scholarly journals Inhibition of c-Jun N-Terminal Kinase 2 Expression Suppresses Growth and Induces Apoptosis of Human Tumor Cells in a p53-Dependent Manner

2000 ◽  
Vol 20 (5) ◽  
pp. 1713-1722 ◽  
Author(s):  
Olga Potapova ◽  
Myriam Gorospe ◽  
Ryan H. Dougherty ◽  
Nicholas M. Dean ◽  
William A. Gaarde ◽  
...  
Keyword(s):  
Cellular Response ◽  
Kinase Inhibitor ◽  
Critical Role ◽  
Human Tumor ◽  
Dependent Manner ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Downstream Effector ◽  
Regulatory Functions ◽  
Hct116 Cells ◽  
Mcf 7

ABSTRACT c-Jun N-terminal kinase (JNK) plays a critical role in coordinating the cellular response to stress and has been implicated in regulating cell growth and transformation. To investigate the growth-regulatory functions of JNK1 and JNK2, we used specific antisense oligonucleotides (AS) to inhibit their expression. A survey of several human tumor cell lines revealed that JNKAS treatment markedly inhibited the growth of cells with mutant p53 status but not that of cells with normal p53 function. To further examine the influence of p53 on cell sensitivity to JNKAS treatment, we compared the responsiveness of RKO, MCF-7, and HCT116 cells with normal p53 function to that of RKO E6, MCF-7 E6, and HCT116 p53−/−, which were rendered p53 deficient by different methods. Inhibition of JNK2 (and to a lesser extent JNK1) expression dramatically reduced the growth of p53-deficient cells but not that of their normal counterparts. JNK2AS-induced growth inhibition was correlated with significant apoptosis. JNK2AS treatment induced the expression of the cyclin-dependent kinase inhibitor p21 Cip1/Waf1 in parental MCF-7, RKO, and HCT116 cells but not in the p53-deficient derivatives. That p21 Cip1/Waf1 expression contributes to the survival of JNK2AS-treated cells was supported by additional experiments demonstrating that p21 Cip1/Waf1 deficiency in HCT116 cells also results in heightened sensitivity to JNKAS treatment. Our results indicate that perturbation of JNK2 expression adversely affects the growth of otherwise nonstressed cells. p53 and its downstream effector p21 Cip1/Waf1 are important in counteracting these detrimental effects and promoting cell survival.

Iron chelation and regulation of the cell cycle: 2 mechanisms of posttranscriptional regulation of the universal cyclin-dependent kinase inhibitor p21CIP1/WAF1 by iron depletion

Blood ◽  
2007 ◽  
Vol 110 (2) ◽  
pp. 752-761 ◽  
Author(s):  
Dong Fu ◽  
Des R. Richardson
Keyword(s):  
Cell Cycle ◽  
Posttranscriptional Regulation ◽  
Antitumor Agents ◽  
Kinase Inhibitor ◽  
Critical Role ◽  
Iron Chelation ◽  
Proteasomal Degradation ◽  
Dependent Manner ◽  
Cyclin Dependent Kinase ◽  
Cyclin Dependent Kinase Inhibitor

Abstract Iron (Fe) plays a critical role in proliferation, and Fe deficiency results in G1/S arrest and apoptosis. However, the precise role of Fe in cell-cycle control remains unclear. We observed that Fe depletion increased the mRNA of the universal cyclin-dependent kinase inhibitor, p21CIP1/WAF1, while its protein level was not elevated. This observation is unique to the G1/S arrest seen after Fe deprivation, as increased p21CIP1/WAF1 mRNA and protein are usually found when arrest is induced by other stimuli. In this study, we examined the posttranscriptional regulation of p21CIP1/WAF1 after Fe depletion and demonstrated that its down-regulation was due to 2 mechanisms: (1) inhibited translocation of p21CIP1/WAF1 mRNA from the nucleus to cytosolic translational machinery; and (2) induction of ubiquitin-independent proteasomal degradation. Iron chelation significantly (P < .01) decreased p21CIP1/WAF1 protein half-life from 61 (± 4 minutes; n = 3) to 28 (± 9 minutes, n = 3). Proteasomal inhibitors rescued the chelator-mediated decrease in p21CIP1/WAF1 protein, while lysosomotropic agents were not effective. In Fe-replete cells, p21CIP1/WAF1 was degraded in an ubiquitin-dependent manner, while after Fe depletion, ubiquitin-independent proteasomal degradation occurred. These results are important for considering the mechanism of Fe depletion–mediated cell-cycle arrest and apoptosis and the efficacy of chelators as antitumor agents.

scholarly journals The binding of NCAM to FGFR1 induces a specific cellular response mediated by receptor trafficking

2009 ◽  
Vol 187 (7) ◽  
pp. 1101-1116 ◽  
Author(s):  
Chiara Francavilla ◽  
Paola Cattaneo ◽  
Vladimir Berezin ◽  
Elisabeth Bock ◽  
Diletta Ami ◽  
...  
Keyword(s):  
Cell Migration ◽  
Cellular Response ◽  
Critical Role ◽  
Biological Significance ◽  
Receptor Activation ◽  
Dependent Manner ◽  
Fgf Receptor ◽  
Neural Cell Adhesion ◽  
Sustained Activation

Neural cell adhesion molecule (NCAM) associates with fibroblast growth factor (FGF) receptor-1 (FGFR1). However, the biological significance of this interaction remains largely elusive. In this study, we show that NCAM induces a specific, FGFR1-mediated cellular response that is remarkably different from that elicited by FGF-2. In contrast to FGF-induced degradation of endocytic FGFR1, NCAM promotes the stabilization of the receptor, which is recycled to the cell surface in a Rab11- and Src-dependent manner. In turn, FGFR1 recycling is required for NCAM-induced sustained activation of various effectors. Furthermore, NCAM, but not FGF-2, promotes cell migration, and this response depends on FGFR1 recycling and sustained Src activation. Our results implicate NCAM as a nonconventional ligand for FGFR1 that exerts a peculiar control on the intracellular trafficking of the receptor, resulting in a specific cellular response. Besides introducing a further level of complexity in the regulation of FGFR1 function, our findings highlight the link of FGFR recycling with sustained signaling and cell migration and the critical role of these events in dictating the cellular response evoked by receptor activation.

scholarly journals Comparison of the effect of rhodium citrate-associated iron oxide nanoparticles on metastatic and non-metastatic breast cancer cells

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Natalia Lemos Chaves ◽  
Danilo Aquino Amorim ◽  
Cláudio Afonso Pinho Lopes ◽  
Irina Estrela-Lopis ◽  
Julia Böttner ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Cell Lines ◽  
Breast Cancer Cells ◽  
Human Tumor ◽  
Metastatic Breast ◽  
Cytotoxic Action ◽  
Dependent Manner ◽  
Metastatic Cells ◽  
Mcf 7

Abstract Background Nanocarriers have the potential to improve the therapeutic index of currently available drugs by increasing drug efficacy, lowering drug toxicity and achieving steady-state therapeutic levels of drugs over an extended period. The association of maghemite nanoparticles (NPs) with rhodium citrate (forming the complex hereafter referred to as MRC) has the potential to increase the specificity of the cytotoxic action of the latter compound, since this nanocomposite can be guided or transported to a target by the use of an external magnetic field. However, the behavior of these nanoparticles for an extended time of exposure to breast cancer cells has not yet been explored, and nor has MRC cytotoxicity comparison in different cell lines been performed until now. In this work, the effects of MRC NPs on these cells were analyzed for up to 72 h of exposure, and we focused on comparing NPs’ therapeutic effectiveness in different cell lines to elect the most responsive model, while elucidating the underlying action mechanism. Results MRC complexes exhibited broad cytotoxicity on human tumor cells, mainly in the first 24 h. However, while MRC induced cytotoxicity in MDA-MB-231 in a time-dependent manner, progressively decreasing the required dose for significant reduction in cell viability at 48 and 72 h, MCF-7 appears to recover its viability after 48 h of exposure. The recovery of MCF-7 is possibly explained by a resistance mechanism mediated by PGP (P-glycoprotein) proteins, which increase in these cells after MRC treatment. Remaining viable tumor metastatic cells had the migration capacity reduced after treatment with MRC (24 h). Moreover, MRC treatment induced S phase arrest of the cell cycle. Conclusion MRC act at the nucleus, inhibiting DNA synthesis and proliferation and inducing cell death. These effects were verified in both tumor lines, but MDA-MB-231 cells seem to be more responsive to the effects of NPs. In addition, NPs may also disrupt the metastatic activity of remaining cells, by reducing their migratory capacity. Our results suggest that MRC nanoparticles are a promising nanomaterial that can provide a convenient route for tumor targeting and treatment, mainly in metastatic cells.

Rho activation in excitatory agonist-stimulated vascular smooth muscle

2001 ◽  
Vol 281 (2) ◽  
pp. C571-C578 ◽  
Author(s):  
Sotaro Sakurada ◽  
Hiroyuki Okamoto ◽  
Noriko Takuwa ◽  
Naotoshi Sugimoto ◽  
Yoh Takuwa
Keyword(s):  
Smooth Muscle ◽  
Kinase Inhibitor ◽  
Contractile Response ◽  
Rho Kinase ◽  
Small Gtpase ◽  
Dependent Manner ◽  
Aortic Smooth Muscle ◽  
Rhoa Activation ◽  
Downstream Effector ◽  
First Time

Small GTPase Rho and its downstream effector, Rho kinase, have been implicated in agonist-stimulated Ca2+ sensitization of 20-kDa myosin light chain (MLC20) phosphorylation and contraction in smooth muscle. In the present study we demonstrated for the first time that excitatory receptor agonists induce increases in amounts of an active GTP-bound form of RhoA, GTP-RhoA, in rabbit aortic smooth muscle. Using a pull-down assay with a recombinant RhoA-binding protein, Rhotekin, we found that a thromboxane A2 mimetic, U-46619, which induced a sustained contractile response, induced a sustained rise in the amount of GTP-RhoA in a dose-dependent manner with an EC50 value similar to that for the contractile response. U-46619-induced RhoA activation was thromboxane A2 receptor-mediated and reversible. Other agonists including norepinephrine, serotonin, histamine, and endothelin-1 (ET-1) also stimulated RhoA, albeit to lesser extents than U-46619. In contrast, ANG II and phorbol 12,13-dibutyrate failed to increase GTP-RhoA. The tyrosine kinase inhibitor genistein substantially inhibited RhoA activation by these agonists, except for ET-1. Thus excitatory agonists induce Rho activation in an agonist-specific manner, which is thought to contribute to stimulation of MLC20 phosphorylation Ca2+ sensitivity.

scholarly journals Critical Role of PICT-1, a Tumor Suppressor Candidate, in Phosphatidylinositol 3,4,5-Trisphosphate Signals and Tumorigenic Transformation

2006 ◽  
Vol 17 (11) ◽  
pp. 4888-4895 ◽  
Author(s):  
Fumiaki Okahara ◽  
Kouichi Itoh ◽  
Akira Nakagawara ◽  
Makoto Murakami ◽  
Yasunori Kanaho ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Hela Cells ◽  
Critical Role ◽  
Human Tumor ◽  
Causative Factor ◽  
Dependent Manner ◽  
Human Neuroblastoma ◽  
Pten Protein ◽  
Nih3t3 Cells ◽  
Tumorigenic Transformation

The tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) regulates diverse cellular functions by dephosphorylating the lipid second messenger, phosphatidylinositol 3,4,5-trisphosphate (PIP3). Recent study revealed that PICT-1/GLTSCR2 bound to and stabilized PTEN protein in cells, implicating its roles in PTEN-governed PIP3 signals. In this study, we demonstrate that RNA interference-mediated knockdown of PICT-1 in HeLa cells down-regulated endogenous PTEN and resulted in the activation of PIP3 downstream effectors, such as protein kinase B/Akt. Furthermore, the PICT-1 knockdown promoted HeLa cell proliferation; however the proliferation of PTEN-null cells was not altered by the PICT-1 knockdown, suggesting its dependency on PTEN status. In addition, apoptosis of HeLa cells induced by staurosporine or serum-depletion was alleviated by the PICT-1 knockdown in the similar PTEN-dependent manner. Most strikingly, the PICT-1 knockdown in HeLa and NIH3T3 cells promoted anchorage-independent growth, a hallmark of tumorigenic transformation. Furthermore, PICT-1 was aberrantly expressed in 18 (41%) of 44 human neuroblastoma specimens, and the PICT-1 loss was associated with reduced PTEN protein expression in spite of the existence of PTEN mRNA. Collectively, these results suggest that PICT-1 plays a role in PIP3 signals through controlling PTEN protein stability and the impairment in the PICT-1–PTEN regulatory unit may become a causative factor in human tumor(s).

scholarly journals Differential activation of target cellular promoters by p53 mutants with impaired apoptotic function.

1996 ◽  
Vol 16 (9) ◽  
pp. 4952-4960 ◽  
Author(s):  
R L Ludwig ◽  
S Bates ◽  
K H Vousden
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Dna Sequences ◽  
Transcriptional Activation ◽  
Cellular Response ◽  
Kinase Inhibitor ◽  
Cell Types ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Cycle Arrest ◽  
P53 Tumor Suppressor Protein

The p53 tumor suppressor protein is a sequence-specific transcriptional activator, a function which contributes to cell cycle arrest and apoptosis induced by p53 in appropriate cell types. Analysis of a series of p53 point mutants has revealed the potential for selective loss of the ability to transactivate some, but not all, cellular p53-responsive promoters. p53 175P and p53 181L are tumor-derived p53 point mutants which were previously characterized as transcriptionally active. Both mutants retained the ability to activate expression of the cyclin-dependent kinase inhibitor p2lcip1/waf1, and this activity correlated with the ability to induce a G1 cell cycle arrest. However, an extension of this survey to include other p53 targets showed that p53 175P was defective in the activation of p53-responsive sequences derived from the bax promoter and the insulin-like growth factor-binding protein 3 gene (IGF-BP3) promoter, while p53 181L showed loss of the ability to activate a promoter containing IGF-BP3 box B sequences. Failure to activate transcription was also reflected in the reduced ability of the mutants to bind the p53-responsive DNA sequences present in these promoters. These specific defects in transcriptional activation correlated with the impaired apoptotic function displayed by these mutants, and the results suggest that activation of cell cycle arrest genes by p53 can be separated from activation of genes with a role in mediating the p53 apoptotic response. The cellular response to p53 activation may therefore depend, at least in part, on which group of p53-responsive genes become transcriptionally activated.

Increased eIF4E Expression and Phosphorylation in Late Phase Chronic Myelogenous Leukemia Occurs in a Bcr-Abl-Dependent Manner, and Can Be Targeted by a Novel Mnk Kinase Inhibitor, CGP57380, To Overcome Imatinib-Resistance.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2193-2193
Author(s):  
Min Zhang ◽  
James C. Moore ◽  
Je Ko ◽  
Wuxia Fu ◽  
Sharmila Prabhu ◽  
...  
Keyword(s):  
Feedback Loop ◽  
Molecular Mechanisms ◽  
Kinase Inhibitor ◽  
Critical Role ◽  
Chronic Phase ◽  
Mrna Translation ◽  
Myelogenous Leukemia ◽  
Synergistic Activity ◽  
Dependent Manner ◽  
Imatinib Resistance

Abstract The molecular mechanisms which mediate progression of chronic phase (CP) CML to accelerated and blast phase (BP) disease remain unclear, although one feature that correlates with progression is increased expression of the Bcr-Abl protein itself (Barnes et al., Can. Res. 2005). Increased Bcr-Abl expression is likely to contribute to the more aggressive behavior of BP disease, but the downstream factors that are dysregulated by the increased amounts of Bcr-Abl protein remain to be determined. In these studies we turned our attention to eIF4E since forced expression of eIF4E is transforming, and because increased levels of eIF4E have been found in BP but not CP CML (Topisirovic et al., Mol. Cell. Bio. 2003). eIF4E plays a critical role in cap-dependent translation and allows recruitment of the translation machinery to mRNA. eIF4E is phosphorylated at Ser209, and phosphorylation correlates with exposure to growth factors and increased cap-dependent translation. Using a panel of primary CML cells representing patients at various stages of disease, we confirmed that both Bcr-Abl and eIF4E protein levels were elevated in BP samples compared to those in CP, and furthermore that phosphorylation at Ser209 was dependent on Bcr-Abl kinase activity in BP but not CP samples. We next went on to explore the role of eIF4E phosphorylation in BP CML. Because eIF4E is exclusively phosphorylated at Ser209 by the MAPK signal-integrating kinases (Mnk1/2), we used a small molecule inhibitor of Mnk1/2, CGP57380, to inhibit eIF4E phosphorylation (kind gift of Dr. H. Gram, Novartis). Using MTS assays, we found that CGP57380 exhibited synergistic activity with imatinib mesyalte (IM) against Ba/F3-Bcr-Abl and K562 cells, and that this was associated with increased caspase-3 activation. Consistent with a role for eIF4E phosphorylation in cap-dependent translation, we found that CGP57380 augmented the IM-mediated inhibition of cap-binding complex (eIF4F) formation, as well as loading of mRNA onto polysomes. Interestingly, we also uncovered the existence of a novel negative-feedback loop regulating Mnk kinase. Here, treatment with CGP57380 resulted in increased phosphorylation of Mnk1 as well as its upstream activator, ERK, in a time- and dose-dependent manner. Because activation of the MEK/ERK pathway is essential to Bcr-Abl-mediated transformation, this finding suggested that the full activity of CGP57380 might be obscured by this feedback loop. In support of this, the addition of the MEK inhibitor, U0126, to the IM/CGP57380combination resulted in increased activity against CML cells. The triple combination was also effective against Ba/F3-Bcr-Abl cells harboring the E255K and T315I mutations, but not parental Ba/F3 cells (reduced by 50, 23, and 15% respectively of DMSO-treated controls by MTS assay). Colony forming assays also demonstrated the activity of the IM/CGP57380 combination against CML progenitor cells. In conclusion, our data demonstrate that: eIF4E protein expression and phosphorylation are upregulated in a Bcr-Abl-dependent manner in BP CML; Inhibition of eIF4E phosphorylation by the novel Mnk kinase inhibitor, CGP57380, synergizes with IM in killing CML cells, as well as overcomes certain forms of IM-resistance; The addition of CGP57380 to IM results in inhibition of key steps in cap-dependent mRNA translation, and may provide a mechanistic explanation for the activity of this agent in CML.

scholarly journals A New Story of the Three Magi: Scaffolding Proteins and lncRNA Suppressors of Cancer

Cancers ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 4264
Author(s):  
Larissa Kotelevets ◽  
Eric Chastre
Keyword(s):  
Tumor Suppressor ◽  
Intracellular Signaling ◽  
Cellular Response ◽  
Critical Role ◽  
Effector Proteins ◽  
Tumor Promoter ◽  
Hippo Signaling ◽  
Dependent Manner ◽  
Scaffolding Proteins ◽  
Wide Range

Scaffolding molecules exert a critical role in orchestrating cellular response through the spatiotemporal assembly of effector proteins as signalosomes. By increasing the efficiency and selectivity of intracellular signaling, these molecules can exert (anti/pro)oncogenic activities. As an archetype of scaffolding proteins with tumor suppressor property, the present review focuses on MAGI1, 2, and 3 (membrane-associated guanylate kinase inverted), a subgroup of the MAGUK protein family, that mediate networks involving receptors, junctional complexes, signaling molecules, and the cytoskeleton. MAGI1, 2, and 3 are comprised of 6 PDZ domains, 2 WW domains, and 1 GUK domain. These 9 protein binding modules allow selective interactions with a wide range of effectors, including the PTEN tumor suppressor, the β-catenin and YAP1 proto-oncogenes, and the regulation of the PI3K/AKT, the Wnt, and the Hippo signaling pathways. The frequent downmodulation of MAGIs in various human malignancies makes these scaffolding molecules and their ligands putative therapeutic targets. Interestingly, MAGI1 and MAGI2 genetic loci generate a series of long non-coding RNAs that act as a tumor promoter or suppressor in a tissue-dependent manner, by selectively sponging some miRNAs or by regulating epigenetic processes. Here, we discuss the different paths followed by the three MAGIs to control carcinogenesis.

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