OBJECTIVETo study mechanisms of reduction of the malignant activities of human naso-pharyngeal carcinoma cell CNE-2L2 induced by ectopic expression of BCSC-1 gene.

METHODSDNA was stained with propidium iodide and assayed upon a flow cytometer. Chromosomes were stained with Hoechest 33258. Adhesion of CNE-2L2 cells was detected by cell aggregation test. Protein expression on CNE-2L2 cells was examined by Western blot.

RESULTSCell cycle analysis showed that the percentage of CNE-2L2 cells was 55.1%, 43.4%, and 39.4% in G0/G1 phase, 25.2%, 28.7%, and 30.9% in S phase, and 19.7%, 27.9%, and 29.7% in G2/M phase for the cell with ectopic expression of BCSC-1 gene, wild type cell (W cells), and the cell transduced with the mock (M cell). Many mitotic cells were found in W cells and M cells. In contrast, almost no mitotic cell was observed in the cells with ectopic expression of BCSC-1 gene. Ectopic BCSC-1 expression resulted in cell aggregation, enhanced expression of E-cadherin, cx-catenin, and p53.

CONCLUSIONSEctopic BCSC-1 expression causes enhancement of adhesion of CNE-2L2 cells associated with enhanced expression of E-cadherin and alpha-catenin, arrest of cell in G1 phase, which may be associated with enhanced expression of p53. These alteration may play a role in the reduction of malignant activities of the cells with ectopic expression of BCSC-1 gene.

Cell Cycle ; Cell Cycle Proteins ; analysis ; antagonists & inhibitors ; physiology ; Cell Differentiation ; Cell Proliferation ; Humans ; Membrane Proteins ; analysis ; antagonists & inhibitors ; physiology ; Neoplasm Proteins ; analysis ; antagonists & inhibitors ; physiology ; Neoplasms ; enzymology ; therapy ; Protein Tyrosine Phosphatases ; analysis ; antagonists & inhibitors ; physiology

Cell cycle progression is tightly regulated in hematopoietic stem cells. The cycle state decides cells' fates, which includes self-renewal, proliferation and differentiation. Proper cell cycle regulation is a pivotal element for the maintenance of hematopoiesis homeostasis. HTm4 is a newly identified specific cell cycle regulator of the hematopoietic cell. Through interacting with KAP-CDK2 complex, it arrests cells in G(0)/G(1) phase. K562 is a human chronic myelogenous leukemia cell; it could be induced to megakaryoblast by phorbol 12-myristate 13-acetate (PMA). Such differentiation must be associated with cell cycle change. To further clarify HTm4's function in hematopoietic cell cycle regulation, K562 cells were treated with PMA. Cell cycle change was analysed using flow cytometric system. And during the induction process gene expression of HTm4 as well as CycleE and CDK2, which are responsible for G(1) to S transition, were analysed using semi-quantitative RT-PCR. The C-terminal domain of HTm4 protein has been shown to be important for HTm4's binding with KAP-CDK2 complex. To determine its impact on HTm4's function, HTm4 and C-terminal truncated HTm4 (HTm4-ct) were transfected into K562 cells using Tet-Off regulation expression system. Their influence on cell cycle was observed. The results showed that PMA induced both expansion and differentiation of K562 cells as measured by cell number count and NBT staining respectively. During PMA treatment, G(0)/G(1) cell proportion and HTm4 expression displayed coordinated change, which suggested that HTm4 might drive K562 cells out of cell cycle but was not involved in the quiescence maintenance. Additionally, transfection of HTm4 caused G(0)/G(1) arrest in K562 cells, while transfection of HTm4-ct did not. It is therefore suggested that the C-terminal domain is important for the function of HTm4 in cell cycle regulation.
Cell Cycle ; physiology ; Cell Cycle Proteins ; genetics ; physiology ; Cells, Cultured ; Gene Expression Regulation ; Hematopoiesis ; physiology ; Hematopoietic Stem Cells ; cytology ; physiology ; Humans ; K562 Cells ; Membrane Proteins ; genetics ; physiology ; Tetradecanoylphorbol Acetate ; pharmacology ; Transfection

The low dose hyper-radiosensitivity (HRS) in human lung cancer cell line A549 was investigated, the changes of ATM kinase, cell cycle and apoptosis of cells at different doses of radiation were observed, and the possible mechanisms were discussed. A549 cells in logarithmic growth phase were irradiated with (60)Co gamma-rays at doses of 0-2 Gy. Together with flow cytometry for precise cell sorting, cell survival fraction was measured by means of conventional colony-formation assay. The expression of ATM1981Ser-P protein was examined by Western blot 1 h after radiation. Apoptosis was detected by Hoechst 33258 fluorescent staining, and Annexin V-FITC/PI staining flow cytometry 24 h after radiation. Cell cycle distribution was observed by flow cytometry 6, 12 and 24 h after radiation. The results showed that the expression of ATM1981Ser-P protein was observed at 0.2 Gy, followed by an increase at >0.2 Gy, and reached the peak at 0.5 Gy, with little further increase as the dose exceeded 0.5 Gy. Twenty-four h after radiation, partial cells presented the characteristic morphological changes of apoptosis, and the cell apoptosis curve was coincident with the survival curve. As compared with control group, the cell cycle almost had no changes after exposure to 0.1 and 0.2 Gy radiation (P>0.05). After exposure to 0.3, 0.4 and 0.5 Gy radiation, G(2)/M phase arrest occurred 6 and 12 h after radiation (P<0.05), and the ratio of G(2)/M phase cells was decreased 24 h after radiation (P<0.05). It was concluded that A549 cells displayed the phenomenon of HRS/IRR. The mode of cell death was mainly apoptosis. The activity of ATM and cell cycle change may take an important role in HRS/IRR.
Cell Cycle Proteins/genetics ; Cell Cycle Proteins/metabolism ; Cell Cycle Proteins/physiology ; Cell Line, Tumor ; DNA-Binding Proteins/antagonists & inhibitors ; DNA-Binding Proteins/metabolism ; DNA-Binding Proteins/*physiology ; Dose-Response Relationship, Radiation ; Lung Neoplasms/*pathology ; Protein-Serine-Threonine Kinases/*metabolism ; Radiation Dosage ; Radiation Tolerance/*physiology ; Tumor Suppressor Proteins/metabolism

Apoptosis ; Cell Cycle ; Cell Differentiation ; Cell Proliferation ; Humans ; Neoplastic Processes ; Proto-Oncogene Proteins c-jun ; genetics ; metabolism ; physiology

Cell cycle plays a crucial role in cell development. Cell cycle progression is mainly regulated by cyclin dependent kinase (CDK), cyclin and endogenous CDK inhibitor (CKI). Among these, CDK is the main cell cycle regulator, binding to cyclin to form the cyclin-CDK complex, which phosphorylates hundreds of substrates and regulates interphase and mitotic progression. Abnormal activity of various cell cycle proteins can cause uncontrolled proliferation of cancer cells, which leads to cancer development. Therefore, understanding the changes in CDK activity, cyclin-CDK assembly and the role of CDK inhibitors will help to understand the underlying regulatory processes in cell cycle progression, as well as provide a basis for the treatment of cancer and disease and the development of CDK inhibitor-based therapeutic agents. This review focuses on the key events of CDK activation or inactivation, and summarizes the regulatory processes of cyclin-CDK at specific times and locations, as well as the progress of research on relevant CDK inhibitor therapeutics in cancer and disease. The review concludes with a brief description of the current challenges of the cell cycle process, with the aim to provide scientific references and new ideas for further research on cell cycle process.
Cyclin-Dependent Kinases/metabolism* ; Cyclins/metabolism* ; Protein Serine-Threonine Kinases ; Cell Cycle Proteins/metabolism* ; Cell Cycle/physiology* ; Cyclin-Dependent Kinase 2

The ubiquitin-proteasome system (UPS) is a proteasome system widely present in the human body, which is composed of ubiquitin (Ub), ubiquitin activating enzymes (E1), ubiquitin conjugating enzymes (E2), ubiquitin protein ligases (E3), 26S proteasome, and deubiquitinating enzymes (DUBs) and involved in cell cycle regulation, immune response, signal transduction, DNA repair as well as protein degradation. Sperm DNA is vulnerable to interference or damage in the progression of chromosome association and homologous recombination. Recent studies show that UPS participates in DNA repair in spermatogenesis by modulating DNA repair enzymes via ubiquitination, assisting in the identification of DNA damage sites, raising damage repair-related proteins, initiating the DNA repair pathway, maintaining chromosome stability, and ensuring the normal process of spermatogenesis.
Cell Cycle Proteins ; physiology ; DNA Damage ; DNA Repair ; physiology ; Humans ; Male ; Proteasome Endopeptidase Complex ; physiology ; Signal Transduction ; physiology ; Spermatogenesis ; physiology ; Spermatozoa ; Ubiquitin ; physiology ; Ubiquitin-Conjugating Enzymes ; physiology ; Ubiquitin-Protein Ligases ; physiology ; Ubiquitination

Chfr, a mitotic stress checkpoint gene, regulates a prophase delay in cells exposed to agents that disrupt microtubules, such as nocodazole and taxol. Chfr expression was ubiquitious in normal human tissues. It is very high conserved between human and mice. Preliminary sutdies indicated that Chfr expression was cell cycle regulated and it dependent on its ubiqitin ligase activity. The direct target of the Chfr pathway was Polo-like kinase 1 (Plk1). Ubiquitination of Plk1 by Chfr delayed the activation of the Cdc25C phosphatase and the inactivation of the Weel kinase, leading to a delay in Cdc 2 activation. The chfr gene was inactivated owing to lack of expression or by mutation in some human cancer cell lines examined. Normal primary cells and tumour cell lines that express wild-type chfr exhibited delayed entry into metaphase when centrosome separation was inhibited by mitotic stress. In contrast, the tumour cell lines that had lost chfr function entered metaphase without delay. Ecotopic expression of wild-type chfr restored the cell cycle delay and increased the ability of the cells to survive mitotic stress. Thus, chfr defines a checkpoint that delays entry into metaphase in response to mitotic stress. The progress of research on structure of Chfr gene and effects of Chfr protein was reviewed.
Cell Cycle ; genetics ; physiology ; Cell Cycle Proteins ; genetics ; metabolism ; physiology ; Humans ; Metaphase ; genetics ; physiology ; Mitosis ; genetics ; physiology ; Neoplasm Proteins ; genetics ; physiology ; Neoplasms ; genetics ; metabolism ; pathology ; Poly-ADP-Ribose Binding Proteins ; Prophase ; genetics ; physiology ; Protein-Serine-Threonine Kinases ; metabolism ; Protein-Tyrosine Kinases ; metabolism ; Proto-Oncogene Proteins ; metabolism ; Ubiquitin-Protein Ligases

Cell Cycle ; Cyclin-Dependent Kinase Inhibitor p21 ; Cyclins ; analysis ; DNA Damage ; Dactinomycin ; pharmacology ; Humans ; Viral Nonstructural Proteins ; physiology

Apoptosis ; physiology ; Cell Cycle ; physiology ; Humans ; Neoplasms ; etiology ; metabolism ; Tankyrases ; genetics ; physiology ; Telomerase ; metabolism ; physiology ; Telomere ; genetics ; metabolism ; Telomere-Binding Proteins ; genetics ; physiology ; Telomeric Repeat Binding Protein 1 ; genetics ; physiology ; Telomeric Repeat Binding Protein 2 ; genetics ; physiology