Carcinoma of the uterine cervix is one of the most common malignancies among women worldwide. Human papillomaviruses (HPV) have been identified as the major etiological factor in cervical carcinogenesis. However, the time lag between HPV infection and the diagnosis of cancer indicates that multiple steps, as well as multiple factors, may be necessary for the development of cervical cancer. The development and progression of cervical carcinoma have been shown to be dependent on various genetic and epigenetic events, especially alterations in the cell cycle checkpoint machinery. In mammalian cells, control of the cell cycle is regulated by the activity of cyclin-dependent kinases (CDKs) and their essential activating coenzymes, the cyclins. Generally, CDKs, cyclins, and CDK inhibitors function within several pathways, including the p16INK4A-cyclin D1-CDK4/6-pRb-E2F, p21WAF1-p27KIP1-cyclinE-CDK2, and p14ARF-MDM2-p53 pathways. The results from several studies showed aberrant regulation of several cell cycle proteins, such as cyclin D, cyclin E, p16 INK4A, p21WAF1, and p27KIP1, as characteristic features of HPV- infected and HPV E6/E7 oncogene-expressing cervical carcinomas and their precursors. These data suggested further that interactions of viral proteins with host cellular proteins, particularly cell cycle proteins, are involved in the activation or repression of cell cycle progression in cervical carcinogenesis.
Uterine Cervical Neoplasms/*pathology ; Tumor Suppressor Protein p53/physiology ; Tumor Suppressor Protein p14ARF/physiology ; Retinoblastoma Protein/physiology ; Proto-Oncogene Proteins c-mdm2/physiology ; Humans ; Female ; E2F Transcription Factors/physiology ; Cyclin-Dependent Kinase Inhibitor p27/physiology ; Cyclin-Dependent Kinase Inhibitor p21/physiology ; Cyclin-Dependent Kinase Inhibitor p16/physiology ; Cyclin-Dependent Kinase 4/physiology ; Cyclin-Dependent Kinase 2/physiology ; Cyclin E/physiology ; Cyclin D1/physiology ; Cell Cycle/*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 study the role of cycline dependent kinase 4 (CDK4) in the malignant transformation of human fetal lung diploid fibroblast cell (2BS) induced by silica.

METHODSRecombination vectors with antisense pXJ41-CDK4 were constructed, and then were transfected into the malignant transformed cells induced by silica. In situ hybridization and immunohistochemistry were used to analyze the expression of CDK4. Cell growth curve, doubling time, cell cycle distribution and the growth capacities on soft agar were analyzed before and after antisense CDK4 RNA was transferred into malignant transformed cells induced by silica.

RESULTSDuring the malignant transformation of 2BS cells induced by silica, CDK4 gene was overexpressed. Antisense pXJ41-CDK4 transduction suppressed CDK4 gene expression in the antisense pXJ41-CDK4 transfected cells. Antisense CDK4 RNA led to cell cycle arrest, resulting in lengthened G1 phase (the percentages of cells in the G1 phase increased from 45.1% to 58.0%), and eventually attenuated the proliferation of malignant transformed cells induced by silica. At the 8th day, the suppression rates decreased by 77.43%. The doubling time prolonged from 21.0 h to 42.7 h. The growth capacities on soft agar of cells transfected by antisense pXJ41-CDK4 were decreased.

CONCLUSIONCDK4 might play an important role in maintaining the transformed phenotype of the cancer cells.

Cell Transformation, Neoplastic ; drug effects ; Cells, Cultured ; Cyclin-Dependent Kinase 4 ; Cyclin-Dependent Kinases ; genetics ; physiology ; Embryo, Mammalian ; Fibroblasts ; cytology ; drug effects ; Humans ; Lung ; cytology ; Proto-Oncogene Proteins ; genetics ; physiology ; RNA, Antisense ; pharmacology ; RNA, Messenger ; genetics ; Silicon Dioxide ; toxicity

OBJECTIVETo observe the biological changes of primary human nasopharyngeal epithelial cells in the early stage of immortalization.

METHODSThe morphological changes of nasopharyngeal epithelial cells were observed by phase contrast microscopy, and the activity profile of senescence-associated beta-galactosidase (SA-beta-Gal) was detected by SA-beta-Gal staining. The expression of p16(INK4a) protein was tested by immunochemical assay, and the life span in vitro of nasopharyngeal epithelial cells was calculated as population doublings. In addition, the expression of Epstein-Barr (EB) virus latent membrane protein 1 (LMP1) was also detected by immunofluorescence staining.

RESULTSMorphologically, cells treated with EB virus and 12-o-tetradecanoyl-phorbol-13-acetate (TPA) formed multi-layer foci, and their cellular life span in vitro was extended (about 155 days of culture). A low percentage of cells (about 4.8%) expressed SA-beta-Gal activity at late primary culture, and did not always express p16(INK4a) protein in the progression of culture.

CONCLUSIONSNasopharyngeal epithelial cells treated with EB virus in cooperation with TPA can pass through the stage of senescence and enter the early stage of immortalization. Some changes of phenotype occur in these cells. Our results provide data for further studying the mechanism of immortalization and the establishment of a human nasopharyngeal epithelial cell line.

Cell Transformation, Viral ; Cellular Senescence ; Cyclin-Dependent Kinase Inhibitor p16 ; analysis ; Epithelial Cells ; physiology ; virology ; Herpesvirus 4, Human ; physiology ; Humans ; Nasopharynx ; cytology ; virology ; Tetradecanoylphorbol Acetate ; pharmacology

OBJECTIVESTo unravel the molecular mechanism of proliferation inhibition induced by transfection of pemt2-cDNA into rat CBRH-7919 hepatoma cells.

METHODSWe started with the highly expressed PEMT2 clone. Cell culture and Western blotting techniques were used to examine the expression of cyclinD1/CDK4, cyclinE/CDK2, phospho-Rb, caspase-3, c-jun and caveolins.

RESULTSOur results showed that CDK4, CDK2, phospho-Rb and c-jun were down regulated in the pemt2 highly expressed cell clone. The high expression clone of pemt2-transfected cells also showed over expression of caspase-3.

CONCLUSIONThe reductions of proliferation and apoptosis of pemt2 transfected cells could be related to the G1 phase arrest induced by down-regulation of the cell cycle-associated proteins.

Animals ; Apoptosis ; physiology ; Caspase 3 ; biosynthesis ; genetics ; Cyclin-Dependent Kinase 2 ; biosynthesis ; genetics ; Cyclin-Dependent Kinase 4 ; biosynthesis ; genetics ; Cyclin-Dependent Kinases ; biosynthesis ; genetics ; Down-Regulation ; Liver Neoplasms, Experimental ; genetics ; metabolism ; Phosphatidylethanolamine N-Methyltransferase ; genetics ; metabolism ; Rats ; Transfection ; Tumor Cells, Cultured

OBJECTIVETo study the role of cyclinD1 and CDK4 in malignant transformation of human fetal lung diploid fibroblast cell line (2BS) induced by silica.

METHODSRecombination vectors with sense and antisense pXJ41-cyclinD1 and pXJ41-CDK4 were constructed, and then transfected into the malignant transformed cells induced by silica, respectively. At the same time, pXJ41-neo was used as the control.

RESULTSDuring the progress of the malignant transformation of 2BS cells induced by silica, cyclinD1 and CDK4 were overexpressed. Antisense RNA suppressed cyclinD1 and CDK4 gene expression in the antisense pXJ41-cyclinD1 and pXJ41-CDK4 transfected cells. Antisense RNA led to cell cycle arrest, resulting in lengthened G1 phase (the percentages of cells in the G1 phase changed from 45.1% to 52.7% and 58.0% for cyclinD1 and CDK4 transfected cells, respectively), and eventually attenuated the increase of the proliferation of malignant transformed cells induced by silica. Compared with malignant transformed cells induced by silica, cells transfected with antisense pXJ41-cyclinD1 and pXJ41-CDK4 showed obviously reduced growth rates. On the 8th day, the suppression rates were 58.69 and 77.43% (the growth rate of malignant transformed cells induced by silica was 100%), doubling time changed from 21.0 h to 31.4 h and 21.0 h to 42.7 h, respectively, the growth capacities on soft agar of cells transfected by antisense pXJ41-cyclinD1 and pXJ41-CDK4 decreased obviously.

CONCLUSIONCyclinD1 and CDK4 play an important role in maintaining transformed phenotype of the cancer cells.

Carcinogens, Environmental ; toxicity ; Cell Line ; Cell Proliferation ; Cell Transformation, Neoplastic ; chemically induced ; Cyclin D1 ; genetics ; metabolism ; physiology ; Cyclin-Dependent Kinase 4 ; genetics ; metabolism ; physiology ; Humans ; Plasmids ; RNA, Antisense ; metabolism ; RNA, Messenger ; analysis ; metabolism ; Silicon Dioxide ; toxicity

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