Hyperplasia of type II pneumocytes in pulmonary lymphangioleiomyomatosis

Cross talk between LAM cells and fibroblasts may influence alveolar epithelial cell behavior in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a female-specific cystic lung disease in which tuberous sclerosis complex 2 (TSC2)-deficient LAM cells, LAM-associated fibroblasts (LAFs), and other cell types infiltrate the lungs. LAM lesions can be associated with type II alveolar epithelial (AT2) cells. We hypothesized that the behavior of AT2 cells in LAM is influenced locally by LAFs. We tested this hypothesis in the patient samples and in vitro. In human LAM lung, nodular AT2 cells show enhanced proliferation when compared with parenchymal AT2 cells, demonstrated by increased Ki67 expression. Furthermore, nodular AT2 cells express proteins associated with epithelial activation in other disease states including matrix metalloproteinase 7, and fibroblast growth factor 7 (FGF7). In vitro, LAF-conditioned medium is mitogenic and positively chemotactic for epithelial cells, increases the rate of epithelial repair, and protects against apoptosis. In vitro, LAM patient-derived TSC2 null cells cocultured with LAFs upregulate LAF expression of the epithelial chemokine and mitogen FGF7, a potential mediator of fibroblast-epithelial cross talk, in a mechanistic target of rapamycin (mTOR)-dependent manner. In a novel in vitro model of LAM, ex vivo cultured LAM lung-derived microtissues promote both epithelial migration and adhesion. Our findings suggest that AT2 cells in LAM display a proliferative, activated phenotype and fibroblast accumulation following LAM cell infiltration into the parenchyma contributes to this change in AT2 cell behavior. Fibroblast-derived FGF7 may contribute to the cross talk between LAFs and hyperplastic epithelium in vivo, but does not appear to be the main driver of the effects of LAFs on epithelial cells in vitro.

Angiotensin-Converting Enzyme 2 (ACE2), Transmembrane Peptidase Serine 2 (TMPRSS2), and Furin Expression Increases in the Lungs of Patients with Idiopathic Pulmonary Fibrosis (IPF) and Lymphangioleiomyomatosis (LAM): Implications for SARS-CoV-2 (COVID-19) Infections

We previously reported higher ACE2 levels in smokers and patients with COPD. The current study investigates if patients with interstitial lung diseases (ILDs) such as IPF and LAM have elevated ACE2, TMPRSS2, and Furin levels, increasing their risk for SARS-CoV-2 infection and development of COVID-19. Surgically resected lung tissue from IPF, LAM patients, and healthy controls (HC) was immunostained for ACE2, TMPRSS2, and Furin. Percentage ACE2, TMPRSS2, and Furin expression was measured in small airway epithelium (SAE) and alveolar areas using computer-assisted Image-Pro Plus 7.0 software. IPF and LAM tissue was also immunostained for myofibroblast marker α-smooth muscle actin (α-SMA) and growth factor transforming growth factor beta1 (TGF-β1). Compared to HC, ACE2, TMPRSS2 and Furin expression were significantly upregulated in the SAE of IPF (p < 0.01) and LAM (p < 0.001) patients, and in the alveolar areas of IPF (p < 0.001) and LAM (p < 0.01). There was a significant positive correlation between smoking history and ACE2 expression in the IPF cohort for SAE (r = 0.812, p < 0.05) and alveolar areas (r = 0.941, p < 0.01). This, to our knowledge, is the first study to compare ACE2, TMPRSS2, and Furin expression in patients with IPF and LAM compared to HC. Descriptive images show that α-SMA and TGF-β1 increase in the IPF and LAM tissue. Our data suggests that patients with ILDs are at a higher risk of developing severe COVID-19 infection and post-COVID-19 interstitial pulmonary fibrosis. Growth factors secreted by the myofibroblasts, and surrounding tissue could further affect COVID-19 adhesion proteins/cofactors and post-COVID-19 interstitial pulmonary fibrosis. Smoking seems to be the major driving factor in patients with IPF.

Lymphangioleiomyomatosis: pathogenesis, clinical features, diagnosis, and management

Lymphangioleiomyomatosis (LAM) is a slowly progressive, low-grade, metastasising neoplasm of women, characterised by infiltration of the lung parenchyma with abnormal smooth muscle-like cells, resulting in cystic lung destruction. The invading cell in LAM arises from an unknown source and harbours mutations in tuberous sclerosis complex (TSC) genes that result in constitutive activation of the mechanistic target of rapamycin (mTOR) pathway, dysregulated cellular proliferation, and a programme of frustrated lymphangiogenesis, culminating in disordered lung remodelling and respiratory failure. Over the past two decades, all facets of LAM basic and clinical science have seen important advances, including improved understanding of molecular mechanisms, novel diagnostic and prognostic biomarkers, effective treatment strategies, and comprehensive clinical practice guidelines. Further research is needed to better understand the natural history of LAM; develop more powerful diagnostic, prognostic, and predictive biomarkers; optimise the use of inhibitors of mTOR complex 1 in the treatment of LAM; and explore novel approaches to the development of remission-inducing therapies.

Resident interstitial lung fibroblasts and their role in alveolar stem cell niche development, homeostasis, injury, and regeneration

Developing, regenerating, and repairing a lung all require interstitial resident fibroblasts (iReFs) to direct the behavior of the epithelial stem cell niche. During lung development, distal lung fibroblasts, in the form of matrix-, myo-, and lipofibroblasts, form the extra cellular matrix (ECM), create tensile strength, and support distal epithelial differentiation, respectively. During de novo septation in a murine pneumonectomy lung regeneration model, developmental processes are reactivated within the iReFs, indicating progenitor function well into adulthood. In contrast to the regenerative activation of fibroblasts upon acute injury, chronic injury results in fibrotic activation. In murine lung fibrosis models, fibroblasts can pathologically differentiate into lineages beyond their normal commitment during homeostasis. In lung injury, recently defined alveolar niche cells support the expansion of alveolar epithelial progenitors to regenerate the epithelium. In human fibrotic lung diseases like bronchopulmonary dysplasia (BPD), idiopathic pulmonary fibrosis (IPF), and chronic obstructive pulmonary disease (COPD), dynamic changes in matrix-, myo-, lipofibroblasts, and alveolar niche cells suggest differential requirements for injury pathogenesis and repair. In this review, we summarize the role of alveolar fibroblasts and their activation stage in alveolar septation and regeneration and incorporate them into the context of human lung disease, discussing fibroblast activation stages and how they contribute to BPD, IPF, and COPD.

Angiotensin-converting enzyme inhibitors may affect pulmonary function in lymphangioleiomyomatosis

INTRODUCTION

A local renin-angiotensin system exists in the pulmonary nodules of lymphangioleiomyomatosis patients. Sirolimus, the standard treatment for lymphangioleiomyomatosis, stabilizes lung function, but all patients do not respond to or tolerate sirolimus. As renin-angiotensin systems may affect tumor growth and metastasis, we questioned if angiotensin-converting enzyme inhibitors affected lymphangioleiomyomatosis disease progression.

METHODS

Retrospective study of 426 patients was performed, examining angiotensin-converting enzyme levels, pulmonary function data, and angiotensin-converting enzyme inhibitor treatment.

RESULTS

Serum angiotensin-converting enzyme levels were elevated in approximately 33% of patients, increased with duration of disease, and were inversely correlated with pulmonary function. Levels decreased significantly over time with sirolimus treatment. Treatment with angiotensin-converting enzyme inhibitors was reported by approximately 15% of patients and was significantly associated with a slower rate of decline in percentage predicted forced expiratory volume (FEV1) and diffusing capacity of the lungs for carbon monoxide (DLCO) in patients not treated with sirolimus. No significant differences in rates of decline of FEV1 or DLCO were seen in patients treated with both inhibitors and sirolimus versus sirolimus alone.

CONCLUSIONS

Angiotensin-converting enzyme inhibitors may slow decline of pulmonary function in patients with lymphangioleiomyomatosis not treated with sirolimus. These inhibitors may be an option or adjunct in the treatment of lymphangioleiomyomatosis. A clinical trial may be warranted to examine this possibility.

FUNDING

NIH.

The Lymphangioleiomyomatosis Lung Cell and Its Human Cell Models

Lymphangioleiomyomatosis (LAM) is a multisystem disease of women, affecting lungs, kidneys, and lymphatics. It is caused by the proliferation of abnormal smooth muscle-like LAM cells, with mutations and loss of heterozygosity in the TSC1 or, more frequently, TSC2 genes. Isolated pulmonary LAM cells have been difficult to maintain in culture, and most studies of LAM lung cells involve mixtures of TSC2 wild-type and TSC2-null cells. A clonal population of LAM lung cells has not been established, making analysis of the cells challenging. Cell lines have been established from angiomyolipomas, a common manifestation of LAM, and from tumors from patients with TSC. Circulating LAM cells have also been isolated from blood and other body fluids. LAM cells may also be identified in clusters apparently derived from lymphatic vessels. Genetics, patterns of antigen expression, and signaling pathways have been studied in LAM lung tissue and in LAM cell models, although rarely all in the same study. We show here that LAM cells manifest differences in these characteristics, depending on the source investigated, suggesting further studies.

Antibody αPEP13h reacts with lymphangioleiomyomatosis cells in lung nodules

BACKGROUND

Lymphangioleiomyomatosis (LAM) is characterized by the proliferation in the lung, axial lymphatics (eg, lymphangioleiomyomas), and kidney (eg, angiomyolipomas) of abnormal smooth muscle-like LAM cells, which express melanoma antigens such as Pmel17/gp100 and have dysfunctional tumor suppressor tuberous sclerosis complex (TSC) genes TSC2 or TSC1. Histopathologic diagnosis of LAM in lung specimens is based on identification of the Pmel17 protein with the monoclonal antibody HMB-45.

METHODS

We compared the sensitivity of HMB-45 to that of antipeptide antibody αPEP13h, which reacts with a C-terminal peptide of Pmel17. LAM lung nodules were laser-capture microdissected to identify proteins by Western blotting.

RESULTS

HMB-45 recognized approximately 25% of LAM cells within the LAM lung nodules, whereas αPEP13h identified > 82% of LAM cells within these structures in approximately 90% of patients. Whereas HMB-45 reacted with epithelioid but not with spindle-shaped LAM cells, αPEP13h identified both spindle-shaped and epithelioid LAM cells, providing greater sensitivity for detection of all types of LAM cells. HMB-45 recognized Pmel17 in premelanosomal organelles; αPEP13h recognized proteins in the cytoplasm as well as in premelanosomal organelles. Both antibodies recognized a Pmel17 variant of approximately 50 kDa.

CONCLUSIONS

Based on its sensitivity and specificity, αPEP13h may be useful in the diagnosis of LAM and more sensitive than HMB-45.

A quantitative proteomic approach to identify significantly altered protein networks in the serum of patients with lymphangioleiomyomatosis (LAM)

Lymphangioleiomyomatosis (LAM) is a rare and progressive cystic lung condition affecting approximately 3.4–7.5/million women, with an average lag time between symptom onset and diagnosis of upwards of 4 years. The aim of this work was to identify altered proteins in LAM serum which may be potential biomarkers of disease. Serum from LAM patient volunteers and healthy control volunteers were pooled and analysis carried out using quantitative 4-plex iTRAQ technology. Differentially expressed proteins were validated using ELISAs and pathway analysis was carried out using Ingenuity Pathway Analysis. Fourteen proteins were differentially expressed in LAM serum compared to control serum (p<0.05). Further screening validated the observed differences in extracellular matrix remodelling proteins including fibronectin (30% decrease in LAM, p = 0.03), von Willebrand Factor (40% reduction in LAM, p = 0.03) and Kallikrein III (25% increase in LAM, p = 0.03). Pathway networks elucidated the relationships between the ECM and cell trafficking in LAM. This study was the first to highlight an imbalance in networks important for remodelling in LAM, providing a set of novel potential biomarkers. These understandings may lead to a new effective treatment for LAM in the future.

Integration of mTOR and estrogen-ERK2 signaling in lymphangioleiomyomatosis pathogenesis

Lymphangioleiomyomatosis (LAM) is a destructive lung disease of women associated with the metastasis of tuberin-null cells with hyperactive mammalian target of rapamycin complex 1 (mTORC1) activity. Clinical trials with the mTORC1 inhibitor rapamycin have revealed partial efficacy but are not curative. Pregnancy appears to exacerbate LAM, suggesting that estrogen (E2) may play a role in the unique features of LAM. Using a LAM patient-derived cell line (bearing biallelic Tuberin inactivation), we demonstrate that E2 stimulates a robust and biphasic activation of ERK2 and transcription of the late response-gene Fra1 associated with epithelial-to-mesenchymal transition. In a carefully orchestrated collaboration, activated mTORC1/S6K1 signaling enhances the efficiency of Fra1 translation of Fra1 mRNA transcribed by the E2-ERK2 pathway, through the phosphorylation of the S6K1-dependent eukaryotic translation initiation factor 4B. Our results indicate that targeting the E2-ERK pathway in combination with the mTORC1 pathway may be an effective combination therapy for LAM.

Lymphatics in lymphangioleiomyomatosis and idiopathic pulmonary fibrosis

The primary function of the lymphatic system is absorbing and transporting macromolecules and immune cells to the general circulation, thereby regulating fluid, nutrient absorption and immune cell trafficking. Lymphangiogenesis plays an important role in tissue inflammation and tumour cell dissemination. Lymphatic involvement is seen in lymphangioleiomyomatosis (LAM) and idiopathic pulmonary fibrosis (IPF). LAM, a disease primarily affecting females, involves the lung (cystic destruction), kidney (angiomyolipoma) and axial lymphatics (adenopathy and lymphangioleiomyoma). LAM occurs sporadically or in association with tuberous sclerosis complex (TSC). Cystic lung destruction results from proliferation of LAM cells, which are abnormal smooth muscle-like cells with mutations in the TSC1 or TSC2 gene. Lymphatic abnormalities arise from infiltration of LAM cells into the lymphatic wall, leading to damage or obstruction of lymphatic vessels. Benign appearing LAM cells possess metastatic properties and are found in the blood and other body fluids. IPF is a progressive lung disease resulting from fibroblast proliferation and collagen deposition. Lymphangiogenesis is associated with pulmonary destruction and disease severity. A macrophage subset isolated from IPF bronchoalveolar lavage fluid (BALF) express lymphatic endothelial cell markers in vitro, in contrast to the same macrophage subset from normal BALF. Herein, we review lymphatic involvement in LAM and IPF.

Matrix metalloproteinase-19 is a key regulator of lung fibrosis in mice and humans

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by epithelial phenotypic changes and fibroblast activation. Based on the temporal heterogeneity of IPF, we hypothesized that hyperplastic alveolar epithelial cells regulate the fibrotic response.

OBJECTIVES

To identify novel mediators of fibrosis comparing the transcriptional signature of hyperplastic epithelial cells and conserved epithelial cells in the same lung.

METHODS

Laser capture microscope and microarrays analysis were used to identify differentially expressed genes in IPF lungs. Bleomycin-induced lung fibrosis was evaluated in Mmp19-deficient and wild-type (WT) mice. The role of matrix metalloproteinase (MMP)-19 was additionally studied by transfecting the human MMP19 in alveolar epithelial cells.

MEASUREMENTS AND MAIN RESULTS

Laser capture microscope followed by microarray analysis revealed a novel mediator, MMP-19, in hyperplastic epithelial cells adjacent to fibrotic regions. Mmp19(-/-) mice showed a significantly increased lung fibrotic response to bleomycin compared with WT mice. A549 epithelial cells transfected with human MMP19 stimulated wound healing and cell migration, whereas silencing MMP19 had the opposite effect. Gene expression microarray of transfected A549 cells showed that PTGS2 (prostaglandin-endoperoxide synthase 2) was one of the highly induced genes. PTGS2 was overexpressed in IPF lungs and colocalized with MMP-19 in hyperplastic epithelial cells. In WT mice, PTGS2 was significantly increased in bronchoalveolar lavage and lung tissues after bleomycin-induced fibrosis, but not in Mmp19(-/-) mice. Inhibition of Mmp-19 by siRNA resulted in inhibition of Ptgs2 at mRNA and protein levels.

CONCLUSIONS

Up-regulation of MMP19 induced by lung injury may play a protective role in the development of fibrosis through the induction of PTGS2.

Lymphangioleiomyomatosis (LAM): molecular insights lead to targeted therapies

LAM is a rare lung disease, found primarily in women of childbearing age, characterized by cystic lung destruction and abdominal tumors (e.g., renal angiomyolipoma, lymphangioleiomyoma). The disease results from proliferation of a neoplastic cell, termed the LAM cell, which has mutations in either of the tuberous sclerosis complex (TSC) 1 or TSC2 genes. Molecular phenotyping of LAM patients resulted in the identification of therapeutic targets for drug trials. Loss of TSC gene function leads to activation of mammalian target of rapamycin (mTOR), and thereby, effects on cell size and number. The involvement of mTOR in LAM pathogenesis is the basis for initiation of therapeutic trials of mTOR inhibitors (e.g., sirolimus). Occurrence of LAM essentially entirely in women is consistent with the hypothesis that anti-estrogen agents might prevent disease progression (e.g., gonadotropin-releasing hormone analogues). Levels of urinary matrix metalloproteinases (MMPs) were elevated in LAM patients, and MMPs were found in LAM lung nodules. In part because of these observations, effects of doxycycline, an anti-MMP, and anti-angiogenic agent, are under investigation. The metastatic properties of LAM cells offer additional potential for targets. Thus, insights into the molecular and biological properties of LAM cells and molecular phenotyping of patients with LAM have led to clinical trials of targeted therapies. Funded by the Intramural Research Program, NIH/NHLBI.

mTOR activation, lymphangiogenesis, and estrogen-mediated cell survival: the "perfect storm" of pro-metastatic factors in LAM pathogenesis

Research interest in lymphangioleiomyomatosis (LAM) has grown dramatically in the past decade, particularly among cancer biologists. There are at least two reasons for this: first, the discovery in the year 2000 that LAM cells carry TSC2 gene mutations, linking LAM with cellular pathways including the PI3K/Akt/mTOR axis, and allowing the Tuberous Sclerosis Complex (TSC)-regulated pathways that are believed to underlie LAM pathogenesis to be studied in cells, yeast, Drosophila, and mice. A second reason for the rising interest in LAM is the discovery that LAM cells can travel to the lung, including repopulating a donor lung after lung transplantation, despite the fact that LAM cells are histologically benign. This "benign metastasis" underpinning suggests that elucidating LAM pathogenesis will unlock a set of fundamental mechanisms that underlie metastatic potential in the context of a cell that has not yet undergone malignant transformation. Here, we will outline the data supporting the metastatic model of LAM, consider the biochemical and cellular mechanisms that may enable LAM cells to metastasize, including both cell autonomous and non-cell autonomous factors, and highlight a mouse model in which estrogen promotes the metastasis and survival of TSC2-deficient cells in a MEK-dependent manner. We propose a multistep model of LAM cell metastasis that highlights multiple opportunities for therapeutic intervention. Taken together, the metastatic behavior of LAM cells and the involvement of tumor-related signaling pathways lead to optimism that cancer-related paradigms for diagnosis, staging, and therapy will lead to therapeutic breakthroughs for women living with LAM.

Lymphangioleiomyomatosis and TSC2-/- cells

The cells comprising pulmonary lymphangioleiomyomatosis (LAM) and renal angiomyolipomas (AMLs) are heterogeneous, with variable mixtures of cells exhibiting differentiation towards smooth muscle, fat, and vessels. Cells grown from LAM and AMLs have likewise tended to be heterogeneous. The discovery that LAM and AMLs contain cells with mutations in the TSC1 or TSC2 genes is allowing investigators to discriminate between "two-hit" cells and neighboring cells, providing insights into disease pathogenesis. In rare cases, it has been possible to derive cells from human tumors, including AMLs and TSC skin tumors that are highly enriched for TSC2(-/-) cells. Cells derived from an Eker rat uterine leiomyoma (ELT3 cells) are Tsc2-null and these have been used in a rodent cell models for LAM. Further improvements in the ability to reliably grow well-characterized TSC2(-/-) cells from human tumors are critical to developing in vitro and in vivo model systems for studies of LAM pathogenesis and treatment.

Mammalian target of rapamycin signaling and autophagy: roles in lymphangioleiomyomatosis therapy

The pace of progress in lymphangioleiomyomatosis (LAM) is remarkable. In the year 2000, TSC2 gene mutations were found in LAM cells; in 2001 the tuberous sclerosis complex (TSC) genes were discovered to regulate cell size in Drosophila via the kinase TOR (target of rapamycin); and in 2008 the results were published of a clinical trial of rapamycin, a specific inhibitor of TOR, in patients with TSC and LAM with renal angiomyolipomas. This interval of just 8 years between a genetic discovery for which the relevant signaling pathway was as yet unknown, to the initiation, completion, and publication of a clinical trial, is an almost unparalleled accomplishment in modern biomedical research. This robust foundation of basic, translational, and clinical research in TOR, TSC, and LAM is now poised to optimize and validate effective therapeutic strategies for LAM. An immediate challenge is to deduce the mechanisms underlying the partial response of renal angiomyolipomas to rapamycin, and thereby guide the design of combinatorial approaches. TOR complex 1 (TORC1), which is known to be active in LAM cells, is a key inhibitor of autophagy. One hypothesis, which will be explored here, is that low levels of autophagy in TSC2-null LAM cells limits their survival under conditions of bioenergetic stress. A corollary of this hypothesis is that rapamycin, by inducing autophagy, promotes the survival of LAM cells, while simultaneously arresting their growth. If this hypothesis proves to be correct, then combining TORC1 inhibition with autophagy inhibition may represent an effective clinical strategy for LAM.

Involvement of lymphatics in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM), a rare multisystem disease, occurs primarily in women, with cystic destruction of the lungs, abdominal tumors, and involvement of the axial lymphatics in the thorax and abdomen. To understand the pathogenesis of LAM, we initiated a longitudinal study of patients with LAM; over 500 patients have been enrolled. LAM results from the proliferation of a neoplastic cell (LAM cell), which has mutations in the tuberous sclerosis complex (TSC) genes, TSC1 or TSC2. Consistent with their metastatic behavior, LAM cells were isolated from blood, urine, and chylous effusions. Surface proteins on LAM cells include those found on metastatic cells and those involved in cell migration. In the lung, LAM cells are found clustered in nodules, which appear in the walls of the cysts, and in the interstitium. LAM lung nodules are traversed by slit-like vascular structures, with lining cells showing reactivity with antibodies against components of lymphatic endothelial cells. The axial lymphatics appear to be infiltrated by LAM cells, which may result in obstruction and formation of chyle-filled lymphangioleiomyomas. LAM cell clusters have been isolated from chylous pleural effusions, and it is hypothesized that these clusters may be responsible for metastatic spread of LAM cells via lymphatic vessels. Consistent with a lymphangiogenic process, levels of VEGF-D, a lymphangiogenic factor, were higher in sera of patients with LAM and lymphatic involvement (i.e., lymphangioleiomyoma, adenopathy) than in healthy volunteers or LAM patients with cystic disease limited to the lung. These findings are consistent with an important function for lymphangiogenesis in LAM.

Sheep pox virus induces proliferation of type II pneumocytes in the lungs

The present study investigated the expression of pulmonary surfactant proteins (surfactant protein [SP]-A, SP-B, proSP-C), thyroid transcription factor-1 (TTF-1), proliferating cell nuclear antigen (PCNA) and the infiltration of CD3(+) T and CD79alphacy(+) B lymphocytes into the lungs of 10 lambs naturally infected with sheep pox virus. Microscopical examination detected marked epithelial hyperplasia, sheep pox cells and neutrophilic infiltration in pock nodules. Immunohistochemistry demonstrated intense expression of SPs in the cytoplasm of the hyperplastic type II pneumocytes in the nodular pock lesions. These cells displayed a gland-like arrangement. The hyperplastic and the normal bronchiolar epithelium did not express SPs. The nuclei of the hyperplastic and normal type II pneumocytes labelled positively for TTF-1. Strong PCNA positivity indicated epithelial cell proliferation in the pock nodules. Moderate to abundant numbers of CD3(+) T cells, but few CD79alphacy B lymphocytes, were detected in the pock lesions. Transmission electron microscopy revealed that the hyperplasia in the pock nodules comprised predominantly type II pneumocytes and that the sheep pox cells and epithelial cells contained virus particles in their cytoplasm. The results of this study show that sheep pox virus induces marked proliferation of type II pneumocytes and bronchiolar epithelial cells and that the lung lesions in diseased lambs are mainly proliferative.

Vascular endothelial growth factors C and D induces proliferation of lymphangioleiomyomatosis cells through autocrine crosstalk with endothelium

Lymphangioleiomyomatosis (LAM) is a potentially fatal lung disease characterized by nodules of proliferative smooth muscle-like cells. The exact nature of these LAM cells and their proliferative stimuli are poorly characterized. Herein we report the novel findings that the lymphangiogenic vascular endothelial growth factors (VEGF) C and D induce LAM cell proliferation through activation of their cognate receptor VEGF-R3 and activation of the signaling intermediates Akt/mTOR/S6. Furthermore, we identify expression of the proteoglycan NG2, a marker of immature smooth muscle cells, as a characteristic of LAM cells both in vitro and in human lung tissue. VEGF-C-induced LAM cell proliferation was in part a result of autocrine stimulation that resulted from cross talk with lymphatic endothelial cells. Ultimately, these findings identify the lymphangiogenic VEGF proteins as pathogenic growth factors in LAM disease and at the same time provide a novel pharmacotherapeutic target for a lung disease that to date has no known effective treatment.

Chemokine-enhanced chemotaxis of lymphangioleiomyomatosis cells with mutations in the tumor suppressor TSC2 gene

Lymphangioleiomyomatosis (LAM) is characterized by cystic lung destruction caused by LAM cells (smooth-muscle-like cells) that have mutations in the tumor suppressor genes tuberous sclerosis complex (TSC) 1 or 2 and have the capacity to metastasize. Since chemokines and their receptors function in chemotaxis of metastatic cells, we hypothesized that LAM cells may be recruited by chemokine(s) in the lung. Quantification of 25 chemokines in bronchoalveolar lavage fluid from LAM patients and healthy volunteers revealed that concentrations of CCL2, CXCL1, and CXCL5 were significantly higher in samples from LAM patients than those from healthy volunteers. In vitro, CCL2 or MCP-1 induced selective migration of cells, showing loss of heterozygosity of TSC2 from a heterogeneous population of cells grown from explanted LAM lungs. Additionally, the frequencies of single-nucleotide polymorphisms in the CCL2 gene promoter region differed significantly in LAM patients and healthy volunteers (p = 0.018), and one polymorphism was associated significantly more frequently with the decline of lung function. The presence (i.e., potential functionality) of chemokine receptors was evaluated using immunohistochemistry in lung sections from 30 LAM patients. Expression of chemokines and these receptors varied among LAM patients and differed from that seen in some cancers (e.g., breast cancer and melanoma cells). These observations are consistent with the notion that chemokines such as CCL2 may serve to determine mobility and specify the site of metastasis of the LAM cell.

Lymphatic involvement in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare, multisystem disease affecting primarily premenopausal women. The disease is characterized by cystic lung disease, at times leading to respiratory compromise, abdominal tumors (in particular, renal angiomyolipomas), and involvement of the axial lymphatics (e.g., adenopathy, lymphangioleiomyomas). Disease results from the proliferation of neoplastic cells (LAM cells), which, in many cases, have a smooth muscle cell phenotype, express melanoma antigens, and have mutations in one of the tuberous sclerosis complex genes (TSC1 or TSC2). In the lung, LAM cells found in the vicinity of cysts are, at times, localized in nodules and may be responsible for cyst formation through the production of proteases. Lymphatic channels, expressing characteristic lymphatic endothelial cell markers, are found within the LAM lung nodules. LAM cells may also be localized within the walls of the axial lymphatics, and, in some cases, penetrate the wall and proliferate in the surrounding adipose tissue. Consistent with extensive lymphatic involvement in LAM, the serum concentration of VEGF-D, a lymphangiogenic factor, is higher in LAM patients than in healthy volunteers.

Tuberous sclerosis complex 2 loss-of-function mutation regulates reactive oxygen species production through Rac1 activation

The products of the TSC1 (hamartin) and TCS2 (tuberin) tumor suppressor genes negatively regulate cell growth by inhibiting mTOR signaling. Recent research has led to the postulation that tuberin and/or hamartin are involved in tumor migration, presumably through Rho activation. Here we show that LEF-8 cells, which contain a Y1571 missense mutation in tuberin, express higher Rac1 activity than tuberin negative and positive cells. We also provide evidence of obvious lamellipodia formation in LEF-8 cells. Since the production of TSC2(Y1571H) cannot form a hetero-complex with hamartin, we further analyzed another mutant, TSC2(R611Q), which also lacks the ability to form a complex with hamartin. Introducing both forms of mutated TSC2 into COS-1 cells increased Rac1 activity as well as cell motility. We also found these two mutants interacted with Rac1. We further demonstrated that the introduction of mutated TSC2 into COS-1 cells can generate higher reactive oxygen species (ROS). These results indicate that loss-of-function mutated tuberin can activate Rac1 and thereby increase ROS production.

[Pulmonary lymphangioleiomyomatosis with or without tuberous sclerosis]

INTRODUCTION

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease affecting young women and presenting with recurrent pneumothorax.

BACKGROUND

Other lesions such as chylothorax or renal angiomyolipoma may suggest the diagnosis. The condition is related to a proliferation of abnormal smooth muscle cells staining for the monoclonal antibody HMB45. LAM can appear sporadically or be associated with tuberous sclerosis with abnormalities of the TSC2 suppressor gene. High resolution thoracic CT scanning shows bilateral, thin walled pulmonary cysts. Pulmonary function tests reveal bronchial obstruction and over-inflation with a reduced DLCO being the earliest abnormality.

VIEWPOINT

Although there are non-progressive forms, LAM usually leads to chronic respiratory insufficiency within a few, or ten or so years. In the absence of a controlled clinical trial hormone therapy has not been shown to be effective. Lung transplantation is the last therapeutic resort; recurrences in the transplanted lung have been occasionally reported.

CONCLUSIONS

Analysis of the molecular mechanisms induced by mutations of the TSC2 suppressor gene and the demonstration of the migratory properties of smooth muscle cells, whose origin may be extra-thoracic, reveal new specific antiproliferative therapeutic options.

Estradiol and tamoxifen stimulate LAM-associated angiomyolipoma cell growth and activate both genomic and nongenomic signaling pathways

Lymphangioleiomyomatosis (LAM) is a progressive lung disease affecting almost exclusively women. The reasons for this strong gender predisposition are poorly understood. Renal angiomyolipomas occur in 50-60% of sporadic LAM patients. The smooth muscle cells of pulmonary LAM and renal angiomyolipomas are nearly indistinguishable morphologically. Here, we report the first successful cell culture of a LAM-associated renal angiomyolipoma. The cells carried inactivating mutations in both alleles of the TSC2 gene and expressed estrogen receptor , estrogen receptor , and androgen receptor. To elucidate the cellular pathways through which steroid hormones influence LAM pathogenesis, we treated the cells with both estradiol and tamoxifen. Cell growth was stimulated by estradiol, associated with phosphorylation of p44/42 MAPK at 5 min and an increase in c-myc expression at 4 h. Tamoxifen citrate also stimulated cell growth, associated with increased phosphorylation of p44/42 MAPK and expression of c-myc, indicating that tamoxifen has agonist effects on angiomyolipoma cells. This response to tamoxifen in human angiomyolipoma cells differs from prior studies of Eker rat leiomyoma cells, possibly reflecting cell type or species differences in cells lacking tuberin. Our data provide the first evidence that estradiol stimulates the growth of angiomyolipoma cells, that tamoxifen has agonist effects in angiomyolipoma cells, and that estradiol and tamoxifen impact both genomic and nongenomic signaling pathways in angiomyolipoma cells. The responsiveness of angiomyolipoma cells to estradiol may be related to the underlying reasons that LAM affects primarily women.

Recurrent lymphangiomyomatosis after transplantation: genetic analyses reveal a metastatic mechanism

Lymphangiomyomatosis (LAM) is characterized by the proliferation of abnormal smooth muscle cells and cystic degeneration of the lung. LAM affects almost exclusively young women. Although lung transplantation provides effective therapy for end-stage LAM, there are reports of LAM recurrence after lung transplantation. Whether these recurrent LAM cells arise from the patient or the lung transplant donor is an area of controversy. We used microsatellite marker fingerprinting and TSC2 gene mutational analysis to study a patient with recurrent LAM after single-lung transplantation. The DNA microsatellite marker pattern indicated the presence of patient-derived LAM cells in the allograft. A somatic one base pair deletion in exon 18 of the TSC2 gene was identified in pulmonary and lymph node LAM cells before transplantation. The same mutation was in the recurrent LAM, demonstrating that the recurrent LAM was derived from the patient. Fluorescence in situ hybridization revealed that cells immunoreactive with the monoclonal antibody HMB-45 did not contain a Y chromosome. These data indicate that histologically benign LAM cells can migrate or metastasize in vivo to the transplanted lung. In addition, the patient had no evidence of a renal angiomyolipoma at autopsy and therefore demonstrated for the first time that somatic TSC2 mutations cause LAM in patients without angiomyolipomas.

Distribution and mRNA expression of insulin-like growth factor system in pulmonary lymphangioleiomyomatosis

BACKGROUND

Insulin-like growth factors (IGF-1 and IGF-2), the IGF-1 receptor (IGF-1R), and IGF-binding proteins (IGFBPs) are involved in normal pulmonary development and in the pathogenesis of smooth muscle cell tumors.

METHODS

To evaluate the role of the IGF system in lymphangioleiomyomatosis (LAM), we used immunohistochemical and in situ hybridization techniques to characterize the expression of IGF-1, IGF-2, IGF-1R, and IGFBP-2, -4, -5, and -6 in lung tissue from 18 LAM patients.

RESULTS

IGF-1, ICGF-2, IGF-1R, IGFBP-1, IGFBP-2, IGFBP-4, IGFBP-5, and IGFBP-6 were expressed by LAM cells. Reactivity and mRNA expression for IGF-2 were observed in LAM cells and resembled that found in normal smooth muscle cells during pulmonary development as well as in smooth muscle cell tumors. IGFBP-2, IGFBP-4, and IGFBP-6 were associated with spindle-shaped LAM cells, whereas IGFBP-5 was associated mainly with epithelioid LAM cells.

CONCLUSIONS

These findings suggest that the IGFBPs modulate the effects of the IGFs on LAM cells. Thus, the patterns of localization and expression of components of the IGF system in LAM strongly suggest that these agents are involved in the proliferation of LAM cells.