Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “G2 Phase”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMed1985

Effects of cytosine arabinoside on DNA synthesis and mitotic activity of HL-60 cells.

HL-60 cells were exposed to tritiated thymidine (3HTdR) alone (control group), to cytosine arabinoside followed by 3HTdR or to tritium labelled cytosine arabinoside (3H-AraC) for one hour followed by incubation with colcemide to arrest them during metaphase. Autoradiographic slides were prepared and cell counts were at 1, 24, 48 and 72 h. The studies demonstrated that HL-60 cells exposed to high concentrations of AraC (10 micrograms ml-1) can pass through the S-phase as the G2-phase of the cell cycle and enter mitosis. Despite completing the S-phase, the cells exposed to AraC were severely damaged and had already begun to die.

Autoradiography↗
PubMed2004

The human immunodeficiency virus Vpr protein binds Cdc25C: implications for G2 arrest.

The human immunodeficiency virus (HIV) encodes a gene product, Vpr, which causes infected cells to arrest or delay in the G2 phase of the cell cycle. The arrest in G2 is characterized by low levels of Cyclin B1-p34Cdc2 activity and corresponding inhibitory phosphorylation of p34Cdc2. We find that Vpr directly inhibits the in vitro activity of a phosphatase, Cdc25C, which normally activates Cyclin B1-p34Cdc2. Vpr binds to Cdc25C both in vitro and in mammalian cells. Vpr is also able to inhibit Cdc25C phosphatase activity in vitro although it binds to a site on Cdc25C that is distinct from the catalytic site of the enzyme. Expression of both a catalytically active mutant of Cdc25C that has reduced binding to Vpr as well as a catalytically inactive mutant of Cdc25C that retains binding to Vpr is able to largely overcome Vpr-mediated G2 arrest. Finally, depletion of Cdc25C from cells also renders them partially resistant to the effects of Vpr.

Amino Acid Sequence↗
PubMed1993

Deoxyribonucleic acid ploidy of core biopsies and metastatic lymph nodes of prostate cancer patients: impact on time to progression. The European Organization for Research and Treatment of Cancer Genitourinary Group.

We studied 98 patients with locally confined but lymph node positive prostatic cancer (1 stage T1, 29 stage T2, 55 stage T3 and 2 stage T4) who were not treated by radical prostatectomy. A retrospective analysis was done of deoxyribonucleic acid (DNA) ploidy of pretreatment core biopsies of the primary tumor and lymph node metastases. While DNA ploidy has been shown to be an important prognostic factor if applied to radical prostatectomy specimens, core biopsy specimens and nodal metastases have rarely been studied. Of the 98 patients 87 were evaluable for DNA ploidy: 45 (52%) had diploid, 13 (15%) had tetraploid and 29 (33%) had aneuploid tumors. The ploidy of the primary tumor and of the lymph node metastases correlated significantly with the rate of progression and interval to progression. Also, significant correlations were noted between the percentages of cells in the S phase or S plus G2 phases of the cell cycle and interval to progression. Most patients in this study are part of the European Organization for Research and Treatment of Cancer protocol 30846, a prospective randomized study of early versus delayed treatment in lymph node positive, otherwise locally confined prostate cancer. This study is ongoing. Early endocrine treatment was associated with a significantly longer interval to progression. In a Cox regression analysis of the prognostic factors involved in this study, early endocrine treatment was more important than ploidy or proliferation patterns. Stage (T category) and histopathological grade did not show a correlation with progression. Followup is still too short and the numbers of patients are too small for relevant subgroup analysis. DNA ploidy measurement by flow cytometry on archival (paraffin embedded) core biopsy and lymph node material is possible, and produces meaningful results in predicting the prognosis of prostatic cancer. Since this information can be made available before treatment decisions, its exact value in the management of locally confined prostate cancer can be determined.

Aged↗
PubMed2002

Premature chromosome condensation and cell separation studies in biopsies from head and neck tumors for radiosensitivity prediction.

BACKGROUND AND PURPOSE: Intrinsic radiosensitivity of tumor cells from biopsies, assayed by colony formation after in vitro irradiation, has shown significant correlations with outcome after radiotherapy. Alternatives to the colony assay have been sought due to its long and cumbersome nature. We have previously shown good correlations between colony formation and radiation-induced chromosome aberrations in human tumor cell lines. In addition, we and others have shown on cell lines that premature chromosome condensation (PCC) induced with phosphatase inhibitors can be used to aid rapid assessment of aberrations in interphase cells, reducing the selection problem with metaphases. The purpose of this study was to translate the in vitro results to human cancer, with the aim of developing a rapid assay for intrinsic radiosensitivity. METHODS AND RESULTS: The problem of admixtures of normal and malignant cells in biopsies was addressed using magnetic bead separation (MACS) employing antibodies to human fibroblasts. This proved to be a reliable and efficient method, enriching mean tumor cell fractions from 20 to almost 80%. PCC could be induced in human normal and tumor cell lines, and in sorted or unsorted suspensions from biopsies, with the phosphatase inhibitor calyculin A. Maximum PCCs were achieved after 1-week culture of biopsy-derived cells. Mean fractions of aneuploid tumor cell PCCs were, however, less than 1%. PCCs were predominantly from S and G2 phase, of which only G2 were scorable for aberrations. Almost no G1 PCCs were found. More scorable PCCs were found after 1h of calyculin A than metaphases after 5h of colcemid, but these were calculated to be too few to yield reliable estimates of chromosome damage after radiation.CONLCUSIONS: Tumor cells can be satisfactorily separated from fibroblasts in fresh suspensions from cancer biopsies, but poor growth of tumor cells in short term culture and low yields of PCCs combine to prevent the routine use of such cytogenetic assays for pre-treatment prediction of radiotherapy outcome.

Adenocarcinoma↗
PubMed1985

Enhancement of DNA-mediated gene transfer by high-Mr carrier DNA in synchronized CV-1 cells.

Synchronized CV-1 cells were transfected with SV40 (simian virus 40) DNA-calcium phosphate co-precipitates. In the presence of carrier DNA, the transfection efficiency of SV40 DNA was decreased 5-fold in S-phase cells and was increased 4-fold in preparations of mitotically enriched cells as compared with asynchronous controls. No difference was observed when carrier DNA was omitted, when cells had progressed through S-phase and into G2-phase, or when the infectivity of cells to intact SV40 virus was tested. These results highlight the importance of cell-cycle-dependent factors on DNA-mediated gene transfer.

Animals↗
PubMed2003

Moscatilin from the orchid Dendrobrium loddigesii is a potential anticancer agent.

The Dendrobrium species have been commonly used in traditional Chinese medicine as a tonic to nourish the stomach, replenish body fluid, and reduce fever. However, their application as possible therapeutic agents for the treatment of cancers has not been examined. In this study, we want to examine the efficacy of using moscatilin, a natural antiplatelet agent extracted from the stems of Dendrobrium loddigesii, as an anticancer agent. Our results have shown that moscatilin exerts potent cytotoxic effect against cancer cell lines derived from different tissue origins, including those from the placenta, stomach, and lung, but not those from the liver. In addition, we have found that the mechanism of action of moscatilin may be related to its ability to induce a G2 phase arrest in responsive cells. However, unlike some G2 arresting agents, moscatilin has no detectable inhibitory effect on cyclin B-cdc-2 kinase activity. Thus, the precise nature of its cytotoxic mechanism remains to be determined. Our results in this study imply that moscatilin is potentially efficacious for chemoprevention and/or chemotherapy against some types of cancer.

Benzyl Compounds↗
PubMed1981

Morphology and kinetics of erythropoiesis in haemoglobin H disease.

Some aspects of erythroblast function have been investigated in two Thai patients with haemoglobin H disease. Electron microscope and high resolution autoradiographic studies revealed that (1) some erythroblasts and marrow reticulocytes contained branching intracytoplasmic inclusions and (2) the presence of such inclusions did not necessarily prevent the entry of cells either from the G1 phase into the S phase or from the G2 phase into mitosis. The distribution of early polychromatic erythroblasts in the different stages of the cell cycle was determined by the technique of combined Feulgen microspectrophotometry and 3H-thymidine autoradiography and found to be essentially normal. It is concluded that although the presence of an excess of alpha-chains in the beta-thalassaemia syndromes has been previously shown to be associated with a gross impairment of erythroblast proliferation, the presence of an excess beta-chains in HbH disease is not.

Adult↗
PubMed2005

Immunohistochemical estimation of cell cycle entry and phase distribution in astrocytomas: applications in diagnostic neuropathology.

An immunohistochemical method for assessing cell cycle phase distribution in neurosurgical biopsies would enable such data to be incorporated into diagnostic algorithms for the estimation of prognosis and response to adjuvant chemotherapy in glial neoplasms, without the requirement for flow cytometric analysis. Paraffin-embedded sections of intracerebral gliomas (n = 48), consisting of diffuse astrocytoma (n = 9), anaplastic astrocytoma (n = 8) and glioblastoma (n = 31), were analysed by immunohistochemistry using markers of cell cycle entry, Mcm-2 and Ki67, and putative markers of cell cycle phase, cyclins D1 (G1-phase), cyclin A (S-phase), cyclin B1 (G2-phase) and phosphohistone H3 (Mitosis). Double labelling confocal microscopy confirmed that the phase markers were infrequently coexpressed. Cell cycle estimations by immunohistochemistry were corroborated by flow cytometric analysis. There was a significant increase in Mcm-2 (P < 0.0001), Ki67 (P < 0.0001), cyclin A (P < 0.0001) and cyclin B1 (P = 0.002) expression with increasing grade from diffuse astrocytoma through anaplastic astrocytoma to glioblastoma, suggesting that any of these four markers has potential as a marker of tumour grade. In a subset of glioblastomas (n = 16) for which accurate clinical follow-up data were available, there was a suggestion that the cyclin A:Mcm-2 labelling fraction might predict a relatively favourable response to radical radiotherapy. These provisional findings, however, require confirmation by a larger study. We conclude that it is feasible to obtain detailed cell cycle data by immunohistochemical analysis of tissue biopsies. Such information may facilitate tumour grading and may enable information of prognostic value to be obtained in the routine diagnostic laboratory.

Adult↗
PubMed1995

Irreversible repression of DNA synthesis in Fanconi anemia cells is alleviated by the product of a novel cyclin-related gene.

Primary fibroblasts from patients with the genetic disease Fanconi anemia, which are hypersensitive to cross-linking agents, were used to screen a cDNA library for sequences involved in their abnormal cellular response to a cross-linking challenge. By using library partition and microinjection of in vitro-transcribed RNA, a cDNA clone, pSPHAR (S-phase response), which is able to correct the permanent repression of semiconservative DNA synthesis rates characteristic of these cells, was isolated. Wild-type SPHAR mRNA is expressed in all fibroblasts so far analyzed, including those of Fanconi anemia patients. Correction of the abnormal response in these cells appears therefore to be due to overexpression after cDNA transfer rather than to genetic complementation. The cDNA contains an open reading frame coding for a polypeptide of 7.5 kDa. Rabbit antiserum directed against a SPHAR peptide detects a protein of 7.9 kDa in Western blots (immunoblots) of whole-cell extracts from proliferating, but not resting, fibroblasts. The deduced amino acid sequence of SPHAR contains a motif found in the cyclins, and it is proposed that SPHAR acts within the injected cell by interfering with the cyclin-controlled maintenance of S phase. In agreement with this proposal, normal cells transfected with an antisense SPHAR expression vector have a significantly reduced rate of DNA synthesis during S phase and a prolonged G2 phase, reflecting the need for postreplicative DNA processing before entry into mitosis.

Amino Acid Sequence↗
PubMed1983

Excision and replication of extrachromosomal DNA of pea (Pisum sativum).

Experiments with cultured pea roots were conducted to determine (i) whether extrachromosomal DNA was produced by cells in the late S phase or in the G2 phase of the cell cycle, (ii) whether the maturation of nascent DNA replicated by these cells achieved chromosomal size, (iii) when extrachromosomal DNA was removed from the chromosomal duplex, and (iv) the replication of nascent chains by the extrachromosomal DNA after its release from the chromosomal duplex. Autoradiography and cytophotometry of cells of carbohydrate-starved root tips revealed that extrachromosomal DNA was produced by a small fraction of cells accumulated in the late S phase after they had replicated about 80% of their DNA. Velocity sedimentation of nascent chromosomal DNA in alkaline sucrose gradients indicated that the DNA of cells in the late S phase failed to achieve chromosomal size. After reaching sizes of 70 X 10(6) to 140 X 10(6) daltons, some of the nascent chromosomal molecules were broken, presumably releasing extrachromosomal DNA several hours later. Sedimentation of selectively extracted extrachromosomal DNA either from dividing cells or from those in the late S phase showed that it replicated two nascent chains, one of 3 X 10(6) daltons and another of 7 X 10(6) daltons. Larger molecules of extrachromosomal DNA were detectable after cells were labeled for 24 h. These two observations were compatible with the idea that the extrachromosomal DNA was first replicated as an integral part of the chromosomal duplex, was cut from the duplex, and then, once free of the chromosome, replicated two smaller chains of 3 X 10(6) and 7 X 10(6) daltons.

Cell Cycle↗
PubMed1984

Cell cycle phases in the unequal mother/daughter cell cycles of Saccharomyces cerevisiae.

During cell division in the yeast Saccharomyces cerevisiae mother cells produce buds (daughter cells) which are smaller and have longer cell cycles. We performed experiments to compare the lengths of cell cycle phases in mothers and daughters. As anticipated from earlier indirect observations, the longer cell cycle time of daughter cells is accounted for by a longer G1 interval. The S-phase and the G2-phase are of the same duration in mother and daughter cells. An analysis of five isogenic strains shows that cell cycle phase lengths are independent of cell ploidy and mating type.

Cell Cycle↗
PubMed2000

Chromosome cohesion, condensation, and separation.

The faithful segregation of genetic information requires highly orchestrated changes of chromosome structure during the mitotic cell cycle. The linkage between duplicated sister DNAs is established during S phase and maintained throughout G2 phase (cohesion). In early mitosis, dramatic structural changes occur to produce metaphase chromosomes, each consisting of a pair of compacted sister chromatids (condensation). At anaphase onset, a signal is produced to disrupt the linkage between sister chromatids (separation), allowing them to be pulled apart to opposite poles of the cell. This review discusses our current understanding of the three stages of large-scale structural changes of chromosomes in eukaryotic cells. Recent genetic and biochemical studies have identified key components involved in these processes and started to uncover hitherto unexpected functional links between mitotic chromosome dynamics and other important chromosome functions.

Adenosine Triphosphatases↗
PubMed2005

The antiangiogenic factor, 16-kDa human prolactin, induces endothelial cell cycle arrest by acting at both the G0-G1 and the G2-M phases.

The 16-kDa N-terminal fragment of human prolactin (16K hPRL) is a potent antiangiogenic factor that has been shown to prevent tumor growth in a xenograph mouse model. In this paper we first demonstrate that 16K hPRL inhibits serum-induced DNA synthesis in adult bovine aortic endothelial cells. This inhibition is associated with cell cycle arrest at both the G(0)-G(1) and the G(2)-M phase. Western blot analysis revealed that 16K hPRL strongly decreases levels of cyclin D1 and cyclin B1, but not cyclin E. The effect on cyclin D1 is at least partially transcriptional, because treatment with 16K hPRL both reduces the cyclin D1 mRNA level and down-regulates cyclin D1 promoter activity. This regulation may be due to inhibition of the MAPK pathway, but it is independent of the glycogen synthase kinase-3beta pathway. Lastly, 16K hPRL induces the expression of negative cell cycle regulators, the cyclin-dependent kinase inhibitors p21(cip1) and p27(kip1). In summary, 16K hPRL inhibits serum-induced proliferation of endothelial cells through combined effects on positive and negative regulators of cell cycle progression.

Angiogenesis Inhibitors↗
PubMed1991

Molecular cloning of the human gene, CCG2, that complements the BHK-derived temperature-sensitive cell cycle mutant tsBN63: identity of CCG2 with the human X chromosomal SCAR/RPS4X gene.

A temperature-sensitive mutant tsBN63 cell line was isolated by the fluorodeoxyuridine method from the BHK21/13 cell line after mutagenesis with nitrosoguanidine. When cultures of tsBN63 cells growing asynchronously at 33.5 degrees C were shifted to 39.5 degrees C, a nonpermissive temperature, the ability for protein synthesis was rapidly reduced and cell proliferation stopped mainly at G1 phase, and partly at G2 phase. Synchronized cultures of tsBN63 cells did not commence DNA synthesis when shifted up in G1 phase. The human gene complementing the tsBN63 mutation was cloned by DNA-mediated gene transfer and its cDNA of 1.1 kb conferring ts+ phenotype on tsBN63 cells was isolated from the cDNA library of Raj (mer+) cells with a frequency of 10(-3). On the basis of the determined nucleotide sequence, the isolated human gene turned out to be the X chromosomal RPS4X encoding the ribosomal protein S4. The size of the CCG2 gene was estimated to be about 12 kb by complementation analysis of the tsBN63 mutation with cloned genomic DNA.

Amino Acid Sequence↗
PubMed2006

IL-22-mediated tumor growth reduction correlates with inhibition of ERK1/2 and AKT phosphorylation and induction of cell cycle arrest in the G2-M phase.

IL-22 is a recently discovered cytokine of the IL-10 family that binds to a class II cytokine receptor composed of IL-22R1 and IL-10R2(c) and influences a variety of immune reactions. As IL-22 has also been shown to modulate cell cycle and proliferation mediators such as ERK1/2 and JNK, we studied the role of IL-22 in proliferation, apoptosis, and cell cycle regulation in EMT6 murine breast cancer cells in vitro and in vivo. In this study, we report that murine breast cancer cells express functional IL-22R as indicated by RT-PCR studies, immunoblotting, and STAT3 activation assays. Importantly, IL-22 exposure of EMT6 cells resulted in decreased levels of phosphorylated ERK1/2 and AKT protein kinases, indicating an inhibitory effect of IL-22 on signaling pathways promoting cell proliferation. Furthermore, IL-22 induced a cell cycle arrest of EMT6 cells in the G(2)-M phase. IL-22 reduced EMT6 cell numbers and the proliferation rate by approximately 50% as measured by [(3)H]thymidine incorporation. IL-22 treatment of EMT6 tumor-bearing mice lead to a decreased tumor size and a reduced tumor cell proliferation in vivo, as determined by 3'-deoxy-3'-fluorothymidine-positron emission tomography scans. Interestingly, IL-22 did not induce apoptosis, as determined in annexin V binding assay and caspase-3 activation assay and had no effect on angiogenesis in vivo. In conclusion, our results indicate that IL-22 reduced tumor growth by inhibiting signaling pathways such as ERK1/2 and AKT phosphorylation that promote tumor cell proliferation in EMT6 cells. Therefore, IL-22 may play a role in the control of tumor growth and tumor progression.

Animals↗
PubMed2002

[Anticancer effect of hydroxycampothecin on oral squamous carcinoma cell line].

BACKGROUND & OBJECTIVE: Studies have demonstrated that hydroxycamptothecin (HCPT) had therapeutic effect on many malignant tumors, but few studies on oral squamous cell carcinoma were reported. This study was designed to investigate the anticancer effect and mechanism of hydroxycampothecin (HCPT) on oral squamous carcinoma cell line (Tca8113). METHODS: The cytotoxicity of HCPT on Tca8113 cell line was measured by MTT assay and cell cycle detected by flow cytometry(FCM). The growth status of Tca8113 cell xenografts following treatment with HCPT was observed. The doubling times and tumor inhibition rate were calculated. RESULTS: HCPT had strong cytotoxicity on Tca8113 cells, the IC50 was 2 mumol/L. After treatment with low concentration of HCPT, the cell cycle was arrested in S phase or G2 + M phase; while at high concentration, apoptosis was obviously found and the rate of apoptosis was increased as the time and concentration of HCPT. Compared with control group, the xenografts of HCPT treated group grew slower and tumor doubling time was prolonged, The tumor volumes of HCPT treated group at 28th day were significantly smaller(P < 0.001) with tumor inhibition rate of 69.6%. CONCLUSION: The result showed that HCPT had strong cytotoxicity effect to oral squamous carcinoma cells and significant growth inhibition on Tca8113 xenografts. HCPT can arrest cell cycle in S phase and G2 + M phase and induce cell apoptosis.

Animals↗