The tumor suppressor gene p53 and p16, both of which play an important role in inhibition of tumorigenesis, are homozygously deleted in human myeloid leukemia cell line K562. To explore the inhibition of K562 cell proliferation by wild type p16 and p53 genes, both p16 and p53 genes were co-transfected into K562 cells mediated by liposome. The expression of the two genes was measured by immunocytochemical method, the cell cycle was analysed by flow cytometry, and the number of recovered viable cells was assessed after transfection. After co-transfection, the p53 and p16 positive cells were 23% and 28%, respectively. The results showed that co-transfection of p16 and p53 genes significantly inhibits cell proliferation comparing with transfection either by p16 gene or by p53 gene (P < 0.05). Expression of p16 and p53 proteins increased the cell number in G(1) phase but decreased the cell number in S phase. It is concluded that co-transfection of p16 and p53 genes has a stronger growth-inhibitory effect on K562 cell growth than that of transfection only by p16 gene or by p53 gene, may be a pathway for gene therapy in leukemia.
Cell Division ; Genes, p16 ; physiology ; Genes, p53 ; physiology ; Humans ; K562 Cells ; Plasmids ; Transfection

Animals ; Cricetinae ; DNA Damage ; physiology ; Genes, p53 ; physiology ; Humans ; Mice ; Signal Transduction ; physiology

Alveolar Epithelial Cells ; metabolism ; pathology ; Animals ; Apoptosis ; physiology ; Cell Survival ; physiology ; Cells, Cultured ; Epithelial Cells ; cytology ; physiology ; Genes, bcl-2 ; genetics ; Genes, p53 ; genetics ; Oxidative Stress ; genetics ; Rats

OBJECTIVETo study the effect of extraneous p53 gene with deletion of c-terminal 356 - 393 amino acids on inhibition of malignant phenotype of human lung cancer cell line.

METHODSRecombinant plasmid pEGFP-p53 (del) with codon deletion of c-terminal 37 amino acids from 393 to 356 region and pEGFP-p53 (wild type) were constructed. The human lung cancer cell line 801D served as a receipt cell had p53 deletion and mutation at 248 codon. 801D cells, having been transfected by pEGFP-p53 (wild type), pEGFP-p53 (del) or pEGFP, were selected by G418. Growing transfected cells were cloned respectively by method of dilution. Presence of extraneous gene was detected by PCR, their expression in cells was examined by fluorescence microscopy. Cloning efficiency was in vitro tested to examine the cellular proliferating ability. The xenograft in nude mice was performed and xenograft tumors were weighed one month later. Expression of GFP in tumor and transplanted cellular mass were detected by blot slices.

RESULTSpEGFP-p53 (del)-801D, pEGFP-p53-801D and pEGFP-801D were established. Extraneous p53 gene and expression of GFP were found in pEGFP-p53 (del)-801D and pEGFP-p53-801D. Inhibitory rate of colony was 99.6% for pEGFP-p53 (del)-801D and 81.0% for pEGFP-p53-801D. Inhibition of malignant proliferation of extraneous p53 (del) was higher than that of p53 (wild type) (P < 0.01). Even when inhibition of malignant proliferation extraneous pEGFP-p53 (del) was obvious, 0.2% colonies were formed, extraneous p53 and expression of GFP were observed. Animal test showed that tumor on the nude mice was positive (4/4, 4/4) in the control group (801D and pEGFP-801D), but negative (0/4, 0/4) in the experiment group [pEGFP-p53 (del) 801D and pEGFP-p53 (wild type) 801D]. Expression of GFP in the cells of cellular mass transplanted by pEGFP-p53 (del) 801D or pEGFP-p53 (wild type) 801D was observed.

CONCLUSIONIn vitro inhibitory effect of extraneous p53 gene with deletion of C-terminal 356 - 393 amino acids on malignant growth of lung cancer cell with p53 mutation or deletion at 248 codon is marked. Inhibitory action of p53 on malignant proliferation of cancer cells is heterogeneous.

Animals ; Cell Cycle ; Cell Line, Tumor ; Genes, p53 ; Humans ; Lung Neoplasms ; genetics ; pathology ; Mice ; Mutation ; Phenotype ; Structure-Activity Relationship ; Transfection ; Tumor Suppressor Protein p53 ; chemistry ; physiology

To investigate the change of telomerase activity and human telomerase reverse transcriptase (hTERT) gene expression in HL-60 cells transfected with wild type p53 gene, wild type p53 gene was introduced into HL-60 cells by Lipofectin transfection. Apoptosis was analyzed by TUNEL assay. Telomerase activity and the level of hTERT mRNA were detected by telomeric repeat amplification protocol (TRAP)-ELISA and RT-PCR, respectively. The results showed that the apoptotic rate of HL-60-pN53cG cells was 8.3% and 21.0% respectively after cultured at 32.5 degrees C for 24 h and 72 h. The level of hTERT mRNA was decreased to 68.4% and 55.8% and telomerase activity to 27.3% and 8.9% of control value in HL-60-pN53cG cells at the same points. In conclusions, hTERT mRNA and telomerase activity were down-regulated in HL-60 cells transfected with p53 gene. This may be one of mechanisms of apoptosis induced by wild type p53 gene.
Apoptosis ; DNA-Binding Proteins ; Gene Expression ; Genes, p53 ; physiology ; HL-60 Cells ; Humans ; RNA, Messenger ; analysis ; Telomerase ; genetics ; metabolism

Tissue homeostasis requires a carefully-orchestrated balance between cell proliferation, cellular senescence and cell death. Cells proliferate through a cell cycle that is tightly regulated by cyclin-dependent kinase activities. Cellular senescence is a safeguard program limiting the proliferative competence of cells in living organisms. Apoptosis eliminates unwanted cells by the coordinated activity of gene products that regulate and effect cell death. The intimate link between the cell cycle, cellular senescence, apoptosis regulation, cancer development and tumor responses to cancer treatment has become eminently apparent. Extensive research on tumor suppressor genes, oncogenes, the cell cycle and apoptosis regulatory genes has revealed how the DNA damage-sensing and -signaling pathways, referred to as the DNA-damage response network, are tied to cell proliferation, cell-cycle arrest, cellular senescence and apoptosis. DNA-damage responses are complex, involving "sensor" proteins that sense the damage, and transmit signals to "transducer" proteins, which, in turn, convey the signals to numerous "effector" proteins implicated in specific cellular pathways, including DNA repair mechanisms, cell-cycle checkpoints, cellular senescence and apoptosis. The Bcl-2 family of proteins stands among the most crucial regulators of apoptosis and performs vital functions in deciding whether a cell will live or die after cancer chemotherapy and irradiation. In addition, several studies have now revealed that members of the Bcl-2 family also interface with the cell cycle, DNA repair/recombination and cellular senescence, effects that are generally distinct from their function in apoptosis. In this review, we report progress in understanding the molecular networks that regulate cell-cycle checkpoints, cellular senescence and apoptosis after DNA damage, and discuss the influence of some Bcl-2 family members on cell-cycle checkpoint regulation.
Animals ; Apoptosis ; Cell Cycle ; Cellular Senescence ; DNA Damage ; DNA Methylation ; Genes, bcl-2 ; Humans ; Tumor Suppressor Protein p53 ; physiology

A human embryonic kidney cell line 293 is widely used for adenovirus production and propagation. With this cell line, however, replication-competent virus (RCV) is frequently generated, especially during large-scale production and successive propagation because 293 cells contain not only E1 gene but also non-E1 adenovirus gene. Homologous recombination between non-E1 region of 293 genomic DNA and its homologous region in the recombinant adenoviral vector generate RCV. To overcome this problem, we developed a new packaging cell line, Hela-E1, which contains minimum E1 region and from which non-E1 adenoviral region that is homologous with recombinant adenovirus vector was excluded. No RCV was detected during adenovirus propagation in Hela-E1 compared to in 293. In addition, adenovirus-p53 produced in HeLa-E1 was able to overexpress p53 protein when introduced into an ovarian cancer cell line, SKOV3. These results may have a significant impact on the development of packaging cell lines for replication-deficient adenovirus production.
Adenoviridae/*genetics/physiology ; Adenovirus E1 Proteins/*genetics/metabolism ; Cell Line ; Genes, Viral ; Genes, p53 ; *Genetic Vectors ; *Hela Cells ; Human ; Protein p53/genetics/metabolism ; Recombination, Genetic ; Support, Non-U.S. Gov't ; Tumor Cells, Cultured ; Virus Cultivation ; Virus Replication

OBJECTIVETo examine whether ischemic preconditioning (IPC) can protect neuron against delayed death in CA1 subfield of hippocampus following reperfusion of a lethal ischemia in rats, and explore the role of p53 and bax in this process.

METHODSWe examined the effect of IPC on delayed neuron death, neuron apoptosis, expressions of p53 and bax gene in the CA1 area of hippocampus in the rats using HE staining, flow cytometry, RT-PCR, and immunohistochemistry technique.

RESULTSIPC enhanced the quantity of survival cells in the CA1 region of hippocampus (216 +/- 9 cells/0.72 mm2 vs. 30 +/- 5 cells/0.72 mm2, P < 0.01) , decreased the percentages of apoptotic neurons of hippocampus caused by ischemia/reperfusion (2.06% +/- 0.21% vs. 4.27% +/- 0.08%, P < 0.01 ), and weakened the expressions of p53 and bax gene of hippocampus compared with ischemia/reperfusion without IPC.

CONCLUSIONIPC can protect the neurons in the CA1 region of hippocampus against apoptosis caused by ischemia/reperfusion, and this process may be related to the reduced expressions of p53 and bax.

Animals ; Gene Expression Regulation ; Genes, p53 ; Hippocampus ; injuries ; Ischemic Preconditioning ; methods ; Neurons ; physiology ; Rats ; Reperfusion Injury ; prevention & control ; Tumor Suppressor Protein p53 ; antagonists & inhibitors ; genetics ; bcl-2-Associated X Protein ; antagonists & inhibitors ; genetics

p53 (encoded by TP53) is undoubtedly one of the most extensively studied genes and proteins. It is a highly potent transcription factor which, under normal circumstances, is maintained at low level. Both genotoxic and non-genotoxic stresses can induce p53 stabilized leading to changes in the expression of p53-responsive genes. The biological outcome inducing this pathway can be either growth arrest and apoptosis or senescence to maintain the integrity of the genome or to delete the damaged cells. The biochemical activity of p53 itself and the cellular environment govern the choice between these outcomes in a cell type- and stress-specific manner. So, p53 is a pivotal tumour suppressor and a mainstay of our body's natural anticancer defence. This review could provide some useful information for further study on the mechanisms of tumorigenesis and its progression, and also could contribute to the discovery of antitumor agents.
Animals ; Apoptosis ; Cell Cycle ; Cell Line, Tumor ; Cell Proliferation ; DNA Damage ; DNA Repair ; Genes, p53 ; Humans ; Proto-Oncogene Proteins c-mdm2 ; metabolism ; Signal Transduction ; Tumor Suppressor Protein p53 ; genetics ; physiology

The inactivation of p53 and p105RB by viral proteins or by mutations plays a key role in the oncogenesis of cervical carcinoma. The E6 and E7 proteins of HPV type 16 can bind to p53 and p105RB tumor suppressor gene products, respectively. In the present study, we tested a simple in vivo model that could explain the interactions between HPV E6 oncoprotein and p53 tumor suppressor protein. Our results showed that the life span of normal cervical epithelial cells was increased up to 4.5 times when transfected with expression vector containing E6/E7 ORF of HPV type 16. However, these cells did not divide after second crisis. Therefore, we employed an established human epidermal keratinocytes, RHEK-1. When transfected with an expression vector containing E6 ORF of HPV type 16, RHEK-1 cells showed anchorage independent growth character. When RHEK-E6 cells were transfected with wild type p53 expression vector, the growth rate of the RHEK-E6 cells was diminished. After 48 hours of transfection, many cells showed apoptotic signal but no more apoptotic signal was observed thereafter. These results suggested that the overexpression of the wild type p53 could overcome the dysfunction of the p53 on the cell cycle regulation imposed by E6 protein although not being of physiological condition.
Animal ; Base Sequence ; Cells, Cultured ; Cervix Uteri/*cytology ; Female ; Genes, p53/*physiology ; Human ; Keratinocytes/*cytology ; Mice ; Molecular Sequence Data ; Oncogene Proteins, Viral/genetics/*physiology ; Papillomavirus, Human/*genetics ; Support, Non-U.S. Gov't ; Transfection