phase arrest might be due to p53-dependent induction of p21 Waf1/Cip1. An enhancement in Fas/APO-1 and its two form ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), might be responsible for the apoptotic effect induced by asperfuranone. Our study reports here for the first time that the induction of p53 and the activity of Fas/Fas ligand apoptotic system may participate in the anti-proliferative activity of asperfuranone in A549 cells. [source] No influence of magnetic fields on cell cycle progression using conditions relevant for patients during MRIBIOELECTROMAGNETICS, Issue 4 2003Ilka B. Schiffer Abstract The purpose of this study was to examine whether exposure to magnetic fields (MFs) relevant for magnetic resonance imaging (MRI) in clinical routine influences cell cycle progression in two tumor cell lines in vitro. HL60 and EA2 cells were exposed to four types of MFs: (i) static MF of 1.5 and 7.05 T, (ii) extremely low frequency magnetic gradient fields (ELFMGFs) with ±,10 mT/m and 100 Hz, as well as ±,100 mT/m and 100 Hz, (iii) pulsed high frequency MF in the radiofrequency (RF) range (63.6 MHz, 5.8 ,T), and (iv) a combination of (i,iii). Exposure periods ranged from 1 to 24 h. Cell cycle distribution (G0/G1, S, and G2/M phases) was analyzed by flow cytometry. Cell cycle analysis did not reveal differences between the exposed and the control cells. As expected, positive controls with irradiated (8 Gy) HL60 and EA2 cells showed a strong G2/M arrest. Using conditions that are relevant for patients during MRI, no influence of MFs on cell cycle progression was observed in these cell lines. Care was taken to control secondary parameters of influence, such as vibration by the MR scanner or temperature to avoid false positive results. Bioelectromagnetics 24:241-250, 2003. © 2003 Wiley-Liss, Inc. [source] Hyperosmotic Stress in Murine Hybridoma Cells: Effects on Antibody Transcription, Translation, Posttranslational Processing, and the Cell CycleBIOTECHNOLOGY PROGRESS, Issue 2 2004Zhe Sun Mechanisms for increased antibody production in batch cultures of murine hybridoma cells in response to hyperosmotic stress were investigated. The rates of immunoglobulin transcription and protein translation and posttranslational processing were determined in control and hyperosmotic cultures. Changes in immunoglobulin transcription played a minor role in the increase in antibody production in response to hyperosmotic stress. In contrast, protein translation increased substantially in response to osmotic stress. However, the antibody translation rate remained relatively constant after correcting for the overall increase in protein translation. Cell size and intracellular antibody pool also increased in response to hyperosmolarity. The intracellular antibody pool increased proportionately with the increase in cell size, indicating that hyperosmotic cultures do not selectively increase their intracellular antibody population. Changes in cell cycle distribution in response to osmotic stress and the relationship between the cell cycle and antibody production were also evaluated. Hyperosmotic stress altered the cell cycle distribution, increasing the fraction of the cells in S-phase. However, this change was uncorrelated with the increase in antibody production rate. Immunoglobulin degradation was relatively low (,15%) and remained largely unchanged in response to hyperosmotic stress. There was no apparent increase in immunoglobulin stability as a result of osmotic stress. Antibody secretion rates increased approximately 50% in response to osmotic stress, with a commensurate increase in the antibody assembly rate. The rate of transit through the entire posttranslational processing apparatus increased, particularly for immunoglobulin light chains. The levels of endoplasmic reticulum chaperones did not increase as a fraction of the total cellular protein but were increased on a per cell basis as the result of an increase in total cellular protein. A difference in the interactions between the immunoglobulin heavy chains and BiP/GRP78 was observed in response to hyperosmotic conditions. This change in interaction may be correlated with the decrease in transit time through the posttranslational pathways. The increase in the posttranslational processing rate appears to be commensurate with the increase in antibody production in response to hyperosmotic stress. [source] Impact of BCR/ABL gene expression on the proliferative rate of different subpopulations of haematopoietic cells in chronic myeloid leukaemiaBRITISH JOURNAL OF HAEMATOLOGY, Issue 1 2006Daniel Primo Summary Despite the effects of BCR ABL on cell proliferation, no study has compared the proliferative rate of different haematopoietic cell compartments from chronic myeloid leukaemia (CML) with those of normal bone marrow (NBM). We comparatively analysed the cell cycle distribution and BCR/ABL expression in different compartments of BM cells from 15 CML and 11 NBM. Overall, our results showed similar proliferative indices in CML patients and NBM. However, CD34+ myeloid precursors from CML patients displayed an increased proportion of S + G2/M-phase cells (P = 0·04), while no significant differences were found between CML and NBM for other BM cell subsets analysed. In BM cells separated by fluorescence-activated cell sorting, decreasing levels of BCR/ABL mRNA were found from CD34+/CD38+ myeloid precursors to myeloblasts; BCR/ABL expression increased afterwards with a peak at the myelocyte/metamyelocyte stage, decreasing in the more mature band/neutrophil compartment. Unexpectedly, BCR/ABL gene expression showed an inverse correlation with the proportion of S + G2/M-phase cells (R = ,0·33; P = 0·04). These results suggest that in CML, BCR/ABL expression is associated with an increased proliferation of CD34+ myeloid haematopoietic progenitor cells but not of other more mature myeloid precursors, as confirmed by the observation of an inverse correlation between the amount of BCR/ABL transcripts and the proportion of S + G2/M-phase cells. [source] Reduction of cell cycle progression in human erythroid progenitor cells treated with tumour necrosis factor alpha occurs with reduced CDK6 and is partially reversed by CDK6 transductionBRITISH JOURNAL OF HAEMATOLOGY, Issue 6 2003Chunhua Dai Summary. Tumor necrosis factor , (TNF,) potently inhibits the in vitro growth of highly purified human d-6 erythroid colony forming cells (ECFC). Unlike the inhibitory effect of TNF, on other cells, including more immature ECFC, this antiproliferative effect of TNF, is not related to apoptosis because the d-6 cell descendants were morphologically normal, without apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling assay and without caspase activation by Western blots after TNF, treatment. TNF, did not appear to affect the cell cycle distribution, but the cell cycle duration was significantly longer in TNF,-treated cells. DNA synthesis was also significantly reduced by TNF,. Studies of various proteins that regulate the cell cycle showed that cyclin-dependent kinase 6 (CDK6) protein and mRNA levels were concomitantly decreased in the presence of TNF,, suggesting that inhibition of cell growth was related to reduced CDK6. To evaluate this, the CDK6 gene was transferred into ECFC using green fluorescence protein-retrovirus-mediated gene transfer. The results showed that the level of cell growth produced by TNF, was increased by 30% when the cells were transfected with CDK6. Therefore, the modification of cell cycle progression in the presence of TNF, through a reduction of CDK6 is an important mechanism in the TNF, inhibition of human ECFC expansion. [source] Simaomicin ,, a polycyclic xanthone, induces G1 arrest with suppression of retinoblastoma protein phosphorylationCANCER SCIENCE, Issue 2 2009Yukio Koizumi Recent progress in cancer biology research has shown that abnormal proliferation in tumor cells can be attributed to aberrations in cell cycle regulation, especially in G1 phase. During the course of searching for microbial metabolites that affect cell cycle distribution, we have found that simaomicin ,, a polycyclic xanthone antibiotic, arrests the cell cycle at G1 phase. Treatment of T-cell leukemia Jurkat cells with 3 nM simaomicin , induced an increase in the number of cells in G1 and a decrease in those in G2,M phase. Cell cycle aberrations induced by simaomicin , were also detected in colon adenocarcinoma HCT15 cells. Simaomicin , had antiproliferative activities in various tumor cell lines with 50% inhibitory concentration values in the range of 0.3,19 nM. Furthermore, simaomicin , induced an increase in cellular caspase-3 activity and DNA fragmentation, indicating that simaomicin , promotes apoptosis. The retinoblastoma protein phosphorylation status of simaomicin ,-treated cell lysate was lower than that of control cells, suggesting that the target molecule of simaomicin , is in a pathway upstream of retinoblastoma protein phosphorylation. In the course of evaluating polycyclic xanthone antibiotics structurally related to simaomicin ,, we also found that cervinomycin A1 stimulated accumulation of treated cells in G1 phase. These results indicate that the polycyclic xanthones, including simaomicin , and cervinomycin A1, may be candidate cancer chemotherapeutic agents. (Cancer Sci 2009; 100: 322,326) [source] The novel ruthenium,, -linolenic complex [Ru2(aGLA)4Cl] inhibits C6 rat glioma cell proliferation and induces changes in mitochondrial membrane potential, increased reactive oxygen species generation and apoptosis in vitroCELL BIOCHEMISTRY AND FUNCTION, Issue 1 2010Geise Ribeiro Abstract The present study reports the synthesis of a novel compound with the formula [Ru2(aGLA)4Cl] according to elemental analyses data, referred to as Ru2GLA. The electronic spectra of Ru2GLA is typical of a mixed valent diruthenium(II,III) carboxylate. Ru2GLA was synthesized with the aim of combining and possibly improving the anti-tumour properties of the two active components ruthenium and , -linolenic acid (GLA). The properties of Ru2GLA were tested in C6 rat glioma cells by analysing cell number, viability, lipid droplet formation, apoptosis, cell cycle distribution, mitochondrial membrane potential and reactive oxygen species. Ru2GLA inhibited cell proliferation in a time and concentration dependent manner. Nile Red staining suggested that Ru2GLA enters the cells and ICP-AES elemental analysis found an increase in ruthenium from <0.02 to 425,mg/Kg in treated cells. The sub-G1 apoptotic cell population was increased by Ru2GLA (22,±,5.2%) when analysed by FACS and this was confirmed by Hoechst staining of nuclei. Mitochondrial membrane potential was decreased in the presence of Ru2GLA (44,±,2.3%). In contrast, the cells which maintained a high mitochondrial membrane potential had an increase (18,±,1.5%) in reactive oxygen species generation. Both decreased mitochondrial membrane potential and increased reactive oxygen species generation may be involved in triggering apoptosis in Ru2GLA exposed cells. The EC50 for Ru2GLA decreased with increasing time of exposure from 285,µM at 24,h, 211,µM at 48,h to 81,µM at 72,h. In conclusion, Ru2GLA is a novel drug with antiproliferative properties in C6 glioma cells and is a potential candidate for novel therapies in gliomas. Copyright © 2009 John Wiley & Sons, Ltd. [source] Modifications in cell cycle kinetics and in expression of G1 phase-regulating proteins in human amniotic cells after exposure to electromagnetic fields and ionizing radiationCELL PROLIFERATION, Issue 5 2004S. Lange Because development of cancer is associated with deregulated cell growth and we previously observed a magnetic field-induced decrease in DNA synthesis [Lange et al. (2002) Alterations in the cell cycle and in the protein level of cyclin D1p, 21CIP1, and p16INK4a after exposure to 50 HZ. MF in human cells. Radiat. Environ. Biophys.41, 131], this study aims to document the influence of 50 Hz, 1 mT magnetic fields (MF), with or without initial ,-ionizing radiation (IR), on the following cell proliferation-relevant parameters in human amniotic fluid cells (AFC): cell cycle distribution, expression of the G1 phase-regulating proteins Cdk4, cyclin D1, p21CIP1 and p16INK4a, and Cdk4 activity. While IR induced a G1 delay and a dose-dependent G2 arrest, no discernible changes in cell cycle kinetics were observed due to MF exposure. However, a significant decrease in the protein expression of cyclin D1 and an increase in p21CIP1 - and p16INK4a -expression could be detected after exposure to MF alone. IR-exposure caused an augmentation of p21CIP1 - and p16INK4a - levels as well, but did not alter cyclin D1 expression. A slight diminution of Cdk4 activity was noticed after MF exposure only, indicating that Cdk4 appears not to act as a mediator of MF- or IR-induced changes in the cell cycle of AFC cells. Co-exposure to MF/IR affected neither cell cycle distribution nor protein expression or kinase activity additionally or synergistically, and therefore MF seems not to modify the mutagenic potency of IR. [source] Extracellular matrix alters the relationship between tritiated thymidine incorporation and proliferation of MC3T3-E1 cells during osteogenesis in vitroCELL PROLIFERATION, Issue 1 2002W. J. Peterson Bone cells in vivo exist in direct contact with extracellular matrix, which regulates their basic biological processes including metabolism, development, growth and differentiation. Thus, the in vitro activity of cells cultured on tissue culture treated plastic could be different from the activity of cells cultured on their natural substrate. We selected MC3T3-E1 pre-osteoblastic cells to study the effect of extracellular matrix on cell proliferation because these cells undergo a progressive developmental sequence of proliferation and differentiation. MC3T3-E1 cells were cultured on plastic or plastic coated with ECM, fibronectin, collagen type I, BSA or poly l -lysine and their ability to proliferate was assessed by incorporation of [3H]dT or by enumeration of cells. Our results show that (1) ECM inhibits incorporation of [3H]dT by MC3T3-E1 cells; (2) collagen type I, but not BSA, poly l -lysine or fibronectin also inhibits incorporation of [3H]dT; (3) the level of ECM inhibition of [3H]dT incorporation is directly related to the number of cells cultured, but unrelated to the cell cycle distribution or endogenous thymidine content; (4) the kinetic profile of [3H]dT uptake suggest that ECM inhibits transport of [3H]dT from the extracellular medium, and (5) cell counts are similar in cultures whether cells are grown on plastic or ECM. These results suggest that decreased incorporation of [3H]dT by cells cultured on ECM is not reflective of bone cell proliferation. [source] Rapamycin reduces hybridoma cell death and enhances monoclonal antibody productionBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2001R. Robert Balcarcel Abstract Rapamycin was used as a medium additive to slow the progression of CRL 1606 hybridomas through the cell cycle, under the hypothesis that such a modulation might reduce cell death. Cell cycle distributions for CRL hybridomas in the G1 phase of the cell cycle ranged from 20% to 35% during batch, fed-batch, and continuous culture experiments, independent of culture time, dilution rate, growth rates, or death rates. Rapamycin, an mTOR signaling inhibitor, immunosuppressant, and G1-phase arresting agent, was identified and tested for efficacy in restraining cell cycle progression in CRL 1606 hybridoma cultures. However, in the presence of 100 nM rapamycin, the percentage of cells in the G1 phase of the cell cycle during fed-batch cultures was only increased from 28% to 31% in control cultures to 37% to 48% for those with rapamycin. Accordingly, rapamycin only slightly reduced culture growth rate. Instead, the use of rapamycin more notably kept viability higher than that of control cultures by delaying cell death for 48 h, thereby enabling viable proliferation to higher maximum viable cell densities. Furthermore, rapamycin enhanced specific monoclonal antibody production by up to 100% during high-viability growth. Thus, over the course of 6-day fed-batch cultivations, the beneficial effects of rapamycin on viable cell density and specific productivity resulted in an increase in final monoclonal antibody titer from 0.25 to 0.56 g/L (124%). As rapamycin is reported to influence a much broader range of cellular functions than cell cycle alone, these findings are more illustrative of the influence that signal transduction pathways related to mTOR can have on overall cell physiology and culture productivity. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 1,10, 2001. [source] | |||||||||||||||||||||||||