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G3BP, vigilin and TSC2 colocalize in stress granules.

Selected list of putative interacting TSC2 partners identified by yeast 2-hybrid analysis.

Tuberous sclerosis complex (TSC) is caused by mutations of either the TSC1 or TSC2 tumor suppressor gene. TSC causes tumors of the brain, heart, kidney, skin and lymphangioleiomyomatosis (LAM). Here we report that the TSC2 protein physically binds to high-density lipoprotein binding protein (HDLBP), also called vigilin, a core stress granule (SG) protein, and that TSC2 localizes to SGs. SGs contain mRNAs and translation initiation complexes, and regulate gene expression by sequestering specific transcripts, thereby serving a cytoprotective role. TSC2 has never before been shown to localize to SGs and knocking down vigilin impacts SG translocation of TSC2. TSC2-deficient cells showed a striking increase in the number of SGs after thermal shock and arsenite treatment relative to Tsc2-expressing cells. Our findings also show that murine kidney lysates from a model of TSC have increased levels of SG components including G3BP1 and Caprin1. G3BP1 and Caprin are elevated in renal angiomyolipomas (a renal tumor common in patients with TSC) compared with control normal kidney. G3BP1 is also elevated in TSC-associated subependymal giant cell astrocytomas. We found that genetic inhibition of G3BP1 inhibits the proliferation of TSC2-deficient cells in vitro. Finally, in a mouse model of TSC, genetic inhibition of SGs suppresses cell growth, suggesting that targeting SGs may have efficacy in the therapy of TSC.Implications:This study demonstrates that TSC2 physically interacts with HDLBP/vigilin, a component of SGs, that TSC2 localizes to SG and that TSC2-deficient cells have more SGs, suggesting that SGs represent a novel therapeutic target in TSC.

Lipidomic analysis of ritanserin treated Tsc2-deficient cells

Metabolites significantly changed by p62 knockdown in Tsc2-/- MEFs

p62/sequestosome-1 (SQSTM1) is a multifunctional adaptor protein and autophagic substrate that accumulates in cells with hyperactive mTORC1, such as kidney cells with mutations in the tumor suppressor genes tuberous sclerosis complex (TSC)1 or TSC2. Here we report that p62 is a critical mediator of TSC2-driven tumorigenesis, as Tsc2+/− and Tsc2f/f CAGGCreERT2+ mice crossed to p62−/− mice were protected from renal tumor development. Metabolic profiling revealed that depletion of p62 in Tsc2-null cells decreased intracellular glutamine, glutamate, and glutathione (GSH). p62 positively regulated the glutamine transporter Slc1a5 and increased glutamine uptake in Tsc2-null cells. We also observed p62-dependent changes in Gcl, Gsr, Nqo1, and Srxn1, which were decreased by p62 attenuation and implicated in GSH production and utilization. p62 attenuation altered mitochondrial morphology, reduced mitochondrial membrane polarization and maximal respiration, and increased mitochondrial reactive oxygen species and mitophagy marker PINK1. These mitochondrial phenotypes were rescued by addition of exogenous GSH and overexpression of Sod2, which suppressed indices of mitochondrial damage and promoted growth of Tsc2-null cells. Finally, p62 depletion sensitized Tsc2-null cells to both oxidative stress and direct inhibition of GSH biosynthesis by buthionine sulfoximine. Our findings show how p62 helps maintain intracellular pools of GSH needed to limit mitochondrial dysfunction in tumor cells with elevated mTORC1, highlighting p62 and redox homeostasis as nodal vulnerabilities for therapeutic targeting in these tumors. Cancer Res; 77(12); 3255–67. ©2017 AACR.

Sod2 overexpression reduces the percentage of MitoSOX positive cells assessed by flow cytometry

Lymphangioleiomyomatosis is a rare destructive lung disease affecting primarily women and is the primary lung manifestation of tuberous sclerosis complex (TSC). In lymphangioleiomyomatosis, biallelic loss of TSC1/2 leads to hyperactivation of mTORC1 and inhibition of autophagy. To determine how the metabolic vulnerabilities of TSC2-deficient cells can be targeted, we performed a high-throughput screen utilizing the “Repurposing” library at the Broad Institute of MIT and Harvard (Cambridge, MA), with or without the autophagy inhibitor chloroquine. Ritanserin, an inhibitor of diacylglycerol kinase alpha (DGKA), was identified as a selective inhibitor of proliferation of Tsc2−/− mouse embryonic fibroblasts (MEF), with no impact on Tsc2+/+ MEFs. DGKA is a lipid kinase that metabolizes diacylglycerol to phosphatidic acid, a key component of plasma membranes. Phosphatidic acid levels were increased 5-fold in Tsc2−/− MEFs compared with Tsc2+/+ MEFs, and treatment of Tsc2−/− MEFs with ritanserin led to depletion of phosphatidic acid as well as rewiring of phospholipid metabolism. Macropinocytosis is known to be upregulated in TSC2-deficient cells. Ritanserin decreased macropinocytic uptake of albumin, limited the number of lysosomes, and reduced lysosomal activity in Tsc2−/− MEFs. In a mouse model of TSC, ritanserin treatment decreased cyst frequency and volume, and in a mouse model of lymphangioleiomyomatosis, genetic downregulation of DGKA prevented alveolar destruction and airspace enlargement. Collectively, these data indicate that DGKA supports macropinocytosis in TSC2-deficient cells to maintain phospholipid homeostasis and promote proliferation. Targeting macropinocytosis with ritanserin may represent a novel therapeutic approach for the treatment of TSC and lymphangioleiomyomatosis.Significance:This study identifies macropinocytosis and phospholipid metabolism as novel mechanisms of metabolic homeostasis in mTORC1-hyperactive cells and suggest ritanserin as a novel therapeutic strategy for use in mTORC1-hyperactive tumors, including pancreatic cancer.

Supplementary Materials and Methods

Raw data and bioinformatic analysis of metabolomics and ion torrent expression profiling

Chromophobe (Ch) renal cell carcinoma (RCC) arises from the intercalated cell in the distal nephron. There are no proven treatments for metastatic ChRCC. A distinguishing characteristic of ChRCC is strikingly high levels of reduced (GSH) and oxidized (GSSG) glutathione. Here, we demonstrate that ChRCC-derived cells exhibit higher sensitivity to ferroptotic inducers compared with clear-cell RCC. ChRCC-derived cells are critically dependent on cystine via the cystine/glutamate antiporter xCT to maintain high levels of glutathione, making them sensitive to inhibitors of cystine uptake and cyst(e)inase. Gamma-glutamyl transferase 1 (GGT1), a key enzyme in glutathione homeostasis, is markedly suppressed in ChRCC relative to normal kidney. Importantly, GGT1 overexpression inhibits the proliferation of ChRCC cells in vitro and in vivo, suppresses cystine uptake, and decreases levels of GSH and GSSG. Collectively, these data identify ferroptosis as a metabolic vulnerability in ChRCC, providing a potential avenue for targeted therapy for these distinctive tumors.

Lymphangioleiomyomatosis is a rare destructive lung disease affecting primarily women and is the primary lung manifestation of tuberous sclerosis complex (TSC). In lymphangioleiomyomatosis, biallelic loss of TSC1/2 leads to hyperactivation of mTORC1 and inhibition of autophagy. To determine how the metabolic vulnerabilities of TSC2-deficient cells can be targeted, we performed a high-throughput screen utilizing the “Repurposing” library at the Broad Institute of MIT and Harvard (Cambridge, MA), with or without the autophagy inhibitor chloroquine. Ritanserin, an inhibitor of diacylglycerol kinase alpha (DGKA), was identified as a selective inhibitor of proliferation of Tsc2−/− mouse embryonic fibroblasts (MEF), with no impact on Tsc2+/+ MEFs. DGKA is a lipid kinase that metabolizes diacylglycerol to phosphatidic acid, a key component of plasma membranes. Phosphatidic acid levels were increased 5-fold in Tsc2−/− MEFs compared with Tsc2+/+ MEFs, and treatment of Tsc2−/− MEFs with ritanserin led to depletion of phosphatidic acid as well as rewiring of phospholipid metabolism. Macropinocytosis is known to be upregulated in TSC2-deficient cells. Ritanserin decreased macropinocytic uptake of albumin, limited the number of lysosomes, and reduced lysosomal activity in Tsc2−/− MEFs. In a mouse model of TSC, ritanserin treatment decreased cyst frequency and volume, and in a mouse model of lymphangioleiomyomatosis, genetic downregulation of DGKA prevented alveolar destruction and airspace enlargement. Collectively, these data indicate that DGKA supports macropinocytosis in TSC2-deficient cells to maintain phospholipid homeostasis and promote proliferation. Targeting macropinocytosis with ritanserin may represent a novel therapeutic approach for the treatment of TSC and lymphangioleiomyomatosis. Significance: This study identifies macropinocytosis and phospholipid metabolism as novel mechanisms of metabolic homeostasis in mTORC1-hyperactive cells and suggest ritanserin as a novel therapeutic strategy for use in mTORC1-hyperactive tumors, including pancreatic cancer.

Therapies with the mechanistic target of rapamycin complex 1 (mTORC1) inhibitors are not fully curative for tuberous sclerosis complex (TSC) patients. Here, we propose that some mTORC1-independent disease facets of TSC involve signaling through redox factor-1 (Ref-1). Ref-1 possesses a redox signaling activity that stimulates the transcriptional activity of STAT3, NF-kB, and HIF-1α, which are involved in inflammation, proliferation, angiogenesis, and hypoxia, respectively. Here, we demonstrate that redox signaling through Ref-1 contributes to metabolic transformation and tumor growth in TSC cell model systems. In TSC2-deficient cells, the clinically viable Ref-1 inhibitor APX3330 was effective at blocking the hyperactivity of STAT3, NF-kB, and HIF-1α. While Ref-1 inhibitors do not inhibit mTORC1, they potently block cell invasion and vasculature mimicry. Of interest, we show that cell invasion and vasculature mimicry linked to Ref-1 redox signaling are not blocked by mTORC1 inhibitors. Metabolic profiling revealed that Ref-1 inhibitors alter metabolites associated with the glutathione antioxidant pathway as well as metabolites that are heavily dysregulated in TSC2-deficient cells involved in redox homeostasis. Therefore, this work presents Ref-1 and associated redox-regulated transcription factors such as STAT3, NF-kB, and HIF-1α as potential therapeutic targets to treat TSC, where targeting these components would likely have additional benefits compared to using mTORC1 inhibitors alone.

Tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM) are caused by aberrant mechanistic Target of Rapamycin Complex 1 (mTORC1) activation due to loss of either TSC1 or TSC2. Cytokine profiling of TSC2-deficient LAM patient-derived cells revealed striking upregulation of Interleukin-6 (IL-6). LAM patient plasma contained increased circulating IL-6 compared with healthy controls, and TSC2-deficient cells showed upregulation of IL-6 transcription and secretion compared to wildtype cells. IL-6 blockade repressed the proliferation and migration of TSC2-deficient cells and reduced oxygen consumption and extracellular acidification. U-13C glucose tracing revealed that IL-6 knockout reduced 3-phosphoserine and serine production in TSC2-deficient cells, implicating IL-6 in de novo serine metabolism. IL-6 knockout reduced expression of phosphoserine aminotransferase 1 (PSAT1), an essential enzyme in serine biosynthesis. Importantly, recombinant IL-6 treatment rescued PSAT1 expression in the TSC2-deficient, IL-6 knockout clones selectively and had no effect on wildtype cells. Treatment with anti-IL-6 (aIL-6) antibody similarly reduced cell proliferation and migration and reduced renal tumors in Tsc2+/- mice, while reducing PSAT1 expression. These data reveal a novel mechanism through which IL-6 regulates serine biosynthesis, with potential relevance to the therapy of tumors with mTORC1 hyperactivity.ClassificationMajor category: Biological Sciences Minor category: Cell Biology

Tuberous Sclerosis Complex (TSC) is caused by TSC1 or TSC2 mutations, resulting in hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1). Transcription factor EB (TFEB), a master regulator of lysosome biogenesis, is negatively regulated by mTORC1 through a RAG GTPase-dependent phosphorylation. Here we show that lysosomal biogenesis is increased in TSC-associated renal tumors, pulmonary lymphangioleiomyomatosis, kidneys from Tsc2+/− mice, and TSC1/2-deficient cells via a TFEB-dependent mechanism. Interestingly, in TSC1/2-deficient cells, TFEB is hypo-phosphorylated at mTORC1-dependent sites, indicating that mTORC1 is unable to phosphorylate TFEB in the absence of the TSC1/2 complex. Importantly, overexpression of folliculin (FLCN), a GTPase activating protein for RAGC, increases TFEB phosphorylation at the mTORC1 sites in TSC2-deficient cells. Overexpression of constitutively active RAGC is sufficient to relocalize TFEB to the cytoplasm. These findings establish the TSC proteins as critical regulators of lysosomal biogenesis via TFEB and RAGC and identify TFEB as a driver of the proliferation of TSC2-deficient cells., Tuberous sclerosis complex (TSC) is a multiorgan disease that can lead to hyperactive mTORC1 due to deficient TSC1 or TSC2 protein function. Here, the authors find that despite high mTORC1 activity, TFEB localizes to the nucleus and drives lysosomal gene expression via a non-canonical Rag-dependent mechanism.

Tuberous sclerosis complex (TSC) is a genetic disorder in which tumors develop due to TSC1/TSC2 loss and activation of mTORC1. Zarei et al. show that TSC tumors are sensitive to CDK7 inhibition, which reduces expression of NRF2 and glutathione synthetic genes, leading to glutathione depletion and ROS-mediated cell death., Tuberous sclerosis complex (TSC) is characterized by tumor development in the brain, heart, kidney, and lungs. In TSC tumors, loss of the TSC1/TSC2 protein complex leads to activation of mTORC1 with downstream effects on anabolism and cell growth. Because mTORC1 activation enhances mRNA transcription, we hypothesized that aberrant mTORC1 activation might confer TSC-null cell dependence on transcriptional regulation. We demonstrate that TSC1- or TSC2-null cells, in contrast to their wild-type counterparts, are sensitive to pharmacological inhibition of CDK7. Mechanistic studies revealed that CDK7 inhibition markedly reduces glutathione levels and increases reactive oxygen species due to reduced expression of NRF2 and glutathione biosynthesis genes. Treatment of both Tsc2+/− mice and a TSC1-null bladder cancer xenograft model with a CDK7 inhibitor showed marked reduction in tumor volume and absence of regrowth in the xenograft model. These results suggest that CDK7 inhibition is a promising therapeutic approach for treatment of TSC-associated tumors and cancers with mutations in either TSC1 or TSC2.

Tuberous sclerosis complex (TSC) is caused by mutations of either the TSC1 or TSC2 tumor suppressor gene. TSC causes tumors of the brain, heart, kidney, skin and lymphangioleiomyomatosis (LAM). Here we report that the TSC2 protein physically binds to high-density lipoprotein binding protein (HDLBP), also called vigilin, a core stress granule (SG) protein, and that TSC2 localizes to SGs. SGs contain mRNAs and translation initiation complexes, and regulate gene expression by sequestering specific transcripts, thereby serving a cytoprotective role. TSC2 has never before been shown to localize to SGs and knocking down vigilin impacts SG translocation of TSC2. TSC2-deficient cells showed a striking increase in the number of SGs after thermal shock and arsenite treatment relative to Tsc2-expressing cells. Our findings also show that murine kidney lysates from a model of TSC have increased levels of SG components including G3BP1 and Caprin1. G3BP1 and Caprin are elevated in renal angiomyolipomas (a renal tumor common in patients with TSC) compared with control normal kidney. G3BP1 is also elevated in TSC-associated subependymal giant cell astrocytomas. We found that genetic inhibition of G3BP1 inhibits the proliferation of TSC2-deficient cells in vitro. Finally, in a mouse model of TSC, genetic inhibition of SGs suppresses cell growth, suggesting that targeting SGs may have efficacy in the therapy of TSC. Implications: This study demonstrates that TSC2 physically interacts with HDLBP/vigilin, a component of SGs, that TSC2 localizes to SG and that TSC2-deficient cells have more SGs, suggesting that SGs represent a novel therapeutic target in TSC.

Chronic obstructive pulmonary disease (COPD) involves aberrant airway inflammatory responses to cigarette smoke (CS) that are associated with epithelial cell dysfunction, cilia shortening, and mucociliary clearance disruption. Exposure to CS reduced cilia length and induced autophagy in vivo and in differentiated mouse tracheal epithelial cells (MTECs). Autophagy-impaired (Becn1+/– or Map1lc3B–/–) mice and MTECs resisted CS-induced cilia shortening. Furthermore, CS increased the autophagic turnover of ciliary proteins, indicating that autophagy may regulate cilia homeostasis. We identified cytosolic deacetylase HDAC6 as a critical regulator of autophagy-mediated cilia shortening during CS exposure. Mice bearing an X chromosome deletion of Hdac6 (Hdac6–/Y) and MTECs from these mice had reduced autophagy and were protected from CS-induced cilia shortening. Autophagy-impaired Becn1–/–, Map1lc3B–/–, and Hdac6–/Y mice or mice injected with an HDAC6 inhibitor were protected from CS-induced mucociliary clearance (MCC) disruption. MCC was preserved in mice given the chemical chaperone 4-phenylbutyric acid, but was disrupted in mice lacking the transcription factor NRF2, suggesting that oxidative stress and altered proteostasis contribute to the disruption of MCC. Analysis of human COPD specimens revealed epigenetic deregulation of HDAC6 by hypomethylation and increased protein expression in the airways. We conclude that an autophagy-dependent pathway regulates cilia length during CS exposure and has potential as a therapeutic target for COPD.

Acute respiratory distress syndrome (ARDS) is a highly lethal condition that impairs lung function and causes respiratory failure. Mechanical ventilation maintains gas exchange in patients with ARDS, but exposes lung cells to physical forces that exacerbate lung injury. Our data demonstrate that mTOR complex 1 (mTORC1) is a mechanosensor in lung epithelial cells and that activation of this pathway during mechanical ventilation exacerbates lung injury. We found that mTORC1 is activated in lung epithelial cells following volutrauma and atelectrauma in mice and humanized in vitro models of the lung microenvironment. mTORC1 is also activated in lung tissue of mechanically ventilated patients with ARDS. Deletion of Tsc2, a negative regulator of mTORC1, in epithelial cells exacerbates physiologic lung dysfunction during mechanical ventilation. Conversely, treatment with rapamycin at the time mechanical ventilation is initiated prevents physiologic lung injury (i.e. decreased compliance) without altering lung inflammation or barrier permeability. mTORC1 inhibition mitigates physiologic lung injury by preventing surfactant dysfunction during mechanical ventilation. Our data demonstrate that in contrast to canonical mTORC1 activation under favorable growth conditions, activation of mTORC1 during mechanical ventilation exacerbates lung injury and inhibition of this pathway may be a novel therapeutic target to mitigate ventilator induced lung injury during ARDS.

Tuberous sclerosis complex (TSC) is an autosomal dominant disease caused by germline inactivating mutations of TSC1 or TSC2. In TSC-associated tumors of the brain, heart, skin, kidney and lung, inactivation of both alleles of TSC1 or TSC2 leads to hyperactivation of the mTORC1 pathway. The TSC/mTORC1 pathway is a key regulator of cellular processes related to growth, proliferation and autophagy. We and others have previously found that mTORC1 regulates microRNA biogenesis, but the mechanisms are not fully understood. Microprocessor, a multi-protein complex including the nuclease Drosha, processes the primary miR transcript. Using a dual-luciferase reporter, we found that inhibition of mTORC1 or downregulation of Raptor decreased Microprocessor activity, while loss of TSC2 led to a striking increase (∼5-fold) in Microprocessor activity. To determine the global impact of TSC2 on microRNAs we quantitatively analyzed 752 microRNAs in Tsc2-expressing and Tsc2-deficient cells. Out of 259 microRNAs expressed in both cell lines, 137 were significantly upregulated and 24 were significantly downregulated in Tsc2-deficient cells, consistent with the increased Microprocessor activity. Microprocessor activity is known to be regulated in part by GSK3β. We found that total GSK3β levels were higher in Tsc2-deficient cells, and the increase in Microprocessor activity associated with Tsc2 loss was reversed by three different GSK3β inhibitors. Furthermore, mTOR inhibition increased the levels of phospho-GSK3β (S9), which negatively affects Microprocessor activity. Taken together these data reveal that TSC2 regulates microRNA biogenesis and Microprocessor activity via GSK3β.

BackgroundBiomarkers of disease progression and treatment response are urgently needed for patients with lymphangioleiomyomatosis (LAM). Activity-based nanosensors, an emerging biosensor class, detect dysregulated proteases in vivo and release a reporter to provide a urinary readout of disease. Because proteases are dysregulated in LAM and may directly contribute to lung function decline, activity-based nanosensors may enable quantitative, real-time monitoring of LAM progression and treatment response. We aimed to assess the diagnostic utility of activity-based nanosensors in a pre-clinical model of pulmonary LAM.MethodsTsc2-null cells were injected intravenously into female nude mice to establish a mouse model of pulmonary LAM. A library of 14 activity-based nanosensors, designed to detect proteases across multiple catalytic classes, was administered into the lungs of LAM mice and healthy controls, urine was collected, and mass spectrometry was performed to measure nanosensor cleavage products. Mice were then treated with rapamycin and monitored with activity-based nanosensors. Machine learning was performed to distinguish diseased from healthy and treated from untreated mice.ResultsMultiple activity-based nanosensors (PP03 (cleaved by metallo, aspartic and cysteine proteases), padjustedadjusted=0.017)) were differentially cleaved in diseased and healthy lungs, enabling strong classification with a machine learning model (area under the curve (AUC) 0.95 from healthy). Within 2 days after rapamycin initiation, we observed normalisation of PP03 and PP10 cleavage, and machine learning enabled accurate classification of treatment response (AUC 0.94 from untreated).ConclusionsActivity-based nanosensors enable noninvasive, real-time monitoring of disease burden and treatment response in a pre-clinical model of LAM.

// Hilaire C. Lam 1 , Heng-Jia Liu 1 , Christian V. Baglini 1 , Harilaos Filippakis 1 , Nicola Alesi 1 , Julie Nijmeh 1 , Heng Du 1 , Alicia Llorente Lope 1 , Katherine A. Cottrill 2 , Adam Handen 2 , John M. Asara 3 , David J. Kwiatkowski 1 , Issam Ben-Sahra 4 , William M. Oldham 1 , Stephen Y. Chan 2 and Elizabeth P. Henske 1 1 Department of Medicine, Pulmonary and Critical Care Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA 2 Department of Medicine, Division of Cardiology, Center for Pulmonary Vascular Biology and Medicine, Pittsburgh Heart, Lung, Blood, and Vascular Medicine Institute, University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center, Pittsburgh, PA, USA 3 Department of Medicine, Division of Signal Transduction, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA 4 Department of Biochemistry and Molecular Genetics, Northwestern University, Chicago, IL, USA Correspondence to: Elizabeth P. Henske, email: // Keywords : tuberous sclerosis complex, mTORC1, rapamycin, miR-21, mitochondria Received : June 20, 2017 Accepted : June 25, 2017 Published : August 04, 2017 Abstract mTORC1 hyperactivation drives the multi-organ hamartomatous disease tuberous sclerosis complex (TSC). Rapamycin inhibits mTORC1, inducing partial tumor responses; however, the tumors regrow following treatment cessation. We discovered that the oncogenic miRNA, miR-21, is increased in Tsc2-deficient cells and, surprisingly, further increased by rapamycin. To determine the impact of miR-21 in TSC, we inhibited miR-21 in vitro . miR-21 inhibition significantly repressed the tumorigenic potential of Tsc2-deficient cells and increased apoptosis sensitivity. Tsc2-deficient cells’ clonogenic and anchorage independent growth were reduced by ~50% ( p

p62/sequestosome-1 (SQSTM1) is a multifunctional adaptor protein and autophagic substrate that accumulates in cells with hyperactive mTORC1, such as kidney cells with mutations in the tumor suppressor genes tuberous sclerosis complex (TSC)1 or TSC2. Here we report that p62 is a critical mediator of TSC2-driven tumorigenesis, as Tsc2+/− and Tsc2f/f CAGGCreERT2+ mice crossed to p62−/− mice were protected from renal tumor development. Metabolic profiling revealed that depletion of p62 in Tsc2-null cells decreased intracellular glutamine, glutamate, and glutathione (GSH). p62 positively regulated the glutamine transporter Slc1a5 and increased glutamine uptake in Tsc2-null cells. We also observed p62-dependent changes in Gcl, Gsr, Nqo1, and Srxn1, which were decreased by p62 attenuation and implicated in GSH production and utilization. p62 attenuation altered mitochondrial morphology, reduced mitochondrial membrane polarization and maximal respiration, and increased mitochondrial reactive oxygen species and mitophagy marker PINK1. These mitochondrial phenotypes were rescued by addition of exogenous GSH and overexpression of Sod2, which suppressed indices of mitochondrial damage and promoted growth of Tsc2-null cells. Finally, p62 depletion sensitized Tsc2-null cells to both oxidative stress and direct inhibition of GSH biosynthesis by buthionine sulfoximine. Our findings show how p62 helps maintain intracellular pools of GSH needed to limit mitochondrial dysfunction in tumor cells with elevated mTORC1, highlighting p62 and redox homeostasis as nodal vulnerabilities for therapeutic targeting in these tumors. Cancer Res; 77(12); 3255–67. ©2017 AACR.

miR-29b has been identified as a rapamycin-induced microRNA (miRNA) in Tsc2-deficient, mTORC1-hyperactive cells. The biological significance of this induction of miR-29b is unknown. We have found that miR-29b acts as an oncogenic miRNA in Tsc2-deficient cells: inhibition of miR-29b suppressed cell proliferation, anchorage-independent cell growth, cell migration, invasion, and the growth of Tsc2-deficient tumors in vivo. Importantly, the combination of miR-29b inhibition with rapamycin treatment further inhibited these tumor-associated cellular processes. To gain insight into the molecular mechanisms by which miR-29b promotes tumorigenesis, we used RNA sequencing to identify the tumor suppressor retinoid receptor beta (RARβ) as a target gene of miR-29b. We found that miR-29b directly targeted the 3′UTR of RARβ. Forced expression of RARβ reversed the effects of miR-29b overexpression in proliferation, migration, and invasion, indicating that it is a critical target. miR-29b expression correlated with low RARβ expression in renal clear cell carcinomas and bladder urothelial carcinomas, tumors associated with TSC gene mutations. We further identified growth family member 4 (ING4) as a novel interacting partner of RARβ. Overexpression of ING4 inhibited the migration and invasion of Tsc2-deficient cells while silencing of ING4 reversed the RARβ-mediated suppression of cell migration and invasion. Taken together, our findings reveal a novel miR-29b/RARβ/ING4 pathway that regulates tumorigenic properties of Tsc2-deficient cells, and that may serve as a potential therapeutic target for TSC, lymphangioleiomyomatosis (LAM), and other mTORC1-hyperactive tumors.

In just the past 5 years, dramatic changes have occurred in the clinical management of tuberous sclerosis complex (TSC). Detailed knowledge about the role of the TSC proteins in regulating the activity of the mammalian target of rapamycin complex 1 (mTORC1) underlies this paradigm-shifting progress. Advances continue to be made in understanding the genetic pathogenesis of the different tumours that occur in TSC, including pivotal discoveries using next-generation sequencing (NGS). For example, the pathogenesis of angiofibromas is now known to involve UV-induced mutations, and the pathogenesis of multifocal renal cell carcinoma (RCC) in TSC is now known to result from distinct second-hit mutations. In parallel, the pathological features of TSC-associated tumours, including TSC-associated renal cell carcinoma, continue to be defined, despite the fact that TSC was first described 180 years ago. Here, we review recent discoveries related to the pathological features and genetic pathogenesis of TSC-associated tumours. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

p62/sequestosome-1 (SQSTM1) is a multifunctional adaptor protein and autophagic substrate which accumulates in cells with hyperactive mTORC1, such as kidney cells with mutations in the tumor suppressor genes TSC1 or TSC2. Here we report that p62 is a critical mediator of TSC2-driven tumorigenesis, as Tsc2+/− and Tsc2f/f Ksp-CreERT2+ mice crossed to p62−/− mice were protected from renal tumor development. Metabolic profiling revealed that depletion of p62 in Tsc2-null cells decreased intracellular glutamine, glutamate, and glutathione (GSH). p62 positively regulated the glutamine transporter Slc1a5 and increased glutamine uptake in Tsc2-null cells. We also observed p62-dependent changes in Gcl, Gsr, Nqo1 and Srxn1 which were decreased by p62 attenuation and implicated in GSH production and utilization. p62 attenuation altered mitochondrial morphology, reduced mitochondrial membrane polarization and maximal respiration, and increased mitochondrial ROS and mitophagy marker PINK1. These mitochondrial phenotypes were rescued by addition of exogenous GSH and overexpression of Sod2, which suppressed indices of mitochondrial damage and promoted growth of Tsc2-null cells. Finally, p62 depletion sensitized Tsc2-null cells to both oxidative stress and direct inhibition of glutathione biosynthesis by buthionine sulfoximine (BSO). Our findings show how p62 helps maintain intracellular pools of glutathione needed to limit mitochondrial dysfunction in tumor cells with elevated mTORC1, highlighting p62 and redox homeostasis as nodal vulnerabilities for therapeutic targeting in these tumors.

Purpose: The mechanistic/mammalian target of rapamycin complex 1 (mTORC1) is constitutively active in many human cancers and in tuberous sclerosis complex (TSC). mTORC1 hyperactivation drives extensive metabolic reprogramming via several interconnected mechanisms, including glucose and glutamine utilization, nucleic acid synthesis, and lipid synthesis. We recently found that treatment with chloroquine (CQ), a lysosomal/autophagy inhibitor, upregulates the uptake and endosomal processing of cholesterol selectively in TSC2-deficient cells, creating a TSC2-specific dependence on exogenous cholesterol. This dependence on exogenous nutrients and the mechanisms of nutrient uptake may be therapeutically targetable. Our central hypothesis is that Tsc2-deficient cells depend on the uptake of exogenous nutrients via macropinocytosis to maintain cellular metabolic homeostasis and proliferation. Methods and Results: To investigate the role of macropinocytosis-mediated nutrient uptake in Tsc2-deficient cells, we measured the uptake of dextran, a polysaccharide taken up via macropinocytosis. Tsc2-deficient cells showed a striking increase in both dextran (3.6-fold, p Conclusions: These data suggest that macropinocytosis is upregulated in Tsc2-deficient cells via a Vps34-dependent mechanism to support tumorigenesis. Macropinocytosis-mediated nutrient uptake represents an unexplored opportunity for therapeutic intervention in TSC and may also be relevant to other diseases characterized by mTORC1 hyperactivation. Citation Format: Charilaos Filippakis, Amine Belaid, Brian Siroky, Constance Wu, Nicola Alesi, Thomas Alesi, Julie Nijmeh, Hilaire Colletta Lam, Ellizabeth Henske. Vps34 promotes macropinocytosis in Tsc2-deficient cells [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr A01.

Tuberous sclerosis complex (TSC) is an incurable multisystem disease associated with hamartomatous tumors of brain, heart, skin, kidney and lung. The TSC proteins (TSC1 and TSC2) inhibit the mechanistic/mammalian target of rapamycin complex 1 (mTORC1), an exquisitely sensitive molecular sensor that regulates cell growth, cell metabolism and autophagy. mTORC1 is hyperactive in many malignancies, including TSC. Treatment of TSC-associated tumors with mTOR inhibitors leads to partial responses, with prompt regrowth upon treatment cessation, highlighting the unmet clinical need for cytocidal therapies. We previously discovered that miR-29b expression is strongly upregulated following rapamycin treatment. However, the functional significance and therapeutic impact of miR-29b induction by rapamycin in the therapy of TSC is unknown. We found that miR-29b expression is induced by rapamycin in vitro in 4 different TSC2-deficient cells and in vivo TSC-2 deficient tumors. Inhibition of miR-29b significantly decreased anchorage-independent cell growth by 40% (p < 0.01), and combined rapamycin treatment and miR-29b inhibition further suppressed growth by 73% (p < 0.0001). In addition, miR-29b knockdown inhibited cell migration and invasion by 68% (p < 0.05) and 50% (p < 0.01), respectively. miR-29b inhibition combined with rapamycin further decreased cell migration and invasion by 77% (p < 0.001) and 74% (p < 0.001), respectively. These findings suggest that miR-29b acts as an “onco-miR” in this context. Importantly, miR-29b knockdown in TSC2-deficient cells significantly suppressed tumorigenesis in vivo by 52% (p < 0.0001). Furthermore, the combination of rapamycin and miR-29b inhibition resulted in a more robust inhibition of tumor volume compared with miR control (47% vs. 24% inhibition) (p < 0.01). To gain insight into the molecular mechanisms by which miR-29b promotes tumorigenesis, we performed RNA-sequencing on miR-29b knockdown and control cells treated with rapamycin. 236 genes were upregulated in miR-29b knockdown cells by at least 2.0-fold and p < 0.05. Retinoid receptor beta (RARβ), one of the candidates, was increased in miR-29b knockdown cells at the mRNA level by 2.25-fold (p < 0.01) and protein expression by 2-fold (p < 0.05). RARβ is a tumor suppressor in many types of tumors. Interestingly, RARβ expression is downregulated by rapamycin (67% (p < 0.001)) and upregulated 4-fold following miR-29b inhibition (p < 0.05). Lastly, we found the 3'UTR activity of RARβ was upregulated in miR-29b knockdown cells by 4-fold (p < 0.001) using a luciferase reporter assay, supporting a model in which RARβ is a direct target of miR-29b. These studies demonstrate that miR-29b induction by rapamycin promotes TSC2-deficient tumorigenesis. miR-29b is a potential therapeutic target for TSC-associated tumors and possibly other mTORC-1 hyperactive tumors. Citation Format: Heng-Jia Liu, Hilaire C. Lam, Christian V. Baglini, Alex K. Conttrill, Stephen Y. Chan, Elizabeth P. Henske. Rapamycin-upregulated miR-29b promotes mTORC1-hyperactivative cell growth by downregulating retinoic acid receptor β (RARβ) [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr A28.

Tuberous sclerosis complex (TSC) is an autosomal dominant disease characterized by hamartomatous tumours of the brain, heart, skin, lung and kidney. Patients with TSC show a diverse range of neurological features (including seizures, cognitive disability and autism) and renal manifestations (including angiomyolipomas, epithelial cysts and renal cell carcinoma (RCC)). TSC is caused by inactivating mutations in TSC1 and TSC2, which encode hamartin and tuberin, respectively. These two proteins form a complex that negatively regulates mechanistic target of rapamycin complex 1 (mTORC1), a master regulator of cellular growth and metabolism. In clinical trials, allosteric inhibitors of mTORC1 decrease angiomyolipoma size, but the tumours regrow after treatment cessation. Therefore, the development of strategies to eliminate rather than suppress angiomyolipomas remains a high priority. This Review describes important advances in the TSC field and highlights several remaining critical knowledge gaps: the factors that promote aggressive behaviour by a subset of TSC-associated RCCs; the molecular mechanisms underlying early-onset cystogenesis in TSC2–PKD1 contiguous gene deletion syndrome; the effect of early, long-term mTORC1 inhibition on the development of TSC renal disease; and the identification of the cell or cells of origin of angiomyolipomas.

Tuberous Sclerosis Complex (TSC), a rare genetic disorder with mechanistic target of rapamycin complex 1 (mTORC1) hyperactivation, is characterized by multi-organ hamartomatous benign tumors including brain, skin, kidney, and lung (Lymphangioleiomyomatosis). mTORC1 hyperactivation drives metabolic reprogramming including glucose and glutamine utilization, protein, nucleic acid and lipid synthesis. To investigate the mechanisms of exogenous nutrients uptake in Tsc2-deficient cells, we measured dextran uptake, a polysaccharide internalized via macropinocytosis. Tsc2-deficient cells showed a striking increase in dextran uptake (3-fold, p −/− MEFs) sensitized cells with Tsc2 downregulation to the Vps34 inhibitor, SAR405, resulting in growth inhibition (75%, p in vivo xenograft model of TSC. Our findings show that macropinocytosis is upregulated with Tsc2-deficiency via a Vps34-dependent mechanism to support their anabolic state. The dependence of Tsc2-deficient cells on exogenous nutrients may provide novel approaches for the treatment of TSC.

Tuberous sclerosis complex (TSC) is an incurable multisystem disease characterized by mTORC1-hyperactive tumors. TSC1/2 mutations also occur in other neoplastic disorders, including lymphangioleiomyomatosis (LAM) and bladder cancer. Whether TSC-associated tumors will respond to immunotherapy is unknown. We report here that the programmed death 1 coinhibitory receptor (PD-1) is upregulated on T cells in renal angiomyolipomas (AML) and pulmonary lymphangioleiomyomatosis (LAM). In C57BL/6J mice injected with syngeneic TSC2-deficient cells, anti-PD-1 alone decreased 105K tumor growth by 67% (P < 0.0001); the combination of PD-1 and CTLA-4 blockade was even more effective in suppressing tumor growth. Anti-PD-1 induced complete rejection of TSC2-deficient 105K tumors in 37% of mice (P < 0.05). Double blockade of PD-1 and CTLA-4 induced rejection in 62% of mice (P < 0.01). TSC2 reexpression in TSC2-deficient TMKOC cells enhanced antitumor immunity by increasing T cell infiltration and production of IFN-γ/TNF-α by T cells, suggesting that TSC2 and mTORC1 play specific roles in the induction of antitumor immunity. Finally, 1 month of anti-PD-1 blockade reduced renal tumor burden by 53% (P < 0.01) in genetically engineered Tsc2+/- mice. Taken together, these data demonstrate for the first time to our knowledge that checkpoint blockade may have clinical efficacy for TSC and LAM, and possibly other benign tumor syndromes, potentially yielding complete and durable clinical responses.

Liang et al. find that the tumor suppressors TSC1 and TSC2, defects in which underlie the genetic disease Tuberous Sclerosis Complex (TSC), drive the mTOR-dependent autophagosomal destruction of the transcriptional activator YAP. Blocking YAP inhibited the abnormal proliferation of TSC1/2-deficient human cells and reversed TSC-like disease symptoms in mosaic Tsc1 mutant mice., Genetic studies have shown that the tuberous sclerosis complex (TSC) 1–TSC2–mammalian target of Rapamycin (mTOR) and the Hippo–Yes-associated protein 1 (YAP) pathways are master regulators of organ size, which are often involved in tumorigenesis. The crosstalk between these signal transduction pathways in coordinating environmental cues, such as nutritional status and mechanical constraints, is crucial for tissue growth. Whether and how mTOR regulates YAP remains elusive. Here we describe a novel mouse model of TSC which develops renal mesenchymal lesions recapitulating human perivascular epithelioid cell tumors (PEComas) from patients with TSC. We identify that YAP is up-regulated by mTOR in mouse and human PEComas. YAP inhibition blunts abnormal proliferation and induces apoptosis of TSC1–TSC2-deficient cells, both in culture and in mosaic Tsc1 mutant mice. We further delineate that YAP accumulation in TSC1/TSC2-deficient cells is due to impaired degradation of the protein by the autophagosome/lysosome system. Thus, the regulation of YAP by mTOR and autophagy is a novel mechanism of growth control, matching YAP activity with nutrient availability under growth-permissive conditions. YAP may serve as a potential therapeutic target for TSC and other diseases with dysregulated mTOR activity.

The tuberous sclerosis complex (TSC) proteins are critical negative regulators of the mammalian/mechanistic target of rapamycin complex 1 pathway. Germline mutations of TSC1 or TSC2 cause TSC, affecting multiple organs, including the kidney and lung, and causing substantial morbidity and mortality. The mechanisms of organ-specific disease in TSC remain incompletely understood, and the impact of TSC inactivation on mesenchymal lineage cells has not been specifically studied. We deleted Tsc2 specifically in mesoderm-derived mesenchymal cells of multiple organs in mice using the Dermo1-Cre driver. The Dermo1-Cre–driven Tsc2 conditional knockout mice had body growth retardation and died approximately 3 weeks after birth. Significant phenotypes were observed in the postnatal kidney and lung. Inactivation of Tsc2 in kidney mesenchyme caused polycystic lesions starting from the second week of age, with increased cell proliferation, tubular epithelial hyperplasia, and epithelial-mesenchymal transition. In contrast, Tsc2 deletion in lung mesenchyme led to decreased cell proliferation, reduced postnatal alveolarization, and decreased differentiation with reduced numbers of alveolar myofibroblast and type II alveolar epithelial cells. Two major findings thus result from this model: inactivation of Tsc2 in mesoderm-derived cells causes increased cell proliferation in the kidneys but reduced proliferation in the lungs, and inactivation of Tsc2 in mesoderm-derived cells causes epithelial-lined renal cysts. Therefore, Tsc2-mTOR signaling in mesenchyme is essential for the maintenance of renal structure and for lung alveolarization.

In just the past 5 years, dramatic changes have occurred in the clinical management of tuberous sclerosis complex (TSC). Detailed knowledge about the role of the TSC proteins in regulating the activity of the mammalian target of rapamycin complex 1 (mTORC1) underlies this paradigm-shifting progress. Advances continue to be made in understanding the genetic pathogenesis of the different tumours that occur in TSC, including pivotal discoveries using next-generation sequencing (NGS). For example, the pathogenesis of angiofibromas is now known to involve UV-induced mutations, and the pathogenesis of multifocal renal cell carcinoma (RCC) in TSC is now known to result from distinct second-hit mutations. In parallel, the pathological features of TSC-associated tumours, including TSC-associated renal cell carcinoma, continue to be defined, despite the fact that TSC was first described 180 years ago. Here, we review recent discoveries related to the pathological features and genetic pathogenesis of TSC-associated tumours. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John WileySons, Ltd.

Toll-like receptors (TLRs) exert important nonimmune functions in lung homeostasis. TLR4 deficiency promotes pulmonary emphysema. We examined the role of TLR4 in regulating cigarette smoke (CS)-induced autophagy, apoptosis, and emphysema. Lung tissue was obtained from chronic obstructive lung disease (COPD) patients. C3H/HeJ ( Tlr4-mutated) mice and C57BL/10ScNJ ( Tlr4-deficient) mice and their respective control strains were exposed to chronic CS or air. Human or mouse epithelial cells (wild-type, Tlr4-knockdown, and Tlr4-deficient) were exposed to CS-extract (CSE). Samples were analyzed for TLR4 expression, and for autophagic or apoptotic proteins by Western blot analysis or confocal imaging. Chronic obstructive lung disease lung tissues and human pulmonary epithelial cells exposed to CSE displayed increased TLR4 expression, and increased autophagic [microtubule-associated protein-1 light-chain-3B (LC3B)] and apoptotic (cleaved caspase-3) markers. Beas-2B cells transfected with TLR4 siRNA displayed increased expression of LC3B relative to control cells, basally and after exposure to CSE. The basal and CSE-inducible expression of LC3B and cleaved caspase-3 were elevated in pulmonary alveolar type II cells from Tlr4-deficient mice. Wild-type mice subjected to chronic CS-exposure displayed airspace enlargement;, however, the Tlr4-mutated or Tlr4-deficient mice exhibited a marked increase in airspace relative to wild-type mice after CS-exposure. The Tlr4-mutated or Tlr4-deficient mice showed higher levels of LC3B under basal conditions and after CS exposure. The expression of cleaved caspase-3 was markedly increased in Tlr4-deficient mice exposed to CS. We describe a protective regulatory function of TLR4 against emphysematous changes of the lung in response to CS.

Tuberous sclerosis complex (TSC) is a multisystem disorder that affects multiple organ systems, including tumors of the brain, heart, kidney, skin and lung. TSC is caused by germline loss-of-function gene mutations in TSC1 or TSC2, which inhibit the mammalian target of rapamycin (mTOR) signaling pathway. Rapalogs are effective cytostatic agents for the treatment of TSC, but continual lifelong therapy is needed. Therapies for TSC that induce a selective cytocidal response in TSC-deficient cells are not currently available, and could have a major clinical impact for TSC patients. We performed a quantitative high-throughput screen (qHTS) of the NCATS Pharmaceutical Collection (NPC) of 2816 compounds, many of which are drugs already approved for other diseases, for their effect on the proliferation of TSC2-deficient ELT3 cells vs. ELT3 cells in which TSC2 was re-expressed. Agents were tested at fifteen concentrations, from 0.6 nM to 46 µM. Six agents selectively inhibited the growth of the TSC2-deficient cells relative to the TSC2-reexpressing cells. One of top inhibitory agents, methotrexate (MTX), a dihydrofolate reductase inhibitor, is FDA-approved, making it a candidate for “repurposing”. In our studies, we confirmed the selective inhibitory effect of MTX on patient-derived TSC2-deficient cells. Flow cytometry analysis demonstrated that MTX (5 µM, 24 h) arrested 60.8% of the TSC2-deficient cells in S-phase, vs. 26.6% of the TSC2-expressing cells. The accumulation of S-phase arrested cells ultimately leads to apoptosis selectively in the TSC2-deficient cells, which was detected by flow cytometry of Propidium Iodide/Annexin V stained cells (52.3% of apoptosis in TSC2-deficient cells vs. 11% in TSC2-reexpressing cells) and immunoblotting for cleaved Caspase3 and cleaved PARP. Co-treatment with the mTOR inhibitor Rapamycin and MTX prevented MTX-induced apoptosis (52.3% apoptotic cells with MTX alone vs. 11.8% with MTX plus Rapamycin). In vivo, mice bearing TSC2-deficient ELT3 cell xenograft tumors were treated with MTX (25mg/kg or 50mg/kg) or rapamycin (1mg/kg) by intraperitoneal injection every other day over 3 weeks. We found that 50mg/kg of MTX significantly decreased the volume of tumors within two weeks of treatment, to a similar extent as Rapamycin treatment did. We conclude that Methotrexate acts as a selective cytotoxic agent in TSC2-deficient cells. This is consistent with recent discoveries that mTOR regulates the de novo purine and pyrimidine synthesis pathways. As an FDA-approved agent, Methotrexate has potential for clinical “repurposing” for the treatment of TSC-deficient tumors. Citation Format: Amine Belaid, Harilaos Filippakis, Hilaire Lam, Alexander Valvezan, Ruili Huang, Menghang Xia, Tianmu Wen, Christian Baglini, Srilatha Sakamuru, John Asara, Nguyen Truong Sinh, Jeffrey J. Heard, Fuyuhiko Tamanoi, Christopher Austin, Brendan Manning, Elizabeth P. Henske. Therapeutic targeting of TSC2-deficient cells with Methotrexate: Results of a drug repurposing screen. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr A09.

Experimental sepsis can be induced in mice using the cecal ligation and puncture (CLP) method, which causes polymicrobial sepsis. Here, a protocol is provided to induce sepsis of varying severity in mice using the CLP technique. Autophagy is a fundamental tissue response to stress and pathogen invasion. Two current protocols to assess autophagy in vivo in the context of experimental sepsis are also presented here. (I) Transgenic mice expressing green fluorescence protein (GFP)-LC3 fusion protein are subjected to CLP. Localized enhancement of GFP signal (puncta), as assayed either by immunohistochemical or confocal assays, can be used to detect enhanced autophagosome formation and, thus, altered activation of the autophagy pathway. (II) Enhanced autophagic vacuole (autophagosome) formation per unit tissue area (as a marker of autophagy stimulation) can be quantified using electron microscopy. The study of autophagic responses to sepsis is a critical component of understanding the mechanisms by which tissues respond to infection. Research findings in this area may ultimately contribute towards understanding the pathogenesis of sepsis, which represents a major problem in critical care medicine.

Tuberous sclerosis complex (TSC) is a multisystem disease associated with tumors of the brain, skin and kidney as well as progressive cystic lung destruction characteristic of lymphangioleiomyomatosis (LAM). TSC and LAM are caused by loss-of-function mutations in TSC1 or TSC2, resulting in hyperactive mechanistic Target of Rapamycin complex 1 (mTORC1) signaling. We previously discovered that mTORC1 hyperactivation in TSC inhibits autophagy and promotes the accumulation of oncogenic p62/sequestosome 1 (PNAS, 2011). p62 exerts a pleiotropic role in tumor progression, including the regulation of NRF2 to combat oxidative stress, NFκB to promote cell survival and the degradation of ubiquitinated proteins to efficiently recycle organelles and proteins by autophagy. Knockdown of p62 in Tsc2-null cells inhibited tumorigenesis in xenografts in vivo, but did not impact proliferation in vitro, leading us to hypothesize that p62 exerts non-cell autonomous functions influencing the tumor microenvironment to promote Tsc2-/- cell tumorigenic potential. In unpublished work, we explored the molecular mechanisms by which p62 promotes tumorigenesis in TSC/LAM. First, we analyzed renal tumor burden in Tsc2+/-; p62-/- mice. Compared to littermate control Tsc2+/-; p62+/+ mice, Tsc2+/-; p62-/- mice have a 2-fold (p Our data point toward a model in which p62 and mTORC1 cooperatively regulate cellular IL6 in Tsc2-null cells to promote tumorigenesis in TSC. IL6 is correlated with poor prognosis, advanced disease and metastatic potential in numerous cancers. Rapamycin dramatically decreases p62 levels in TSC-deficient cells. Therefore, the induction of IL6 by rapamycin through decreased p62 expression may represent one of the first non-cell autonomous mechanisms by which mTORC1 inhibition impacts tumorigenesis. Since mTORC1 is hyperactivated in the majority of malignant tumors and more than 100 cancer clinical trials are ongoing with mTORC1 inhibitors, our findings may yield insights with broad therapeutic potential. Citation Format: Hilaire C. Lam, Andrey Parkhitko, Alicia Llorente Lope, Nicola Alesi, Damir Khabibullin, Harilaos Filippakis, Ana Pereira, Barbara Ogorek, Erik Zhang, Jane Yu, Carmen Priolo, Elizabeth P. Henske. Regulation of the tumor microenvironment by oncogenic p62 in mTORC1-hyperactive diseases: Tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM). [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr A35.

Background: Tuberous sclerosis complex (TSC) is a multisystem, hamartomatous disease associated with tumors of the brain, skin and kidney, as well as progressive cystic lung destruction characteristic of lymphangioleiomyomatosis (LAM). TSC is caused by mutations in TSC1 or TSC2, resulting in hyperactive mechanistic Target of Rapamycin (mTOR) 1 signaling. Rapamycin and related rapalogs inhibit mTORC1 activity and stabilize tumors in TSC patients, but tumor progression proceeds at pretreatment rates following cessation of therapy. MicroRNA repress target gene expression and are commonly dysregulated in cancers. In previously published work, we identified a group of rapamycin responsive miRNA, rapa-miRs. Surprisingly the most upregulated rapa-miRs, miR-21 in particular, are known pro-survival oncogenic miRNA (oncomiRs). We hypothesize that inhibiting miR-21 and downstream targets may lead to more complete and durable responses to mTORC1 inhibitors. Methods: We utilized qRT-PCR to determine the kinetics of miR-21 induction with rapamycin in various cell types and in mouse xenografts. Mimics and inhibitors were used to determine the functional consequences of miR-21 in TSC2-null cells. Expression profiling was used to identify miRNA target genes. Bioinformatics and network analysis approaches were implemented to identify biological relationships between the miR-21 targets. Results: Our initial screens identified miR-29b, -21, -24, -221, -106a and -199a as candidate rapa-miRs. Rapamycin induced miR-21 greater than 1.5 fold in diverse cell lines and in mouse xenografts. We have identified pro-cell death targets, PPIF, TP53BP2 and PDCD4, which are negatively regulated by miR-21 upon rapamycin treatment. Network analysis using the Consolidated Interactome (CI) revealed that rapa-miRs inhibit multiple key pro-apoptotic targets. These data suggest that rapa-miRs regulate proteins critical for cell fate determination and survival in response to rapamycin treatment. Conclusions: Rapamycin induces pro-survival oncomiR, miR-21, which may be a valuable target for therapeutic intervention in TSC. Citation Format: Hilaire C. Lam, Harilaos Filippakis, Katherine A. Cottrill, Alicia Llorente Lope, Damir Khabibullin, Carmen Priolo, Barbara Ogorek, Stephen Y. Chan, Ana Pereira, Elizabeth P. Henske. Rapamycin-induced miR-21 promotes the survival of mTORC1 hyperactivated cells in tuberous sclerosis complex models. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr B12.

Pulmonary epithelial cells can be isolated from the respiratory tract of mice and cultured at air-liquid interface (ALI) as a model of differentiated respiratory epithelium. A protocol is described for isolating and exposing these cells to mainstream cigarette smoke (CS), in order to study epithelial cell responses to CS exposure. The protocol consists of three parts: the isolation of airway epithelial cells from mouse trachea, the culturing of these cells at air-liquid interface (ALI) as fully differentiated epithelial cells, and the delivery of calibrated mainstream CS to these cells in culture. The ALI culture system allows the culture of respiratory epithelia under conditions that more closely resemble their physiological setting than ordinary liquid culture systems. The study of molecular and lung cellular responses to CS exposure is a critical component of understanding the impact of environmental air pollution on human health. Research findings in this area may ultimately contribute towards understanding the etiology of chronic obstructive pulmonary disease (COPD), and other tobacco-related diseases, which represent major global health problems.