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PubMed2005

Heterologous regulation of chemokine receptor signaling by the lipid phosphatase SHIP in lymphocytes.

The SH2 domain-containing inositol polyphosphate 5-phosphatase (SHIP) is known to play an important role in the negative regulation by FcgammaRIIB of PI3K-dependent signaling cascades activated by the B cell antigen receptor (BCR) as well as several tyrosine-kinase coupled cytokine receptors. However, to date the role of SHIP in the regulation of PI3K-dependent signals elicited by G-protein-coupled receptors (GPCR) such as chemokine receptors has not been investigated. In this study, we report that ligation of the G-protein-coupled chemokine receptor CXCR4 by SDF-1/CXCL12 has no effect on the tyrosine phosphorylation of SHIP in the murine B cell lymphoma A20. However, co-ligation of the B cell antigen receptor and FcgammaRIIB inhibits the PI3K-dependent phosphorylation of PKB and ERK1/2 in response to CXCL12. We have also utilised a constitutively active membrane-localised SHIP mutant expressed in the Jurkat leukaemic T cell line (which do not normally express SHIP), in order to investigate the effect of this mutant on CXCL12 stimulated PI3K-dependent signaling events. Experiments have revealed that CXCL12-mediated PKB phosphorylation, chemotaxis and lipid accumulation are inhibited in the presence of this SHIP mutant. Thus, it appears that heterologous activation of SHIP by non-G-protein-coupled receptor-mediated routes can impinge on PI3K-dependent signaling pathways activated by independently ligated G-protein-coupled chemokine receptors.

Animals↗
PubMed2026

In silico screening of anti-atherosclerotic compounds from Morus alba leaves by machine learning and network pharmacology.

OBJECTIVE: This study integrates machine learning with network pharmacology, molecular docking, and molecular dynamics simulations to screen bioactive compounds from Mulberry leaves and elucidate their potential mechanisms against atherosclerosis (AS). METHODS: A training dataset of anti-AS active compounds was compiled and encoded as Morgan fingerprints. Three machine learning classifiers, specifically Random Forest (RF), Support Vector Machine (SVM), and Extreme Gradient Boosting (XG-Boost), were constructed and evaluated using multiple performance metrics. Potential active components from Mulberry leaves and AS-related targets were retrieved, followed by protein-protein interaction network construction and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Molecular docking was then performed to evaluate binding affinities between core targets and candidate compounds, and the most stable complex was subjected to molecular dynamics simulations using GROMACS (2025). RESULTS: The RF model achieved superior performance (accuracy= 0.8354, F1 = 0.8408, AUC = 0.9119) with 100% external validation accuracy. Thirteen anti-AS candidates were prioritized from mulberry leaves, four of which have been previously documented. Network pharmacology revealed AKT1 and IL6 as core targets, enriched in pathways such as endocrine resistance. Molecular docking and dynamics simulations confirmed strong binding between oxysanguinarine and AKT1, with the complex exhibiting high stability. CONCLUSION: The RF model provides a reliable computational tool for prioritizing anti-AS compounds from Mulberry leaves. The integrated analysis reveals that Mulberry leaves exert anti-atherosclerotic effects through multi-target (e.g., AKT1, IL6) and multi-pathway (e.g., PI3K-Akt) mechanisms, offering a framework for further experimental validation.

Morus↗
PubMed2006

Mutation of the Lyn tyrosine kinase delays the progression of Friend virus induced erythroleukemia without affecting susceptibility.

During the initial phase of Friend virus (FV) induced erythroleukemia, the interaction between the viral envelope glycoprotein gp55, the Erythropoietin receptor (EpoR) and the naturally occurring truncated version of the Mst1r receptor tyrosine kinase, called Sf-Stk, drives the polyclonal expansion of infected progenitors in an erythropoietin independent manner. Sf-Stk provides signals that cooperate with EpoR signals to effect expansion of erythroid progenitors. The latter phase of disease is characterized by a clonal expansion of transformed leukemic cells causing an acute erythroleukemia in mice. Signaling by Sf-Stk and EpoR mediated by gp55 renders erythroid progenitors Epo independent through the activation of the EpoR downstream pathways such as PI3K, MAPK and JAK/STAT. Previous work has shown that Src family kinases also play an important role in erythropoiesis. In particular, mutation of Src and Lyn can affect erythropoiesis. In this report we analyze the role of the Lyn tyrosine kinase in the pathogenesis of Friend virus. We demonstrate that during FV infection of primary erythroblasts, Lyn is not required for expansion of viral targets. Lyn deficient bone marrow and spleen cells are able to form Epo independent FV colonies in vitro. In vivo infection of Lyn deficient animals also results in a massive splenomegaly characteristic of the virus. However, we observe differences in the pathogenesis of Friend erythroleukemia in Lyn-/- mice. Lyn-/- mice infected with the polycythemia inducing strain of FV, FVP, do not develop polycythemia suggesting that Lyn-/- infected erythroblasts have a defect in terminal differentiation. Furthermore, the expansion of transformed cells in the spleen is reduced in Lyn-/- mice. Our data show that Lyn signals are not required for susceptibility to Friend erythroleukemia, but Lyn plays a role in later events, the terminal differentiation of infected cells and the expansion of transformed cells.

Animals↗
PubMed2006

Exercise training improves insulin-induced and insulin-like growth factor-1-induced vasorelaxation in rat aortas.

Improved vasorelaxant response is one of the beneficial effects of exercise training on vascular function. The mechanism for this response is, however, poorly understood. The aim of this study was to investigate the effects of exercise training on insulin-induced and insulin-like growth factor-1 (IGF-1)-induced vasorelaxation. Fourteen 6-week-old male Wistar rats were randomly divided into sedentary control and exercise groups. For 12 weeks, the exercise group ran on a treadmill 60 min/day, 5 days/week. After exercise training, insulin-induced and IGF-1-induced vasorelaxant responses were evaluated by measuring the isometric tension of aortic rings. The vasorelaxant role of phosphatidylinositol 3-kinase (PI3K) and nitric oxide synthase (NOS) was examined by applying inhibitors, such as wortmannin (an inhibitor of PI3K) and N(omega)-nitro-L-arginine methyl ester (L-NAME, a NOS inhibitor). In addition, we examined the vascular response to the NO donor, sodium nitroprusside (SNP). We found that: (1) exercise training significantly enhanced both insulin-induced and IGF-1-induced vasorelaxation in rat aortas; (2) this vasorelaxant effect disappeared after the use of wortmannin or L-NAME; (3) there was no significant difference in SNP-induced vasorelaxation between control and exercise groups. Our findings indicate that exercise training enhances insulin-induced and IGF-1-induced vasorelaxant responses which are mediated through the PI3K-NOS-dependent pathway.

Animals↗
PubMed2005

Differential regulation by protein kinases of activity and cell surface expression of glutamate transporters in neuron-enriched cultures.

This study described the involvement of short-term PKA, PKC or PI3K phosphorylation-mediated processes in the regulation of activity and trafficking of the excitatory amino acid transporters EAAC1, GLAST and GLT-1 endogenously expressed in neuron-enriched cultures. Glutamate uptake was dose-dependently decreased by inhibitors of protein kinase A (PKA), [N-[2-(p-bromocinnamylamino)-ethyl]-5-(isoquinolinesulfonamide)] (H89) or phosphatidylinositol 3-kinase (PI3K) (wortmannin), but not altered after protein kinase C (PKC) inhibition (staurosporine) or activation phorbol-12-myristate-13-acetate (PMA). Biotinylation and immunoblotting results (% of controls) showed that EAAC1 membrane expression was significantly decreased by H89 (71.9+/-4.7%) and wortmannin (63.3+/-20.0%) and increased by PMA (137.7+/-15.5%). H89 and PMA induced a significant decrease of the cell surface fraction of GLAST (54.0+/-34.1% and 73.3+/-14.3%, respectively) whereas wortmannin significantly increased this fraction (119.8+/-9.3%). After treatment with H89, the GLT-1 membrane level showed a two-fold increase (179.4+/-19.7%). Conversely, PMA and wortmannin induced a significant decrease of the cell surface expression of GLT-1 (49.0+/-15.4% and 40.7+/-33.7%, respectively). Confocal microscopy revealed a wortmannin-induced clustering of EAAC1 in the intracellular compartment. These data suggest that trafficking of glutamate transporters can be differentially regulated by PKA-, PKC- and PI3K-dependent signaling pathways and could therefore control total glutamate uptake activity. These processes may represent rapid adaptive responses to changes in the cellular environment, which significantly contribute to regulation of EAA transmission and further prevent possible excitotoxic events.

Amino Acid Transport System X-AG↗
PubMed2006

Characterization of the pro-inflammatory signaling induced by protein acetylation in microglia.

Protein acetylation regulates the extent of inflammatory responses and disturbances in protein acetylation have been proposed to play an important role in inflammatory and neurodegenerative diseases. We have recently observed that histone deacetylase inhibitors, such as trichostatin A (TSA) and SAHA, strongly potentiate the LPS induced inflammatory response in several rat and mouse inflammatory models. Our aim here was to characterise pro-inflammatory signaling mediated via increased protein acetylation and protein phosphorylation in microglial N9 cells. First we observed that TSA induced pro-inflammatory response was independent of the different Toll-like receptors activated, since LPS, flagellin and unmethylated CpG oligonucleotides, equally potentiated IL-6 secretion from N9 microglia. Next we compared the protein acetylation induced potentiation to that induced by okadaic acid, a well-known inducer of pro-inflammatory responses. The time scale of the IL-6 responses showed that the effects of okadaic acid were clearly early-response effects appearing as soon as 6h after exposure, whereas TSA evoked a significant inhibition in IL-6 secretion up to 12h but after that it induced an exponential increase in cytokine and nitric oxide production up to 24h. It seems that okadaic acid induces an early moderate response and TSA a late but exponential potentiation of microglial inflammatory responses. The pro-inflammatory responses of TSA and okadaic acid were both dependent on NF-kappaB signaling but independent on the DNA-binding capacity of nuclear NF-kappaB complexes. Interestingly, we observed that the transactivation of the NF-kappaB-Luc reporter gene was clearly activated during TSA induced pro-inflammatory potentiation. Our studies imply that the potentiation of the inflammatory response by increased acetylation is due to the enhancement of transactivation of NF-kappaB driven inflammatory genes. Our studies on signaling pathways revealed that PI3K inhibitors LY294002 and Wortmannin blocked the TSA induced pro-inflammatory response but surprisingly did not affect the okadaic acid induced response. Furthermore, LY294002 did not inhibit DNA-binding activity of NF-kappaB but still inhibited NF-kappaB-Luc reporter gene transactivation. These results indicate that PI 3-kinase regulates the transactivation efficiency of NF-kappaB-dependent transcription rather than transduction of NF-kappaB signaling.

Acetylation↗
PubMed2006

Melanocortin-3 receptor activates MAP kinase via PI3 kinase.

HEK 293 cells stably expressing human melanocortin-3 receptor (MC3R) were exposed to melanocortin receptor agonist, NDP-MSH (10(-)(10)-10(-)(6) M). ERK1/2 was phosphorylated in a dose-dependent manner with an EC(50) of 3.3+/-1.5 x 10(-)(9) M, similar to the IC(50) of NDP-MSH binding to the MC3R. ERK1/2 phosphorylation was blocked by the melanocortin receptor antagonists SHU9119. NDP-MSH-induced ERK1/2 phosphorylation was sensitive to pertussis toxin and the PI3K inhibitor, wortmannin. Rp-cAMPS, BAPTA-AM and Myr-PKC did not inhibit the NDP-MSH-induced ERK1/2 phosphorylation. NDP-MSH stimulated cellular proliferation in a dose-dependent manner with a similar EC(50) to ERK1/2 phosphorylation, 2.1+/-0.6 x 10(-)(9) M. Cellular proliferation was blocked by AGRP (86-132) and by the MEK inhibitor, PD98059. The NDP-MSH did not inhibit serum deprivation-induced apoptosis. MC3R activation induces ERK1/2 phosphorylation via PI3K and this pathway is involved in cellular proliferation in HEK cells expressing MC3R.

Agouti-Related Protein↗
PubMed2006

The coffee diterpene kahweol inhibits tumor necrosis factor-alpha-induced expression of cell adhesion molecules in human endothelial cells.

Endothelial cells produce adhesion molecules after being stimulated with various inflammatory cytokines. These adhesion molecules play an important role in the development of atherogenesis. Recent studies have highlighted the chemoprotective and anti-inflammatory effects of kahweol, a coffee-specific diterpene. This study examined the effects of kahweol on the cytokine-induced monocyte/human endothelial cell interaction, which is a crucial early event in atherogenesis. Kahweol inhibited the adhesion of TNFalpha-induced monocytes to endothelial cells and suppressed the TNFalpha-induced protein and mRNA expression of the cell adhesion molecules, VCAM-1 and ICAM-1. Furthermore, kahweol inhibited the TNFalpha-induced JAK2-PI3K/Akt-NF-kappaB activation pathway in these cells. Overall, kahweol has anti-inflammatory and anti-atherosclerotic activities, which occurs partly by down-regulating the pathway that affects the expression and interaction of the cell adhesion molecules on endothelial cells.

Cell Adhesion↗
PubMed2006

Targeting of EGFR tyrosine kinase by ZD1839 ("Iressa") in androgen-responsive prostate cancer in vitro.

EGFR, highly expressed in a variety of human malignancies, is correlated with poor tumour differentiation, high tumour growth and metastatic rate. EGF and several other ligands, such as transforming growth factor-alpha, amphiregulin, heparin-binding EGF, and betacellulin, activate Ras/Raf mitogen-activated protein kinases (MAPKs) and phosphatidyl inositol 3'-kinase (PI3K)/Akt signalling pathways. Therefore, EGFR can regulate multiple processes, i.e., gene expression, cellular proliferation, angiogenesis, and inhibition of apoptosis, which contribute to the development of malignancy. In this review, we discuss the inhibition of EGFR by the specific tyrosine kinase inhibitor Iressa (ZD1839) focusing on its effects in prostate cancer.

Androgens↗
PubMed2001

ErbB-4 activation inhibits apoptosis in PC12 cells.

Neuregulins, a large family of polypeptide growth factors, exert various distinctive effects in the nervous system. neuregulins and their receptors are widely expressed in neurons implying important roles in neuronal cell functions. Recently, we have shown that ErbB-4 receptors expressed in PC12 cells mediate neuregulin-induced differentiation. In the present study we demonstrate that in the PC12-ErbB-4 cells, neuregulin rescues cells from apoptosis induced by serum deprivation or tumor necrosis factor (TNF)alpha treatment. The neuregulin-induced survival is comparable to the effect mediated by the neurotrophic factor nerve growth factor (NGF). Both neuregulin and NGF protect cells from apoptosis induced by serum deprivation and TNF alpha treatment. Moreover, neuregulin like NGF induces the survival of neuronal differentiated PC12-ErbB-4 cells. The survival effect of neuregulin is probably mediated by the phosphoinositide 3-kinase (PI3K) and protein kinase B/Akt signaling pathways. Neuregulin induces the activation of PI3K and prolonged activation of protein kinase B/Akt. In addition, inhibition of the PI3K activity prevented the neuregulin-induced survival effect. Taken together, these results indicate that survival induced by neuregulin in PC12-ErbB-4 cells requires PI3K signaling networks.

Animals↗
PubMed2003

High-density lipoprotein increases the abundance of eNOS protein in human vascular endothelial cells by increasing its half-life.

OBJECTIVES: Given the importance of endothelial nitric oxide synthase (eNOS) in regulating endothelium-dependent vasorelaxation, we investigated the effects of high-density lipoprotein in (HDL) on eNOS protein abundance in cultured human vascular endothelial cells. BACKGROUND: Endothelial dysfunction, characterized by decreased nitric oxide production, is one of the early features in the development of atherosclerosis. We have recently shown in vivo that niacin therapy increases plasma HDL concentration and improves endothelium-dependent vasorelaxation in patients with coronary artery disease. METHODS: Human vascular endothelial cells were cultured in the presence or absence of HDL or apolipoprotein (apo)A-I. The eNOS protein abundance was assessed by immunoblotting, and protein half-life was assessed by pulse-chase techniques. The eNOS messenger ribonucleic acid (mRNA) abundance was measured using real-time quantitative polymerase chain reaction. RESULTS: High density lipoprotein, or apoA-I alone, increased eNOS protein abundance by 3.5 +/- 0.7 and 2.7 +/- 0.5-fold, respectively (p < 0.05 for both). However, neither HDL nor apoA-I increased eNOS mRNA abundance. It was shown that HDL increased eNOS protein half-life up to 3.3 +/- 0.2-fold (p = 0.001). Both HDL and apoA-I activated mitogen-activated protein-kinase and phosphatidylinositol 3-kinase (PI3K) Akt-pathways in human arterial endothelial cells, and inhibition of either of these pathways by specific pharmacologic inhibitors abolished the effect of HDL on eNOS. CONCLUSIONS: We demonstrate that HDL activates both extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt, resulting in enhanced eNOS protein stability and subsequent accumulation of eNOS protein. This posttranslational regulation represents a previously unrecognized mechanism for regulating eNOS.

Apolipoprotein A-I↗
PubMed2002

Lysophosphatidic acid as a novel cell survival/apoptotic factor.

Lysophosphatidic acid (LPA) activates its cognate G protein-coupled receptors (GPCRs) LPA(1-3) to exert diverse cellular effects, including cell survival and apoptosis. The potent survival effect of LPA on Schwann cells (SCs) is mediated through the pertussis toxin (PTX)-sensitive G(i/o)/phosphoinositide 3-kinase (PI3K)/Akt signaling pathways and possibly enhanced by the activation of PTX-insensitive Rho-dependent pathways. LPA promotes survival of many other cell types mainly through PTX-sensitive G(i/o) proteins. Paradoxically, LPA also induces apoptosis in certain cells, such as myeloid progenitor cells, hippocampal neurons, and PC12 cells, in which the activation of the Rho-dependent pathways and caspase cascades has been implicated. The effects of LPA on both cell survival and apoptosis underscore important roles for this lipid in normal development and pathological processes.

Animals↗
PubMed2003

Cardiotrophin-1: expression in experimental myocardial infarction and potential role in post-MI wound healing.

Cardiotrophin-1 (CT-1), a member of the IL-6 family of cytokines, has been shown to be elevated in the serum of patients with ischemic heart disease and valvular heart disease, and induces cardiomyocyte hypertrophy in vitro. We investigated expression of CT-1 in post-MI rat heart and the effect of CT-1 on cultured primary adult rat cardiac fibroblasts. Elevated CT-1 expression was observed in the infarct zone at 24 h and continued through 2, 4 and 8 weeks post-MI, compared to sham-operated animals. CT-1 induced rapid phosphorylation of Jak, Jak2, STAT1, STAT3, p42/44 MAPK and Akt in cultured adult cardiac fibroblasts. CT-1 induced cardiac fibroblast protein synthesis and proliferation. Protein and DNA synthesis were dependent on activation of Jak/STAT, MEK1/2, PI3K and Src pathways as evidenced by decreased 3H-leucine and 3H-thymidine incorporation after pretreatment with AG490, PD98059, LY294002 and genistein respectively. Furthermore, CT-1 treatment increased procollagen-1-carboxypropeptide (PICP) synthesis, a marker of mature collagen synthesis. CT-1 induced cell migration of rat cardiac fibroblasts. Our results suggest that CT-1, as expressed in post-MI heart, may play an important role in infarct scar formation and ongoing remodeling of the scar. CT-1 was able to initiate each of the processes considered important in the formation of infarct scar including cardiac fibroblast migration as well as fibroblast proliferation and collagen synthesis. Further work is required to determine factors that induce CT-1 expression and interplay with other mediators of cardiac infarct wound healing in the setting of acute cardiac ischemia and chronic post-MI heart failure.

Animals↗
PubMed2001

Shc signaling in differentiating neural progenitor cells.

Previously we found that the availability of ShcA adapter is maximal in neural stem cells but that it is absent in mature neurons. Here we report that ShcC, unlike ShcA, is not present in neural stem/progenitor cells, but is expressed after cessation of their division and becomes selectively enriched in mature neurons. Analyses of its activity in differentiating neural stem/progenitor cells revealed that ShcC positively affects their viability and neuronal maturation via recruitment of the PI3K-Akt-Bad pathway and persistent activation of the MAPK pathway. We suggest that the switch from ShcA to ShcC modifies the responsiveness of neural stem/progenitor cells to extracellular stimuli, generating proliferation (with ShcA) or survival/differentiation (with ShcC).

Adaptor Proteins, Signal Transducing↗
PubMed2005

Maternal segregation of the Dutch preeclampsia locus at 10q22 with a new member of the winged helix gene family.

Preeclampsia is a pregnancy-associated disease with maternal symptoms but placental origin. Epigenetic inheritance is involved in some populations. By sequence analysis of 17 genes in the 10q22 region with maternal effects, we narrowed the minimal critical region linked with preeclampsia in the Netherlands to 444 kb. All but one gene in this region, which lies within a female-specific recombination hotspot, encode DNA- or RNA-binding proteins. One gene, STOX1 (also called C10orf24), contained five different missense mutations, identical between affected sisters, cosegregating with the preeclamptic phenotype and following matrilineal inheritance. Four STOX1 transcripts are expressed in early placenta, including invasive extravillus trophoblast, generating three different isoforms. All contain a winged helix domain related to the forkhead (FOX) family. The largest STOX1 isoform has exclusive nuclear or cytoplasmic expression, indicating activation and inactivation, respectively, of the PI3K-Akt-FOX pathway. Because all 38 FOX proteins and all 8 STOX1 homologs have either tyrosine or phenylalanine at position 153, the predominant Y153H variation is highly mutagenic by conservation criteria but subject to incomplete penetrance. STOX1 is a candidate for preeclampsia controlling polyploidization of extravillus trophoblast.

Chromosomes, Human, Pair 10↗
PubMed2004

The RAB25 small GTPase determines aggressiveness of ovarian and breast cancers.

High-density array comparative genomic hybridization (CGH) showed amplification of chromosome 1q22 centered on the RAB25 small GTPase, which is implicated in apical vesicle trafficking, in approximately half of ovarian and breast cancers. RAB25 mRNA levels were selectively increased in stage III and IV serous epithelial ovarian cancers compared to other genes within the amplified region, implicating RAB25 as a driving event in the development of the amplicon. Increased DNA copy number or RNA level of RAB25 was associated with markedly decreased disease-free survival or overall survival in ovarian and breast cancers, respectively. Forced expression of RAB25 markedly increased anchorage-dependent and anchorage-independent cell proliferation, prevented apoptosis and anoikis, including that induced by chemotherapy, and increased aggressiveness of cancer cells in vivo. The inhibition of apoptosis was associated with a decrease in expression of the proapoptotic molecules, BAK and BAX, and activation of the antiapoptotic phosphatidylinositol 3 kinase (PI3K) and AKT pathway, providing potential mechanisms for the effects of RAB25 on tumor aggressiveness. Overall, these studies implicate RAB25, and thus the RAB family of small G proteins, in aggressiveness of epithelial cancers.

Animals↗
PubMed2005

Interaction between gemcitabine and topotecan in human non-small-cell lung cancer cells: effects on cell survival, cell cycle and pharmacogenetic profile.

The pyrimidine analogue gemcitabine is an established effective agent in the treatment of non-small-cell lung cancer (NSCLC). The present study investigates whether gemcitabine would be synergistic with the topoisomerase I inhibitor topotecan against the NSCLC A549 and Calu-6 cells. Cells were treated with gemcitabine and topotecan for 1 h and the type of drug interaction was assessed using the combination index (CI). Cell cycle alterations were analysed by flow cytometry, while apoptosis was examined by the occurrence of DNA internucleosomal fragmentation, nuclear condensation and caspase-3 activation. Moreover, the possible involvement of the PI3K-Akt signalling pathway was investigated by the measurement of Akt phosphorylation. Finally, quantitative, real-time PCR (QRT-PCR) was used to study modulation of the gemcitabine-activating enzyme deoxycytidine kinase (dCK) and the cellular target enzyme ribonucleotide reductase (RR). In results, it was found that simultaneous and sequential topotecan --> gemcitabine treatments were synergistic, while the reverse sequence was antagonistic in both cell lines. DNA fragmentation, nuclear condensation and enhanced caspase-3 activity demonstrated that the drug combination markedly increased apoptosis in comparison with either single agent, while cell cycle analysis showed that topotecan increased cells in S phase. Furthermore, topotecan treatment significantly decreased the amount of the activated form of Akt, and enhanced the expression of dCK (+155.0 and +115.3% in A549 and Calu-6 cells, respectively), potentially facilitating gemcitabine activity. In conclusion, these results indicate that the combination of gemcitabine and topotecan displays schedule-dependent activity in vitro against NSCLC cells. The gemcitabine --> topotecan sequence is antagonistic while drug synergism is obtained with the simultaneous and the sequential topotecan --> gemcitabine combinations, which are associated with induction of decreased Akt phosphorylation and increased dCK expression.

Antimetabolites, Antineoplastic↗
PubMed2003

PTEN expression in PTEN-null leukaemic T cell lines leads to reduced proliferation via slowed cell cycle progression.

The balance of activities between the proto-oncogene phosphoinositide 3-kinase (PI3K) and the tumour suppressor gene PTEN has been shown to affect cellular growth and proliferation, as well as tumorigenesis. Previously, PTEN expression in the PTEN-null Jurkat T cell leukaemia line was shown to cause reduced proliferation without cell cycle arrest. Here, we further these investigations by determining the basis for this phenomenon. By BrdU pulse-chase and cell cycle arrest and release assays, we find that PTEN expression reduced proliferation by slowing progression through all phases of the cell cycle. This was associated with reduced levels of cyclins A, B1 and B2, cdk4, and cdc25A and increased p27KIP1 expression. Apoptosis played no role in the antiproliferative effect of PTEN, since only marginal increases in the rate of apoptosis were detected upon PTEN expression, and inhibitors of effector caspases did not restore proliferative capacity. Active Akt blocked the antiproliferative effects of PTEN, indicating that PTEN mediates its effects through conventional PI3K-linked signalling pathways. Similar results were obtained from a different PTEN-null leukaemia T cell line, CEM. Together, these results show that PTEN expression in leukaemic T cells leads to reduced proliferation via an apoptosis-independent mechanism involving slower passage through the cell cycle.

Apoptosis↗