scholarly journals ARF Differentially Modulates Apoptosis Induced by E2F1 and Myc

2002 ◽  
Vol 22 (5) ◽  
pp. 1360-1368 ◽  
Author(s):  
Jamie L. Russell ◽  
John T. Powers ◽  
Robert J. Rounbehler ◽  
Pamela M. Rogers ◽  
Claudio J. Conti ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
S Phase ◽  
Negative Regulator ◽  
Mouse Embryo Fibroblast ◽  
Apoptotic Pathway ◽  
Downstream Target ◽  
Induced Apoptosis ◽  
Active Can

ABSTRACT The ARF tumor suppressor participates in a p53-dependent apoptotic pathway that is stimulated in response to some oncogenic stimuli. The E2F1 transcription factor is a critical downstream target of the Rb tumor suppressor and, when active, can promote proliferation as well as apoptosis. The finding that E2F1 transcriptionally regulates the ARF gene has led to the suggestion that ARF contributes to E2F1-induced apoptosis. Counter to this hypothesis, this study demonstrates not only that ARF is unnecessary for E2F1 to induce apoptosis but also that inactivation of ARF actually enhances the ability of E2F1 to promote apoptosis. Inactivation of ARF also cooperates with E2F1 activity to promote entry into the S phase of the cell cycle. This relationship between ARF and E2F1 is demonstrated in transgenic epidermis in vivo and in mouse embryo fibroblast cultures in vitro. In contrast, the ability of Myc to induce apoptosis is diminished in the absence of ARF. E2F1 induces the accumulation of p53 in the absence of ARF, and this is associated with the phosphorylation of p53 on several residues. These findings demonstrate that ARF is a negative regulator of E2F1 activity and is not required for E2F1-induced apoptosis.

scholarly journals Apigenin Suppresses Angiogenesis by Inhibiting Tube Formation and Inducing Apoptosis

2016 ◽  
Vol 11 (10) ◽  
pp. 1934578X1601101
Author(s):  
Hyun Ju Kim ◽  
Mok-Ryeon Ahn
Keyword(s):  
Umbilical Vein ◽  
Chorioallantoic Membrane ◽  
Tube Formation ◽  
Anticancer Activities ◽  
Apoptotic Pathway ◽  
Inhibition Of Angiogenesis ◽  
Induced Apoptosis ◽  
Umbilical Vein Endothelial Cells

Apigenin has been reported to exert angiogenic and anticancer activities in vitro. The mechanism of inhibition of angiogenesis by apigenin, however, has not been well-established. In this study, we investigated whether apigenin not only inhibited tube formation but also induced apoptosis in human umbilical vein endothelial cells (HUVECs). Furthermore, strong antiangiogenic activity of apigenin was observed in the in vivo assay using chick embryo chorioallantoic membrane (CAM). We also analyzed changes in survival signals and the apoptotic pathway through Western blotting. The results indicate that apigenin exerts its antiangiogenic effects through induction of endothelial apoptosis.

scholarly journals MDM2-Mediated p21 Proteasomal Degradation Promotes Fluoride Toxicity in Ameloblasts

Cells ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 436 ◽  
Author(s):  
Huidan Deng ◽  
Atsushi Ikeda ◽  
Hengmin Cui ◽  
John D. Bartlett ◽  
Maiko Suzuki
Keyword(s):  
Health Hazard ◽  
Proteasomal Degradation ◽  
Fluoride Toxicity ◽  
Potential Therapeutic Target ◽  
Downstream Target ◽  
Mdm2 Antagonist ◽  
Apoptosis Inhibition ◽  
Induced Apoptosis

Fluoride overexposure is an environmental health hazard and can cause enamel and skeletal fluorosis. Previously we demonstrated that fluoride increased acetylated-p53 and its downstream target p21 in ameloblast-derived LS8 cells. However, p21 function in fluoride toxicity is not well characterized. This study seeks to gain a better understanding of how p53 down-stream mediators, p21 and MDM2, respond to fluoride toxicity. LS8 cells were treated with NaF with/without MG-132 (proteasome inhibitor) or Nutlin-3a (MDM2 antagonist). NaF treatment for 2–6 h increased phospho-p21, which can inhibit apoptosis. However, phospho-p21 and p21 were decreased by NaF at 24 h, even though p21 mRNA was significantly increased at this time point. MG-132 reversed the fluoride-mediated p21 decrease, indicating that fluoride facilitates p21 proteasomal degradation. MG-132 suppressed fluoride-induced caspase-3 cleavage, suggesting that the proteasome plays a pro-apoptotic role in fluoride toxicity. NaF increased phospho-MDM2 in vitro and in mouse ameloblasts in vivo. Nutlin-3a suppressed NaF-mediated MDM2-p21 binding to reverse p21 degradation which increased phospho-p21. This suppressed apoptosis after 24 h NaF treatment. These results suggest that MDM2-mediated p21 proteasomal degradation with subsequent phospho-p21 attenuation contributes to fluoride-induced apoptosis. Inhibition of MDM2-mediated p21 degradation may be a potential therapeutic target to mitigate fluoride toxicity.

Azacytidine Suppressors Autocrine IL-6 Secretion and Demonstrates In Vitro and In Vivo Activity Against Multiple Myeloma.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1566-1566
Author(s):  
Tiffany Khong ◽  
Janelle Sharkey ◽  
Andrew Spencer
Keyword(s):  
Multiple Myeloma ◽  
Murine Model ◽  
Dna Methyltransferase ◽  
Myeloma Cell ◽  
Apoptotic Pathway ◽  
P16 Gene ◽  
Induced Apoptosis ◽  
The Impact

Abstract Azacytidine (AZA), a DNA methyltransferase inhibitor, has been shown to inhibit cell growth and induce apoptosis in some cancer cells. We determined the impact of AZA on a panel of human myeloma cell lines (HMCL); KMS 12PE, KMS 18, LP-1, NCI-H929, OPM-2, RPMI-8226 and U266 and in an in vivo murine model of multiple myeloma (5T33 model). Dose responsiveness to AZA was determined via MTS assays with a range of AZA doses (1–10mM) for 72 hours. FACS and cell cycle analysis were used to evaluate the profile of the cells after exposure to AZA for 72 hours. MTS assays demonstrated a dose and time dependent AZA-induced inhibition of HMCL viability with effective concentrations of AZA ranging from 1–10 mM. This was associated with accumulation of cells in the Go/G1 phase with decreasing number of cells in the S and G2/M phases. Western Blot analysis using antibodies against caspases 3,8,10, PARP, phospho-ERK, ERK, Stat3 and phospho -Stat3 were performed to help characterize the mechanism(s) of cell killing. Cleavage of caspases 3,8,10 and PARP within 24 hours of AZA treatment confirmed early AZA-induced HMCL apoptosis. phospho-ERK which was absent in untreated U266 appeared after 48 hours exposure to 5mM AZA. Similarly inhibitors of caspases 3,8 and 9 were used to determine which apoptotic pathway was being preferentially activated by AZA. Inhibitors of both caspase 3 and 9 effectively abrogated AZA-induced apoptosis in U266 and NCI-H929. In contrast caspase 8 inhibitor was less effective which is consistent with AZA acting via the mitochondrial apoptotic pathway. Reactivation of p16 gene by AZA-induced hypomethylation was assessed with methylation specific PCR. MSP-PCR of the p16 gene indicated a loss of methylation and up-regulated transcription after 48 hours treatment with 5 mM AZA. The level of IL-6 in conditioned media from U266 cells treated with AZA was determined by ELISA assay and demonstrated a rapid fall in autocrine IL-6 production. RT-PCR demonstrated rapid AZA-induced cessation of IL-6 transcription temporarily associated with the disappearance of upstream phospho -Stat3. Addition of exogenous IL-6 did not rescue U266 from AZA-induced apoptosis. AZA was also administered to a 5T33 murine model of multiple myeloma at increasing concentrations (1, 3, 10 mg/kg). At 10 mg/kg the median survival of vehicle versus AZA treated mice was 28 days versus 30+ days (p=0.003). These findings justify further evaluation of AZA as a potential therapeutic agent for multiple myeloma.

scholarly journals The Mechanisms of Chansu in Inducing Efficient Apoptosis in Colon Cancer Cells

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Chun Li ◽  
Saeed M. Hashimi ◽  
Siyu Cao ◽  
Albert S. Mellick ◽  
Wei Duan ◽  
...  
Keyword(s):  
Colon Cancer ◽  
Cancer Cells ◽  
Surrogate Marker ◽  
Apoptotic Pathway ◽  
Lung Cancers ◽  
Cancer Cell Death ◽  
Prostate Cancers ◽  
Induced Apoptosis

Chansu is one of the most widely used traditional Chinese medicines in China, Japan, and other Southeast Asian countries primarily for antipain, anti-inflammation, and recently anticancer. Over 10 recipes and remedies contained Chansu, which are easily available in pharmacies and hospitals, but the mechanisms of action were not clearly articulated. In the present study, Cinobufagin (CBF), the major compound of Chansu, was employed as a surrogate marker to determine its ability in inducing cancer cell death. As expected, CBF has significant cancer-killing capacity for a range of cancers, but such ability differs markedly. Colon and prostate cancers are more sensitive than skin and lung cancers. Interestingly, cancer cells die through apoptotic pathway either being biphasic caspase-3-dependent (HCT116) or independent (HT29). Multipathway analysis reveals that CBF-induced apoptosis is likely modulated by the hypoxia-inducing factor-1 alpha subunit (HIF-1α) as its inhibition was evidentin vitroandin vivo. Taken together, these results demonstrate that CBF is a potent apoptotic inducer with potential for further development as a novel and effective anticancer agent for a range of cancers, especially colon cancer.

scholarly journals The RASSF1A Tumor Suppressor Binds the RasGAP DAB2IP and Modulates RAS Activation in Lung Cancer

Cancers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3807
Author(s):  
Desmond R. Harrell Stewart ◽  
M. Lee Schmidt ◽  
Howard Donninger ◽  
Geoffrey J. Clark
Keyword(s):  
Lung Cancer ◽  
Tumor Suppressor ◽  
Promoter Hypermethylation ◽  
Negative Regulator ◽  
Ras Signaling ◽  
Mitogenic Signaling ◽  
Protein Levels ◽  
Ras Activation

Lung cancer is the leading cause of cancer-related death worldwide. Lung cancer is commonly driven by mutations in the RAS oncogenes, the most frequently activated oncogene family in human disease. RAS-induced tumorigenesis is inhibited by the tumor suppressor RASSF1A, which induces apoptosis in response to hyperactivation of RAS. RASSF1A expression is suppressed in cancer at high rates, primarily owing to promoter hypermethylation. Recent reports have shown that loss of RASSF1A expression uncouples RAS from apoptotic signaling in vivo, thereby enhancing tumor aggressiveness. Moreover, a concomitant upregulation of RAS mitogenic signaling upon RASSF1A loss has been observed, suggesting RASSF1A may directly regulate RAS activation. Here, we present the first mechanistic evidence for control of RAS activation by RASSF1A. We present a novel interaction between RASSF1A and the Ras GTPase Activating Protein (RasGAP) DAB2IP, an important negative regulator of RAS. Using shRNA-mediated knockdown and stable overexpression approaches, we demonstrate that RASSF1A upregulates DAB2IP protein levels in NSCLC cells. Suppression of RASSF1A and subsequent downregulation of DAB2IP enhances GTP loading onto RAS, thus increasing RAS mitogenic signaling in both mutant- and wildtype-RAS cells. Moreover, co-suppression of RASSF1A and DAB2IP significantly enhances in vitro and in vivo growth of wildtype-RAS cells. Tumors expressing wildtype RAS, therefore, may still suffer from hyperactive RAS signaling when RASSF1A is downregulated. This may render them susceptible to the targeted RAS inhibitors currently in development.

scholarly journals Regulatory T cells are less sensitive to glucocorticoid hormone induced apoptosis than CD4+ T cells

APOPTOSIS ◽  
2020 ◽  
Vol 25 (9-10) ◽  
pp. 715-729 ◽  
Author(s):  
Lilla Prenek ◽  
Tímea Litvai ◽  
Noémi Balázs ◽  
Réka Kugyelka ◽  
Ferenc Boldizsár ◽  
...  
Keyword(s):  
T Cells ◽  
Regulatory T Cells ◽  
Treg Cells ◽  
High Dose ◽  
Apoptosis Resistance ◽  
Apoptotic Pathway ◽  
Glucocorticoid Hormone ◽  
Induced Apoptosis

Abstract Earlier we have reported that thymic regulatory T cells (Treg) are resistant to in vivo glucocorticoid hormone (GC)-induced apoptosis, while the most GC-sensitive DP thymocytes died through the activation of mitochondrial apoptotic pathway. Here we analyzed the apoptosis-inducing effect of high dose (10–6 M) in vitro dexamethasone (DX) treatment in mouse thymic- and splenic Tregs and CD4+ T cells. Activation of both extrinsic and intrinsic apoptotic pathways started after 2 h of DX treatment in CD4 SP thymocytes and was 3 × higher than in CD4+ splenocytes, while in Treg cells, weak activation of the extrinsic apoptotic pathway started only after 3 h. We also investigated the expression of 21 apoptosis-related molecules using a protein array and found higher level of both pro-and anti-apoptotic molecules in Tregs compared to CD4+ T cells. 4 h in vitro DX treatment induced upregulation of most apoptosis-related molecules both in Tregs and CD4+ T cells, except for the decrease of Bcl-2 expression in CD4+ T cells. We found high basal cytosolic Ca2+ levels in untreated Treg cells, which further increased after DX treatment, while the specific TCR-induced Ca2+ signal was lower in Tregs than in CD4+ T cells. Our results suggest that in the background of the relative apoptosis resistance of Treg cells to GCs might be their high basal cytosolic Ca2+ level and upregulated Bcl-2 expression. In contrast, downregulation of Bcl-2 expression in CD4+ T cells can explain their higher, DX-induced apoptosis sensitivity.

scholarly journals Deubiquitination of Tip60 by USP7 Determines the Activity of the p53-Dependent Apoptotic Pathway

2013 ◽  
Vol 33 (16) ◽  
pp. 3309-3320 ◽  
Author(s):  
Ashraf Dar ◽  
Etsuko Shibata ◽  
Anindya Dutta
Keyword(s):  
Tumor Suppressor ◽  
Small Molecule ◽  
Genotoxic Stress ◽  
Ubiquitin Proteasome System ◽  
Apoptotic Pathway ◽  
Nonhistone Proteins ◽  
Molecule Inhibitor ◽  
Ubiquitin Proteasome

Tip60 is an essential acetyltransferase required for acetylation of nucleosomal histones and other nonhistone proteins. Tip60 acetylates the p53 tumor suppressor at lysine 120 (K120), a modification essential for p53-dependent induction of PUMA and apoptosis. It is known that Tip60 is turned over in cells by the ubiquitin-proteasome system. However, the deubiquitinase activity for stabilizing Tip60 is unknown. Here we show that USP7 interacts with and deubiquitinates Tip60 bothin vitroandin vivo. USP7 deubiquitinase activity is required for the stabilization of Tip60 in order to operate an effective p53-dependent apoptotic pathway in response to genotoxic stress. Inhibiting USP7 with the small-molecule inhibitor P22077 attenuates the p53-dependent apoptotic pathway by destabilizing Tip60. P22077, however, is still cytotoxic, and this is partly due to destabilization of Tip60.

scholarly journals TSC2-extracellular matrix crosstalk controls pulmonary vascular proliferation and pulmonary hypertension

2021 ◽  
Author(s):  
Yuanjun Shen ◽  
Dmitry A Goncharov ◽  
Andressa Pena ◽  
Jeffrey Baust ◽  
Andres Chavez Barragan ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Pulmonary Hypertension ◽  
Therapeutic Option ◽  
Pulmonary Arteries ◽  
Negative Regulator ◽  
Vascular Proliferation ◽  
Induced Apoptosis ◽  
Mtor Complex 1

Increased proliferation and survival of resident cells in small pulmonary arteries (PA) are important drivers of pulmonary hypertension (PH). Tuberous sclerosis complex 2 (TSC2) is a negative regulator of mTOR complex 1 and cell growth. Here we show that TSC2 is deficient in small remodeled PA/PA vascular smooth muscle cells (PAVSMC) from human PAH and experimental PH lungs. TSC2 deficiency was reproduced in vitro by maintaining PAVSMC on pathologically stiff substrates and was required for stiffness-induced proliferation, accumulation of transcriptional co-activators YAP/TAZ and up-regulation of mTOR. Depletion of TSC2 reproduced PH features in vitro in human PAVSMC and in vivo in SM22-Tsc2+/- mice. TSC2 loss in PAVSMC was supported by YAP and led to the up-regulation of YAP/TAZ and mTOR via modulating the extracellular matrix (ECM) composition. ECM, produced by TSC2-deficient PAVSMC, promoted growth of non-diseased PA adventitial fibroblasts and PAVSMC, which, in turn, was prevented by α5β1 integrin receptor antagonist ATN161. In vitro, molecular and pharmacological (SRT2104) restoration of TSC2 down-regulated YAP/TAZ, mTOR, and ECM pro-duction, inhibited proliferation and induced apoptosis in human PAH PAVSMC. In vivo, orally administrated SRT2104 restored TSC2, resolved pulmonary vascular remodeling, PH, and improved right heart in two rodent models of PH. Thus, PAVSMC TSC2 is a critical integrator of ECM composition and stiffness with pro-proliferative signaling and PH, and the restoration of functional TSC2 could be an attractive therapeutic option to treat PH.

scholarly journals Anti-Proliferative and Pro-Apoptotic Activities of Hederacolchiside A1 On MCF-7 Cells Via ROS Regulation and JAK2/STAT3 Inactivation

2021 ◽  
Author(s):  
Aijun Chen ◽  
Shushu Zhang ◽  
Dandan Zhang ◽  
Xingjiang Hu ◽  
Nana Xu ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Ros Generation ◽  
Caspase 9 ◽  
Apoptotic Pathway ◽  
Hct 116 ◽  
Hct 116 Cells ◽  
Induced Apoptosis ◽  
Mcf 7

Abstract Many studies have shown that hederacolchiside A1 (HA1) is an important anticancer saponin, although its mechanism of action and in vivo investigations are still lacking. Our previous results revealed that HA1 may have the potential to treat breast cancer. Therefore, we attempted to verify the potential anti-breast cancer effect of HA1 in vitro and in vivo. MTT, flow cytometry, DCFH-DA fluorescence microscopy, and western blotting were used to evaluate the activities and mechanisms of action of HA1. Athymic nude mice were used to demonstrate the antitumor activity of HA1 in vivo. HA1 exhibited significant cytotoxic effects on HepG2, MCF-7, MDA-MB-231, SKBr-3, HT-29, and HCT-116 cells, especially MCF-7 cells. HA1 blocked the sub-G1 and G0/G1 phases, induced apoptosis, promoted reactive oxygen species (ROS) generation, and decreased the mitochondrial membrane potential of MCF-7 cells. HA1 upregulated Bax and downregulated Bcl-2 levels and activated caspase-9 and caspase-3 in MCF-7 cells Meanwhile, HA1 inhibited the phosphorylation of JAK2/STAT3 in MCF-7 cells. In addition, 50 and 100 mg/kg HA1 significantly inhibited the growth of transplanted tumors with inhibition rates of 46.95 ± 26.72% and 48.45 ± 22.36%, respectively. This preliminary study demonstrated that HA1 could inhibit proliferation and induce the apoptosis of MCF-7 cells via ROS-mediated activation of the mitochondrial apoptotic pathway and JAK2/STAT3 inactivation. HA1 may therefore be developed as a novel agent for breast cancer therapy.

scholarly journals Targeting of C-Terminal Binding Protein (CtBP) by ARF Results in p53-Independent Apoptosis

2006 ◽  
Vol 26 (6) ◽  
pp. 2360-2372 ◽  
Author(s):  
Seema Paliwal ◽  
Sandhya Pande ◽  
Ramesh C. Kovi ◽  
Norman E. Sharpless ◽  
Nabeel Bardeesy ◽  
...  
Keyword(s):  
Tumor Suppression ◽  
Negative Regulator ◽  
Interacting Proteins ◽  
Yeast Two Hybrid ◽  
Induced Apoptosis ◽  
Interfering Rna ◽  
Two Hybrid ◽  
Potent Tumor

ABSTRACT ARF encodes a potent tumor suppressor that antagonizes MDM2, a negative regulator of p53. ARF also suppresses the proliferation of cells lacking p53, and loss of ARF in p53-null mice, compared with ARF or p53 singly null mice, results in a broadened tumor spectrum and decreased tumor latency. To investigate the mechanism of p53-independent tumor suppression by ARF, potential interacting proteins were identified by yeast two-hybrid screen. The antiapoptotic transcriptional corepressor C-terminal binding protein 2 (CtBP2) was identified, and ARF interactions with both CtBP1 and CtBP2 were confirmed in vitro and in vivo. Interaction with ARF resulted in proteasome-dependent CtBP degradation. Both ARF-induced CtBP degradation and CtBP small interfering RNA led to p53-independent apoptosis in colon cancer cells. ARF induction of apoptosis was dependent on its ability to interact with CtBP, and reversal of ARF-induced CtBP depletion by CtBP overexpression abrogated ARF-induced apoptosis. CtBP proteins represent putative targets for p53-independent tumor suppression by ARF.

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