Eukaryotic initiation factor 5A (eIF-5A) contains an unusual amino acid, hypusine, which is formed post-translationally. Although eIF-5A and its hypusine modification are essential for eukaryotic cell viability, the precise physiological function of it has remained elusive. The aim of the study is to investigate how hypusine formation modulate the proliferation, cell cycle and apoptosis in leukaemia cells. The effects of 1,7-diaminoheptane (DAH), a potent inhibitor of deoxyhypusine synthase, on proliferation and cell viability of leukemia cell lines (Mo7e, TF-1 and THP-1) and MCF-7 cells, were investigated. eIF-5A expression level was detected after cell synchronization. The results showed that inhibition of cell proliferation by DAH was in a concentration-dependent manner while apoptosis was also induced at the same time. Upon treatment of the cell lines with DAH, cell growth was inhibited. Cell cycle analysis showed that DAH induced cell growth arrest at the G(1)-S boundary of the cell cycle. In synchronized MCF-7 cells, the expression level of eIF-5A peaked at G(1) phase but very low at S and G(2)/M phases. It is concluded that hypusine formation of eIF-5A exits in the regulation of cell cycle and the results suggest that eIF-5A is involved in the expression of proteins regulating transition of G(1)-S phase of cell cycle.
Cell Line, Tumor ; Diamines ; pharmacology ; G1 Phase ; physiology ; Humans ; Lysine ; analogs & derivatives ; metabolism ; Peptide Initiation Factors ; physiology ; RNA-Binding Proteins ; S Phase ; physiology

Very late antigen-4 (VLA-4), which binds to the extracellular matrix protein fibronectin, is an integrin molecule known to be modulated during mobilization of CD34+ cells, and to be involved in signaling the mobilization stimuli. On the hypothesis that cell cycling status might be different depending on the level of VLA-4 expression, we investigated the DNA contents of human cord blood CD34+ cells during ex vivo expansion by recombinant human thrombopoietin and flt3-ligand with simultaneous measurement of surface VLA-4 at the 1st and 4th week. During this ex vivo expansion, expression of VLA-4 increased and almost all cells became VLA-4+ until the 4th day of culture. Expression of VLA-4 was maintained in the major population of the cultured cells until the 4th week. The cells in S/G2/M phase were greater in number in VLA-4 high fraction than in VLA-4 low fraction (n=4, p<.001). Furthermore, the fraction of cells in S/G2/M phase increased as the expression of VLA-4 became higher. These results suggest that cord blood CD34+ cells expressing high levels of VLA-4 have more proliferative activities.
Antigens, CD34/analysis* ; Cells, Cultured ; DNA/analysis ; Fetal Blood/cytology* ; G2 Phase ; Hematopoietic Stem Cells/physiology* ; Human ; Immunophenotyping ; Infant, Newborn ; Integrins/analysis* ; Receptors, Lymphocyte Homing/analysis* ; S Phase

OBJECTIVETo study the expression of peptidyl-prolyl cis/trans isomerase (PPIase or Pin1) in malignant hematopoietic cells and its relation with cell cycle.

METHODSRealtime quantitative PCR with fluorescence probe hybridization was used to measure expression of Pin1 mRNA in malignant hematopoietic cell lines and normal mononuclear cells separated from bone marrow. HeLa cells were blocked with Thymidine and Nocodazole in different cell phases and then the expression of Pin1 mRNA and protein were detected by realtime-PCR and immunoblotting.

RESULTSThe expression of Pin1 in malignant hematopoietic cell lines was significantly higher than that in normal controls (0.339 +/-0.093 compared with 0.038 +/-0.005, P<0.01). Its expression in myeloid malignant hematopoietic cell lines was significantly higher than that in normal controls (0.388 +/-0.115 compared with 0.038 +/-0.005, P<0.01) and so was the malignant lymphocytic cell lines (0.226 +/-0.166 compared with 0.038 +/-0.005, P<0.01). The expression of Pin1 was closely correlated with cell cycle. It was the highest in G1 phase and the lowest in S phase (110.762 +/-16.737 compared with 4.080 +/-0.634, P<0.01).

CONCLUSIONPin1 is overexpressed in malignant hematopoietic cell lines and its expression is different during cell cycle that is highest in G1 phase and lowest in S phase.

Cell Cycle ; physiology ; G1 Phase ; Humans ; Leukemia, Lymphoid ; enzymology ; pathology ; Leukemia, Myeloid ; enzymology ; pathology ; Peptidylprolyl Isomerase ; biosynthesis ; genetics ; RNA, Messenger ; biosynthesis ; genetics ; S Phase ; Tumor Cells, Cultured

BACKGROUNDExposure to cigarette smoke stimulates the proliferation of human pulmonary artery smooth muscle cells (HPASMCs) in vivo and in vitro. However, the molecular mechanism remains unclear. This study aimed at investigating the role of signaling pathways involving protein kinase C alpha (PKCα) and cyclin D1 in the cigarette smoke extract (CSE)-induced HPASMCs proliferation.

METHODSSynchronized HPASMCs were treated with different concentrations of CSE. Cell proliferation was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell counting. Cell cycle was analyzed by flow cytometry with propidium iodide staining. Activation of PKCα was measured by detecting the expression of PKCα protein in the cytosolic and membrane fractions using Western blotting analysis. Small interfering RNA (siRNA) was used to knockdown PKCα and cyclin D1. The cyclin D1 mRNA was assessed by real-time RT-PCR. The PKCα and cyclin D1 protein levels were detected by Western blotting.

RESULTSLow concentrations of CSE (1% - 10%) stimulated proliferation of HPASMCs, with its maximal effect at 5%. CSE (5%) led to PKCα activation. Inhibition of PKCα activity using Gö 6976 or siRNA-mediated knockdown of PKCα significantly attenuated CSE-induced cell proliferation and G1/S transition. Cyclin D1, one of key regulators of G1/S transition, was found to be upregulated by 5% CSE at both the mRNA and protein levels. CSE-stimulated cell proliferation and G1/S transition was abolished by cyclin D1 siRNA. Moreover, Gö 6976 or PKCα siRNA significantly suppressed CSE-induced upregulation of cyclin D1 at both the mRNA and protein levels.

CONCLUSIONPKCα-cyclin D1 pathway at least partially mediates the CSE-induced proliferation in HPASMCs.

Cell Proliferation ; Cells, Cultured ; Cyclin D1 ; physiology ; G1 Phase ; Humans ; Muscle, Smooth, Vascular ; pathology ; Myocytes, Smooth Muscle ; pathology ; Protein Kinase C-alpha ; physiology ; Pulmonary Artery ; pathology ; S Phase ; Signal Transduction ; Smoke ; adverse effects ; Tobacco ; adverse effects

Partial hepatectomy (PH) endorses quiescent hepatocytes to reenter the cell cycle. The regenerating liver returns to its preresection weight after 7 days, following one or two cell division and maintains nearly its original volume after then. We focused on the inhibition of further hepatocyte proliferation, hypothesizing possible involvement of cell cycle upregulators and inhibitors. We studied protein levels in expression of cyclins, cyclin dependent kinases (CDKs) and CDK inhibitors (CKIs), and their in situ hepatic lobular distributions in partial hepatectomized rat liver. Cyclin E was expressed in the same levels in normal liver and after PH. Expression of cyclin A, not detected in normal liver, increased in following times after PH and reached a maximum at 7 day. CDK2 and 4 showed increased expression toward terminal period. Contradictory findings of cyclin A and these CDKs might play an important role in the inhibition of further cell division, although still unclear. Constitutively expressed CDK6 decreased after 1 day. p18 showed peak expression within 1 day, and p16, p21, p27 and p57 were stronger at terminal periods. During the expected period of their activity, intranuclear translocations were observed in cyclin E, p18 and p16. There was no evidence of regional distribution in hepatic lobular architecture, instead, diffuse in situ expression, corroborating synchronous event, was found.
Animal ; Cell Cycle/physiology* ; Cyclin-Dependent Kinases/metabolism ; Cyclin-Dependent Kinases/antagonists & inhibitors ; Cyclins/metabolism* ; Cyclins/immunology ; Flow Cytometry ; Hepatectomy ; Immunoblotting ; Immunohistochemistry ; Interphase/physiology ; Liver/metabolism* ; Liver Regeneration/physiology* ; Male ; Rats ; Rats, Sprague-Dawley ; S Phase/physiology

OBJECTIVETo explore the influence of different nutritional support routes on the intestinal mucosal epithelial cell cycle in burned rats.

METHODSSixty-six Wistar rats inflicted with 30% TBSA III degree burns on the back were employed as the model and were randomly divided into enteral feeding group (EF) and intravenously parenteral nutrition group (PN). Equal volume of nutritional support fluid containing predetermined equal amount of calories and nitrogen was applied via feeding or intravenously infusion through external jugular vein. The indices were observed on 6, 12, 24, 48 and 72 postburn hours (PBHs) with the reference to those in 6 normal rats. The intestinal epithelial cell cycle in jejunal and ileal mucous membrane was analyzed by flow cytometry. Western blotting method was employed in the examination of the expression of cyclin D1, E and that of cyclin dependent kinase (CDK)2 and CDK4.

RESULTS(1) lntestinal mucosal epithelial G0/G1 ratio in jejunum in EF group was significantly lower than that in PN group at 72 PBHs (P < 0.05). While the ratio in ileum in EF was obviously higher than that in PN groups at 6, 12, 48 and 72 PBHs (P < 0.05). (2) The cell percentage of S phase in EF group was evidently higher than that in PN group (P < 0.05 - 0.01) at 48 and 72 PBHs. (3) Intestinal mucosal cyclin D1 expression increased significantly in EF group at 24 PBHs and in PN group at 48 PBHs (P < 0.05) and which in EF group was obviously higher than that in PN group at 72 PBHs (P < 0.05). (4) The expression of the intestinal mucosal cyclin E in EF group at 72 PBHs was evidently higher than the control value and that in PN group (P < 0.05). (5) The expression of CDK2 exhibited no obvious difference among PN,EF and control group (P < 0.05). The CDK4 expression in EF group increased obviously at 72 PBHs (P < 0.05).

CONCLUSIONEarly postburn enteral feeding was beneficial to the progression of intestinal mucosal epithelial cell cycle and to the repairing and renovation of injured intestinal mucosal membrane. Cyclin and CDK might be important in the modulation of the intestinal mucosal epithelial cell cycle.

Animals ; Burns ; metabolism ; pathology ; CDC2-CDC28 Kinases ; Cell Cycle ; physiology ; Cyclin D1 ; metabolism ; Cyclin-Dependent Kinase 2 ; Cyclin-Dependent Kinase 4 ; Cyclin-Dependent Kinases ; metabolism ; Disease Models, Animal ; Enteral Nutrition ; Female ; G1 Phase ; physiology ; Intestinal Mucosa ; metabolism ; pathology ; Male ; Protein-Serine-Threonine Kinases ; metabolism ; Proto-Oncogene Proteins ; Rats ; Rats, Wistar ; Resting Phase, Cell Cycle ; physiology ; S Phase ; physiology

OBJECTIVETo investigate whether the connection of p27(Kip1) to S-phase kinase-associated protein 2 (Skp2) plays an oncogenic role in intraductal proliferative lesions of the breast.

METHODSHere we investigated the mechanism involved in association of Skp2’s degradation of p27(Kip1) with the breast carcinogenesis by immunohistochemical method through detection of Skp2 and p27(Kip1) protein levels in 120 paraffin-embedded tissues of intraductal proliferative lesions including usual ductal hyperplasia (UDH, n=30), atypical ductal hyperplasia (n=30), flat epithelial atypia (FEA, n=30), and ductal carcinoma in situ (DCIS, n=30). Moreover, the expression status of Skp2 and p27(Kip1) in 30 cases of the normal breast paraffin-embedded tissues were explored.

RESULTSThe DCIS group was with the highest Skp2 level and the lowest p27(Kip1) level, and the UDH group was with the lowest Skp2 level and the highest p27(Kip1) level.Both Skp2 and p27(Kip1) levels in the DCIS group were significantly different from those in the UDH group (all P<0.01).The levels of Skp2 and p27(Kip1) in the FEA group were significantly different from both the DCIS and UDH groups (all P<0.05).p27(Kip1) was negatively correlated with Skp2 in both the UDH group (r=-0.629, P=0.026) and DCIS group (r=-0.893, P=0.000).

CONCLUSIONOverexpression of Skp2 might be the mechanism underlying p27(Kip1) over degradation.

Adult ; Aged ; Breast ; pathology ; Breast Neoplasms ; etiology ; Carcinoma, Intraductal, Noninfiltrating ; etiology ; Cell Proliferation ; Cyclin-Dependent Kinase Inhibitor p27 ; physiology ; Female ; Humans ; Hyperplasia ; Middle Aged ; S-Phase Kinase-Associated Proteins ; physiology

OBJECTIVETo study the molecular mechanism of the inhibitory effects of vitamin C on benzo[a]pyrene (B[a]P)-induced changes of cell cycle in human embryo lung fibroblast (HELF) cells.

METHODSThe stable transfectants, HELF transfected with antisense cyclin D1 and antisense CDK4, were established. Cells were cultured and pretreated with vitamin C before stimulation with B[a]P for 24 h. The expression levels of cyclin D1, CDK4, E2F1, and E2F4 were determined by Western blot. Flow cytometric analysis was employed to detect the distributions of cell cycle.

RESULTSB[a]P significantly elevated the expression levels of cyclin D1, E2F1, and E2F4 in HELF cells. Vitamin C decreased the expression levels of cyclin D1, E2F1, and E2F4 in B[a]P-stimulated HELF cells. Dose-dependent relationships were not found between the different concentrations of vitamin C (10, 100, 500, 1000, and 5000 micromol/L) and the expression levels of cyclin D1, E2F1, and E2F4 in HELF cells. The expression levels of cyclin D1, E2F1, and E2F4 in B[a]P-treated transfectants were lower than those in B[a]P-treated HELF cells. The expression levels of cyclin D1 and E2F4 treated with vitamin C and antisense cyclin D1 were decreased compared with those treated with antisense cyclin D1 alone. The effects of vitamin C combined with antisense CDK4 on the expression levels of cyclin D1 and E2F1/E2F4 were similar to those of antisense CDK4 alone. B[a]P progressed HELF cells from G1 to S phase. Both vitamin C and antisense cyclin D1 suppressed the changes of cell cycle progressed by B[a]P. However, antisense CDK4 did not attenuate the above changes. Vitamin C combined with antisense CDK4 markedly suppressed B[a]P-induced changes of cell cycle as compared with antisense CDK4. But the inhibitory effects of vitamin C combined with antisense cyclin D1 on B[a]P-induced changes of cell cycle were similar to those of vitamin C alone or antisense cyclin D1 alone.

CONCLUSIONSB[a]P progressed HELF cells from G1 to S phase via intracellular signaling pathway of cyclin D1/E2F. Vitamin C may modulate this signaling pathway to protect cells from injury caused by B[a]P.

Ascorbic Acid ; pharmacology ; Benzo(a)pyrene ; Blotting, Western ; methods ; Cell Cycle ; drug effects ; physiology ; Cells, Cultured ; Cyclin D1 ; metabolism ; Cyclin-Dependent Kinase 4 ; metabolism ; Dose-Response Relationship, Drug ; E2F1 Transcription Factor ; metabolism ; Fibroblasts ; cytology ; drug effects ; metabolism ; G1 Phase ; drug effects ; physiology ; Humans ; Lung ; cytology ; embryology ; RNA, Antisense ; genetics ; S Phase ; drug effects ; physiology ; Transfection ; methods

OBJECTIVETo study effects of the expression of transforming growth factor (TGF)-beta1 on the growth of Smad4-null pancreatic cancer cells.

METHODSTGF-beta1 eukaryotic expression vector was transfected into pancreatic cancer cell line BxPC3. Effects of the expressison of TGF-beta1 was studied by growth curve analysis and flow cytometry. Cell motility was monitored by wound-healing assay. Western blot was used to estimate the expression level of p21(WAF/CLIP1), a cyclin-dependent kinase inhibitor.

RESULTSTransfection of TGF-beta1 changed the morphology of BxPC3 into spindle shaped cells. The growth rate of BxPC3 began to decrease after the fourth day of TGF-beta1 transfection, compared with the control groups. Flow cytometry showed that the percentages of cells in the S phase were (27.53 +/- 0.02)%, (26.32 +/- 0.01)% and (17.01 +/- 0.03)% in naïve BxPC3, vector-control group and TGF-beta1 transfection group respectively. Lesser cells entered the S phase after TGF-beta1 transfection (P < 0.01), but no difference was seen between the BxPC3 and vector groups (P > 0.05). The expression of p21(WAF/CLIP1) increased upon the expression of TGF-beta1.

CONCLUSIONThe Smad4-independent pathway of TGF-beta1 not only induces epithelial-mesenchymal transition in pancreatic cancer BxPC3, but also inhibits its growth through the up-regulation of p21(WAF/CLIP1).

Cell Line, Tumor ; Cell Movement ; Cell Proliferation ; Cyclin-Dependent Kinase Inhibitor p21 ; metabolism ; Gene Deletion ; Genetic Vectors ; Humans ; Pancreatic Neoplasms ; genetics ; metabolism ; pathology ; S Phase ; Smad4 Protein ; genetics ; Transfection ; Transforming Growth Factor beta1 ; biosynthesis ; genetics ; physiology ; Up-Regulation

S-phase kinase-associated protein 2 (Skp2) belongs to the F-box protein family. It is a component of the SCF E3 ubiquitin ligase complex. Skp2 has been shown to regulate cellular proliferation by targeting several cell cycle-regulated proteins for ubiquitination and degradation, including cyclin-dependent kinase inhibitor p27. Skp2 has also been demonstrated to display an oncogenic function since its overexpression has been observed in many human cancers. This review discusses the recent discoveries on the novel roles of Skp2 in regulating cellular senescence, cancer progression, and metastasis, as well as the therapeutic potential of targeting Skp2 for human cancer treatment.
Animals ; Cell Movement ; Cellular Senescence ; Cyclopentanes ; pharmacology ; Disease Progression ; Drug Delivery Systems ; methods ; Gene Expression Regulation, Neoplastic ; Humans ; Neoplasms ; metabolism ; pathology ; therapy ; Pyrimidines ; pharmacology ; S-Phase Kinase-Associated Proteins ; antagonists & inhibitors ; metabolism ; physiology ; Ubiquitination