Critical Regulator Of Cellular Metabolism Research Articles

Lysosomes in Stem Cell Quiescence: A Potential Therapeutic Target in Acute Myeloid Leukemia.

Simple SummaryLysosomes are a critical component of the inner membrane system and are involved in various cellular biological processes, including macromolecular degradation, antigen presentation, intracellular pathogen destruction, plasma membrane repair, exosome release, cell adhesion/migration, and apoptosis. Lysosomes are a critical regulator of cellular metabolism, cancer, metastasis, and resistance to anticancer therapy. Additionally, lysosomal activities play a crucial role in acute myeloid leukemia (AML) development and progression, as well as maintaining the hematopoietic stem cells (HSCs) pool. It has been shown that AML cells undergo metabolic alterations due to chemotherapy or targeted treatment. Thus, depending on the molecular subtypes of AML or the treatments involved, lysosomes could have a therapeutic potential.Lysosomes are cellular organelles that regulate essential biological processes such as cellular homeostasis, development, and aging. They are primarily connected to the degradation/recycling of cellular macromolecules and participate in cellular trafficking, nutritional signaling, energy metabolism, and immune regulation. Therefore, lysosomes connect cellular metabolism and signaling pathways. Lysosome’s involvement in the critical biological processes has rekindled clinical interest towards this organelle for treating various diseases, including cancer. Recent research advancements have demonstrated that lysosomes also regulate the maintenance and hemostasis of hematopoietic stem cells (HSCs), which play a critical role in the progression of acute myeloid leukemia (AML) and other types of cancer. Lysosomes regulate both HSCs’ metabolic networks and identity transition. AML is a lethal type of blood cancer with a poor prognosis that is particularly associated with aging. Although the genetic landscape of AML has been extensively described, only a few targeted therapies have been produced, warranting the need for further research. This review summarizes the functions and importance of targeting lysosomes in AML, while highlighting the significance of lysosomes in HSCs maintenance.

Quantitative Analyses Reveal How Hypoxia Reconfigures the Proteome of Primary Cytotoxic T Lymphocytes.

Metabolic and nutrient-sensing pathways play an important role in controlling the efficacy of effector T cells. Oxygen is a critical regulator of cellular metabolism. However, during immune responses T cells must function in oxygen-deficient, or hypoxic, environments. Here, we used high resolution mass spectrometry to investigate how the proteome of primary murine CD8+ cytotoxic T lymphocytes (CTLs) is reconfigured in response to hypoxia in vitro. We identified and quantified over 7,600 proteins and discovered that hypoxia increased the abundance of a selected number of proteins in CTLs. This included glucose transporters, metabolic enzymes, transcription factors, cytolytic effector molecules, checkpoint receptors and adhesion molecules. While some of these proteins may augment the effector functions of CTLs, others may limit their cytotoxicity. Moreover, we determined that hypoxia could inhibit IL-2-induced proliferation cues and antigen-induced pro-inflammatory cytokine production in CTLs. These data provide a comprehensive resource for understanding the magnitude of the CTL response to hypoxia and emphasise the importance of oxygen-sensing pathways for controlling CD8+ T cells. Additionally, this study provides new understanding about how hypoxia may promote the effector function of CTLs, while contributing to their dysfunction in some contexts.

Gastric Cancer Mesenchymal Stem Cells Inhibit NK Cell Function through mTOR Signalling to Promote Tumour Growth.

The dysfunction of natural killer (NK) cells has been increasingly reported in malignancies, especially in solid tumours. Mesenchymal stem cells (MSCs) exhibit pleiotropic functions that include mediating immune cell exhaustion which is implicated in cancer progression. However, the association of MSCs derived from gastric cancer (gastric cancer mesenchymal stem cells: GCMSCs) with the dysfunction of NK cells remains poorly understood. In this study, we demonstrated that GCMSCs effectively contributed to the exhaustion of NK cells through the release of soluble factors. Furthermore, passivation of the antitumour effect in NK cells was closely associated with their dysfunctional state. The GCMSC-conditioned medium prevented the frequency and effector function of infiltrating NK cells in tumour-bearing mouse models, thus promoting tumour growth. Mechanistically, mammalian target of rapamycin (mTOR) signalling, a critical regulator of cellular metabolism that mediates the function of immune cells, was inhibited in NK cells treated with GCMSCs. However, the checkpoint receptor PD-1 was still present at minimal levels with or without GCMSCs. The study results revealed that GCMSCs contributed to dysfunctional NK cells involved at least partially in the inhibition of mTOR signalling, suggesting potential directions for NK cell-based cancer immunotherapy.

Human Double-Negative Regulatory T-Cells Induce a Metabolic and Functional Switch in Effector T-Cells by Suppressing mTOR Activity.

The recently discovered population of TCRαβ+ CD4–/CD8– (double-negative, DN) T-cells are highly potent suppressor cells in mice and humans. In preclinical transplantation models, adoptive transfer of DN T-cells specifically inhibits alloreactive T-cells and prevents transplant rejection or graft-vs.-host disease (GvHD). Interestingly, clinical studies in patients who underwent allogeneic stem cell transplantation reveal an inverse correlation between the frequency of circulating DN T-cells and the severity of GvHD, suggesting a therapeutic potential of human DN T-cells. However, their exact mode of action has not been elucidated yet. Investigating the impact of DN T-cells on conventional T-cells, we found that human DN T-cells selectively inhibit mTOR signaling in CD4 T-cells. Given that mTOR is a critical regulator of cellular metabolism, we further determined the impact of DN T-cells on the metabolic framework of T-cells. Intriguingly, DN T-cells diminished expression of glucose transporters and glucose uptake, whereas fatty acid uptake was not modified, indicating that DN T-cells prevent metabolic adaptation of CD4 T-cells upon activation (i.e., glycolytic switch) thereby contributing to their suppression. Further analyses demonstrated that CD4 T-cells also do not upregulate homing receptors associated with inflammatory processes. In contrast, expression of central memory-cell associated cell surface markers and transcription factors were increased by DN T-cells. Moreover, CD4 T-cells failed to produce inflammatory cytokines after co-culture with DN T-cells, whereas IL-2 secretion was enhanced. Taken together DN T-cells impair metabolic reprogramming of conventional CD4 T-cells by abrogating mTOR signaling, thereby modulating CD4 T-cell functionality. These results uncover a new mechanism of DN T-cell-mediated suppression, pointing out that DN T-cells could serve as cell-based therapy to limit alloreactive immune response.

UCP2 overexpression enhanced glycolysis via activation of PFKFB2 during skin cell transformation.

Uncoupling protein 2 (UCP2) is an inner mitochondrial membrane transporter which is often upregulated in human cancers. However, how this anion transporter affects tumorigenesis is not well understood. Using the skin cell transformation JB6 model, we demonstrated that UCP2 overexpression activated phosphofructokinase 2/fructose-2,6-bisphosphatase 2 (PFKFB2), a key regulator of glycolysis. In conjunction, upregulation of PFKFB2 expression correlated with elevated fructose 2,6-bisphosphate (Fru-2,6-P2) levels, 6-phosphofructo-1-kinase (PFK-1) activity, glucose uptake, and lactate production. Inhibiting PFKFB2 expression suppressed UCP2-mediated skin cell transformation, decreased cell proliferation, and enhanced mitochondrial respiration, while dampening aerobic glycolysis. The AKT signaling pathway was activated in the UCP2 overexpressed cells; furthermore, the activated AKT signaling contributed to the activation of PFKFB2. Whereas AKT inactivation blocked PFKFB2 activation, suggesting that AKT activation is an important step in PFKFB2 activation. Collectively, our data suggest that UCP2 is a critical regulator of cellular metabolism during cell transformation. Our data also demonstrate a potentially novel mechanism to understand UCP2's tumor-promoting role, which is through the AKT-dependent activation of PFKFB2 and thereby, the metabolic shift to glycolysis (the Warburg effect).

Metabo-miR: miR-211 Regulates Mitochondrial Energy Metabolism in Vitiligo

The study by Sahoo etal. established miR-211 as a critical regulator of cellular metabolism in vitiligo cells. miR-211, which is expressed from the transient receptor potential melastatin 1 intronic region, regulates oxidative phosphorylation and mitochondrial energy metabolism in vitiligo. Loss of miR-211 in melanocytes was shown to alter expression patterns of newly identified target genes, and those that regulate respiratory functions in melanocytes are among them. This study highlights the importance of miR-211 for the melanocyte biology and development of vitiligo.

Human Double-Negative Regulatory T Cells Selectively Suppress mTOR Signaling and Metabolic Reprogramming of Conventional T Cells

Regulatory T (Treg) cells have been shown to be involved in downregulating immune responses in autoimmunity, transplant rejection, and graft-versus-host disease (GvHD). The subpopulation of TCRαβ+ CD4- CD8- (double-negative, DN) T cells has been described to suppress immune responses in both mice and humans. Of particular interest, infusion and/or activation of murine DN T cells specifically suppressed alloreactive T cells and prevented development of GvHD after allogeneic hematopoietic stem cell transplantation (SCT). Moreover, clinical studies in patients after SCT revealed an inverse correlation between the frequency of circulating DN T cells and the severity of GvHD, suggesting a therapeutic potential of human DN T cells. However, the molecular mechanism of suppression still remains unclear. To gain a better understanding of DN T-cell functionality, we investigated whether human DN T cells modulate distinct TCR signaling processes in conventional T cells. We found that DN T cells selectively inhibit the mechanistic target of rapamycin (mTOR) signaling pathway but not activation of mitogen-activated protein kinases (MAPK). The crucial function of mTOR signaling was confirmed by treating effector T cells with a chemical activator of protein kinase Akt, which induces mTOR phosphorylation. Indeed, enforced activation of the mTOR pathway rendered conventional T cells unsusceptible to DN T cell-mediated suppression. Given that mTOR is a critical regulator of cellular metabolism, we further determined the impact of DN T cells on the metabolic framework of conventional T cells. Intriguingly, DN T cells significantly diminished upregulation of the glycolytic machinery, expression of glucose transporters and glucose uptake in conventional T cells. These findings indicate that DN T cells inhibit metabolic reprogramming of conventional T cells by abrogating mTOR signaling, thereby inducing a quiescent phenotype. Further understanding of the mechanisms involved in human DN T-cell suppression may have important implications for using them as a cellular-based therapy to limit alloreactive immune responses. DisclosuresNo relevant conflicts of interest to declare.

Abstract 12448: AMPKα1 Knockout Mice Have Dysfunctional Perivascular Adipose Tissue (PVAT) and Impaired Vascular Function

Introduction: Perivascular adipose tissue (PVAT) surrounds blood vessels and releases many mediators which regulate vascular tone. AMP-activated protein kinase (AMPK) is a critical regulator of cellular metabolism and although expressed throughout the vessel wall, its function in PVAT is unknown. Although aortic PVAT from mice with global AMPKα1 knockout releases significantly less adiponectin and does not augment vasodilator responses in isolated vessels, these mice remain normotensive. Hypothesis: Mice with global AMPKα1 deficiency will have inflamed PVAT and that high fat feeding will increase PVAT inflammation further and raise blood pressure. Methods: Unfixed samples of wild-type (WT) and KO aortic PVAT (n>3 for each) were incubated with dihydroethidium (DHE) or 4,5 diaminofluorescein diacetate (DAF-2DA) to detect superoxide and NO respectively. Images were captured using a fluorescence microscope. Nitrotyrosine expression and macrophages in the PVAT were examined using immunohistochemistry and FACS respectively. Matched KO and WT littermates were fed either chow diet or hfd (21% lard, 0.15% chol.) for up to 12 weeks and BP measured by tail-cuff plethysmography every 4 weeks. Measurement of vascular function in aortic rings was via wire myography and adiponectin release was measured using ELISA assay. Results: In aortic PVAT, superoxide and NO production was unchanged in KO mice but nitrotyrosine expression and macrophage content was significantly higher. In WT mice, 12 weeks of hfd attenuated vasodilator responses of aortic rings containing PVAT (n=6; p<0.05) and reduced adiponectin production by PVAT. In KO rings containing PVAT the vasodilator response was already suppressed and hfd did not lower it further or alter production of adiponectin. High fat diet increased PVAT macrophage content of both WT and KO but did not alter mean arterial BP after 8 weeks in either strain. Conclusions: AMPK in aortic PVAT regulates production of adiponectin and suppresses inflammation. Mice lacking AMPKα1 lose the beneficial effects of PVAT on vascular relaxation and while fat feeding increases inflammation of the PVAT, BP did not rise, perhaps through compensation effects in smooth muscle or endothelial function.

Obese women experience impaired in vitro decidualization due to decreased autophagy

Endometrial Stromal Cell (ESC) decidualization is the process by which ESCs undergo morphologic and functional change in order to differentiate into decidual cells and become receptive to embryonic implantation. This process is metabolically regulated and defective decidualization can lead to infertility and poor pregnancy outcomes. Autophagy is the process of intracellular recycling and a critical regulator of cellular metabolism. In addition, autophagy has been shown to be defective in obese tissue.

Abstract 4963: A distinct AMP-activated protein kinase phosphorylation site is associated with metastasis and castration-resistance in prostate cancer

Abstract AMP-activated protein kinase (AMPK) is a critical regulator of cellular metabolism and plays important role in the development and progression of several human diseases including cancer. We have previously shown that AMPKα activity is significantly inhibited by Ser-485/491 phosphorylation in cell culture and in vivo models of metastatic and castration-resistant prostate cancer. To determine potential translatability, we investigated AMPKα-Ser-485/491 phosphorylation status in clinical prostate cancer specimens and its correlation with metastasis and progression to castration-resistance. Metastasis and matched primary tumor specimens from 45 metastatic prostate cancer patients, 31.1% of which were post-androgen deprivation therapy failure (castration-resistant prostate cancer), and primary tumor specimens from 30 non-metastatic, hormone-dependent prostate cancer patients with undetectable PSA for a mean of 97.1 ± 17.5 months were obtained from the University Hospitals Case Medical Center Pathology Archive. Slides were cut from paraffin blocks, immunostained for p-Ser-485/491 AMPKα and total AMPKα, analyzed by a pathologist, and statistical significance determined by T-test, Kruskal-Wallis test, Fisher's exact test, or Chi-Square test. Mean pre-diagnostic biopsy PSA was 6.5 ng/mL (range 1.20-25.3 ng/mL) in non-metastatic patients and 501.9 ng/mL (range 1.82-3200 ng/mL) in metastatic patients (p < 0.0001). Mean total Gleason score of primary tumors was 6.5 in the non-metastatic group and 8.2 in the metastatic group (p < 0.0001); primary prostate tumor volume (mean ± S.D.) was 22.1 ± 19.5% in the non-metastatic group and 68.1 ± 28.7% in the metastatic group (p < 0.0001). The intensity of overall p-Ser-485/491 AMPKα staining and the number of p-Ser-485/491 AMPKα positively-stained cells was significantly increased in primary prostate tumors (p = 0.0003 and p = 0.0008, respectively) and metastases (p = 0.0011 and p = 0.0062, respectively) of metastatic prostate cancer patients when compared to staining of primary tumor specimens from non-metastatic prostate cancer patients. Further, the intensity of overall p-Ser-485/491 AMPKα staining increased 2.21-fold (p = 0.0050) and the number of p-Ser-485/491 AMPKα positively-stained cells increased 1.77-fold (p = 0.0041) in castration-resistant metastatic prostate cancer specimens compared to androgen-dependent prostate cancer specimens. Therefore, AMPKα Ser-485/491 phosphorylation is associated with metastasis and castration-resistance in clinical prostate cancer and may be a novel target for treatment. Citation Format: Melissa A. Babcook, Mahmut Akgul, Seunghee Margevicius, Gregory T. MacLennan, Pingfu Fu, Robert Abouassaly, Sanjay Gupta. A distinct AMP-activated protein kinase phosphorylation site is associated with metastasis and castration-resistance in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4963.

Abstract B1-23: Early growth response (EGR1) is a critical regulator of cellular metabolism and predicts increased responsiveness to antiestrogens in breast cancer

Abstract Breast cancer is the most commonly diagnosed cancer in women and about 1 million new cases per year are diagnosed worldwide. About 70% of all breast cancers are estrogen receptor alpha positive (ER+). Antiestrogens (e.g., Tamoxifen or Faslodex) or aromatase inhibitors (e.g., Letrozole) are often used to treat ER+ breast cancers. However, resistance to these therapies (endocrine resistance) is prevalent in the clinic and the underlying mechanisms remain unclear. We have recently shown that the oncogene MYC is overexpressed in ER+ breast cancer and up-regulates glucose and glutamine uptake in endocrine resistant breast cancer cells, which suggests that the metabolomic profile of endocrine resistant breast cancer cells may contain features that are distinct from sensitive cells. In this study, to identify the biochemical pathways that are differentially regulated in endocrine resistance in breast cancer cells, we have analyzed gene expression data and untargeted metabolite profiles of ER+ MCF7-derived breast cancer cells that are antiestrogen sensitive (LCC1) or antiestrogen resistant (LCC9) under basal conditions. Glycolysis and glutamine-dependent pathways were increased in endocrine resistant cells. Integration of the transcriptomics and metabolomics data predicted an essential role for a gene-metabolite network associated with early growth response (EGR1) and glutamine metabolism in endocrine resistant cells. EGR1 is an immediate-early gene induced by E2, growth factors, or stress signals, and has been reported to exhibit both tumor suppressor and promoter activities, based on cellular context. While EGR1 mediated signaling is important for the normal development of female reproductive organs, its precise role in breast cancer remains unknown. EGR1 gene expression and protein levels were significantly higher in LCC1 cells compared with LCC9 cells. Kaplan-Meier survival curves with gene expression data obtained from ER+ human breast tumors treated with endocrine therapy show that higher EGR1 expression is associated with a more favorable prognosis: GSE17705 [HR=0.38 (0.21-0.69); p=0.00083], GSE6532 (ER+ samples on GPL96 platform) [HR=0.55 (0.34-0.9); p=0.017]. In GSE20181, pre-treatment vs 90 days post-treatment comparisons show significantly increased levels of EGR1 expression (p<0.0001) only in the responder group. Interestingly, in both LCC1 and LCC9 cells, EGR1 overexpression increased ER protein levels and cell proliferation while EGR1 knockdown decreased ER protein levels and cell proliferation. Therefore, to understand the precise role of down-regulated EGR1 in regulating cellular metabolism and survival in endocrine resistance, we compared metabolite profiles in LCC9 cells following knockdown or overexpression of EGR1. Several major biochemical pathways such as glycolysis, lipid metabolism, glutathione, and polyamine metabolism were shown to be regulated by EGR1 in LCC9 cells. Collectively, these findings indicate that down-regulated EGR1 is an important regulator of the aberrant cellular metabolic pathways specific to endocrine resistance. Furthermore, high levels of EGR1 may serve as a favorable prognostic marker in endocrine treatment strategies in breast cancer. Citation Format: Ayesha N. Shajahan-Haq, Lu Jin, Amrita K. Cheema, Simina M. Boca, Yuriy Gusev, Krithika Bhuvaneshwar, Diane M. Demas, Habtom Ressom, Ryan Michalek, Xi Chen, Jianhua Xuan, Subha Madhavan, Robert Clarke. Early growth response (EGR1) is a critical regulator of cellular metabolism and predicts increased responsiveness to antiestrogens in breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Computational and Systems Biology of Cancer; Feb 8-11 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 2):Abstract nr B1-23.

Protein phosphatase 2C-alpha knockdown reduces angiotensin II-mediated skeletal muscle wasting via restoration of mitochondrial recycling and function.

BackgroundCirculating angiotensin II (AngII) is elevated in congestive heart failure (CHF), and leads to skeletal muscle wasting, which is strongly associated with poor patient outcomes. We previously found that AngII upregulates protein phosphatase 2C-alpha (PP2Cα) and dephosphorylates AMP-activated protein kinase (AMPK), a critical regulator of cellular metabolism, in skeletal muscle.MethodsTo determine the role of PP2Cα in AngII-induced wasting, gastrocnemius (Gas) muscles of FVB mice were injected with scrambled or PP2Cα siRNA and mice were infused with saline or AngII for 4 days.ResultsKnockdown of PP2Cα reduced AngII wasting, blocked AngII upregulation of PP2Cα, increased p-T172-AMPK, and inhibited AngII-mediated reductions in peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), nuclear respiratory factor 1 (NRF1), mitochondrial transcription factor A (TFAM), in complex IV activity, and in ATP levels. AngII impaired the rate of autophagy as determined by a 2.4-fold increase in p62/SQSTM1 (p62) accumulation. This induction was reduced by PP2Cα knockdown, which also increased beclin-1 expression and microtubule-associated protein 1 light chain 3 (LC3)-II conversion in AngII-infused Gas. AngII reduced activating S555 phosphorylation of UNC-51-like kinase 1 (ULK1), a critical regulator of autophagosome formation, and increased inhibitory S757 ULK1 phosphorylation and these effects were prevented by PP2Cα siRNA.ConclusionsAngII inhibited AMPK activity and reduced PGC-1α and TFAM expression (thereby inhibiting mitochondrial biogenesis) and impaired ULK1 activation and autophagy (thereby also inhibiting clearance of damaged mitochondria), resulting in mitochondrial dysfunction, decreased ATP, and wasting. Knockdown of PP2Cα normalized AMPK activity, PGC-1α, NRF1, and TFAM levels and blocked AngII inhibition of ULK1, leading to improved mitochondrial biogenesis/recycling/function, energy production, and inhibition of AngII-induced wasting. These results demonstrate novel effects of AngII on cellular metabolism that are likely critical in mediating the muscle wasting that is a hallmark of CHF.

Acute tubular necrosis associated with mTOR inhibitor therapy: a real entity biopsy-proven

BackgroundThe protein kinase mTOR (mammalian target of rapamycin) is a critical regulator of cellular metabolism, growth, and proliferation. Inhibitors of mTOR have immunosuppressive and anti-cancer effects, but their effects on the progression of kidney disease are not fully understood. Their most common side-effects include stomatitis, rash, dyslipidemia, hyperglycemia, fatigue, and pneumonitis. However, to the best of our knowledge these agents have not been previously reported to cause severe acute kidney injury (AKI). Case presentationWe describe four cases of patients with cancer who developed AKI after starting mTOR inhibitor therapy. A kidney biopsy showed acute tubular necrosis (ATN) with prominent tubular dysfunction. Withdrawal of the drug leads to a rapid recovery in two cases. However, a fixed renal dysfunction was noted in the other two cases, one of which will remain dialysis-dependent. Such patients lead to a broad differential diagnosis of AKI including prerenal AKI, ATN, cancer-related GN, and drug-induced acute interstitial nephritis. Accurate history, physical examination, laboratory data, and kidney biopsy are highlighted in establishing the correct diagnosis in such patients. ConclusionsATN have not been reported with mTOR inhibitor use. These cases demonstrated a potentially new and serious adverse consequence occurring with the use of an mTOR inhibitor, of which physicians need to be aware.

Abstract SY29-01: mTOR, metabolism, and cell growth control

Abstract The mTOR complex 1 (mTORC1) is a ser/thr protein kinase complex and critical regulator of cellular metabolism, protein synthesis, autophagy and cell growth. This signaling system is normally carefully controlled by the integration of inputs from growth factors, nutrients, cellular energy status, oxygen availability and stress. A variety of loss-of-function or gain-of-function alterations in key mTORC1 regulatory proteins, very often results in inappropriate regulation of this signaling system. Uncontrolled mTORC1 activation contributes on its own or in combination with other pathways to metabolic diseases ranging from diabetes and obesity, cardiac hypertrophy, neurodegeneration, aging, benign tumor syndromes to highly malignant cancers. Mechanistically, uncontrolled mTORC1 activation leads to a constant positive input into anabolic processes and suppression of many catabolic processes. As a result, these cells require increased energy and carbon sources to meet their high metabolic needs for cell growth. To meet this demand, we have found in cells that are PTEN or TSC1/2 null, that activated mTORC1 uses distinct mechanisms to increase glutamine consumption (glutaminolysis) by elevating the expression of glutaminase and the activity of glutamate dehydrogenase. Furthermore, under nutrient-rich conditions, these tumor cells sense the increased energy production and in a positive feedback loop, promote more mTORC1 assembly via an AMP kinase (AMPK)-dependent, and a novel AMPK-independent mechanism. This acquired addiction to glutamine provides a novel therapeutic strategy for treating patients with activated mTORC1. Indeed, by acutely blocking the ability of energetically stressed cells with hyperactive mTORC1 to metabolize glutamine, we can selectively kill some tumor cells without damaging normal cells. We anticipate that these studies will lead to the development of “synthetic-lethal” drugs useful in the treatment of patients with diseases linked to inappropriate activation of mTORC1. Research supported by NIH RO1-GM51405 and the LAM Foundation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr SY29-01. doi:1538-7445.AM2012-SY29-01

MTOR downregulates iodide uptake in thyrocytes

Phosphoinositide-3-kinase (PI3K) inhibition increases functional sodium iodide symporter (NIS) expression in both FRTL-5 rat thyroid cell line and papillary thyroid cancer lineages. In several cell types, the stimulation of PI3K results in downstream activation of the mechanistic target of rapamycin (MTOR), a serine-threonine protein kinase that is a critical regulator of cellular metabolism, growth, and proliferation. MTOR activation is involved in the regulation of thyrocyte proliferation by TSH. Here, we show that MTOR inhibition by rapamycin increases iodide uptake in TSH-stimulated PCCL3 thyroid cell line, although the effect of rapamycin was less pronounced than PI3K inhibition. Thus, NIS inhibitory pathways stimulated by PI3K might also involve the activation of proteins other than MTOR. Insulin downregulates iodide uptake and NIS protein expression even in the presence of TSH, and both effects are counterbalanced by MTOR inhibition. NIS protein expression levels were correlated with iodide uptake ability, except in cells treated with TSH in the absence of insulin, in which rapamycin significantly increased iodide uptake, while NIS protein levels remained unchanged. Rapamycin avoids the activation of both p70 S6 and AKT kinases by TSH, suggesting the involvement of MTORC1 and MTORC2 in TSH effect. A synthetic analog of rapamycin (everolimus), which is clinically used as an anticancer agent, was able to increase rat thyroid iodide uptake in vivo. In conclusion, we show that MTOR kinase participates in the control of thyroid iodide uptake, demonstrating that MTOR not only regulates cell survival, but also normal thyroid cell function both in vitro and in vivo.