scholarly journals Phosphorylation of DEPDC5, a component of the GATOR1 complex, releases inhibition of mTORC1 and promotes tumor growth

2019 ◽  
Vol 116 (41) ◽  
pp. 20505-20510 ◽  
Author(s):  
Sathish K. R. Padi ◽  
Neha Singh ◽  
Jeremiah J. Bearss ◽  
Virginie Olive ◽  
Jin H. Song ◽  
...  
Keyword(s):  
Amino Acid ◽  
Tumor Growth ◽  
Cancer Cells ◽  
Regulatory Protein ◽  
Mammalian Target Of Rapamycin ◽  
Animal Experiments ◽  
Amino Acid Starvation ◽  
Inhibitory Protein

The Pim and AKT serine/threonine protein kinases are implicated as drivers of cancer. Their regulation of tumor growth is closely tied to the ability of these enzymes to mainly stimulate protein synthesis by activating mTORC1 (mammalian target of rapamycin complex 1) signaling, although the exact mechanism is not completely understood. mTORC1 activity is normally suppressed by amino acid starvation through a cascade of multiple regulatory protein complexes, e.g., GATOR1, GATOR2, and KICSTOR, that reduce the activity of Rag GTPases. Bioinformatic analysis revealed that DEPDC5 (DEP domain containing protein 5), a component of GATOR1 complex, contains Pim and AKT protein kinase phosphorylation consensus sequences. DEPDC5 phosphorylation by Pim and AKT kinases was confirmed in cancer cells through the use of phospho-specific antibodies and transfection of phospho-inactive DEPDC5 mutants. Consistent with these findings, during amino acid starvation the elevated expression of Pim1 overcame the amino acid inhibitory protein cascade and activated mTORC1. In contrast, the knockout of DEPDC5 partially blocked the ability of small molecule inhibitors against Pim and AKT kinases both singly and in combination to suppress tumor growth and mTORC1 activity in vitro and in vivo. In animal experiments knocking in a glutamic acid (S1530E) in DEPDC5, a phospho mimic, in tumor cells induced a significant level of resistance to Pim and the combination of Pim and AKT inhibitors. Our results indicate a phosphorylation-dependent regulatory mechanism targeting DEPDC5 through which Pim1 and AKT act as upstream effectors of mTORC1 to facilitate proliferation and survival of cancer cells.

scholarly journals POU2F2 promotes the proliferation and motility of lung cancer cells by activating AGO1

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ronggang Luo ◽  
Yi Zhuo ◽  
Quan Du ◽  
Rendong Xiao
Keyword(s):  
Lung Cancer ◽  
Tumor Growth ◽  
Cancer Cells ◽  
Cancer Progression ◽  
Human Lung ◽  
Lung Cancer Cells ◽  
Human Lung Cancer ◽  
Cancer Tissues

Abstract Background To detect and investigate the expression of POU domain class 2 transcription factor 2 (POU2F2) in human lung cancer tissues, its role in lung cancer progression, and the potential mechanisms. Methods Immunohistochemical (IHC) assays were conducted to assess the expression of POU2F2 in human lung cancer tissues. Immunoblot assays were performed to assess the expression levels of POU2F2 in human lung cancer tissues and cell lines. CCK-8, colony formation, and transwell-migration/invasion assays were conducted to detect the effects of POU2F2 and AGO1 on the proliferaion and motility of A549 and H1299 cells in vitro. CHIP and luciferase assays were performed for the mechanism study. A tumor xenotransplantation model was used to detect the effects of POU2F2 on tumor growth in vivo. Results We found POU2F2 was highly expressed in human lung cancer tissues and cell lines, and associated with the lung cancer patients’ prognosis and clinical features. POU2F2 promoted the proliferation, and motility of lung cancer cells via targeting AGO1 in vitro. Additionally, POU2F2 promoted tumor growth of lung cancer cells via AGO1 in vivo. Conclusion We found POU2F2 was highly expressed in lung cancer cells and confirmed the involvement of POU2F2 in lung cancer progression, and thought POU2F2 could act as a potential therapeutic target for lung cancer.

scholarly journals Hsp90 Binds and Regulates the Ligand-Inducible α Subunit of Eukaryotic Translation Initiation Factor Kinase Gcn2

1999 ◽  
Vol 19 (12) ◽  
pp. 8422-8432 ◽  
Author(s):  
Olivier Donzé ◽  
Didier Picard
Keyword(s):  
Amino Acid ◽  
Constitutive Expression ◽  
Amino Acid Starvation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Restrictive Temperature ◽  
Α Subunit ◽  
Macbecin I

ABSTRACT The protein kinase Gcn2 stimulates translation of the yeast transcription factor Gcn4 upon amino acid starvation. Using genetic and biochemical approaches, we show that Gcn2 is regulated by the molecular chaperone Hsp90 in budding yeast Saccharomyces cerevisiae. Specifically, we found that (i) several Hsp90 mutant strains exhibit constitutive expression of a GCN4-lacZ reporter plasmid; (ii) Gcn2 and Hsp90 form a complex in vitro as well as in vivo; (iii) the specific inhibitors of Hsp90, geldanamycin and macbecin I, enhance the association of Gcn2 with Hsp90 and inhibit its kinase activity in vitro; (iv) in vivo, macbecin I strongly reduces the levels of Gcn2; (v) in a strain expressing the temperature-sensitive Hsp90 mutant G170D, both the accumulation and activity of Gcn2 are abolished at the restrictive temperature; and (vi) the Hsp90 cochaperones Cdc37, Sti1, and Sba1 are required for the response to amino acid starvation. Taken together, these data identify Gcn2 as a novel target for Hsp90, which plays a crucial role for the maturation and regulation of Gcn2.

scholarly journals TGF-βRII Knock-down in Pancreatic Cancer Cells Promotes Tumor Growth and Gemcitabine Resistance. Importance of STAT3 Phosphorylation on S727

Cancers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 254 ◽  
Author(s):  
Vincent Drubay ◽  
Nicolas Skrypek ◽  
Lucie Cordiez ◽  
Romain Vasseur ◽  
Céline Schulz ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Tumor Growth ◽  
Cancer Cells ◽  
Locally Advanced ◽  
Western World ◽  
Pancreatic Cancer Cells ◽  
Stat3 Phosphorylation ◽  
The Impact

Pancreatic adenocarcinoma (PDAC) is one of the most deadly cancers in the Western world because of a lack of early diagnostic markers and efficient therapeutics. At the time of diagnosis, more than 80% of patients have metastasis or locally advanced cancer and are therefore not eligible for surgical resection. Pancreatic cancer cells also harbour a high resistance to chemotherapeutic drugs such as gemcitabine that is one of the main palliative treatments for PDAC. Proteins involved in TGF-β signaling pathway (SMAD4 or TGF-βRII) are frequently mutated in PDAC (50–80%). TGF-β signalling pathway plays antagonistic roles during carcinogenesis by initially inhibiting epithelial growth and later promoting the progression of advanced tumors and thus emerged as both tumor suppressor and oncogenic pathways. In order to decipher the role of TGF-β in pancreatic carcinogenesis and chemoresistance, we generated CAPAN-1 and CAPAN-2 cell lines knocked down for TGF-βRII (first actor of TGF-β signaling). The impact on biological properties of these TGF-βRII-KD cells was studied both in vitro and in vivo. We show that TGF-βRII silencing alters tumor growth and migration as well as resistance to gemcitabine. TGF-βRII silencing also leads to S727 STAT3 and S63 c-Jun phosphorylation, decrease of MRP3 and increase of MRP4 ABC transporter expression and induction of a partial EMT phenotype. These markers associated with TGF-β signaling pathways may thus appear as potent therapeutic tools to better treat/manage pancreatic cancer.

scholarly journals Branched-chain amino acid aminotransferase 2 regulates ferroptotic cell death in cancer cells

2020 ◽  
Author(s):  
Kang Wang ◽  
Zhengyang Zhang ◽  
Hsiang-i Tsai ◽  
Yanfang Liu ◽  
Jie Gao ◽  
...  
Keyword(s):  
Cell Death ◽  
Amino Acid ◽  
Cancer Cells ◽  
Ectopic Expression ◽  
Branched Chain Amino Acid ◽  
Pancreatic Cancer Cells ◽  
Key Enzyme ◽  
Branched Chain

Abstract Ferroptosis, a form of iron-dependent cell death driven by cellular metabolism and iron-dependent lipid peroxidation, has been implicated as a tumor-suppressor function for cancer therapy. Recent advance revealed that the sensitivity to ferroptosis is tightly linked to numerous biological processes, including metabolism of amino acid and the biosynthesis of glutathione. Here, by using a high-throughput CRISPR/Cas9-based genetic screen in HepG2 hepatocellular carcinoma cells to search for metabolic proteins inhibiting ferroptosis, we identified a branched-chain amino acid aminotransferase 2 (BCAT2) as a novel suppressor of ferroptosis. Mechanistically, ferroptosis inducers (erastin, sorafenib, and sulfasalazine) activated AMPK/SREBP1 signaling pathway through iron-dependent ferritinophagy, which in turn inhibited BCAT2 transcription. We further confirmed that BCAT2 as the key enzyme mediating the metabolism of sulfur amino acid, regulated intracellular glutamate level, whose activation by ectopic expression specifically antagonize system Xc– inhibition and protected liver and pancreatic cancer cells from ferroptosis in vitro and in vivo. On the contrary, direct inhibition of BCAT2 by RNA interference, or indirect inhibition by blocking system Xc– activity, triggers ferroptosis. Finally, our results demonstrate the synergistic effect of sorafenib and sulfasalazine in downregulating BCAT2 expression and dictating ferroptotic death, where BCAT2 can also be used to predict the responsiveness of cancer cells to ferroptosis-inducing therapies. Collectively, these findings identify a novel role of BCAT2 in ferroptosis, suggesting a potential therapeutic strategy for overcoming sorafenib resistance.

scholarly journals ERα-Targeted Therapy in Ovarian Cancer Cells by a Novel Estradiol-Platinum(II) Hybrid

Endocrinology ◽  
2013 ◽  
Vol 154 (7) ◽  
pp. 2281-2295 ◽  
Author(s):  
K. Brasseur ◽  
V. Leblanc ◽  
F. Fabi ◽  
S. Parent ◽  
C. Descôteaux ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Cancer Cells ◽  
High Efficiency ◽  
Mammalian Target Of Rapamycin ◽  
Ovarian Cancer Cells ◽  
New Family ◽  
17Β Estradiol ◽  
Apoptosis Inducing Factor

Abstract As we previously showed, we have synthesized a new family of 17β-estradiol-platinum(II) hybrids. Earlier studies revealed the VP-128 hybrid to show high efficiency compared with cisplatin toward hormone-dependent breast cancer cells. In the present research, we have studied the antitumor activity of VP-128 in vitro and in vivo against ovarian cancer. In nude mice with ovarian xenografts, VP-128 displayed selective activity toward hormone-dependent tumors and showed higher efficiency than cisplatin to inhibit tumor growth. Similarly, in vitro, transient transfection of estrogen receptor (ER)-α in ERα-negative A2780 cells increased their sensitivity to VP-128-induced apoptosis, confirming the selectivity of VP-128 toward hormone-dependent tumor cells. In agreement, Western blot analysis revealed that VP-128 induced higher caspase-9, caspase-3, and poly (ADP-ribose) polymerase cleavage compared with cisplatin. The activation of caspase-independent apoptosis was also observed in ERα-negative A2780 cells, in which VP-128 rapidly induced the translocation of apoptosis-inducing factor to the nucleus. Conversely, subcellular localization of apoptosis-inducing factor was not modified in ERα-positive Ovcar-3 cells. We also discovered that VP-128 induces autophagy in ovarian cancer cells because of the formation of acidic vesicular organelles (AVOs) and increase of Light Chain 3B-II protein responsible for the formation of autophagosomes; pathways related to autophagy (AKT and mammalian target of rapamycin) were also down-regulated, supporting this mechanism. Finally, the inhibition of autophagy using chloroquine increased VP-128 efficiency, indicating a possible combination therapy. Altogether these results highlight the beneficial value of VP-128 for the treatment of hormone-dependent ovarian cancers and provide preliminary proof of concept for the efficient targeting of ERα- by 17β-estradiol-Pt(II)-linked chemotherapeutic hybrids in these tumors.

Estrogen receptor β represses breast tumor growth and angiogenesis in vivo

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 10101-10101
Author(s):  
J. Hartman ◽  
K. Lindberg ◽  
J. Inzunza ◽  
J. Wan ◽  
A. Ström ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Tumor Growth ◽  
Cancer Cells ◽  
Breast Tumor ◽  
Breast Cancer Cells ◽  
Cancer Cell Growth ◽  
Breast Cancer Cell Growth ◽  
Angiogenic Effect

10101 Background: Estrogens are well known stimulators of breast cancer cell growth in vitro as well as in vivo. Two different estrogen receptors exist, namely estrogen receptor (ER) α and β. ERα mediates the proliferative effect of estrogen in breast cancer cells and we have earlier shown that ERβ inhibits cell-cycle progression in vitro. Estrogens are well known stimulators of in vivo breast cancer cell growth as well as angiogenesis, and the effect is mediated through ERα. The function of ERβ in this context is not well understood. Methods: We have used ERα-positive T47D breast cancer cells stably transfected with a Tet/Off regulated ERβ expression vector system. The ERβ-inducible tumor cells are studied in vitro as well as in vivo. Results: By transplanting ERβ-inducible breast cancer cells into SCID-mice, we show that ERβ inhibits tumor growth and reduces the volume of established tumors. Furthermore, we show by immunohistochemistry, that the number of blood microvessels in the tumor periphery is decreased by ERβ expression, counteracting the well-known pro-angiogenic effect of ERα. By Western blot analysis on tumor extracts, we show that the concentration of the important pro-angiogenic growth factors VEGF and bFGF, normally expressed by breast tumor cells, is decreased in the ERβ-expressing tumors compared to the normal tumors. To exclude that the observed anti-angiogenic effect is just a result of reduced tumor growth, we incubated Tet/Off regulated ERβ expressing cells in vitro, during non-hypoxic conditions. We found that the expression of ERβ leads to decreased expression of VEGF and PDGFβ at the mRNA and protein-levels. In transient transfection assays, we found estrogen-ERα mediated up regulation of VEGF, PDGFβ and bFGF-promoter activities in T47D cells, and these activities were all suppressed following co-transfection with an ERβ-expression vector. Conclusions: We conclude that ERβ inhibits growth factor expression at transcriptional level in breast cancer cells; taken together, our data indicates that ERβ inhibits growth and angiogenesis of tumors formed by T47D breast cancer cells. This makes ERβ an interesting therapeutic target in breast cancer and perhaps treatment with the newly designed ERβ-selective ligands might work as a new anti-proliferative and anti-angiogenic therapy. No significant financial relationships to disclose.

Effect of NVP-BEZ235, a dual PI3K/mTOR inhibitor, on chemotherapy and antiangiogenic response in pancreatic cancer.

2012 ◽  
Vol 30 (4_suppl) ◽  
pp. 243-243 ◽  
Author(s):  
Katherine T. Ostapoff ◽  
Niranjan Awasthi ◽  
Peter L. Yen ◽  
Changhua Zhang ◽  
Margaret A. Schwarz ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Combination Therapy ◽  
Mtor Inhibitor ◽  
Mammalian Target Of Rapamycin ◽  
Animal Experiments ◽  
Ductal Adenocarcinoma ◽  
Clinical Benefits ◽  
Induced Apoptosis

243 Background: The phosphatidylinositol-3-kinase (PI3K)/AKT and mammalian target of rapamycin (mTOR) signaling pathway dysregulation is a prominent feature of pancreatic ductal adenocarcinoma (PDAC). Gemcitabine (GEM), a standard systemic treatment for PDAC, has limited clinical benefits. The present study investigated the effects of NVP-BEZ235 (BEZ235), a novel dual PI3K/mTOR inhibitor, in combination with gemcitabine and endothelial monocyte activating polypeptide II (EMAP) in experimental PDAC. Methods: Protein expression and cell proliferation were analyzed by Western blotting and WST-1 assay. Animal experiments were performed in murine xenografts. Results: BEZ235 inhibited phospho-AKT (Ser473) and phospho-mTOR (Ser2448) expression in PDAC (AsPC-1), endothelial (HUVECs) and fibroblast (WI-38) cells. NVP-BEZ235 also caused a significant dephosphorylation of downstream mTORC1 target proteins phospho-p70 S6K (Thr389) and phospho-4E-BP1 (Thr37/46). In vitro 72-hour proliferation of four PDAC cell lines was significantly inhibited by BEZ235. Additive effects on proliferation inhibition were observed in the BEZ235 and GEM combination in PDAC cells and in combination of BEZ235 or EMAP with gemcitabine in HUVECs and WI-38 cells. BEZ235, alone or in combination with GEM and EMAP, induced apoptosis in AsPC-1, HUVECs and WI-38 cells as observed by increased expression of cleaved poly (ADP-ribose) polymerase-1 (PARP-1) and caspase-3 proteins. PDAC in vivo therapy demonstrated that compared to controls (median survival: 16 days), animal survival increased after BEZ235 and EMAP therapy alone (both 21 days) and GEM monotherapy (28 days). Further increases in survival occurred in combination therapy groups BEZ235+GEM (30 days, p=0.007), BEZ235+EMAP (27 days, p=0.02), GEM+EMAP (31 days, p=0.001) and BEZ235+GEM +EMAP (33 days, p=0.004). Conclusions: BEZ235 has experimental PDAC antitumor activity in vitro and in vivo that can be enhanced in combination with cytotoxic (GEM) and antiendothelial (EMAP) agents. These findings demonstrate advantages of combination therapy strategies targeting multiple pathways in pancreatic cancer treatment.

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