PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-18 (18)
 

Clipboard (0)
None

Select a Filter Below

Journals
more »
Year of Publication
Document Types
1.  Novel Application of a Multiscale Entropy Index as a Sensitive Tool for Detecting Subtle Vascular Abnormalities in the Aged and Diabetic 
Although previous studies have shown the successful use of pressure-induced reactive hyperemia as a tool for the assessment of endothelial function, its sensitivity remains questionable. This study aims to investigate the feasibility and sensitivity of a novel multiscale entropy index (MEI) in detecting subtle vascular abnormalities in healthy and diabetic subjects. Basic anthropometric and hemodynamic parameters, serum lipid profiles, and glycosylated hemoglobin levels were recorded. Arterial pulse wave signals were acquired from the wrist with an air pressure sensing system (APSS), followed by MEI and dilatation index (DI) analyses. MEI succeeded in detecting significant differences among the four groups of subjects: healthy young individuals, healthy middle-aged or elderly individuals, well-controlled diabetic individuals, and poorly controlled diabetic individuals. A reduction in multiscale entropy reflected age- and diabetes-related vascular changes and may serve as a more sensitive indicator of subtle vascular abnormalities compared with DI in the setting of diabetes.
doi:10.1155/2013/645702
PMCID: PMC3590579
2.  Defective Antiviral Responses of Induced Pluripotent Stem Cells to Baculoviral Vector Transduction 
Journal of Virology  2012;86(15):8041-8049.
Genetic engineering of induced pluripotent stem cells (iPSCs) is important for their clinical applications, and baculovirus (BV) holds promise as a gene delivery vector. To explore the feasibility of using BV for iPSCs transduction, in this study we first examined how iPSCs responded to BV. We determined that BV transduced iPSCs efficiently, without inducing appreciable negative effects on cell proliferation, apoptosis, pluripotency, and differentiation. BV transduction slightly perturbed the transcription of 12 genes involved in the Toll-like receptor (TLR) signaling pathway, but at the protein level BV elicited no well-known cytokines (e.g., interleukin-6 [IL-6], tumor necrosis factor alpha [TNF-α], and beta interferon [IFN-β]) except for IP-10. Molecular analyses revealed that iPSCs expressed no TLR1, -6, -8, or -9 and expressed merely low levels of TLR2, -3, and -4. In spite of evident expression of such RNA/DNA sensors as RIG-I and AIM2, iPSCs barely expressed MDA5 and DAI (DNA-dependent activator of IFN regulatory factor [IRF]). Importantly, BV transduction of iPSCs stimulated none of the aforementioned sensors or their downstream signaling mediators (IRF3 and NF-κB). These data together confirmed that iPSCs responded poorly to BV due to the impaired sensing and signaling system, thereby justifying the transduction of iPSCs with the baculoviral vector.
doi:10.1128/JVI.00808-12
PMCID: PMC3421682  PMID: 22623765
3.  Ethylene response pathway is essential for ARABIDOPSIS A-FIFTEEN function in floral induction and leaf senescence 
Plant Signaling & Behavior  2012;7(4):457-460.
ARABIDOPSIS A-FIFTEEN (AAF) encodes a plastid protein and was originally identified as a SENESCENCE-ASSOCIATED GENE. Previously, we found that overexpression of AAF (AAF-OX) in Arabidopsis led to accumulated reactive oxygen species and promoted leaf senescence induced by oxidative stress, which was suppressed by a null mutant, ein2-5, in ethylene response pathway. Whether AAF function is involved in ethylene biosynthesis and/or the response pathway remained unknown. Here we show that neither overexpression (AAF-OX) nor a null mutant (aaf-KO) of AAF generates a higher level of ethylene than the wild type and display a typical triple-response phenotype in etiolated seedlings treated with 1-aminocyclopropane-1-carboxylic acid (ACC). Nevertheless, ein2-5 suppresses the phenotypes of early flowering and age-dependent leaf senescence in AAF-OX plants. We reveal that a functional ethylene response is essential for AAF function in leaf senescence and floral induction, but AAF is unlikely a regulatory component integral to the ethylene pathway.
doi:10.4161/psb.19645
PMCID: PMC3419032  PMID: 22499170
Arabidopsis; leaf senescence; oxidative stress; ethylene; EIN2; reactive oxygen species
4.  MK2 Regulates Ras Oncogenesis through Stimulating ROS Production 
Genes & Cancer  2012;3(7-8):521-530.
Ras signals through both mitogenic and stress pathways and studies of Ras regulatory effects of stress pathways hold great promise to control Ras-dependent malignancies. Our previous work showed Ras activation of a stress kinase (MAPK-activated protein kinase 2 [MK2]), and here, we examine regulatory effects of MK2 on Ras oncogenesis. MK2 knockout was shown to increase Ras transformation in mouse embryonic fibroblasts (MEFs) in vitro and to enhance the resultant tumor growth in mice, indicating a tumor suppressor activity. In Ras-dependent and -independent human colon cancer, however, MK2-forced expression increases and MK2 depletion decreases the malignant growth, suggesting its oncogenic activity. The oncogenic activity of MK2 couples with its activation by both stress and mitogenic signals through extracellular signal–regulated kinase and p38α pathways, whereas its tumor-suppressing effect links to its stimulation only by stress downstream of p38α. Of interest, MK2 was shown to decrease intracellular levels of reactive oxygen species (ROS) in MEFs but increase its production in human colon cancer cells, and experiments with antioxidants revealed that ROS is required for Ras oncogenesis in both systems. These results indicate that MK2 can increase or decrease Ras oncogenesis dependent of its ROS regulatory activities.
doi:10.1177/1947601912462718
PMCID: PMC3527985  PMID: 23264852
MK2; Ras; Ros
5.  Synthesis and Biological Evaluation of Phenanthrenes as Cytotoxic Agents with Pharmacophore Modeling and ChemGPS-NP Prediction as Topo II Inhibitors 
PLoS ONE  2012;7(5):e37897.
In a structure-activity relationship (SAR) study, 3-methoxy-1,4-phenanthrenequinones, calanquinone A (6a), denbinobin (6b), 5-OAc-calanquinone A (7a) and 5-OAc-denbinobin (7b), have significantly promising cytotoxicity against various human cancer cell lines (IC50 0.08–1.66 µg/mL). Moreover, we also established a superior pharmacophore model for cytotoxicity (r = 0.931) containing three hydrogen bond acceptors (HBA1, HBA2 and HBA3) and one hydrophobic feature (HYD) against MCF-7 breast cancer cell line. The pharmacophore model indicates that HBA3 is an essential feature for the oxygen atom of 5-OH in 6a–b and for the carbonyl group of 5-OCOCH3 in 7a–b, important for their cytotoxic properties. The SAR for moderately active 5a–b (5-OCH3), and highly active 6a–b and 7a–b, are also elaborated in a spatial aspect model. Further rational design and synthesis of new cytotoxic phenanthrene analogs can be implemented via this model. Additionally, employing a ChemGPS-NP based model for cytotoxicity mode of action (MOA) provides support for a preliminary classification of compounds 6a–b as topoisomerase II inhibitors.
doi:10.1371/journal.pone.0037897
PMCID: PMC3362575  PMID: 22666407
6.  Traffic-Related Air Pollution and DNA Damage: A Longitudinal Study in Taiwanese Traffic Conductors 
PLoS ONE  2012;7(5):e37412.
Background
There is accumulating epidemiologic evidence that exposure to traffic-related air pollutants, including particulate matter (PM) and polyaromatic hydro carbons (PAHs), plays a role in etiology and prognosis of a large scale of illnesses, although the role of specific causal agents and underlying mechanisms for different health outcomes remains unknown.
Objective
Our general objective was to assess the relations between personal exposure to traffic exhausts, in particular ambient PM2.5 and PAHs, and the occurrence of DNA strand breaks by applying personal monitoring of PM and biomarkers of exposure (urinary 1-hydroxypyrene-glucuronide, 1-OHPG) and effect (urinary 8-hydroxydeoxyguanosine, 8-OHdG and DNA strand breaks).
Methods
We recruited 91 traffic conductors and 53 indoor office workers between May 2009 and June 2011 in Taipei City, Taiwan. We used PM2.5 personal samplers to collect breathing-zone particulate PAHs samples. Spot urine and blood samples after work shift of 2 consecutive days were analyzed for 1-OHPG, 8-OHdG and DNA strand breaks, respectively. Statistical methods included linear regression and mixed models.
Results
Urinary 8-OHdG levels and the occurrence of DNA strand breaks in traffic conductors significantly exceeded those in indoor office workers in mixed models. Particulate PAHs levels showed a positive association with urinary 1-OHPG in the regression model (β = 0.056, p = 0.01). Urinary 1-OHPG levels were significantly associated with urinary 8-OHdG levels in the mixed model (β = 0.101, p = 0.023). Our results provide evidence that exposure to fine particulates causes DNA damage. Further, particulate PAHs could be biologically active constituents of PM2.5 with reference to the induction of oxidative DNA damages.
doi:10.1371/journal.pone.0037412
PMCID: PMC3357412  PMID: 22629390
7.  PTPH1 cooperates with vitamin D receptor to stimulate breast cancer growth through their mutual stabilization 
Oncogene  2010;30(14):1706-1715.
Tyrosine phosphorylation is tightly regulated by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs), and plays a critical role in malignant transformation and progression. While PTKs have a well-established role in regulating breast cancer growth, contribution of PTPs remains mostly unknown. Here, we report that the tyrosine phosphatase PTPH1 stimulates breast cancer growth through regulating vitamin D receptor (VDR) expression. PTPH1 was shown to be over-expressed in 49% of primary breast cancer and levels of its protein expression positively correlate with the clinic metastasis, suggesting its oncogenic activity. Indeed, PTPH1 promotes breast cancer growth by a mechanism independent of its phosphatase activity but dependent of its stimulatory effect on the nuclear receptor VDR protein expression and depletion of induced VDR abolishes the PTPH1 oncogenic activity. Additional analyses showed that PTPH1 binds VDR and increases its cytoplasmic accumulation leading to their mutual stabilization and stable expression of a nuclear localization deficient VDR abolishes the growth-inhibitory activity of the receptor independent of 1, 25-dihydroxyvitamin D3 (vitamin D3). These results reveal a new paradigm in which a protein tyrosine phosphatase may stimulate breast cancer growth through increasing cytoplasmic translocation of a nuclear receptor leading to their mutual stabilization.
doi:10.1038/onc.2010.543
PMCID: PMC3072445  PMID: 21119599
PTPH1; VDR; VDR cytoplasmic translocation; mutual stabilization; breast cancer
8.  Role of ARABIDOPSIS A-FIFTEEN in regulating leaf senescence involves response to reactive oxygen species and is dependent on ETHYLENE INSENSITIVE2 
Journal of Experimental Botany  2011;63(1):275-292.
Leaf senescence is a highly regulated developmental process that is coordinated by several factors. Many senescence-associated genes (SAGs) have been identified, but their roles during senescence remain unclear. A sweet potato (Ipomoea batatas) SAG, named SPA15, whose function was unknown, was identified previously. To understand the role of SPA15 in leaf senescence further, the orthologue of SPA15 in Arabidopsis thaliana was identified and characterized, and it was named ARABIDOPSIS A-FIFTEEN (AAF). AAF was expressed in early senescent leaves and in tissues with highly proliferative activities. AAF was localized to the chloroplasts by transient expression in Arabidopsis mesophyll protoplasts. Overexpression of AAF (AAF-OX) in Arabidopsis promoted, but the T-DNA insertion mutant (aaf-KO), delayed age-dependent leaf senescence. Furthermore, stress-induced leaf senescence caused by continuous darkness was enhanced in AAF-OX but suppressed in aaf-KO. Transcriptome analysis of expression profiles revealed up-regulated genes related to pathogen defence, senescence, and oxidative stress in 3-week-old AAF-OX plants. Indeed, elevated levels of reactive oxygen species (ROS) and enhanced sensitivity to oxidative and dark stress were apparent in AAF-OX but reduced in aaf-KO. ETHYLENE INSENSITIVE2 (EIN2) was required for the dark- and ROS-induced senescence phenotypes in AAF-OX and the induction of AAF expression by treatment with the immediate precursor of ethylene, 1-aminocyclopropane-1-carboxylic acid. The results indicate the functional role of AAF is an involvement in redox homeostasis to regulate leaf senescence mediated by age and stress factors during Arabidopsis development.
doi:10.1093/jxb/err278
PMCID: PMC3245469  PMID: 21940719
Arabidopsis thaliana; chloroplast; ethylene; leaf senescence; oxidative stress; reactive oxygen species; senescence-associated gene (SAG)
9.  PTPH1 dephosphorylates and cooperates with p38γ MAPK to increase Ras oncogenesis through PDZ-mediated interaction 
Cancer research  2010;70(7):2901-2910.
Protein phosphatases are believed to coordinate with kinases to execute biological functions and examples of such integrated activities however are still missing. In this report, we have identified PTPH1 (protein tyrosine phosphatase H1) as a specific phosphatase for p38γ MAPK (mitogen-activated protein kinase) and demonstrated their cooperative oncogenic activity through direct binding. p38γ, a Ras effector known to act independent of its phosphorylation, was first shown to require its unique PDZ-binding motif to increase Ras transformation. Yeast two-hybrid screening and in vitro and in vivo analysis further identified PTPH1 as a specific p38γ phosphatase through PDZ-mediated binding. Additional experiments showed that PTPH1 itself plays a role in Ras-dependent malignant growth in vitro and/or in mice by mechanism depending on its p38γ-binding activity. Moreover, Ras increases both p38γ and PTPH1 protein expression and there is a coupling of increased p38γ and PTPH1 protein expression in primary colon cancer tissues. These results reveal a coordinative oncogenic activity of a MAPK with its specific phosphatase and suggest that PDZ-mediated p38γ/PTPH1 complex may be a novel target for Ras-dependent malignancies.
doi:10.1158/0008-5472.CAN-09-3229
PMCID: PMC2848905  PMID: 20332238
10.  4-Bromo-2-[1-(4-eth­oxy­phen­yl)-1-methyl­eth­yl]-1-methyl­benzene 
In title compound, C18H21BrO, the dihedral angle between two rings is 85.72°. No classical hydrogen bonds are found and only van der Waals forces stabilize the crystal packing.
doi:10.1107/S1600536810049445
PMCID: PMC3050309  PMID: 21522710
11.  Baculovirus Transduction of Mesenchymal Stem Cells Triggers the Toll-Like Receptor 3 Pathway ▿ †  
Journal of Virology  2009;83(20):10548-10556.
Human mesenchymal stem cells (hMSCs) can be genetically modified with viral vectors and hold promise as a cell source for regenerative medicine, yet how hMSCs respond to viral vector transduction remains poorly understood, leaving the safety concerns unaddressed. Here, we explored the responses of hMSCs against an emerging DNA viral vector, baculovirus (BV), and discovered that BV transduction perturbed the transcription of 816 genes associated with five signaling pathways. Surprisingly, Toll-like receptor-3 (TLR3), a receptor that generally recognizes double-stranded RNA, was apparently upregulated by BV transduction, as confirmed by microarray, PCR array, flow cytometry, and confocal microscopy. Cytokine array data showed that BV transduction triggered robust secretion of interleukin-6 (IL-6) and IL-8 but not of other inflammatory cytokines and beta interferon (IFN-β). BV transduction activated the signaling molecules (e.g., Toll/interleukin-1 receptor domain-containing adaptor-inducing IFN-β, NF-κB, and IFN regulatory factor 3) downstream of TLR3, while silencing the TLR3 gene with small interfering RNA considerably abolished cytokine expression and promoted cell migration. These data demonstrate, for the first time, that a DNA viral vector can activate the TLR3 pathway in hMSCs and lead to a cytokine expression profile distinct from that in immune cells. These findings underscore the importance of evaluating whether the TLR3 signaling cascade plays roles in the immune response provoked by other DNA vectors (e.g., adenovirus). Nonetheless, BV transduction barely disturbed surface marker expression and induced only transient and mild cytokine responses, thereby easing the safety concerns of using BV for hMSCs engineering.
doi:10.1128/JVI.01250-09
PMCID: PMC2753105  PMID: 19656899
12.  In Utero and Postnatal Exposure to Arsenic Alters Pulmonary Structure and Function 
Toxicology and applied pharmacology  2008;235(1):105-113.
In addition to cancer endpoints, arsenic exposures can also lead to non-cancerous chronic lung disease. Exposures during sensitive developmental time points can contribute to the adult disease. Using a mouse model, in utero and early postnatal exposures to arsenic (100 ppb or less in drinking water) were found to alter airway reactivity to methacholine challenge in 28 day old pups. Removal of mice from arsenic exposure 28 days after birth did not reverse the alterations in sensitivity to methacholine. In addition, adult mice exposed to similar levels of arsenic in drinking water did not show alterations. Therefore, alterations in airway reactivity were irreversible and specific to exposures during lung development. These functional changes correlated with protein and gene expression changes as well as morphological structural changes around the airways. Arsenic increased the whole lung levels of smooth muscle actin in a dose dependent manner. The level of smooth muscle mass around airways was increased with arsenic exposure, especially around airways smaller than 100 μm in diameter. This increase in smooth muscle was associated with alterations in extracellular matrix (collagen, elastin) expression. This model system demonstrates that in utero and postnatal exposure to environmentally relevant levels of arsenic can irreversibly alter pulmonary structure and function in the adults.
doi:10.1016/j.taap.2008.11.012
PMCID: PMC2669654  PMID: 19095001
arsenic; lung development; pulmonary function; airway smooth muscle; extracellular matrix
13.  9-Ethyl-3-(imidazo[1,2-a]pyrimidin-3-yl)-9H-carbazole 
The title compound, C20H16N4, is a precursor for the production of electron-transporting and -emitting materials. The bond lengths and angles in this compound are normal. In the crystal structure, there are no significant hydrogen-bonding inter­actions or π–π stacking inter­actions between mol­ecules.
doi:10.1107/S1600536808038300
PMCID: PMC2959935  PMID: 21581376
14.  Large scale variation in Enterococcus faecalis illustrated by the genome analysis of strain OG1RF 
Genome Biology  2008;9(7):R110.
A comparison of two strains of the hospital pathogen Enterococcus faecalis suggests that mediators of virulence differ between strains and that virulence does not depend on mobile gene elements
Background
Enterococcus faecalis has emerged as a major hospital pathogen. To explore its diversity, we sequenced E. faecalis strain OG1RF, which is commonly used for molecular manipulation and virulence studies.
Results
The 2,739,625 base pair chromosome of OG1RF was found to contain approximately 232 kilobases unique to this strain compared to V583, the only publicly available sequenced strain. Almost no mobile genetic elements were found in OG1RF. The 64 areas of divergence were classified into three categories. First, OG1RF carries 39 unique regions, including 2 CRISPR loci and a new WxL locus. Second, we found nine replacements where a sequence specific to V583 was substituted by a sequence specific to OG1RF. For example, the iol operon of OG1RF replaces a possible prophage and the vanB transposon in V583. Finally, we found 16 regions that were present in V583 but missing from OG1RF, including the proposed pathogenicity island, several probable prophages, and the cpsCDEFGHIJK capsular polysaccharide operon. OG1RF was more rapidly but less frequently lethal than V583 in the mouse peritonitis model and considerably outcompeted V583 in a murine model of urinary tract infections.
Conclusion
E. faecalis OG1RF carries a number of unique loci compared to V583, but the almost complete lack of mobile genetic elements demonstrates that this is not a defining feature of the species. Additionally, OG1RF's effects in experimental models suggest that mediators of virulence may be diverse between different E. faecalis strains and that virulence is not dependent on the presence of mobile genetic elements.
doi:10.1186/gb-2008-9-7-r110
PMCID: PMC2530867  PMID: 18611278
15.  p38γ Mitogen-Activated Protein Kinase Integrates Signaling Crosstalk between Ras and Estrogen Receptor to Increase Breast Cancer Invasion 
Cancer research  2006;66(15):7540-7547.
Ras is believed to stimulate invasion and growth by different effector pathways, and yet, the existence of such effectors under physiologic conditions has not been shown. Estrogen receptor (ER), on the other hand, is both anti-invasive and proliferative in human breast cancer, with mechanisms for these paradoxical actions remaining largely unknown. Our previous work showed an essential role of p38γ mitogen-activated protein kinase in Ras transformation in rat intestinal epithelial cells, and here, we show that p38γ integrates invasive antagonism between Ras and ER to increase human breast cancer invasion without affecting their proliferative activity. Ras positively regulates p38γ expression, and p38γ in turn mediates Ras nonmitogenic signaling to increase invasion. Expression of the Ras/p38γ axis, however, is trans-suppressed by ER that inhibits invasion and stimulates growth also by distinct mechanisms. Analysis of ER and its cytoplasmic localized mutant reveals that ER additionally binds to p38γ protein, leading to its specific down-regulation in the nuclear compartment. A p38γ-antagonistic activity of ER was further shown in a panel of breast cancer cell lines and was shown independent of estrogens by both ER depletion and ER expression. These results revealed that both Ras and ER use distinct pathways to regulate breast cancer growth and invasion, and that p38γ specifically integrates their antagonistic activity to stimulate cell invasion. Selective targeting of p38γ-dependent invasion pathways may be a novel strategy to control breast cancer progression.
doi:10.1158/0008-5472.CAN-05-4639
PMCID: PMC2174269  PMID: 16885352
16.  Essential role of p38γ in K-Ras transformation independent of phosphorylation 
The Journal of biological chemistry  2005;280(25):23910-23917.
Summary
MAPK cascades play the critical role in regulating Ras oncogene activity by phosphorylation-dependent mechanisms. Whereas the ERK MAPK pathway is required for Ras transformation, our previous works established that the p38 activity is inhibitory to Ras signaling in both experimental and ras-mutated cancer cells [Chen, G., Hitomi, M., Han, J., and Stacey, D. W. (2000) J. Biol. Chem. 275, 38973–38980; Qi, X., Tang, J., Pramanik, R., Schultz, R. M., Shirasawa, S., Sasazuki, T., Han, J., and Chen, G. (2004) J. Biol. Chem., 279, 22138–22144]. Here we report that K-Ras activates p38γ, a p38 MAPK family member, by inducing its expression without increasing its phosphorylation and depletion of induced p38γ suppresses Ras transformation in rat intestinal epithelial cells. This p38γ activity contrasts with that of its family member p38α, which is activated by Ras through phosphorylation, leading to an inhibition of Ras transformation. Mechanistic analyses show that unphosphorylated p38γ may promote Ras transformation through an increased complex formation with ERK proteins. Significantly, functional p38γ protein is expressed only in K-ras mutated human colon cancer cells, and p38γ transcripts are ubiquitously increased in a set of primary human colon cancer tissues. These studies thus demonstrate the essential role of p38γ in K-Ras transformation independent of phosphorylation and elevated p38γ may serve as a novel diagnostic marker and therapeutic target for human colon cancer.
doi:10.1074/jbc.M500699200
PMCID: PMC1224721  PMID: 15851477
17.  Deep lingual arterial chemoembolization of tongue carcinoma with microcapsuled anticancer drug 
Objective: Microcapsule chemoembolism is a promising treatment of tumors. We describe a deep lingual arterial embolization of tongue carcinoma with microcapsuled carboplatinum. Methods: Lingual artery cast specimens from cadavers were microscopically examined, and 78 patients with tongue cancer were recruited and treated with the deep lingual arterial embolization therapy. Results: Microcapsule embolism occurred approximately at the fifth or sixth level of the deep lingual artery branches. The five-year survival rate was 88.5% (69 out of 78), and the ten-year survival rate 52.6% (41 out of 78). Conclusion: The deep lingual arterial embolization of tongue carcinoma with microcapsuled carboplatinum is an effective therapy to treat carcinoma in mid-margin or mid-body of the tongue.
doi:10.1631/jzus.2007.B0704
PMCID: PMC1997222  PMID: 17910111
Tongue carcinoma; Artery cast; Arterial chemoembolization; Deep lingual arterial embolization; Anticancer drug; Carboplatinum
18.  Influence of Cell Cycle and Oncogene Activity upon Topoisomerase IIα Expression and Drug Toxicity 
Molecular and Cellular Biology  2000;20(24):9127-9137.
The cell cycle, oncogenic signaling, and topoisomerase (topo) IIα levels all influence sensitivity to anti-topo II drugs. Because the cell cycle and oncogenic signaling influence each other as well as topo IIα levels, it is difficult to assess the importance of any one of these factors independently of the others during drug treatment. Such information, however, is vital to an understanding of the cellular basis of drug toxicity. We, therefore, developed a series of analytical procedures to individually assess the role of each of these factors during treatment with the anti-topo II drug etoposide. All studies were performed with asynchronously proliferating cultures by the use of time-lapse and quantitative fluorescence staining procedures. To our surprise, we found that neither oncogene action nor the cell cycle altered topo IIα protein levels in actively cycling cells. Only a minor population of slowly cycling cells within these cultures responded to constitutively active oncogenes by elevating topo IIα production. Thus, it was possible to study the effects of the cell cycle and oncogene action on drug-treated cells while topo IIα levels remained constant. Toxicity analyses were performed with two consecutive time-lapse observations separated by a brief drug treatment. The cell cycle phase was determined from the first observation, and cell fate was determined from the second. Cells were most sensitive to drug treatment from mid-S phase through G2 phase, with G1 phase cells nearly threefold less sensitive. In addition, the presence of an oncogenic src gene or microinjected Ras protein increased drug toxicity by approximately threefold in actively cycling cells and by at least this level in the small population of slowly cycling cells. We conclude that both cell cycle phase and oncogenic signaling influence drug toxicity independently of alterations in topo IIα levels.
PMCID: PMC102171  PMID: 11094065

Results 1-18 (18)