Lymphangioleiomyomatosis Cells Research Articles

Lymphangioleiomyomatosis: A Review.

Lymphangioleiomyomatosis is a rare multisystem disorder belonging to the family of neoplasms exhibiting perivascular epithelioid differentiation. It primarily affects women of childbearing age. The disease is characterized by a proliferation of smooth muscle-like cells (lymphangioleiomyomatosis cells) within all lung compartments, leading to cystic parenchymal destruction and, in some cases, respiratory failure. These cells carry mutations in one or both tuberous sclerosis (TSC) genes and coexpress smooth muscle and melanocytic markers. Female hormones, particularly estrogens, influence the course of the disease. Symptoms of lymphangioleiomyomatosis vary significantly among patients, ranging from exertional dyspnea and coughing to chest pain and recurrent pneumothorax. To present the latest advancements in the understanding of disease pathogenesis and diagnosis, illustrate the pathologic and radiologic findings, provide a reference for pathologists and other health care professionals, briefly discuss recent evidence-based therapeutic approaches, and emphasize the importance of adopting a multidisciplinary approach to diagnosis and optimization of patient care. A comprehensive review of pertinent medical literature published in the last 30 years, focusing on publications written in the English language, was performed. Despite the recent significant advancements in the understanding and management of lymphangioleiomyomatosis, there are still significant gaps in our knowledge of its pathophysiology and the role of the immune system in the genesis and progression of the disease. The current changes in diagnostic algorithms favor the adoption of minimally invasive procedures as the standard of care. As a result, the clinical laboratory will play a larger role in the diagnosis of lymphangioleiomyomatosis, and surgical pathologists will likely be less involved in the diagnosis of pulmonary lymphangioleiomyomatosis than they currently are.

Enhanced Gαq Signaling in TSC2-deficient Cells Is Required for Their Neoplastic Behavior.

Inherited or sporadic loss of the TSC2 gene can lead to pulmonary lymphangioleiomyomatosis (LAM), a rare cystic lung disease caused by protease-secreting interstitial tumor nodules. The nodules arise by metastasis of cells that exhibit features of neural crest and smooth muscle lineage ('LAM cells'). Their aberrant growth is attributed to increased activity of 'mechanistic target of rapamycin complex 1' (mTORC1), an anabolic protein kinase that is normally suppressed by the TSC1-TSC2 protein complex. The mTORC1 inhibitor rapamycin slows the progression of LAM, but fails to eradicate disease, indicating a role for mTORC1-independent mechanisms in LAM pathogenesis. Our previous studies revealed G-protein coupled urotensin-II receptor (UT) signaling as a candidate mechanism, but how it promotes oncogenic signaling in TSC2-deficient cells remained unknown. Using a human pluripotent stem cell-derived in vitro model of LAM, we now show hyperactivation of UT, which was required for their enhanced migration and pro-neoplastic signaling in a rapamycin-insensitive mechanism that required heterotrimeric Gαq/11 (Gαq). Bioluminescence resonance energy transfer assays in HEK 293T cells lacking TSC2 demonstrated selective and enhanced activation of Gαq and its RhoA-associated effectors compared to wild-type control cells. By immunoprecipitation, recombinant UT was physically associated with Gαq and TSC2. The augmented Gαq signaling in TSC2-deleted cells was independent of mTOR activity, and associated with increased endosomal targeting of p63RhoGEF, a known RhoA-activating effector of Gαq. These studies identify potential mTORC1-independent pro-neoplastic mechanisms that can be targeted for prevention or eradication of pulmonary and extrapulmonary LAM tumors.

8636 Characterization Of The Role Of Neutrophils In Promoting Progression Of Lymphangioleiomyomatosis

Abstract Disclosure: T.R. Henson: None. B. Minor: None. S.R. Hammes: None. Lymphangioleiomyomatosis (LAM) is a rare, multisystemic disease that is associated with cystic lung destruction. LAM is caused by small smooth muscle cell-like tumors throughout the lung that contain deleterious mutations in the tuberous sclerosis complex genes TSC1 or TSC2. This attenuates the activity of the mammalian target of rapamycin complex 1 (mTORC1) causing increased proliferation of the smooth muscle cells. LAM is a sexually dimorphic disease that primarily affects genetic females. Clinical observations implicate the role of estrogen in disease progression, as it is exacerbated during pregnancy and by use of exogenous estrogens in birth control. LAM tumor-derived cells lines have shown that direct estrogen stimulation of cell proliferation is modest compared to the dramatic in vivo effects of estradiol (E2) stimulation in a uterine-specific TSC2-null mouse model. Creation of a monoclonal cell line from these mice resulted in the generation of the LTM3 cell line, which also demonstrates low response to direct estrogen stimulation in vitro. This indicates that direct E2 stimulation may act upon other cell types in the tumor microenvironment. Immunophenotyping of uterine-specific TSC2-null mice has shown that the tumor microenvironment is enriched with myeloid cells specifically neutrophils. Functional analysis of neutrophil suppression in vivo has shown a reduction in myometrial growth in the uterine-specific TSC2-null mice, indicating a key role for neutrophil-mediated LAM tumor growth. Altered transcriptional regulation of neutrophils further highlights the importance of neutrophils in LAM progression. Bulk messenger RNA sequencing revealed E2 dependent increase in the neutrophil derived serine protease neutrophil elastase (NE). NE in vitro has been shown to increase migration, invasion, and proliferation of LAM cell lines, while inhibition in vivo has shown a reduction to the myometrial growth. Previously published data by the lab has shown that E2 increases tumor induced expansion of neutrophils in the bone marrow. Isolation and purification of Neutrophils from mouse bone marrow stimulated with tumor conditioned media from the LTM3 cells has shown signs of activation via upregulated gene expression. The focus of the current research has been the characterization of bone marrow derived neutrophils. Currently working with an in vitro system to study the proliferation of LTM3 and the rat leiomyoma (ELT3) cell lines when they are co-cultured with neutrophils. Understanding the mechanism by which neutrophils are activated and interact with LAM cells can give understanding to disease progression may provide insight into future treatment options. Presentation: 6/3/2024

7908 GPNMB Promotes Tumor Growth And Is A Biomarker For Lymphangioleiomyomatosis (LAM)

Abstract Disclosure: E. Gibbons: None. M. Taya: None. H. Wu: None. S. Lopa: None. J. Moss: None. E.P. Henske: None. F.X. McCormack: None. S.R. Hammes: None. Lymphangioleiomyomatosis (LAM) is a rare, progressive cystic lung disease affecting almost exclusively female-sexed individuals. The cysts represent regions of lung destruction caused by smooth muscle tumors containing mutations in one of the two tuberous sclerosis (TSC) genes. mTORC1 inhibition slows but does not stop LAM advancement. Furthermore, monitoring disease progression is hindered by insufficient biomarkers. Therefore, new treatment options and biomarkers are needed. LAM cells express melanocytic markers, including Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB). The function of GPNMB in LAM is currently unknown; however, GPNMB’s unique cell surface expression on tumor versus benign cells makes GPNMB a potential therapeutic target, and persistent release of its extracellular ectodomain suggests potential as a serum biomarker. Here we establish that GPNMB regulates TSC2-null tumor cell invasion as well as TSC2-null xenograft tumor growth, and that GPNMB expression is dependent on mTORC1 signaling. Further, we show that GPNMB’s ectodomain is released from the cell surface of TSC2-null cells by ADAM10 and 17 proteases, and we identify the protease target sequence on GPNMB. In fact, mutating this cleavage sequence so that the GPNMB ectodomain can no longer be shed results in cessation of TSC2-null tumor growth. Finally, we demonstrate that GPNMB’s ectodomain is present at higher levels in LAM patient serum compared to healthy controls, and that ectodomain levels decrease with mTORC1 inhibition, making it a potential LAM biomarker. Presentation: 6/3/2024

7908 GPNMB Promotes Tumor Growth and is a Biomarker for Lymphangioleiomyomatosis (LAM)

Abstract Disclosure: E. Gibbons: None. M. Taya: None. H. Wu: None. S. Lopa: None. J. Moss: None. E.P. Henske: None. F.X. McCormack: None. S.R. Hammes: None. Lymphangioleiomyomatosis (LAM) is a rare, progressive cystic lung disease affecting almost exclusively female-sexed individuals. The cysts represent regions of lung destruction caused by smooth muscle tumors containing mutations in one of the two tuberous sclerosis (TSC) genes. mTORC1 inhibition slows but does not stop LAM advancement. Furthermore, monitoring disease progression is hindered by insufficient biomarkers. Therefore, new treatment options and biomarkers are needed. LAM cells express melanocytic markers, including Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB). The function of GPNMB in LAM is currently unknown; however, GPNMB’s unique cell surface expression on tumor versus benign cells makes GPNMB a potential therapeutic target, and persistent release of its extracellular ectodomain suggests potential as a serum biomarker. Here we establish that GPNMB regulates TSC2-null tumor cell invasion as well as TSC2-null xenograft tumor growth, and that GPNMB expression is dependent on mTORC1 signaling. Further, we show that GPNMB’s ectodomain is released from the cell surface of TSC2-null cells by ADAM10 and 17 proteases, and we identify the protease target sequence on GPNMB. In fact, mutating this cleavage sequence so that the GPNMB ectodomain can no longer be shed results in cessation of TSC2-null tumor growth. Finally, we demonstrate that GPNMB’s ectodomain is present at higher levels in LAM patient serum compared to healthy controls, and that ectodomain levels decrease with mTORC1 inhibition, making it a potential LAM biomarker. Presentation: 6/3/2024

9308 GPNMB Promotes Tumor Growth And Is A Biomarker For Lymphangioleiomyomatosis (LAM)

Abstract Disclosure: E. Gibbons: None. M. Taya: None. H. Wu: None. S. Lopa: None. J. Moss: None. E.P. Henske: None. F.X. McCormack: None. S.R. Hammes: None. Lymphangioleiomyomatosis (LAM) is a rare, progressive cystic lung disease affecting almost exclusively female-sexed individuals. The cysts represent regions of lung destruction caused by smooth muscle tumors containing mutations in one of the two tuberous sclerosis (TSC) genes. mTORC1 inhibition slows but does not stop LAM advancement. Furthermore, monitoring disease progression is hindered by insufficient biomarkers. Therefore, new treatment options and biomarkers are needed. LAM cells express melanocytic markers, including Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB). The function of GPNMB in LAM is currently unknown; however, GPNMB’s unique cell surface expression on tumor versus benign cells makes GPNMB a potential therapeutic target, and persistent release of its extracellular ectodomain suggests potential as a serum biomarker. Here we establish that GPNMB regulates TSC2-null tumor cell invasion as well as TSC2-null xenograft tumor growth, and that GPNMB expression is dependent on mTORC1 signaling. Further, we show that GPNMB’s ectodomain is released from the cell surface of TSC2-null cells by ADAM10 and 17 proteases, and we identify the protease target sequence on GPNMB. In fact, mutating this cleavage sequence so that the GPNMB ectodomain can no longer be shed results in cessation of TSC2-null tumor growth. Finally, we demonstrate that GPNMB’s ectodomain is present at higher levels in LAM patient serum compared to healthy controls, and that ectodomain levels decrease with mTORC1 inhibition, making it a potential LAM biomarker. Presentation: 6/3/2024

Extracellular vesicles regulate metastable phenotypes of lymphangioleiomyomatosis cells via shuttling ATP synthesis to pseudopodia and activation of integrin adhesion complexes.

Pulmonary lymphangioleiomyomatosis (LAM) is metastatic sarcoma but mechanisms regulating LAM metastasis are unknown. Extracellular vesicle (EV) regulate cancer metastasis but their roles in LAM have not yet been investigated. Here, we report that EV biogenesis is increased in LAM and LAM EV cargo is enriched with lung tropic integrins, metalloproteinases, and cancer stem cell markers. LAM-EV increase LAM cell migration and invasion via the ITGα6/β1-c-Src-FAK-AKT axis. Metastable (hybrid) phenotypes of LAM metastasizing cells, pivotal for metastasis, are regulated by EV from primary tumor or metastasizing LAM cells via shuttling ATP synthesis to cell pseudopodia or activation of integrin adhesion complex, respectively. In mouse models of LAM, LAM-EV increase lung metastatic burden through mechanisms involving lung extracellular matrix remodeling. Collectively, these data provide evidence for the role of EV in promoting LAM lung metastasis and identify novel EV-dependent mechanisms regulating metastable phenotypes of tumor cells. Clinical impact of research is that it establishes LAM pathway as novel target for LAM therapy.

Glycoprotein non-metastatic melanoma protein B promotes tumor growth and is a biomarker for lymphangioleiomyomatosis.

Lymphangioleiomyomatosis (LAM) is a rare, progressive cystic lung disease affecting almost exclusively female-sexed individuals. The cysts represent regions of lung destruction caused by smooth muscle tumors containing mutations in one of the two tuberous sclerosis (TSC) genes. mTORC1 inhibition slows but does not stop LAM advancement. Furthermore, monitoring disease progression is hindered by insufficient biomarkers. Therefore, new treatment options and biomarkers are needed. LAM cells express melanocytic markers, including glycoprotein non-metastatic melanoma protein B (GPNMB). The function of GPNMB in LAM is currently unknown; however, GPNMB's unique cell surface expression on tumor versus benign cells makes GPNMB a potential therapeutic target, and persistent release of its extracellular ectodomain suggests potential as a serum biomarker. Here, we establish that GPNMB expression is dependent on mTORC1 signaling, and that GPNMB regulates TSC2-null tumor cell invasion in vitro. Further, we demonstrate that GPNMB enhances TSC2-null xenograft tumor growth in vivo, and that ectodomain release is required for this xenograft growth. We also show that GPNMB's ectodomain is released from the cell surface of TSC2-null cells by proteases ADAM10 and 17, and we identify the protease target sequence on GPNMB. Finally, we demonstrate that GPNMB's ectodomain is present at higher levels in LAM patient serum compared to healthy controls and that ectodomain levels decrease with mTORC1 inhibition, making it a potential LAM biomarker.

A 32-Year-Old Female with Incidentally Detected Multifocal Cystic Pulmonary Lesions on Chest Computed Tomography

Lymphangioleiomyomatosis (LAM) is a rare condition that exclusively affects women and is characterized by lung parenchymal destruction and the formation of cysts due to infiltration by LAM cells. It can also impact the lymphatic system, leading to the development of fluid-filled cystic structures and abdominal involvement, including renal angiomyolipomas (AML) or lymphangioleiomyoma. LAM can occur sporadically or be associated with tuberous sclerosis complex. Common symptoms include respiratory issues such as dyspnea, pneumothorax, chylothorax, along with other manifestations like renal AML and lymphatic involvement. The diagnosis of LAM relies on a combination of clinical, radiological, and laboratory findings, and treatment options vary depending on symptoms and patient status, with mTOR inhibitors being considered as a treatment option. This case outlines the diagnostic journey and clinical course of a 32-year-old female patient with LAM.

Pathomorphological Characteristic of Pulmonary Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a polysystemic disease based on the formation of granulomas prone to degenerate into cysts in the lungs, abdominal and pelvic organs. Lung involvement in LAM is accompanied by respiratory dysfunction and can be fatal. WHO classifies this disease into a group of mesenchymal tumors and considers it as a low-grade destructive metastasizing neoplasm. LAM is a rare disease and earlier it was only detected in women, but nowadays cases of pulmonary LAM in men (include teenagers) have been described. The etiology of LAM and the inducing factors are still unknown. Objective – to collect and systematize data on pathomorphological characteristic of changes in lung tissue in LAM to evaluate the completeness and sufficiency of the available data. Material and methods. There were analyzed 912 articles and monographs (including duplicates) from PubMed, eLibrary, and Cyberleninka databases over a fifty-year period from 1973 to August of 2023, with an emphasis on more relevant publications and articles in highly rated scientific journals that include information on the review topic. Eventually 55 original sources were selected. Results. The article presents summary data on macroscopic and microscopic picture of pulmonary LAM, data on morphological and antigenic characterization of cells forming the basis of granulomas and their surroundings, the results of experiments demonstrating dynamics of pathological changes in LAM. Conclusion. Despite the relatively large amount of data about morphological characteristics that is enough for diagnosis, he main issue is still open: what is the origin of LAM cells? A systematic pathomorphology analyze can help us to find an answer for this question.

Hyperactive mTORC1 in lung mesenchyme induces endothelial cell dysfunction and pulmonary vascular remodeling.

Lymphangioleiomyomatosis (LAM) is a progressive cystic lung disease caused by tuberous sclerosis complex 1/2 (TSC1/2) gene mutations in pulmonary mesenchymal cells, resulting in activation of the mechanistic target of rapamycin complex 1 (mTORC1). A subset of patients with LAM develop pulmonary vascular remodeling and pulmonary hypertension. Little, however, is known regarding how LAM cells communicate with endothelial cells (ECs) to trigger vascular remodeling. In end-stage LAM lung explants, we identified EC dysfunction characterized by increased EC proliferation and migration, defective angiogenesis, and dysmorphic endothelial tube network formation. To model LAM disease, we used an mTORC1 gain-of-function mouse model with a Tsc2 KO (Tsc2KO) specific to lung mesenchyme (Tbx4LME-Cre Tsc2fl/fl), similar to the mesenchyme-specific genetic alterations seen in human disease. As early as 8 weeks of age, ECs from mice exhibited marked transcriptomic changes despite an absence of morphological changes to the distal lung microvasculature. In contrast, 1-year-old Tbx4LME-Cre Tsc2fl/fl mice spontaneously developed pulmonary vascular remodeling with increased medial thickness. Single-cell RNA-Seq of 1-year-old mouse lung cells identified paracrine ligands originating from Tsc2KO mesenchyme, which can signal through receptors in arterial ECs. These ECs had transcriptionally altered genes including those in pathways associated with blood vessel remodeling. The proposed pathophysiologic mesenchymal ligand-EC receptor crosstalk highlights the importance of an altered mesenchymal cell/EC axis in LAM and other hyperactive mTORC1-driven diseases. Since ECs in patients with LAM and in Tbx4LME-Cre Tsc2fl/fl mice did not harbor TSC2 mutations, our study demonstrates that constitutively active mTORC1 lung mesenchymal cells orchestrated dysfunctional EC responses that contributed to pulmonary vascular remodeling.

THU551 Glycoprotein-NMB (GPNMB) Is A Potential Lymphangioleiomyomatosis (LAM) Therapeutic Target And Biomarker

Abstract Disclosure: E. Gibbons: None. S.R. Hammes: None. Lymphangioleiomyomatosis (LAM) is a rare, progressive, destructive cystic lung disease affecting almost exclusively female-sexed individuals. Mutations in the tuberous sclerosis (TSC1 or TSC2) genes constitutively activate the mTORC1 pathway, promoting hyperproliferation of smooth muscle cells, creating small tumors throughout the lungs. These tumors, through largely unknown mechanisms, result in the formation of large cysts that replace normal alveolar space. Inhibition of mTORC1 with Sirolimus slows but does not stop LAM progression; therefore, there is a need for new LAM treatment options and biomarkers. Due to LAM’s estrogen sensitivity, female specificity, and metastatic nature, we previously proposed LAM cells originate from the uterine myometrium. We therefore designed a uterine-specific TSC2-null mouse model where all the mice generate uterine tumors characteristic of LAM and half develop lung metastases, suggesting that indeed LAM tumors may be derived from the uterus. Using bulk RNASeq analysis of uterine tissue from our mouse model, when focusing on genes regulated by estrogen and TSC2, we discovered increased expression of melanocytic markers, including Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB), a known oncogenic protein in other cancers. GPNMB was not only highly expressed in our mouse model; it was also expressed intracellularly and on the cell surface of TSC2-null cell lines and in LAM tumor cells from patient lungs and uteri. Notably, the extracellular domain of GPNMB was released from the surface of TSC2-null cell lines, suggesting that the ectodomain may also be released from TSC2-null cells in LAM patients. Here we show that, GPNMB protein and mRNA expression increased when the cells were serum starved, mimicking conditions of a tumor microenvironment. This increase was dependent on mTORC1 signaling and mRNA transcription. Knocking down GPNMB expression by siRNA had minimal effects on TSC2-null cells pro-tumorigenic functions in vitro aside from decreasing invasion. However, knocking out GPNMB in TSC2-null cells using CRISPR/Cas9 significantly decreased mouse xenograft tumor growth. Additionally, treating mice with a GPNMB antibody drug conjugate abrogated xenograft growth, highlighting GPNMB’s potential as a therapeutic target. Also, GPNMB’s ectodomain was released from the cell surface of TSC2-null cells by the proteases Adam10 and 17. Of note, the ectodomain is implicated in mediating GPNMB’s effects on tumor growth, suggesting that Adam10/17 inhibition may mitigate TSC2-null tumor growth. Importantly, the GPNMB ectodomain is a potential serum biomarker of LAM, as there was a significant increase in GPNMB ectodomain levels in patient serum as compared with healthy controls. Furthermore, serum GPNMB levels decreased in most patients after Sirolimus treatment, implicating GPNMB as a potential marker for responsiveness to treatment. Presentation: Thursday, June 15, 2023

Clinicopathological Impacts of Expression of Neuronal Markers in Lymphangioleiomyomatosis.

Lymphangioleiomyomatosis (LAM) is a tuberous sclerosis complex (TSC)-associated tumor, characterized by the expression of neural crest lineages including neuronal markers. Neural crest cells can differentiate into multiple cell types that contribute to tissues associated with TSC-related tumors, and TSC-related tumors could be specifically associated with distinct neural crest subtypes. This study aimed to clarify the clinicopathological effects of expression of neuronal markers in LAM. Lung tissues from 40 patients with LAM (of whom 13, 1, and 26 had undergone lung transplantation, lobectomy, and partial lung resection, respectively) were immunohistochemically analyzed. All patients were women, and their median age was 36 years (range: 24-62y). All patients who underwent lung transplantation or lobectomy were classified as LAM histologic score (LHS)-3, whereas those who underwent partial lung resection were classified as LHS-1. LAM cells expressed peripherin (65%), and neuron-specific βIII-tubulin (43%). A comparison of the early (LHS-1) and advanced (LHS-3) stages of LAM revealed that neuron-specific βIII-tubulin was significantly expressed in the early stage of LAM ( P = 0.0009). Neuron-specific βIII-tubulin-positive LAM was associated with younger age ( P < 0.0001), the coexistence of renal angiomyolipoma ( P = 0.027), and the absence of retroperitoneal LAM ( P = 0.045). Furthermore, based on the expression levels of immunohistochemical markers in LAM, 2 distinct clusters with different expression levels of neuronal markers were observed. Approximately 40% to 60% of patients with LAM expressed neuron-specific βIII-tubulin and peripherin. Neuronal expression may be associated with disease severity.

Tissue-Engineered Disease Modeling of Lymphangioleiomyomatosis Exposes a Therapeutic Vulnerability to HDAC Inhibition.

Lymphangioleiomyomatosis (LAM) is a rare disease involving cystic lung destruction by invasive LAM cells. These cells harbor loss-of-function mutations in TSC2, conferring hyperactive mTORC1 signaling. Here, tissue engineering tools are employed to model LAM and identify new therapeutic candidates. Biomimetic hydrogel culture of LAM cells is found to recapitulate the molecular and phenotypic characteristics of human disease more faithfully than culture on plastic. A 3D drug screen is conducted, identifying histone deacetylase (HDAC) inhibitors as anti-invasive agents that are also selectively cytotoxic toward TSC2-/- cells. The anti-invasive effects of HDAC inhibitors are independent of genotype, while selective cell death is mTORC1-dependent and mediated by apoptosis. Genotype-selective cytotoxicity is seen exclusively in hydrogel culture due to potentiated differential mTORC1 signaling, a feature that is abrogated in cell culture on plastic. Importantly, HDAC inhibitors block invasion and selectively eradicate LAM cells in vivo in zebrafish xenografts. These findings demonstrate that tissue-engineered disease modeling exposes a physiologically relevant therapeutic vulnerability that would be otherwise missed by conventional culture on plastic. This work substantiates HDAC inhibitors as possible therapeutic candidates for the treatment of patients with LAM and requires further study.

Glutaredoxin-1 promotes lymphangioleiomyomatosis progression through inhibiting Bim-mediated apoptosis via COX2/PGE2/ERK pathway.

Lymphangioleiomyomatosis (LAM) is a female-predominant interstitial lung disease, characterized by progressive cyst formation and respiratory failure. Clinical treatment with the mTORC1 inhibitor rapamycin could relieve partially the respiratory symptoms, but not curative. It is urgent to illustrate the fundamental mechanisms of TSC2 deficiency to the development of LAM, especially mTORC1-independent mechanisms. Glutaredoxin-1 (Glrx), an essential glutathione (GSH)-dependent thiol-oxidoreductase, maintains redox homeostasis and participates in various processes via controlling protein GSH adducts. Redox signalling through protein GSH adducts in LAM remains largely elusive. Here, we demonstrate the underlying mechanism of Glrx in the pathogenesis of LAM. 1. Abnormal Glrx expression in various kinds of human malignancies was identified by the GEPIA tumour database, and the expression of Glrx in LAM-derived cells was detected by real-time quantitative reverse transcription (RT-qPCR) and immunoblot. 2. Stable Glrx knockdown cell line was established to evaluate cellular impact. 3. Cell viability was determined by CCK8 assay. 4. Apoptotic cell number and intracellular reactive oxygen species (ROS) level were quantified by flow cytometry. 5. Cox2 expression and PGE2 production were detected to clarify the mechanism of Bim expression modulated by Glrx. 6. S-glutathionylated p65 was enriched and detected by immunoprecipitation and the direct regulation of Glrx on p65 was determined. 7. The xenograft animal model was established and photon flux was analyzed using IVIS Spectrum. In LAM, TSC2 negatively regulated abnormal Glrx expression and activation in a mTORC1-independent manner. Knockdown of Glrx increased the expression of Bim and the accumulation of ROS, together with elevated S-glutathionylated proteins, contributing to the induction of apoptotic cell death and inhibited cell proliferation. Knockdown of Glrx in TSC2-deficient LAM cells increased GSH adducts on nuclear factor-kappa B p65, which contributed to a decrease in the expression of Cox2 and the biosynthesis of PGE2. Inhibition of PGE2 metabolism attenuated phosphorylation of ERK, which led to the accumulation of Bim, due to the imbalance of its phosphorylation and proteasome degradation. In xenograft tumour models, knockdown of Glrx in TSC2-deficient LAM cells inhibited tumour growth and increased tumour cell apoptosis. Collectively, we provide a novel redox-dependent mechanism in the pathogenesis of LAM and propose that Glrx may be a beneficial strategy for the treatment of LAM or other TSC-related diseases.

Unexpected sirolimus-stimulated airway hyperreactivity in lymphangioleiomyomatosis.

Lymphangioleiomyomatosis (LAM) is a multisystem disease affecting primarily women, characterised in the lung by proliferation of LAM cells, abnormal smooth muscle-like cells with dysfunctional tuberous sclerosis complex genes. This dysfunction results in activation of mechanistic target of rapamycin (mTOR), leading to LAM cell proliferation. Sirolimus (rapamycin) is the only United States Food and Drug Administration-approved treatment for pulmonary LAM, resulting in decreased LAM cell growth/size and stabilised lung function [1].

Single-cell multiomic analysis identifies a HOX-PBX gene network regulating the survival of lymphangioleiomyomatosis cells.

Lymphangioleiomyomatosis (LAM) is a rare, progressive lung disease that predominantly affects women. LAM cells carry TSC1/TSC2 mutations, causing mTORC1 hyperactivation and uncontrolled cell growth. mTORC1 inhibitors stabilize lung function; however, sustained efficacy requires long-term administration, and some patients fail to tolerate or respond to therapy. Although the genetic basis of LAM is known, mechanisms underlying LAM pathogenesis remain elusive. We integrated single-cell RNA sequencing and single-nuclei ATAC-seq of LAM lungs to construct a gene regulatory network controlling the transcriptional program of LAM cells. We identified activation of uterine-specific HOX-PBX transcriptional programs in pulmonary LAMCORE cells as regulators of cell survival depending upon HOXD11-PBX1 dimerization. Accordingly, blockage of HOXD11-PBX1 dimerization by HXR9 suppressed LAM cell survival in vitro and in vivo. PBX1 regulated STAT1/3, increased the expression of antiapoptotic genes, and promoted LAM cell survival in vitro. The HOX-PBX gene network provides promising targets for treatment of LAM/TSC mTORC1-hyperactive cancers.

Cell survival pathways targeted in rare lung disease affecting women

Novel drug targets are identified in lymphangioleiomyomatosis (LAM), a rare disease in women. These targets focus on uterine transcription factors necessary for LAM cell survival.

Tyrosine Kinase Inhibitors Diminish Renal Neoplasms in a Tuberous Sclerosis Model Via Induction of Apoptosis.

Tuberous sclerosis complex (TSC) tumors are presently incurable despite a cytostatic response to mTOR pathway inhibition because recurrence of disease occurs after treatment is discontinued. Here, we explored the hypothesis that inhibiting tyrosine kinase activity in mesenchymal lineage-specific platelet-derived growth factor receptor β (PDGFRβ) signaling in TSC tumors is cytocidal and attenuates tumorigenesis at significantly higher levels than treatment with an mTOR inhibitor. Rapamycin-induced versus tyrosine kinase inhibitor (TKI)-induced renal angiomyolipoma (AML) and pulmonary lymphangioleiomyomatosis (LAM) tumor cells were comparatively analyzed using cell survival assays, RNA sequencing, and bioinformatics to distinguish tumoricidal mechanisms adopted by each drug type. The efficacy of imatinib therapy was validated against spontaneously developing renal cystadenomas in tuberous sclerosis Tsc2+/- mouse models (C57BL/6J mice; N = 6; 400 mg/kg/d; oral gavage) compared with Tsc2+/- mice treated with PBS (C57BL/6J mice; N = 6). Our study revealed that TKIs imatinib and nilotinib were cytocidal to both pulmonary LAM and renal AML cell cultures through the downregulation of the glycoprotein GPVI pathway and resultant disruption in mitochondrial permeability, increased cytosolic cytochrome C, and caspase 3 activation. Importantly, renal tumor growth was significantly attenuated in imatinib-treated Tsc2+/- mice compared with PBS treatment. The preclinical studies reported here provide evidence documenting the effectiveness of TKIs in limiting LAM and AML cell growth and viability with important clinical potential. Furthermore, these drugs elicit their effects by targeting a PDGF pathway-dependent apoptotic mechanism supporting the investigation of these drugs as a novel class of TSC therapeutics.

Abstract 1230: The pre-metastatic niche establishment through the induction of the epithelial-to-mesenchymal transition by circulating exosomes in lymphangioleiomyomatosis (LAM): implication of the complement cascade

Abstract Exosomes are a class of extra cellular vesicles (EVs), with a multi vesicular endosomal origin, that are released by all cell types, with sizes ranging from 30-150nm and a lipid bilayer membrane. They have been shown to play key roles in disease progression and have diagnostic and disease monitoring potential. This study aims to characterize exosomes from the serum of patients with Lymphangioleiomyomatosis (LAM), a rare, low-grade, metastasizing neoplasm that occurs predominantly in females. Using Nanoparticle Tracking Analysis (NTA), serum from LAM patients (n=19) have significantly increased numbers of exosomes compared to serum samples from healthy controls (n=20) (8.9x109 vs 13.8x109 particles/ml; p=0.024). Furthermore, particles counts are significantly negatively correlated with the forced expiratory volume (FEV1) (r=-0.4667; p-value=0.0295) in LAM patients. Metalloproteinase activity in exosomes was measured by zymography. Interestingly, these LAM-derived exosomes had significantly higher activity of Pro-MMP-9 (3-fold increase; p-value=0.0278). We analyzed the effects of serum-derived exosomes on cells from an A549 cell line. Increased expression of vimentin, a major marker of EMT, was observed in cells treated with LAM-derived exosomes compared to healthy controls (1.4-fold increase; p=0.0217). Moreover, we showed by a modified Boyden chamber assay that exosomes derived from serum treatment increases the invasive capacity of A549 cells (fold change of 2.2; p-value=0.0004). We interrogated the LAM Single Cell Atlas and identified increased expression of TWIST1, a key transcription factor for EMT. TWIST1 was increased 8-fold in the lung and was uniquely expressed in 'LAM cells', which had metastasized. Furthermore, proteomic analysis revealed high expression of C3 and C5 in LAM-derived exosomes (respectively 1.4- and 2.1-fold change; p=0.0276 and p=0.0034) suggesting the potential regulatory role of the compliment system in the EMT mediated by exosomes These preliminary results highlight the urge to study the specific mechanistic interplay between MMPs and EMT, mediated by exosomes, and whether exosomes are involved in the metastatic spread of LAM cells to the lung and their role in influencing innate and adaptive immune cell response to this invasion. Citation Format: Amina Jouida, Patrick McFadden, Grace Buckley, Evelyn Lynn, O'Callaghan Marissa, Yasuhito Sekimoto, Aurelie Fabre, Michael P. Keane, Cormac McCarthy. The pre-metastatic niche establishment through the induction of the epithelial-to-mesenchymal transition by circulating exosomes in lymphangioleiomyomatosis (LAM): implication of the complement cascade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1230.