Biomedical subjects

G Gao

Publications and source records attributed to G Gao.

At least 37 records · Page 2Linked to original sources

PubMed2001

The effect of magnetic stent on coronary restenosis after percutaneous transluminal coronary angioplasty in dogs.

OBJECTIVE: To investigate the effects of magnetic stents on coronary restenosis after percutaneous transluminal coronary angioplasty (PTCA). METHODS: Twenty dogs were randomly divided into the control and experimental groups, each with 10 dogs. The control group was given common Palmaz-stents in the 6-8 segment of left anterior descending coronary artery or in the 11-14 segment of the left circumflexus. The experimental group was given magnetic stents in the same parts of the coronary arteries. The dogs were not given antiplatelet or anticoagulant drugs before or after the operation. Six months later, the 20 dogs were subjected to coronary angiographies, and then were sacrificed. Three centimeter long segments of the target vessels were cut for pathological examination. RESULTS: The degree of restenosis in 3 dogs of the control group was more than 50%, but none in the experimental group experienced restenosis. The average thickness of the tunica intima of the target artery was 2.98 +/- 0.56 mm in the control and 1.13 +/- 0.41 mm in the experimental group (P < 0.05). CONCLUSION: Magnetic stents could have a significant preventive effect on coronary restenosis.

Angioplasty, Balloon, Coronary↗

PubMed2001

High-throughput identification, database storage and analysis of SNPs in EST sequences.

Single nucleotide polymorphisms (SNPs) are the most frequent form of DNA variation and disease-causing mutations in many genes. Due to their abundance and slow mutation rate within generations, they are thought to be the next generation of genetic markers that can be used in a myriad of important biological, genetic, pharmacological, and medical applications. There are several strategies both experimental, and in-silico for SNP discovery and mapping. Experimental SNP discovery consists of a number of labourious steps that make this process complex and expensive. In-silico discovery has been proposed as an alternative discovery method that makes use and takes advantage of large data sets with potential SNP information that have been generated with other purposes and have not been used as a SNP information source yet. However, in order to successfully apply the in-silico method to large data sets, the following challenges need to be addressed: First it is necessary to build an integrated SNP pipeline that handles data processing steps smoothly from the beginning (collecting sequence information) to end (SNPs in the database). Also, SNP detection tool parameters have to be optimized to satisfy specific goals of the project. Finally, SNP data could not be fully used until the in-silico method is validated experimentally. In this paper we present a design and implementation of an in-silico SNP detection software pipeline that exploits the existence of large EST (expressed sequence tag) data sets and effectively addresses the above challenges. First, the pipeline allows for smooth data transition between its different components by implementing data interfaces that translate the data formats of the different tools in the different stages. Second, we optimized PolyBayes parameters for SNP detection in maize EST. Finally, we implemented a user interface that along with the database structure created allows the scientist to perform preliminary analysis of the data and to perform basic statistics on the SNP data prior to experimental validation. The pipeline works with two different types of sequence assemblers (PHRAP (http://www.phrap.org/) and CAT from DoubleTwist (http://www.doubletwist.com/). It uses a Bayesian engine for SNP detection (PolyBayes), selects relevant polymorphism information which is then uploaded into a database. We detected 2439 SNPs and 822 insertion deletions (INDELs) with a PolyBayes probability higher than 0.99 on the public set of 68,000 maize ESTs. The user interface allowed us analyzing the polymorphism information right after discovery in several ways that allowed us to gain insight into the distribution and significance of the newly acquired data.

Animals↗

PubMed2001

[Stratified 'capture-recaptured' methodology in the estimation on the number of cancer incidence cases].

OBJECTIVE: To develop a new method in estimating the number of cancer incidence in Yuexiu district in Guangzhou. METHODS: Data of cancer incidence was collected through hospital records and death certificates to develop a stratified capture-recaptured model. Related procedures for the parameter estimation were given and implemented on SAS language. RESULTS: Estimated numbers of both male and female cancer incidence in Yuexiu district were 610 and 520 respectively. The estimated miss-reporting rates on both male and female cancer incidence from hospital records and death certificates were 8.5% and 5.4% respectively. CONCLUSION: The result of simulation studies showed that stratified "capture-recaptured" model proposed in this paper was reliable for the estimation of the number of cancer incidence cases.

Female↗

PubMed2001

[A study on polymorphism of salivary esterase in personal identification].

OBJECTIVE: To research the value of polymorphism of salivary esterase(Set) in paternity and personal identification. METHODS: Phenotype and genotype of human salivary esterase were detected in 114 liquid saliva samples from the Chinese population by disc electrophoresis and fast blue RR staining assay. RESULTS: The frequency of Set type was F 22.81%, FS 50.88%, S2 6.31%. The estimated gene frequency of SetF was 0.4825 and SetS was 0.5175. The PE was 0.1875 and the DP was 0.6199. CONCLUSION: Polymorphism of salivary esterase (Set) was practical in paternity and personal identification.

Esterases↗

PubMed2001

[Biochemical remodeling of myocardial collagen and its relation to cardiac renin-angiotensin system in rats after myocardial infarction].

OBJECTIVE: This study aimed at the biochemical remodeling of myocardial collagen and its relation to cardiac renin-angiotensin system (RAS) after myocardial infarction(MI). METHODS: The ventricular and plasma angiotensin II (Ang II) content, total collagen content, and collagen concentration in left ventricle(LV) and right ventricle(RV) of MI and sham-operated control(SOC) rats on 3, 15 and 42 days after operation were measured dynamically by means of radioimmunoassay etc. RESULTS: The plasma Ang II content increased only in MI rats on day 3. The Ang II content in LV of the MI group increased markedly on day 3 after MI as compared with that of the SOC group. It sustained at this higher level on the 15th and 42th days, and the similar changes were observed in RV as well. The biochemical remodeling of collagen in LV and RV occurred after MI and the remodeling of collagen showed similar patterns with its Ang II content, except that collagen remodeling in RV was delayed than the change of Ang II content. CONCLUSION: The cardiac RAS was obviously activated after MI. Ventricular Ang II might play an important role in the biochemical remodeling of myocardial collagen, and its role was independent of circulating RAS.

Angiotensin II↗

PubMed2000

Nitric oxide synthase is induced in tumor promoter-sensitive, but not tumor promoter-resistant, JB6 mouse epidermal cells cocultured with interferon-gamma-stimulated RAW 264.7 cells: the role of tumor necrosis factor-alpha.

Expression of inducible nitric oxide synthase (iNOS) has been reported to be involved in certain organs of potential tumorigenesis, including the stomach and colon. The mechanisms for iNOS expression in epithelial cells, however, are not fully understood. In the present study, we investigated the role of macrophages in epithelial iNOS expression by coculturing a stimulated murine macrophage-like cell line, RAW 264.7, with either tumor promoter-sensitive (P+) or promoter-resistant (P-) JB6 murine epidermal cells. After monoculture, treatment of RAW 264.7 cells with IFN-gamma for 24 h generated a large amount of nitrite (NO2-), as reported previously, whereas no increase in NO2- concentration was observed in the IFN-gamma-treated P+ or P-subclones. Interestingly, when IFN-gamma-treated RAW 264.7 cells were cocultured with P+ but not P- cells, we observed a marked increase in NO2- concentration (30.8+/-3.6 microM), which significantly exceeded (P < 0.01) the sum of the concentrations (20.0+/-2.3 microM) added from each cell line monoculture. Western blotting analysis revealed that, after coculture, iNOS protein was up-regulated 55-fold more than the control in JB6 P+ but not in P- cells. IFN-gamma-treated RAW 264.7 cells secreted proinflammatory cytokines, including tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta. The addition of IFN-gamma-treated RAW 264.7 cell-conditioned media to P+ subclones led to a significant enhancement of NO2- formation that was diminished by the TNF-alpha-specific but not IL-1beta-specific antibody. When combined with IFN-gamma, the recombinant TNF-alpha (1-100 ng/ml) enhanced NO2- formation in JB6 P+ cells, whereas IL-1beta (1-100 ng/ml) did not. These results led us to conclude that IFN-gamma-treated RAW 264.7 cells release TNF-alpha to induce iNOS expression in promoter-sensitive JB6 cells. Thus, we propose the hypothesis that macrophages stimulate neoplastic cells with TNF-alpha via a paracrine loop to induce epithelial iNOS protein expression.

Animals↗

PubMed2000

Mitogen-activated protein kinase inhibitors suppress prostaglandin F(2alpha)-induced myosin-light chain phosphorylation and contraction in iris sphincter smooth muscle.

The purpose of this study was to investigate the potential role of mitogen-activated protein (MAP) kinase in contraction by monitoring MAP kinase phosphorylation (activation) and contraction during agonist stimulation of cat iris sphincter smooth muscle. Changes in tension in response to prostaglandin F(2alpha), latanoprost, a prostaglandin F(2alpha) analog used as an anti-glaucoma drug, and carbachol were recorded isometrically, and MAP kinase activation was monitored by Western blot using a phosphospecific p42/p44 MAP kinase antibody. We found that treatment of the muscle with 2'-Amino-3'-methoxyflavone (PD98059) (10 microM), a specific inhibitor of MAP kinase kinase (MEK), inhibited significantly prostaglandin F(2alpha)- and latanoprost-induced phosphorylation and contraction, but had little effect on those evoked by carbachol. Prostaglandin F(2alpha) increased MAP kinase phosphorylation in a concentration-dependent manner with EC(50) value of 1.1 x 10(-8) M and increased contraction with EC(50) of 0.92 x 10(-9) M. The MAP kinase inhibitors PD98059, Apigenin and 1,4-Diamino-2,3-dicyano-1, 4bis(2-aminophenylthio)butadiene (UO126) inhibited prostaglandin F(2alpha)-induced contraction in a concentration-dependent manner with IC(50) values of 2.4, 3.0 and 4.8 microM, respectively. PD98059 had no effect on prostaglandin F(2alpha)- or on carbachol-stimulated inositol-1,4,5-trisphosphate (IP(3)) production. In contrast, the MAP kinase inhibitor inhibited prostaglandin F(2alpha)-induced myosin-light chain (MLC) phosphorylation, but had no effect on that of carbachol. N-[2-(N-(4-Chloro-cinnamyl)-N-methylaminomethyl)phenyl]-N-[2- hydroxyethyl]-4-methoxybenzenesulfonamide (KN-93) (10 microM), a Ca(2+)-calmodulin-dependent protein kinase inhibitor, and Wortmannin (10 microM), an MLC kinase inhibitor, inhibited significantly (by 80%) prostaglandin F(2alpha)- and carbachol-induced contraction. It can be concluded that in this smooth muscle p42/p44 MAP kinases are involved in the mechanism of prostaglandin F(2alpha)-, but not in that of carbachol, induced contraction. In addition, these data clearly indicate that the stimulation of the iris sphincter with prostaglandin F(2alpha) and carbachol activate two distinct pathways, the MAP kinase pathway and the Ca(2+) mobilization pathway.

Animals↗

PubMed2000

Purification of recombinant adeno-associated virus vectors by column chromatography and its performance in vivo.

Recombinant adeno-associated virus (AAV) holds much promise for human gene therapy. While evidence indicates that AAV mediates long-term gene transfer in several different tissues, difficulty in preparing and purifying this viral vector in large quantities remains a major obstacle for evaluating AAV vectors in clinical trials. The current method of purification, based on sedimentation through cesium chloride, is not scaleable and yields product of insufficient quality. In this article we report a new technique for purifying AAV, using a fully closed two-column chromatography system. Yields of AAV vectors purified by this method are high, potency is increased, and the purity of column-purified preparations is substantially improved. We previously reported a novel method to generate AAV based on an AAV Rep/Cap-containing cell line (B50) and an Ad-AAV hybrid virus, which is amenable to scale-up in bioreactors. By combining the new, fully scaleable purification process we report here with the B50/hybrid production method, it would be feasible to prepare AAV vectors to the scale and purity required for clinical and potential commercial applications.

Animals↗

PubMed2000

N-terminal cleavage of bax by calpain generates a potent proapoptotic 18-kDa fragment that promotes bcl-2-independent cytochrome C release and apoptotic cell death.

Upon apoptosis induction, the proapoptotic protein Bax is translocated from the cytosol to mitochondria, where it promotes release of cytochrome c, a caspase-activating protein. However, the molecular mechanisms by which Bax triggers cytochrome c release are unknown. Here we report that before the initiation of apoptotic execution by etoposide or staurosporin, an active calpain activity cleaves Bax at its N-terminus, generating a potent proapoptotic 18-kDa fragment (Bax/p18). Both the calpain-mediated Bax cleavage activity and the Bax/p18 fragment were found in the mitochondrial membrane-enriched fraction. Cleavage of Bax was followed by release of mitochondrial cytochrome c, activation of caspase-3, cleavage of poly(ADP-ribose) polymerase, and fragmentation of DNA. Unlike the full-length Bax, Bax/p18 did not interact with the antiapoptotic Bcl-2 protein in the mitochondrial fraction of drug-treated cells. Pretreatment with a specific calpain inhibitor calpeptin inhibited etoposide-induced calpain activation, Bax cleavage, cytochrome c release, and caspase-3 activation. In contrast, transfection of a cloned Bax/p18 cDNA into multiple human cancer cell lines targeted Bax/p18 to mitochondria, which was accompanied by release of cytochrome c and induction of caspase-3-mediated apoptosis that was not blocked by overexpression of Bcl-2 protein. Therefore, Bax/p18 has a cytochrome c-releasing activity that promotes cell death independent of Bcl-2. Finally, Bcl-2 overexpression inhibited etoposide-induced calpain activation, Bax cleavage, cytochrome c release, and apoptosis. Our results suggest that the mitochondrial calpain plays an essential role in apoptotic commitment by cleaving Bax and generating the Bax/p18 fragment, which in turn mediates cytochrome c release and initiates the apoptotic execution.

Apoptosis↗

PubMed2000

Tissue inhibitor of metalloproteinases-1 undergoes microsecond to millisecond motions at sites of matrix metalloproteinase-induced fit.

The N-terminal, matrix metalloproteinase (MMP)-inhibitory fragment of recombinant, human tissue inhibitor of metalloproteinases (TIMP-1) exhibits varied backbone dynamics and rigidity. Most striking is the presence of chemical exchange in the MMP-binding ridge reported to undergo conformational change upon MMP binding. Conformational exchange fluctuations in microseconds to milliseconds map to the sites of MMP-induced fit at residues Val29 through Leu34 of the AB loop and to the Ala65 and Cys70 "hinges" of the CD loop of TIMP-1. Slow chemical exchange is also present at the type I turn of the EF loop at the base of the MMP-binding ridge. These functional slow motions and other fast internal motions are evident from backbone (15)N spin relaxation at 500 and 750 MHz, whether interpreted by the model-free formalism with axial diffusion anisotropy or by the reduced spectral density approach. The conformational exchange is confirmed by its deviation from the trend between R(2) and the cross-correlation rate eta. The magnetic field-dependence indicates that the chemical exchange broadening in the AB and CD loops is fast on the time-scale of chemical shift differences. The conformational exchange rates for most of these exchanging residues, which can closely approach MMP, appear to be a few thousand to several thousand per second. The slow dynamics of the TIMP-1 AB loop contrast the picosecond to nanosecond dynamics reported in the longer TIMP-2 AB loop.

Extracellular Matrix↗

PubMed2000

Interleukin-2 expression in human carcinoma cell lines and its role in cell cycle progression.

Human carcinomas were shown to express mRNA and protein for IL-2R alpha, beta and gamma chains. Recently, human carcinomas were also shown to constitutively express protein and mRNA for IL-2 in vivo and in vitro. Here we report that the expression levels of cytoplasmic IL-2 as well as IL-2Rbeta- and gamma-chain in human carcinoma cells change during the cell cycle progression. Carcinoma cells synchronized in the G2/M phase of the cell cycle expressed significantly more intracytoplasmic IL-2 as well as IL-2Rbeta and gamma proteins than tumor cells in the G0/G1 phase. The level of mRNA for IL-2 was 5-10-fold higher in the M phase than in the G0/G1-phase, as shown by quantitative competitive RT-PCR. Expression of the cyclin-dependent kinase (CDK) inhibitor p27kip1 in these carcinoma cells was found to be high in the G0/G1 phase, nearly absent in the S phase, and it increased again in the G2/M phase of the cell cycle. In synchronized cells, the decrease in p27 expression coincided with high levels of expression of IL-2. Using the IL-2 specific antisense oligonucleotide to block synthesis of endogenous IL-2 in tumor cells, we observed increased levels of p27 as well as p21. The antisense oligonucleotides specific for p27 or p21 blocked expression of these proteins but not of IL-2. Thus, endogenous IL-2 is important in regulating expression of p27 as well as p21 and, therefore, in controlling cell cycle progression of tumor cells, while its own expression remains independent of the CDK inhibitors.

Blotting, Western↗

PubMed2000

NMR structure of tissue inhibitor of metalloproteinases-1 implicates localized induced fit in recognition of matrix metalloproteinases.

A high quality solution structure of the matrix metalloproteinase inhibitory N-terminal domain of recombinant human tissue inhibitor of metalloproteinases-1 (N-TIMP-1) has been determined. For the rigidly packed residues, the average RMSD to the mean structure is 0. 57 A for the backbone atoms and 1.00 A for all heavy atoms. Comparison of the solution structure of free N-TIMP-1 with the crystal structure of TIMP-1 bound to the catalytic domain of MMP-3 ( Gomis-R]uth et al., 1997 ) shows that the structural core of the beta barrel flanked by helices is nearly unchanged by the association with MMP-3, evident from a backbone RMSD of 1.15 A. However, clear differences in the conformation of the MMP-binding ridge of free and MMP-bound TIMP-1 suggest induced fit throughout the ridge. The MMP-dependent conformational changes in the ridge include a dramatic bending of AB loop residues Glu28 through Leu34, moderate hinge bending of the CD-loop about residues Ala65 and Cys70, and modest bending of the Cys1 through Pro6 segment. A large number of interresidue Nuclear Overhauser enhancements (NOEs) augmented by stereospecific assignments, torsion restraints, and dipolar couplings (an average of 18 non-trivial restraints per residue) engender confidence in these structural inferences. A tight cluster of three lysine residues and one arginine residue atop beta-strands A and B, and identical among TIMP sequences, form the heart of a highly conserved electropositive patch that may interact with anionic components of the extracellular matrix.

Catalytic Domain↗

PubMed2000

1,1-Dimethylallylcoumarins potently suppress both lipopolysaccharide- and interferon-gamma-induced nitric oxide generation in mouse macrophage RAW 264.7 cells.

We investigated the suppressive effects of 16 coumarin-related compounds on both lipopolysaccharide (LPS)- and interferon (IFN)-gamma-induced nitric oxide (NO) generation in a mouse macrophage cell line, RAW 264.7. Notably, coumarins possessing prenyl unit(s) were found to be highly active, a tendency consistent with our previous study. Among the coumarins tested, 1,1-dimethylallylcoumarins showed the highest inhibitory activity. Western blotting analysis revealed that they inhibited NO generation by suppressing inducible NO synthase (iNOS) protein expression. Our ongoing studies suggest that coumarins are prominent natural compounds that attenuate excessive and prolonged NO generation at inflammatory sites.

Animals↗

PubMed2000

Rescue of skeletal muscles of gamma-sarcoglycan-deficient mice with adeno-associated virus-mediated gene transfer.

In humans, a subset of cases of Limb-girdle muscular dystrophy (LGMD) arise from mutations in the genes encoding one of the sarcoglycan (alpha, beta, gamma, or delta) subunits of the dystrophin-glycoprotein complex. While adeno-associated virus (AAV) is a potential gene therapy vector for these dystrophies, it is unclear if AAV can be used if a diseased muscle is undergoing rapid degeneration and necrosis. The skeletal muscles of mice lacking gamma-sarcoglycan (gsg-/- mice) differ from the animal models that have been evaluated to date in that the severity of the skeletal muscle pathology is much greater and more representative of that of humans with muscular dystrophy. Following direct muscle injection of a recombinant AAV [in which human gamma-sarcoglycan expression is driven by a truncated muscle creatine kinase (MCK) promoter/enhancer], we observed significant numbers of muscle fibers expressing gamma-sarcoglycan and an overall improvement of the histologic pattern of dystrophy. However, these results could be achieved only if injections into the muscle were prior to the development of significant fibrosis in the muscle. The results presented in this report show promise for AAV gene therapy for LGMD, but underscore the need for intervention early in the time course of the disease process.

Age Factors↗

PubMed2000

Adeno-associated virus mediates long-term gene transfer and delivery of chondroprotective IL-4 to murine synovium.

Treatments for rheumatoid arthritis and other inflammatory arthropathies are often ineffective at preventing joint destruction. Long-term genetic modification of the cells lining the joint space (synoviocytes) in vivo represents a potential method for the treatment of these chronic conditions. However, a vector capable of efficiently transducing synoviocytes in vivo for a persistent period has not been available. The present report describes the genetic modification of synoviocytes in vivo using recombinant adeno-associated virus. High-titer adeno-associated virus encoding the gene for Escherichia coli beta-galactosidase was injected into the knee joints of mice. Synovial tissues were then examined for beta-galactosidase transgene expression by in situ staining and by fluorometry. High-efficiency, persistent transgene expression was observed in the synovium with no evidence of vector-induced inflammation. Expression was observed for at least 7 months and was higher in arthritic than nonarthritic mice. Gene transfer of murine IL-4 to the joints of mice with collagen-induced arthritis led to detectable levels of IL-4 in the joint and protection from articular cartilage destruction. These data suggest that adeno-associated virus may be a useful vector for gene delivery to the synovium for the treatment of inflammatory arthropathies.

Animals↗

PubMed2000

Prolonged correction of hyperlipidemia in mice with familial hypercholesterolemia using an adeno-associated viral vector expressing very-low-density lipoprotein receptor.

Adeno-associated viral vectors were used to deliver the gene for very-low-density lipoprotein (VLDL) receptor (VLDLR) to liver of a murine model of familial hypercholesterolemia (FH). Infusion of adeno-associated virus-VLDLR into the portal circulation of FH mice resulted in a 40% reduction in serum cholesterol and triglyceride that was stable for the duration of the study (30 weeks). Fractionation of serum lipids revealed a reduction of both VLDL and low-density lipoprotein. Expression of transgene-derived VLDLR was confirmed in livers of recipient animals by Western blot analysis and immunohistochemistry; vector DNA was present at 1 copy/cell. Vector-treated animals had significantly less lipid accumulation in liver and reduced atherosclerosis in the aorta.

Animals↗

PubMed2000

Randomized comparative trial in parous women of the frameless GyneFix and the TCu380A intrauterine devices: long-term experience in a Chinese family planning clinic.

OBJECTIVE: To compare the clinical performance of two intrauterine devices (the frameless GyneFix intrauterine device (IUD) and the TCu380A IUD) during long-term use. STUDY DESIGN: This was a randomized comparative study. A total of 157 insertions of the GyneFix IUD were compared with 156 insertions of the TCu380A IUD in the Tianjin Municipal Institute for Family Planning, China. Only parous women were included in the study. Insertions were conducted by the first three authors. The trial extended over a 9-year period, with over 10,000 woman-months of experience. RESULTS: The study showed that both devices are highly efficacious. No pregnancies occurred with the GyneFix IUD (cumulative pregnancy rate 0.0), compared to one pregnancy with the TCu380A IUD (cumulative pregnancy rate 0.64). The cumulative expulsion rate with the GyneFix IUD was 1.91 (three expulsions occurred, two of which were during the first 6 months), compared to a cumulative expulsion rate of 5.13 (eight expulsions) with the TCu380A (p = 0.1112). The total use-related discontinuation rate (terminations were mainly due to bleeding disturbances) was significantly lower (p = 0.0051) with the GyneFix IUD (4.46) than with the TCu380A IUD (14.10) and resulted in a higher rate of continuation with the GyneFix IUD compared to the TCu380A IUD (92.36 versus 83.97). Neither perforations nor cases of pelvic inflammatory disease were encountered with either device in this study, demonstrating the safety of the anchoring system. CONCLUSION: The results of the present clinical trial are in agreement with the findings of other multicenter, randomized, comparative, clinical trials that have investigated these two IUDs in China, as well as with the findings of other large-scale international studies conducted with the frameless IUD.

Adult↗

PubMed2000

G(1) phase-dependent expression of bcl-2 mRNA and protein correlates with chemoresistance of human cancer cells.

Recent experiments suggest an interconnection between cell proliferation and programmed cell death (apoptosis), although the detailed molecular mechanisms remain unclear. We have hypothesized that expression of some apoptosis regulators is cell cycle-dependent, which in turn influences tumor cell chemosensitivity in a cell cycle-dependent fashion. To test these hypotheses, we synchronized human leukemia Jurkat T, Neo (using aphidicolin), breast cancer MCF-7, normal fibroblast, and simian virus 40-transformed cells (by aphidicolin or serum starvation), and measured levels of several Bcl-2 family proteins. The highest expression of Bcl-2 protein was found in the G(1) phase of all the five cell lines tested. In contrast, levels of Bax protein remained relatively unchanged in four of the cell lines, and levels of Bcl-X(L), Bcl-X(S), and Bak proteins showed little or no cell cycle-dependent changes in Jurkat T cells. Similar to the changes in Bcl-2 protein levels, its mRNA expression was also G(1) phase-specific, whereas the level of a Bcl-2 cleavage activity remained constitutive. When treated with an anticancer drug (etoposide or cisplatin) or the kinase inhibitor staurosporin, the cells containing a high G(1) population and a high Bcl-2 protein level were much more resistant to the induced apoptosis than the cells containing a high S phase population and a low Bcl-2 protein level. Constitutive overexpression of Bcl-2 protein in Jurkat T cells completely blocked the S phase-associated sensitivity to these apoptosis stimuli. The cell cycle-dependent Bcl-2 protein expression seems to contribute to the regulation of chemosensitivity and apoptotic commitment of human tumor cells.

Apoptosis↗