TOR complex 2 is needed for cell cycle progression and anchorage-independent growth of MCF7 and PC3 tumor cells

<p>Abstract</p> <p>Background</p> <p>AKT signaling promotes cell growth, proliferation and survival and is hyperactivated in many cancers. TOR complex 2 (TORC2) activates AKT by phosphorylating it on the 'hydrophobic motif' site. Hydrophobic motif site phosphorylation is needed only for a subset of AKT functions. Whether proliferation of tumor cells depends on TORC2 activity has not been thoroughly explored.</p> <p>Methods</p> <p>We used RNAi-mediated knockdown of rictor to inhibit TORC2 activity in MCF7 and PC3 tumor cells to analyze the importance of TORC2 on proliferation of tumor cells.</p> <p>Results</p> <p>TORC2 inhibition reduced proliferation and anchorage-independent growth of both cell lines. Rictor depleted cells accumulated G1 phase, and showed prominent downregulation of Cyclin D1.</p> <p>Conclusion</p> <p>This study provides further evidence that inhibition of TORC2 activity might be a useful strategy to inhibit proliferation of tumor cells and subsequent tumor growth.</p

EXPLORING THE MITIGATION OF GREENHOUSE GAS EMISSIONS FROM THE CURRENT MUNICIPAL SOLID WASTE SYSTEM OF KAZAKHSTAN: CASE STUDY OF NUR-SULTAN CITY

As we move forward, municipal solid waste (MSW) landfills, particularly in developing countries, contribute notably to global greenhouse gas (GHG) emissions. Therefore, the MSW sector plays a key role in planning strategies for developing countries such as Kazakhstan to decrease GHG emissions. With respect to the Paris Agreement, Kazakhstan has set the target of reducing GHG emissions to 15-25% by 2030 compared to the level of 1991, which will undoubtedly require certain measures in the field of MSW management. Several recent articles have been published on the waste management sector of Kazakhstan; however, none have explicitly focused on the impact of greenhouse gas emissions and possible pathways towards sustainable management. Thus, this paper describes the existing MSW system in Nur Sultan city as representative for the rest of the country. The quantitative evaluation of GHG emissions from the existing MSW system in the capital is carried out based on the IPCC methodology using the SWM-GHG calculator developed by the Institute for Energy and Environmental Research (IFEU). An assessment and cost analysis of a set of several suitable MSW management scenarios, such as scenario 1: existing case (15% recycling rate and 85% disposal), scenario 2: 30% recyclable materials, and 70% sanitary landfill with gas collection; scenario 3: 30% recyclable materials and 70% biological stabilization and landfill without gas collection; scenario 4: 30% recyclable materials, 20% composting and 50% waste to be sent to the WtE plant (incineration). The level of GHG emissions decreases with the introduction of more integrated waste management methods, but requires more financial investments. Therefore, Scenario 3 is the most efficient to implement in terms of the combination of cost of €19.4 million/year and magnitude of GHG emissions of 48 kt of CO2 eq/year. The outcomes of this work will help to extrapolate the model to other large cities in Kazakhsta

Rictor, a Novel Binding Partner of mTOR, Defines a Rapamycin-Insensitive and Raptor-Independent Pathway that Regulates the Cytoskeleton

AbstractThe mammalian TOR (mTOR) pathway integrates nutrient- and growth factor-derived signals to regulate growth, the process whereby cells accumulate mass and increase in size. mTOR is a large protein kinase and the target of rapamycin, an immunosuppressant that also blocks vessel restenosis and has potential anticancer applications. mTOR interacts with the raptor and GβL proteins [1–3] to form a complex that is the target of rapamycin. Here, we demonstrate that mTOR is also part of a distinct complex defined by the novel protein rictor (rapamycin-insensitive companion of mTOR). Rictor shares homology with the previously described pianissimo from D. discoidieum[4], STE20p from S. pombe[5], and AVO3p from S. cerevisiae[6, 7]. Interestingly, AVO3p is part of a rapamycin-insensitive TOR complex that does not contain the yeast homolog of raptor and signals to the actin cytoskeleton through PKC1 [6]. Consistent with this finding, the rictor-containing mTOR complex contains GβL but not raptor and it neither regulates the mTOR effector S6K1 nor is it bound by FKBP12-rapamycin. We find that the rictor-mTOR complex modulates the phosphorylation of Protein Kinase C α (PKCα) and the actin cytoskeleton, suggesting that this aspect of TOR signaling is conserved between yeast and mammals

Ornithine Decarboxylase mRNA is Stabilized in an mTORC1-dependent Manner in Ras-transformed Cells

Upon Ras activation, ODC (ornithine decarboxylase) is markedly induced, and numerous studies suggest that ODC expression is controlled by Ras effector pathways. ODC is therefore a potential target in the treatment and prevention of Ras-driven tumours. In the present study we compared ODC mRNA translation profiles and stability in normal and Ras12V-transformed RIE-1 (rat intestinal epithelial) cells. While translation initiation of ODC increased modestly in Ras12V cells, ODC mRNA was stabilized 8-fold. Treatment with the specific mTORC1 [mTOR (mammalian target of rapamycin) complex 1] inhibitor rapamycin or siRNA (small interfering RNA) knockdown of mTOR destabilized the ODC mRNA, but rapamycin had only a minor effect on ODC translation initiation. Inhibition of mTORC1 also reduced the association of the mRNA-binding protein HuR with the ODC transcript. We have shown previously that HuR binding to the ODC 3′UTR (untranslated region) results in significant stabilization of the ODC mRNA, which contains several AU-rich regions within its 3′UTR that may act as regulatory sequences. Analysis of ODC 3′UTR deletion constructs suggests that cis-acting elements between base 1969 and base 2141 of the ODC mRNA act to stabilize the ODC transcript. These experiments thus define a novel mechanism of ODC synthesis control. Regulation of ODC mRNA decay could be an important means of limiting polyamine accumulation and subsequent tumour development

Rictor Phosphorylation on the THR-1135 Site Does Not Require Mammalian Target of Rapamycin Complex 2

available in PMC 2012 January 1.In animal cells, growth factors coordinate cell proliferation and survival by regulating the phosphoinositide 3-kinase/Akt signaling pathway. Deregulation of this signaling pathway is common in a variety of human cancers. The PI3K-dependent signaling kinase complex defined as mammalian target of rapamycin complex 2 (mTORC2) functions as a regulatory Ser-473 kinase of Akt. We find that activation of mTORC2 by growth factor signaling is linked to the specific phosphorylation of its component rictor on Thr-1135. The phosphorylation of this site is induced by the growth factor stimulation and expression of the oncogenic forms of ras or PI3K. Rictor phosphorylation is sensitive to the inhibition of PI3K, mTOR, or expression of integrin-linked kinase. The substitution of wild-type rictor with its specific phospho-mutants in rictor null mouse embryonic fibroblasts did not alter the growth factor–dependent phosphorylation of Akt, indicating that the rictor Thr-1135 phosphorylation is not critical in the regulation of the mTORC2 kinase activity. We found that this rictor phosphorylation takes place in the mTORC2-deficient cells, suggesting that this modification might play a role in the regulation of not only mTORC2 but also the mTORC2-independent function of rictor. Mol Cancer Res; 8(6); 896–906.University of Texas M.D. Anderson Cancer Center (Fellow Trust fund)American Cancer Society (M.D. Anderson Cancer Center Breast Specialized Programs of Research Excellence (RSG-09-026-01CCG01))National Institutes of Health (U.S.) (NIH grant CA133522)National Institutes of Health (U.S.) (NIH grant AI104389

ENHANCING AN OXIDATIVE “TROJAN HORSE” ACTION OF VITAMIN C WITH ARSENIC TRIOXIDE FOR EFFECTIVE SUPPRESSION OF KRAS-MUTANT CANCERS: A PROMISING PATH AT THE BEDSIDE

The turn-on mutations of the KRAS gene, coding a small GTPase coupling growth factor signaling, are contributing to nearly 25% of all human cancers, leading to highly malignant tumors with poor outcomes. Targeting of oncogenic KRAS remains a most challenging task in oncology. Recently, the specific G12C mutant KRAS inhibitors have been developed but with a limited clinical outcome because they acquire drug resistance. Alternatively, exploiting a metabolic breach of KRAS-mutant cancer cells related to a glucose-dependent sensitivity to oxidative stress is becoming a promising indirect cancer targeting approach. Here, we discuss the use of a vitamin C (VC) acting in high dose as an oxidative “Trojan horse” agent for KRAS-mutant cancer cells that can be potentiated with another oxidizing drug arsenic trioxide (ATO) to obtain a potent and selective cytotoxic impact. Moreover, we outline the advantages of VC’s non-natural enantiomer, D-VC, because of its distinctive pharmacokinetics and lower toxicity. Thus, the D-VC and ATO combination shows a promising path to treat KRAS-mutant cancers in clinical settings

Tsc/mTORC1 signaling in oocytes governs the quiescence and activation of primordial follicles

To maintain the female reproductive lifespan, the majority of ovarian primordial follicles are preserved in a quiescent state in order to provide ova for later reproductive life. However, the molecular mechanism that maintains the long quiescence of primordial follicles is poorly understood. Here we provide genetic evidence to show that the tumor suppressor tuberous sclerosis complex 1 (Tsc1), which negatively regulates mammalian target of rapamycin complex 1 (mTORC1), functions in oocytes to maintain the quiescence of primordial follicles. In mutant mice lacking the Tsc1 gene in oocytes, the entire pool of primordial follicles is activated prematurely due to elevated mTORC1 activity in the oocyte, ending up with follicular depletion in early adulthood and causing premature ovarian failure (POF). We further show that maintenance of the quiescence of primordial follicles requires synergistic, collaborative functioning of both Tsc and PTEN (phosphatase and tensin homolog deleted on chromosome 10) and that these two molecules suppress follicular activation through distinct ways. Our results suggest that Tsc/mTORC1 signaling and PTEN/PI3K (phosphatidylinositol 3 kinase) signaling synergistically regulate the dormancy and activation of primordial follicles, and together ensure the proper length of female reproductive life. Deregulation of these signaling pathways in oocytes results in pathological conditions of the ovary, including POF and infertility

Targeted Morphoproteomic Profiling of Ewing's Sarcoma Treated with Insulin-Like Growth Factor 1 Receptor (IGF1R) Inhibitors: Response/Resistance Signatures

Insulin-like growth factor 1 receptor (IGF1R) targeted therapies have resulted in responses in a small number of patients with advanced metastatic Ewing's sarcoma. We performed morphoproteomic profiling to better understand response/resistance mechanisms of Ewing's sarcoma to IGF1R inhibitor-based therapy.This pilot study assessed two patients with advanced Ewing's sarcoma treated with IGF1R antibody alone followed by combined IGF1R inhibitor plus mammalian target of rapamycin (mTOR) inhibitor treatment once resistance to single-agent IGF1R inhibitor developed. Immunohistochemical probes were applied to detect p-mTOR (Ser2448), p-Akt (Ser473), p-ERK1/2 (Thr202/Tyr204), nestin, and p-STAT3 (Tyr 705) in the original and recurrent tumor. The initial remarkable radiographic responses to IGF1R-antibody therapy was followed by resistance and then response to combined IGF1R plus mTOR inhibitor therapy in both patients, and then resistance to the combination regimen in one patient. In patient 1, upregulation of p-Akt and p-mTOR in the tumor that relapsed after initial response to IGF1R antibody might explain the resistance that developed, and the subsequent response to combined IGF1R plus mTOR inhibitor therapy. In patient 2, upregulation of mTOR was seen in the primary tumor, perhaps explaining the initial response to the IGF1R and mTOR inhibitor combination, while the resistant tumor that emerged showed activation of the ERK pathway as well.Morphoproteomic analysis revealed that the mTOR pathway was activated in these two patients with advanced Ewing's sarcoma who showed response to combined IGF1R and mTOR inhibition, and the ERK pathway in the patient in whom resistance to this combination emerged. Our pilot results suggests that morphoproteomic assessment of signaling pathway activation in Ewing's sarcoma merits further investigation as a guide to understanding response and resistance signatures

Evaluation of the dual mTOR / PI3K inhibitors Gedatolisib (PF-05212384) and PF-04691502 against ovarian cancer xenograft models

We are grateful to Wyeth/Pfizer (ONC-EU-150) and to the Scottish Funding Council (SRDG HR07005) for support of this study.This study investigated the antitumour effects of two dual mTOR/PI3K inhibitors, gedatolisib (WYE-129587/PKI-587/PF-05212384) and PF-04691502 against a panel of six human patient derived ovarian cancer xenograft models. Both dual mTOR/PI3K inhibitors demonstrated antitumour activity against all xenografts tested. The compounds produced tumour stasis during the treatment period and upon cessation of treatment, tumours re-grew. In several models, there was an initial rapid reduction of tumour volume over the first week of treatment before tumour stasis. No toxicity was observed during treatment. Biomarker studies were conducted in two xenograft models; phospho-S6 (Ser235/236) expression (as a readout of mTOR activity) was reduced over the treatment period in the responding xenograft but expression increased to control (no treatment) levels on cessation of treatment. Phospho-AKT (Ser473) expression (as a readout of PI3K) was inhibited by both drugs but less markedly so than phospho-S6 expression. Initial tumour volume reduction on treatment and regrowth rate after treatment cessation was associated with phospho-S6/total S6 expression ratio. Both drugs produced apoptosis but minimally influenced markers of proliferation (Ki67, phospho-histone H3). These results indicate that mTOR/PI3K inhibition can produce broad spectrum tumour growth stasis in ovarian cancer xenograft models during continuous chronic treatment and this is associated with apoptosis.Publisher PDFPeer reviewe