OBJECTIVETo determine the expression of Skp2 in different prostate cancer (PCa) cell lines and tissues, and explore its influence on the androgen receptor (AR) signaling pathway and development of castration-resistant prostate cancer (CRPC).

METHODSThe expression levels of Skp2 and AR in different PCa cell lines were detected by Western blot. After knockdown of Skp2 in the C4-2 and 22RV1 cells transfected with shRNA, the expressions of AR and P27 were determined and the activity of ARR3-Luc measured by dual-luciferase reporter gene assay following treatment with dihydrotestosterone (DHT). The expressions of AR and Skp2 in human naïve PCa or CRPC specimens were detected by immunohistochemical staining followed by analysis of their differences and correlation.

RESULTSThe Skp2 protein expression level was significantly higher in the C4-2 or 22RV1 cells than in the LNCaP cells. DHT treatment increased the expression of Skp2 in the C4-2 cells, but knock-down of Skp2 significantly up-regulated the expression of the well-known downstream protein P27 and down-regulated that of AR. Consistently, DHT treatment increased the activity of ARR3-Luc, while knockdown of Skp2 remarkably decreased it in the C4-2 and 22RV1 cells (P < 0.05). In addition, significantly higher expressions of Skp2 and AR were observed in the CRPC than in the naïve specimens (P < 0.05), with a positive correlation between the two proteins (r = 0.658 1, P < 0.05).

CONCLUSIONSkp2 can enhance the expression and transcription activity of the AR protein in CRPC cells or tissues and is promising to be a critical molecular therapeutic target.

Androgens ; pharmacology ; Cell Line, Tumor ; Dihydrotestosterone ; pharmacology ; Disease Progression ; Gene Knockdown Techniques ; Humans ; Male ; Neoplasm Proteins ; genetics ; metabolism ; Prostatic Neoplasms, Castration-Resistant ; metabolism ; Receptors, Androgen ; genetics ; metabolism ; S-Phase Kinase-Associated Proteins ; physiology ; Transcriptional Activation ; Up-Regulation

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

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

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

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 construct an eukaryotic expression vector of open reading frame of unknown KH gene (KH-ORF), and investigate its effect on cell proliferation.

METHODSThe pCI-neo-KH-ORF expression vector was constructed by DNA recombinant technique and was introduced into COS-7 cells and K562 cells by lipofectactin-mediated DNA transfection. Expression of KH-ORF mRNA was detected by RT-PCR. The effect of KH-ORF on cell cycle of COS-7 cells and K562 cells was evaluated by flow cytometry (FCM). Effect on cell proliferation of COS-7 cells was tested by MTT assay and that on K562 cells was analyzed by growth curves and LDH activity measurement.

RESULTS(1) KH-ORF mRNA was expressed both in COS-7 cells and K562 cells. (2) The cell cycle and cell proliferation of COS-7 cells were unaffected significantly. (3) The proportion of cells in S phase was increased in pCI-neo-KH-ORF-transfected K562 cells; and growth curves and LDH activity indicated enhanced cell proliferation.

CONCLUSIONKH gene may be a leukemia gene related to proliferation of K562 cells.

Animals ; COS Cells ; Cell Proliferation ; Cercopithecus aethiops ; Gene Expression Regulation, Neoplastic ; Genes, Neoplasm ; genetics ; physiology ; Genetic Vectors ; Humans ; K562 Cells ; L-Lactate Dehydrogenase ; metabolism ; Open Reading Frames ; genetics ; physiology ; Plasmids ; RNA, Messenger ; biosynthesis ; genetics ; RNA-Binding Proteins ; genetics ; S Phase ; Transfection

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

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

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

The aim of this study was to investigate whether and how phosphodiesterase (PDE) inhibitors modulate the proliferation, cell cycle and apoptosis in lymphoma cells. The effects of aminophylline (AM), a non-specific PDE inhibitor, on Raji cells were explored in vitro. MTT assay, light and transmission electron microscopy and annexin V staining were used to observe cell proliferation, morphologic changes and apoptosis rate in AM-treated cells, and FCM and RT-PCR techniques were adopted to detect the effect on cell cycle, the expression of cyclin B1 and Bcl-2 and mitochondrial transmembrane potential in AM-treated cells. The results showed that AM inhibited the growth of Raji cells in a concentration-dependent manner. Morphologic observations showed apoptosis changes in AM-treated cells, including cytoplamic shrinkage, cytoplasmic bubbling, karyopyknosis and nuclear fragmentation. FCM and RT-PCR detection showed that AM intervention increased the fraction of annexin V(+) cells, reduced the value of mitochondrial transmembrane potential, induced S phase arrest, and down-regulated the expression of Bcl-2 at both mRNA and protein level and cyclin B1 protein in a concentration-dependent manner. It is concluded that PDE inhibitor aminophylline may induce Raji cell growth inhibition, S phase arrest, apoptosis via down-regulation of Bcl-2 and reduction of mitochondrial transmembrane potential.
Aminophylline ; pharmacology ; Apoptosis ; drug effects ; Burkitt Lymphoma ; drug therapy ; genetics ; pathology ; Cell Division ; drug effects ; Cyclin B ; genetics ; metabolism ; Cyclin B1 ; Dose-Response Relationship, Drug ; Flow Cytometry ; Gene Expression Regulation, Neoplastic ; drug effects ; Humans ; Intracellular Membranes ; drug effects ; physiology ; Membrane Potentials ; drug effects ; Mitochondria ; drug effects ; physiology ; Phosphodiesterase Inhibitors ; pharmacology ; Proto-Oncogene Proteins c-bcl-2 ; genetics ; metabolism ; RNA, Messenger ; drug effects ; genetics ; metabolism ; S Phase ; Tumor Cells, Cultured ; drug effects ; metabolism ; ultrastructure