Lymphangiogenesis-Mediated Shedding of LAM Cell Clusters as a Mechanism for Dissemination in Lymphangioleiomyomatosis

Synergistic effects of mTOR inhibitors with VEGFR3 inhibitors on the interaction between TSC2-mutated cells and lymphatic endothelial cells

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease affecting the lung, kidney, and lymphatic system with a molecular mechanism of tuberous sclerosis complex 2 (TSC2) mutations. Vascular endothelial growth factor D (VEGF-D), a ligand for vascular endothelial growth factor receptor 3 (VEGFR3), is a diagnostic biomarker of LAM and is associated with lymphatic circulation abnormalities. This study explored the interaction between LAM cells and lymphatic endothelial cells (LECs) and the effects of rapamycin on this interaction, which may help to identify new targets for LAM treatment. This study used direct and indirect cocultures of TSC2-null cells and LECs. The xenograft model was applied to explore the therapeutic feasibility. Single-cell sequencing revealed increased LECs in the lungs of LAM patients through activation of pathways involved in lymphangiogenesis. TSC2-null cells attracted LECs and promoted tube formation. VEGF-D/VEGFR3 was a key mediator of the above interaction. Rapamycin can directly inhibit recruitment but not the tube formation of LECs in vitro. The combination of rapamycin with VEGFR3 inhibitors not only enhanced the effect of rapamycin but also inhibited lymphatic related manifestations including the tube formation and the lymphatic metastasis. Our findings demonstrated that LAM cells recruit LECs and promote tube formation via VEGF-D/VEGFR3. Rapamycin only partially blocked this interaction. The synergistic effects of rapamycin and VEGFR3 inhibitors suggest a novel strategy for the treatment of LAM and other TSC2-mutated diseases.

Targeting fibroblast-endothelial cell interactions in LAM pathogenesis using 3D spheroid models and spatial transcriptomics

Lymphangioleiomyomatosis (LAM) is a progressive lung disease with limited treatments, largely because of an incomplete understanding of its pathogenesis. Lymphatic endothelial cells (LECs) invade LAM cell clusters, which include human melanoma black-45-positive epithelioid cells and smooth muscle α-actin-expressing LAM-associated fibroblasts (LAMFs). Recent evidence shows that LAMFs resemble cancer-associated fibroblasts, with LAMF-LEC interactions contributing to disease progression. To explore these mechanisms, we used spatial transcriptomics on LAM lung tissues and identified a gene cluster enriched in kinase signaling pathways linked to myofibroblasts and coexpressed with LEC markers. Kinase arrays revealed elevated PDGFR and FGFR in LAMFs. Using a 3D coculture spheroid model of primary LAMFs and LECs, we observed increased invasion in LAMF-LEC spheroids compared with non-LAM fibroblasts. Treatment with sorafenib, a multikinase inhibitor, significantly reduced invasion, outperforming rapamycin. We also verified tuberous sclerosis complex 2-deficient renal angiomyolipoma (TSC2-null AML) cells as key VEGF-A secretors; VEGF-A was suppressed by sorafenib in both TSC2-null AML cells and LAMFs. These findings highlight VEGF-A and basic FGF as potential therapeutic targets and suggest multikinase inhibition as a promising strategy for LAM.

Diffuse Cystic Lung Disease: A Clinical Guide to Recognition and Management

TOPIC IMPORTANCE

Diffuse cystic lung diseases (DCLDs) represent a group of pathophysiologically heterogeneous entities that share a common radiologic phenotype of multiple thin-walled pulmonary cysts. DCLDs differ from the typical fibroinflammatory interstitial lung diseases in their epidemiology, clinical presentation, molecular pathogenesis, and therapeutic approaches, making them worthy of a distinct classification. The importance of timely and accurate identification of DCLDs is heightened by the impact on patient management including recent discoveries of targeted therapeutic approaches for some disorders.

REVIEW FINDINGS

This article offers a practical framework for evaluating patients with DCLD, indicating the most appropriate and current diagnostic and management approaches. We focus on the DCLDs that are most likely to be encountered by practicing pulmonologists: lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis, Birt-Hogg-Dubé syndrome, and lymphoid interstitial pneumonia. Chest CT scan is the most informative noninvasive diagnostic modality to identify DCLDs. Thereafter, instituting a structured approach to high-yield associated factors (eg, medical, social, and family history; renal and dermatologic findings) increases the likelihood of identifying DCLDs and achieving a diagnosis.

SUMMARY

Although the individual diseases that comprise the DCLD family are rare, taken together, DCLDs can be encountered more frequently in clinical practice than commonly perceived. An increased eagerness among general pulmonary physicians to recognize these entities, coupled with a practical and systematic clinical approach to examinations and investigations, is required to improve case findings, allow earlier intervention, and reduce morbidity and mortality.

The development for emerging biomarkers of lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare, slowly progressing, low-grade metastatic tumor primarily affecting women. Currently, vascular endothelial growth factor-D (VEGF-D) is the only validated diagnostic biomarker, enabling diagnosis of LAM without the need for lung biopsy in appropriate clinical settings. However, VEGF-D concentrations are normal in about 30% of patients, rendering it insufficient for diagnosing all cases of LAM. There remains a need to identify more non-invasive, safe, sensitive, and specific biomarkers associated with LAM. Therefore, it is imperative to explore novel non-invasive, safe, and specific diagnostic methods for LAM. This article aims to review biomarkers associated with LAM, including potential biomarkers newly discovered or showing advancements in classical biomarkers widely used in LAM, and discuss their application in LAM diagnosis, assessment of disease severity, prediction of treatment response, and prognosis. （LAM） 、，。，-D （VEGF-D） ， LAM。， 30% VEGF-D ， LAM 。 LAM 、、。，、 LAM 。 LAM ， LAM ， LAM 、、。.

Targeting Fibroblast-Endothelial Interactions in LAM Pathogenesis: 3D Spheroid and Spatial Transcriptomic Insights for Therapeutic Innovation

Lymphangioleiomyomatosis (LAM) is a progressive lung disease with limited treatments, largely due to an incomplete understanding of its pathogenesis. Lymphatic endothelial cells (LECs) invade LAM cell clusters, which include HMB-45-positive epithelioid cells and smooth muscle α-actin-expressing LAM-associated fibroblasts (LAMFs). Recent evidence shows that LAMFs resemble cancer-associated fibroblasts, with LAMF-LEC interactions contributing to disease progression. To explore these mechanisms, we used spatial transcriptomics on LAM lung tissues and identified a gene cluster enriched in kinase signaling pathways linked to myofibroblasts and co-expressed with LEC markers. Kinase arrays revealed elevated PDGFR and FGFR in LAMFs. Using a 3D co-culture spheroid model of primary LAMFs and LECs, we observed increased invasion in LAMF-LEC spheroids compared to non-LAM fibroblasts. Treatment with sorafenib, a multikinase inhibitor, significantly reduced invasion, outperforming Rapamycin. We also confirmed TSC2-null AML cells as key VEGF-A secretors, which was suppressed by sorafenib in both AML cells and LAMFs. These findings highlight VEGF-A and bFGF as potential therapeutic targets and suggest multikinase inhibition as a promising strategy for LAM.

Lymphangioleiomyomatosis as a potent lung cancer risk factor: Insights from a Japanese large cohort study

BACKGROUND AND OBJECTIVE

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease associated with the functional tumour suppressor genes TSC1 and TSC2 and causes structural destruction in the lungs, which could potentially increase the risk of lung cancer. However, this relationship remains unclear because of the rarity of the disease.

METHODS

We investigated the relative risk of developing lung cancer among patients diagnosed with LAM between 2001 and 2022 at a single high-volume centre in Japan, using data from the Japanese Cancer Registry as the reference population. Next-generation sequencing (NGS) was performed in cases where tumour samples were available.

RESULTS

Among 642 patients diagnosed with LAM (sporadic LAM, n = 557; tuberous sclerosis complex-LAM, n = 80; unclassified, n = 5), 13 (2.2%) were diagnosed with lung cancer during a median follow-up period of 5.13 years. All patients were female, 61.5% were never smokers, and the median age at lung cancer diagnosis was 53 years. Eight patients developed lung cancer after LAM diagnosis. The estimated incidence of lung cancer was 301.4 cases per 100,000 person-years, and the standardized incidence ratio was 13.6 (95% confidence interval, 6.2-21.0; p = 0.0008). Actionable genetic alterations were identified in 38.5% of the patients (EGFR: 3, ALK: 1 and ERBB2: 1). No findings suggested loss of TSC gene function in the two patients analysed by NGS.

CONCLUSION

Our study revealed that patients diagnosed with LAM had a significantly increased risk of lung cancer. Further research is warranted to clarify the carcinogenesis of lung cancer in patients with LAM.

Lymphangioleiomyomatosis and Other Cystic Lung Diseases

Cysts and cavities in the lung are commonly encountered on chest imaging. It is necessary to distinguish thin-walled lung cysts (≤2 mm) from cavities and characterize their distribution as focal or multifocal versus diffuse. Focal cavitary lesions are often caused by inflammatory, infectious, or neoplastic processes in contrast to diffuse cystic lung diseases. An algorithmic approach to diffuse cystic lung disease can help narrow the differential diagnosis, and additional testing such as skin biopsy, serum biomarkers, and genetic testing can be confirmatory. An accurate diagnosis is essential for the management and disease surveillance of extrapulmonary complications.

Lymphangioleiomyomatosis: Searching for potential biomarkers

Background

Vascular endothelial growth factor-D (VEGF-D) is the most commonly used biomarker for diagnosing lymphangioleiomyomatosis (LAM). However, lung biopsy is often necessary as well; therefore, defining new biomarkers for LAM is crucial. The aim of this study was to describe the diagnostic accuracy of a variety of biomarkers.

Methods

We assessed 13 analytes in serum related to extracellular matrix remodeling, lymphatic involvement and angiogenesis in a cohort of patients with LAM, comparing them with patients with other cystic lung diseases (OCLD) and healthy women. A scoring method based on the cut-point of each VEGF-D and metalloproteinase-2 (MMP-2) was used to evaluate the diagnostic performance of the marker combination.

Results

A total of 97 subjects were recruited: 59 (61%) LAM patients, 18 (19%) OCLD patients, and 20 (20%) healthy female controls. MMP-2 was the only extracellular matrix remodeling biomarker able to differentiate LAM patients from OCLD and healthy patients. Serum MMP-2 was higher in LAM patients [median 578 (465-832) ng/ml] than in patients with OCLD and healthy controls [medians 360 (314-546) and 427 (365-513) ng/ml, respectively (p < 0.0001)]. The area under ROC curve (AUC) of MMP-2 was 0.785 and that of VEGF-D 0.815 (p = 0.6214). The sensitivity/specificity profiles of each biomarker (54/92% for MMP-2, 59/95% for VEGF-D) yielded a composite score (-6.36 + 0.0059 × VEGF-D + 0.0069 × MMP-2) with higher accuracy than each component alone (AUC 0.88 and sensitivity/specificity 79/87%).

Conclusion

Combining MMP-2 and VEGF-D may increase diagnostic accuracy for LAM.

Vasohibin-1 and -2 in pulmonary lymphangioleiomyomatosis (LAM) cells associated with angiogenic and prognostic factors

Lymphangioleiomyomatosis (LAM) is a rare pulmonary neoplasm, clinically associated with dyspnea and respiratory failure. Current therapeutic modalities do not necessarily reach satisfactory outcome and novel therapeutic approaches are currently warranted. Therefore, in this study, we focused on vasohibin-1 (VASH1) and -2 (VASH2); VASH1 terminated and VASH2 promoted angiogenesis. In addition, both VASH1/2 were reported to influence the progression of various human malignancies. We first performed hierarchical clustering analysis to attempt to classify 36 LAM cases into three different clusters according to immunoreactivity of VASH1/2 and other angiogenic and prognostic factors of LAM; VEGFR1/2/3, p-mTOR, p-S6, p-4EBP, ERα, PgR, MMP2, and MMP9. The cluster harboring higher angiogenic factors had higher VASH1/2 status. VASH1 was significantly positively correlated with VEGFR2, MMP9, and p-mTOR (p-value <0.05), and VASH2 with both angiogenic and prognostic factors including VEGFR1, PgR, MMP9, p-mTOR, p-S6, and p-4EBP (p-value <0.05). Subsequent PCR array of angiogenic genes demonstrated that high VASH1 mRNA was significantly positively associated with the status of SPHK1 and TYPM, lower EGF and EFNB2 (p-value <0.05), and high VASH2 mRNA negatively with MMP2 (p-value <0.05). VASH1 was considered to be up-regulated by activation of angiogenesis, whereas VASH2 could influence the angiogenesis and progression of LAM.

Chylothorax and Pseudochylothorax

Classically, both chylothorax and pseudochylothorax present as a pleural effusion with a characteristic milky white appearance to the pleural fluid. Although both are rare causes of pleural effusion, they have distinct etiologies and clinical implications, and as a result require different management strategies. Pleural fluid analysis of cholesterol and triglyceride levels is key to differentiating the 2 entities from one another and then guide the clinician to determine the best next steps in evaluation and management.

Tuberous sclerosis complex for the pulmonologist

Tuberous sclerosis complex (TSC) is a rare multisystem genetic disorder affecting almost all organs with no sex predominance. TSC has an autosomal-dominant inheritance and is caused by a heterozygous mutation in either the TSC1 or TSC2 gene leading to hyperactivation of the mammalian target of rapamycin (mTOR). TSC is associated with several pulmonary manifestations including lymphangioleiomyomatosis (LAM), multifocal micronodular pneumocyte hyperplasia (MMPH) and chylous effusions. LAM is a multisystem disorder characterised by cystic destruction of lung parenchyma, and may occur in either the setting of TSC (TSC-LAM) or sporadically (S-LAM). LAM occurs in 30–40% of adult females with TSC at childbearing age and is considered a nonmalignant metastatic neoplasm of unknown origin. TSC-LAM is generally milder and, unlike S-LAM, may occur in males. It manifests as multiple, bilateral, diffuse and thin-walled cysts with normal intervening lung parenchyma on chest computed tomography. LAM is complicated by spontaneous pneumothoraces in up to 70% of patients, with a high recurrence rate. mTOR inhibitors are the treatment of choice for LAM with moderately impaired lung function or chylous effusion. MMPH, manifesting as multiple solid and ground-glass nodules on high-resolution computed tomography, is usually harmless with no need for treatment.

Tuberous sclerosis complex is associated with diverse pulmonary manifestations including LAM, multiple micronodular pneumocyte hyperplasia and chylous effusions. LAM occurs in 30–40% of adult females with tuberous sclerosis complex.https://bit.ly/3iLqZ08

A 34-Year-Old Woman from Brazil with Pulmonary Lymphangioleiomyomatosis Diagnosed by Raised Serum Vascular Endothelial Growth Factor-D (VEGF-D) Levels and Lung Cysts on Computed Tomography Imaging Presenting with COVID-19 Pneumonia

Patient: Female, 34-year-old

Final Diagnosis: COVID-19 • lymphangioleiomyomatosis

Symptoms: Dyspnea • fever • hypoxemia • myalgia

Medication: Sirolimus

Clinical Procedure: —

Specialty: Pulmonology

Sporadic uterine Lymphangioleiomyomatosis (LAM): Report of a unique case arising in the lower uterine segment with short review

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Extrapulmonary lymphangioleiomyomatosis is rare and can be associated with tuberous sclerosis.

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Recognition of lymphangioleiomyomatosis is important for early disease screening and genetic testing.

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Lymphangioleiomyomatosis in lower uterine segment is very rare and can be overlooked.

Spindle cell lesion on fine needle aspiration as an initial step for diagnosis of lymphangioleiomyomatosis: Report of a rare case

Lymphangioleiomyomatosis (LAM) is a rare systemic disease of women of reproductive age characterized by proliferation of abnormal smooth muscle like cells (LAM cells). Patients with LAM characteristically present with chronic dyspnea and cough and less commonly with spontaneous pneumothorax. Manifestation of extrapulmonary LAM as an initial presenting symptom is rare with a renal angiomyolipoma and lymphangioleiomyoma being most common. Although histologic findings of LAM are well-described, the cytological features; however, have been described only in few case reports, which focus on pulmonary LAM. Here, we report a case where initial diagnosis of LAM was made on pelvic "lymph node" fine needle aspiration (FNA) and biopsy in otherwise asymptomatic 25-year-old female, leading to further investigation and detection of developing cystic lung lesions. FNA cytology from the pelvic "lymph node" yielded proliferation of spindle cells without cytologic atypia. This case presented both clinical and histopathologic challenge, requiring clinical correlation and immunohistochemical staining for diagnosis. While rare, it is important to consider LAM in the differential diagnosis of spindle cell lesions in aspirate from nodules around vascular bundles in women of reproductive age even without history of lung lesion.

Isolation and characterisation of lymphatic endothelial cells from lung tissues affected by lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare pulmonary disease characterised by the proliferation of smooth muscle-like cells (LAM cells), and an abundance of lymphatic vessels in LAM lesions. Studies reported that vascular endothelial growth factor-D (VEGF-D) secreted by LAM cells contributes to LAM-associated lymphangiogenesis, however, the precise mechanisms of lymphangiogenesis and characteristics of lymphatic endothelial cells (LECs) in LAM lesions have not yet been elucidated. In this study, human primary-cultured LECs were obtained both from LAM-affected lung tissues (LAM-LECs) and normal lung tissues (control LECs) using fluorescence-activated cell sorting (FACS). We found that LAM-LECs had significantly higher ability of proliferation and migration compared to control LECs. VEGF-D significantly promoted migration of LECs but not proliferation of LECs in vitro. cDNA microarray and FACS analysis revealed the expression of vascular endothelial growth factor receptor (VEGFR)-3 and integrin α9 were elevated in LAM-LECs. Inhibition of VEGFR-3 suppressed proliferation and migration of LECs, and blockade of integrin α9 reduced VEGF-D-induced migration of LECs. Our data uncovered the distinct features of LAM-associated LECs, increased proliferation and migration, which may be due to higher expression of VEGFR-3 and integrin α9. Furthermore, we also found VEGF-D/VEGFR-3 and VEGF-D/ integrin α9 signaling play an important role in LAM-associated lymphangiogenesis.

Lymphangioleiomyoma of the Uterus and Pelvic Lymph Nodes: A Report of 3 Cases, Including the Potentially Earliest Manifestation of Extrapulmonary Lymphangioleiomyomatosis

We present 3 cases of extrapulmonary lymphangioleiomyomatosis (LAM) identified incidentally in the uterine corpus and pelvic nodes resected for other reasons. One patient, a 47-yr-old female with corpus cancer, underwent a total hysterectomy and nodal dissection; the other 2 patients, aged 44 and 49 yr, underwent simple hysterectomy for corpus leiomyomas. None of the patients had evidence of tuberous sclerosis complex or any significant lesions in other organs. An area of spindle cell proliferation, intimately associated with dilated and tortuous lymphatic vessels, was found in the myometrium of all 3 patients, and nodal involvement with spindle cell proliferation was observed in the patient with corpus cancer. The spindle cells had faintly eosinophilic cytoplasm and a bland appearance. They were immunoreactive for α-SMA, gp100 (HMB45), and Melan-A. Tumor cell clusters lined with a single layer of lymphatic endothelium were floating in the lymphatic vessel lumen. These lesions were diagnosed as lymphangioleiomyoma in the uterine corpus and associated lymph nodes. Two of the cases seemed to be the earliest manifestations of extrapulmonary LAM, and the other case represents early-phase metastasis of LAM from the uterus. The present cases support the speculation that the uterus is the primary source of LAM cells.

Single-Cell Transcriptomic Analysis Identifies a Unique Pulmonary Lymphangioleiomyomatosis Cell

Rationale: Lymphangioleiomyomatosis (LAM) is a metastatic neoplasm of reproductive-age women associated with mutations in tuberous sclerosis complex genes. LAM causes cystic remodeling of the lung and progressive respiratory failure. The sources and cellular characteristics of LAM cells underlying disease pathogenesis remain elusive.Objectives: Identification and characterization of LAM cells in human lung and uterus using a single-cell approach.Methods: Single-cell and single-nuclei RNA sequencing on LAM (n = 4) and control (n = 7) lungs, immunofluorescence confocal microscopy, ELISA, and aptamer proteomics were used to identify and validate LAMCORE cells and secreted biomarkers, predict cellular origins, and define molecular and cellular networks in LAM.Measurements and Main Results: A unique cell type termed LAMCORE was identified, which was distinct from, but closely related to, lung mesenchymal cells. LAMCORE cells expressing signature genes included known LAM markers such as PMEL, FIGF, CTSK, and MLANA and novel biomarkers validated by aptamer screening, ELISA, and immunofluorescence microscopy. LAM cells in lung and uterus are morphologically indistinguishable and share similar gene expression profiles and biallelic TSC2 mutations, supporting a potential uterine origin for the LAMCORE cell. Effects of LAM on resident pulmonary cell types indicated recruitment and activation of lymphatic endothelial cells.Conclusions: A unique population of LAMCORE cells was identified in lung and uterus of patients with LAM, sharing close transcriptomic identity. LAM cell selective markers, secreted biomarkers, and the predicted cellular molecular features provide new insights into the signaling and transcriptional programs that may serve as diagnostic markers and therapeutic targets to influence the pathogenesis of LAM.

Properties of rapamycin solid lipid nanoparticles for lymphatic access through the lungs & part I: the effect of size

Background: Lymphangioleiomyomatosis (LAM) is characterized by growth of smooth muscle-like cells in the lungs that spread to other organs via lymphatic vessels. Current oral rapamycin treatment is limited by low bioavailability of approximately 15%. Aim: The effect of inhaled rapamycin solid lipid nanoparticles (Rapa-SLNs) size on its penetration through the lymphatics. Method: Three Rapa-SLN formulations (200-1000 nm) were produced and assessed for particle characteristics and further for toxicity and performance in vitro. Results: Rapa-SLNs of 200 nm inhibited proliferation in TSC2-negative mouse embryonic fibroblast cells and penetrated the respiratory epithelium and lymphatic endothelium significantly faster compared with free rapamycin and larger Rapa-SLNs. Conclusion: Rapa-SLN approximately 200 nm allows efficient entry of rapamycin into the lymphatic system and is therefore a promising treatment for LAM patients.

Properties of rapamycin solid lipid nanoparticles for lymphatic access through the lungs & part II: the effect of nanoparticle charge

Aim: Lymphangioleiomyomatosis is characterized by smooth muscle-like cells in the lungs that spread to other organs via lymphatic vessels. Oral rapamycin is restricted by low bioavailability approximately 15%. The aim of the present study is to systematically investigate the effect of inhaled rapamycin solid lipid nanoparticles (Rapa-SLN) surface charge on efficacy and penetration into the lymphatics. Materials & methods: Rapa-SLN formulations with different charge: neutral, positive and negative, were produced and assessed for their physicochemical particle characteristics and efficacy in vitro. Results: Negative Rapa-SLNs were significantly faster at entering the lymphatic endothelium and more potent at inhibiting lymphanigiogenesis compared with neutral and positive Rapa-SLNs. Conclusion: Negative Rapa-SLNs showed efficient lymphatic access and should therefore be investigated further as a treatment for targeting extrapulmonary lymphangioleiomyomatosis.

Pulmonary Lymphangioleiomyomatosis originates in the pleural mesothelial cell population

Lymphangioleiomyomatosis (LAM) is a cystic lung disease mainly affecting women, in which degradation of the lung parenchyma is associated with a cell of unknown provenance, known as a LAM cell. LAM cells carry TSC2 mutations and can be identified in the lung parenchyma by their expression of both smooth muscle actin and antigens characteristic of melanocytes and melanocytic tumors. The nature of the cell-of-origin of LAM is controversial, and despite continued research effort remains elusive. Further, it has not been possible to culture pulmonary LAM cells in vitro, and current research relies on cells and animal models which may not recapitulate all features of the disease. We noted aberrant expression of melanoma antigens in pleural mesothelial cells in lung tissue from LAM patients, indicating that these cells could be the precursors of parenchymal LAM cells. We hypothesise that loss of tuberin function following TSC2 mutation in the mesothelial cell lineage gives rise to the cell-of-origin of pulmonary LAM (P-LAM), and of other associated conditions commonly noted in LAM patients. The unique properties of mesothelial cells provide a straightforward explanation of the diverse presentation of LAM.

The efficacy and safety of pharmacological treatments for lymphangioleiomyomatosis

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a rare, low-grade multisystem neoplastic disease. Most LAM patients are at a high risk of losing lung function at an accelerated rate and developing progressive dyspnea. Recently, several studies have reported their experience with pharmacological treatments for LAM. Therefore, we conducted a systematic review and meta-analysis to assess the efficacy and safety of these therapies.

METHODS

PubMed (Medline), EMBASE, Cochrane Library, Web of Science and EBSCO Host were searched (until March 31, 2019) for eligible prospective studies regarding LAM patients treated with pharmacological treatments. Random effect models were used for quantitative analysis.

RESULTS

Fourteen prospective studies regarding five pharmacological treatments (including sirolimus, everolimus, doxycycline, triptorelin, and a combination therapy of sirolimus and hydroxychloroquine) were enrolled in our systematic review, and ten of them were used for the meta-analysis. Seven prospective studies reported that sirolimus was effective at improving or stabilizing lung function and alleviating renal angiomyolipoma (AML) in LAM patients. Subsequent quantitative analyses showed that during sirolimus treatment, the pooled values of lung function and 6-min walk distance (6MWD) were not significantly changed (P > 0.05), with the pooled response rate of AML being 0.62 (95% confidence intervals [CIs]: 0.43 to 0.82, I2 = 65%). Regarding everolimus, three prospective studies reported similar effects to those of sirolimus with regard to preserving lung function and reducing AMLs. The meta-analysis showed that the changes in lung function during everolimus treatment were not statistically significant (P > 0.05), while the pooled response rate of AML was 0.78 (95% CI: 0.68 to 0.88, I2 = 8%). Neither the qualitative nor the quantitative results confirmed the benefits of doxycycline or triptorelin treatment, and the effects of the combination therapy were unclear in LAM patients. Most of the adverse events during pharmacological treatments were low or moderate grade and tolerable.

CONCLUSIONS

Overall, sirolimus and everolimus were recommended for the treatment of LAM because they could stabilize lung function and alleviate renal AML. Doxycycline and triptorelin were not recommended for the treatment of LAM because no beneficial outcomes were consistently observed. The efficacy and safety of combination therapy remain to be further explored.

Serum vascular endothelial growth factor-D as a diagnostic and therapeutic biomarker for lymphangioleiomyomatosis

BACKGROUND

In lymphangioleiomyomatosis (LAM), tuberous sclerosis gene mutations activate the mechanistic target of the rapamycin pathway, resulting in vascular endothelial growth factor-D (VEGF-D) overproduction. While the utility of serum VEGF-D testing for the diagnosis of LAM is outlined in ATS/JRS LAM Guidelines, the assay has not been fully validated for Asian populations. Our aims were to validate serum VEGF-D testing in Japan, by directly comparing measurements in Japan and the U.S., determining the diagnostic cut-off for serum VEGF-D levels among the Japanese women with typical thin walled cystic change on CT, and determining the performance of VEGF-D as a prognostic biomarker.

SUBJECTS AND METHODS

We determined serum VEGF-D levels from 108 LAM patients, 14 disease controls, and 51 healthy volunteers from the Japanese population. Measurements of 61 LAM patients were compared to those from the principal VEGF-D laboratory in the U.S at Cincinnati Children's Hospital Medical Center. We correlated baseline serum VEGF-D levels with baseline and longitudinal clinical data to determine how pregnancy, sirolimus or gonadotrophin-releasing hormone (GnRH) agonists influence serum VEGF-D levels.

RESULTS

Serum VEGF-D measurements in Japan and the U.S. were very similar. Baseline serum VEGF-D levels effectively distinguished LAM from other diseases and healthy volunteers at a cut-off level of 645 pg/ml and were diagnostically specific at 800 pg/ml, consistent with the recommendations of the ATS/JRS LAM Guidelines. Baseline serum VEGF-D correlated negatively with the DLco baseline % predicted and with the annual decrease in DLco % predicted. There was no significant association between baseline serum VEGF-D level and the outcomes of death or transplant. Serum VEGF-D levels markedly decreased during treatment with sirolimus, but not with GnRH analogues. Serum VEGF-D levels of most LAM patients did not increase over time, and neither pregnancy nor menopause significantly modulated serum VEGF-D levels.

CONCLUSIONS

Serum VEGF-D is a useful diagnostic and therapeutic biomarker for LAM. Satisfactory precision and international inter-laboratory agreement of the clinical assay support VEGF-D recommendations in the ATS/JRS LAM Guidelines for the Japanese population.

Dysregulation of the endothelin pathway in lymphangioleiomyomatosis with no direct effect on cell proliferation and migration

LAM is a rare low-grade metastasizing lung neoplasm. Inhibitors of mTOR improve clinical outcome of LAM patients by preventing loss of lung function. Nevertheless, other cell targets may be of interest for drug development. Therefore, we explored the potential role of EDN1 (endothelin) in LAM. We report an increased endothelin blood level in LAM patients as well as EDN1 overexpression and EDN1 receptor downregulation in LAM-derived primary cells and in TSC2^NEG cells mutated in TSC2. We evidenced EDN pathway dysregulation based on EDN1, EDNRA, EDNRB and ARRB1 mRNA expression in LAM-derived primary cells. We showed overexpression of EDN1 and ARRB1 mRNAs in TSC2^NEG cells; these cells lost their ability to respond to stimulation by endothelin. We analyzed the effects of endothelin receptor antagonists alone or in combination with rapamycin, an mTOR inhibitor, on proliferation and migration of LAM cells. Rapamycin treatment of TSC2^NEG cells significantly reduced cell proliferation or migration, while none of the tested inhibitors of EDN receptors impaired these functions. We showed that TSC2^NEG cells have acquired a transformed phenotype as showed by their ability to grow as spheroids in semi-solid medium and that unlike endothelin receptors antagonists, rapamycin reduced anchorage-independent cell growth and prevented expansion of TSC2^NEG spheroids.

Roles of human epidermal growth factor receptor family in pulmonary lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare and refractory disease that affects women of reproductive age. Several target therapies are used to manage LAM, but no curative modes of treatment have been reported yet. Therefore, in this study, we focused on targeting human epidermal growth factor receptor (HER) family proteins as a treatment strategy for LAM. In antibody array analysis, HER signaling was detected in the proteins extracted from LAM tissues. We then evaluated the expression of HER family members in 34 pulmonary LAM specimens using both immunohistochemistry and quantitative reverse-transcription polymerase chain reaction. Hierarchical clustering analysis was performed to classify the cases based on the immunohistochemistry results. Both epidermal growth factor receptor (EGFR) and HER4 were expressed in all 34 cases. HER3 was expressed in 25 of 34 cases, but HER2 was not expressed in any case. In addition, results of quantitative reverse-transcription polymerase chain reaction analysis confirmed the expression of EGFR and HER4 expression in LAM cells. Patients with HER3- or HER4-positive tissues were younger and had a history of pneumothorax. The cases were classified into 4 different clusters based on the results of hierarchical cluster analysis. One of these clusters was associated with EGFR, HER3, and HER4; the patients in this cluster were significantly younger and had a history of pneumothorax. These results indicated that HER family could contribute to the progression of pulmonary LAM, and treatments targeted against HER family might be effective for treating pulmonary LAM.

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.

Immunohistological features related to functional impairment in lymphangioleiomyomatosis

Background

Lymphangioleiomyomatosis (LAM) is a low-grade neoplasm characterized by the pulmonary infiltration of smooth muscle-like cells (LAM cells) and cystic destruction. Patients usually present with airway obstruction in pulmonary function tests (PFTs). Previous studies have shown correlations among histological parameters, lung function abnormalities and prognosis in LAM. We investigated the lung tissue expression of proteins related to the mTOR pathway, angiogenesis and enzymatic activity and its correlation with functional parameters in LAM patients.

Methods

We analyzed morphological and functional parameters of thirty-three patients. Two groups of disease severity were identified according to FEV1 values. Lung tissue from open biopsies or lung transplants was immunostained for SMA, HMB-45, mTOR, VEGF-D, MMP-9 and D2-40. Density of cysts, density of nodules and protein expression were measured by image analysis and correlated with PFT parameters.

Results

There was no difference in the expression of D2-40 between the more severe and the less severe groups. All other immunohistological parameters showed significantly higher values in the more severe group (p ≤ 0.002). The expression of VEGF-D, MMP-9 and mTOR in LAM cells was associated with the density of both cysts and nodules. The density of cysts and nodules as well as the expression of MMP-9 and VEGF-D were associated with the impairment of PFT parameters.

Conclusions

Severe LAM represents an active phase of the disease with high expression of VEGF-D, mTOR, and MMP-9, as well as LAM cell infiltration. Our findings suggest that the tissue expression levels of VEGF-D and MMP-9 are important parameters associated with the loss of pulmonary function and could be considered as potential severity markers in open lung biopsies of LAM patients.

Pulmonary lymphangioleiomyomatosis associated with aggressive renal angiomyolipoma

Lymphangioleiomyomatosis (LAM) is a rare cystic pulmonary disease that may occur in association with mutations in the tuberous sclerosis genes or arise sporadically. The histologic hallmark of the disease is the "LAM" cell, a spindled to epithelioid smooth muscle-like cell that bears morphologic and immunohistochemical resemblance to the perivascular epithelioid cell tumors (PEComas). The origin of the "LAM" cell is unknown; emerging theories suggest that a member of the PEComa family, the renal angiomyolipoma, may be the primary source and that both LAM and angiomyolipomas are associated with the genetic syndrome tuberous sclerosis. We present a young woman with LAM with an aggressive renal angiomyolipoma confirmed at autopsy.

Emerging Roles for VEGF-D in Human Disease

Blood vessels and lymphatic vessels are located in many tissues and organs throughout the body, and play important roles in a wide variety of prevalent diseases in humans. Vascular endothelial growth factor-D (VEGF-D) is a secreted protein that can promote the remodeling of blood vessels and lymphatics in development and disease. Recent fundamental and translational studies have provided insight into the molecular mechanisms by which VEGF-D exerts its effects in human disease. Hence this protein is now of interest as a therapeutic and/or diagnostic target, or as a potential therapeutic agent, in a diversity of indications in cardiovascular medicine, cancer and the devastating pulmonary condition lymphangioleiomyomatosis. This has led to clinical trial programs to assess the effect of targeting VEGF-D signaling pathways, or delivering VEGF-D, in angina, cancer and ocular indications. This review summarizes our understanding of VEGF-D signaling in human disease, which is largely based on animal disease models and clinicopathological studies, and provides information about the outcomes of recent clinical trials testing agonists or antagonists of VEGF-D signaling.

New insights in lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis

Lymphangioleiomyomatosis (LAM) and pulmonary Langerhans cell histiocytosis (PLCH) are rare diseases that lead to progressive cystic destruction of the lungs. Despite their distinctive characteristics, these diseases share several features. Patients affected by LAM or PLCH have similar radiological cystic patterns, a similar age of onset, and the possibility of extrapulmonary involvement. In this review, the recent advances in the understanding of the molecular pathogenesis, as well as the current and most promising biomarkers and therapeutic approaches, are described.

Understanding of LAM/PLCH pathogenesis has improved over the past years, leading to new therapeutic approacheshttp://ow.ly/7wjR30erSJY

Official American Thoracic Society/Japanese Respiratory Society Clinical Practice Guidelines: Lymphangioleiomyomatosis Diagnosis and Management

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a rare cystic lung disease that primarily affects women. The purpose of these guidelines is to provide recommendations for the diagnosis and treatment of LAM.

METHODS

Systematic reviews were performed to summarize evidence pertinent to our questions. The evidence was summarized and discussed by a multidisciplinary panel. Evidence-based recommendations were then formulated, written, and graded using the Grading of Recommendations, Assessment, Development, and Evaluation approach.

RESULTS

After considering the panel's confidence in the estimated effects, the balance of desirable (i.e., benefits) and undesirable (i.e., harms and burdens) consequences of treatment, patient values and preferences, cost, and feasibility, recommendations were formulated for or against specific interventions. These included recommendations for sirolimus treatment and vascular endothelial growth factor D testing and recommendations against doxycycline and hormonal therapy.

CONCLUSIONS

Evidence-based recommendations for the diagnosis and treatment of patients with LAM are provided. Frequent reassessment and updating will be needed.

New developments in the genetics and pathogenesis of tumours in tuberous sclerosis complex

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.

Proapoptotic protein Bim attenuates estrogen-enhanced survival in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a progressive lung disease that primarily affects young women. Genetic evidence suggests that LAM cells bearing TSC2 mutations migrate to the lungs, proliferate, and cause cystic remodeling. The female predominance indicates that estrogen plays a critical role in LAM pathogenesis, and we have proposed that estrogen promotes LAM cell metastasis by inhibition of anoikis. We report here that estrogen increased LAM patient-derived cells' resistance to anoikis in vitro, accompanied by decreased accumulation of the proapoptotic protein Bim, an activator of anoikis. The resistance to anoikis was reversed by the proteasome inhibitor, bortezomib. Treatment of LAM patient-derived cells with estrogen plus bortezomib promoted anoikis compared with estrogen alone. Depletion of Bim by siRNA in TSC2-deficient cells resulted in anoikis resistance. Treatment of mice with bortezomib reduced estrogen-promoted lung colonization of TSC2-deficient cells. Importantly, molecular depletion of Bim by siRNA in Tsc2-deficient cells increased lung colonization in a mouse model. Collectively, these data indicate that Bim plays a key role in estrogen-enhanced survival of LAM patient-derived cells under detached conditions that occur with dissemination. Thus, targeting Bim may be a plausible future treatment strategy in patients with LAM.

Nonmalignant Adult Thoracic Lymphatic Disorders

The thoracic lymphatic disorders are a heterogeneous group of uncommon conditions that are associated with thoracic masses, interstitial pulmonary infiltrates, and chylous complications. Accurate diagnosis of the thoracic lymphatic disorders has important implications for the newest approaches to management, including embolization and treatment with antilymphangiogenic drugs. New imaging techniques to characterize lymphatic flow, such as dynamic contrast-enhanced magnetic resonance lymphangiogram, are redefining approaches to disease classification and therapy.

Isolation of individual cellular components from lung tissues of patients with lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease entailing cystic destruction of the lungs and progressive respiratory failure. LAM lungs are histologically characterized by the proliferation of smooth muscle-like cells (LAM cells) and an abundance of lymphatic vessels. To elucidate the pathophysiological processes of LAM, cell-type-specific analyses are required. However, no method exists for isolating the individual types of cells in LAM lesions. Therefore, we established a fluorescence-activated cell sorting (FACS)-based method for the direct isolation of LAM cells and other various cellular components from LAM-affected lung tissue. We obtained LAM-affected lung tissue from resections or transplant recipients and prepared single-cell suspensions. FACS, immunohistochemical, and molecular analysis were used cooperatively to isolate HMB45-positive LAM cells with tuberous sclerosis complex (TSC) 2 loss of heterozygosity (LOH). Using a combination of antibodies against an epithelial cell adhesion molecule (EpCAM) and podoplanin, we fractionated CD45-negative lung cells into three groups: lymphatic endothelial cells (LEC) (EpCAM(-)/podoplanin(hi) subset), alveolar type II cells (EpCAM(hi)/podoplanin(-) subset), and mesenchymal cells (EpCAM(-)/podoplanin(-/low) subset). During subsequent analysis of HMB45 expression, as a LAM-specific marker, we clearly identified LAM cells in the mesenchymal cell population. We then discovered that CD90(+)/CD34(-) cells in the mesenchymal cell population are not only positive for HBM45 but also had TSC2 LOH. These isolated cells were viable and subsequently amenable to cell culture. This method enables us to isolate LAM cells and other cellular components, including LAM-associated LEC, from LAM-affected lung tissues, providing new research opportunities in this field.

Lymphangioleiomyomatosis: Current understanding and potential treatments

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease affecting predominantly young women. Clinical symptoms of this progressive disease include dyspnoea, cough, recurrent pneumothorax, hemoptysis and chylothorax. LAM is generally aggressive in nature and ultimately results in respiratory failure. Important hallmark features of this metastatic disease include the formation of lesions of abnormal smooth muscle cells, cystic destruction of the lung tissue and lymphangiogenesis affecting the lungs, abdomen and lymphatics. Research over the last 10-15 years has significantly enhanced our understanding of the molecular and cellular processes associated with LAM. These processes include mutational inactivation of the tuberous sclerosis complex genes, TSC1 and TSC2, activation of the mammalian target of rapamycin (mTOR) pathway, enhanced cell proliferation and migration, lymphangiogenesis, metastatic spread through the blood and lymphatic circulations, sex steroid sensitivity and dysregulated autophagy. Despite this increased knowledge there is currently no cure for LAM and treatment options remain limited. Whilst the mTOR inhibitor rapamycin has shown some benefit in patients with LAM, with stabilisation of lung function and improved quality of life, cessation of treatment results in recurrence of the disease progression. This highlights the urgent need to identify novel targets and new treatment regimens. The focus of this review is to summarise our current understanding of the cellular and molecular processes associated with LAM and highlight emerging treatments.

Incidental Nodal Lymphangioleiomyomatosis Is Not a Harbinger of Pulmonary Lymphangioleiomyomatosis: A Study of 19 Cases With Evaluation of Diagnostic Immunohistochemistry

Lymphangioleiomyomatosis (LAM) is a proliferation of perivascular epithelioid cells typically affecting the lung as a low-grade, destructive and progressive disease but may also be found in lymph nodes and other organs. LAM is sometimes seen as an incidental finding in lymph node dissections performed for staging of gynecologic tumors. To our knowledge, no study has investigated the clinical significance of incidental nodal LAM in relation to subsequent development of pulmonary LAM. We identified 19 patients from our institution with LAM in lymph nodes. Follow-up was available for 100% of patients and ranged from 3 to 123 months (mean 33.8 mo). All were women, ranging in age from 35 to 71 years (mean 56.3 y). None had a history of tuberous sclerosis, renal angiomyolipoma, or pulmonary LAM. LAM involvement spanned 1 to 6 nodes (mean 2), ranging from 1% to 100% of the total excised lymph nodes. The single largest focus of nodal LAM ranged from 1 to 9 mm (mean 4.3 mm) in 18 patients without evidence of persistent or recurrent nodal LAM. In the 1 patient with persistent local nodal LAM, the greatest diameter was 25 mm. Affected lymph node sites were regional pelvic and retroperitoneal chains routinely sampled in staging operations. An immunohistochemical panel of HMB45, A103, and β-catenin was evaluated in 18 cases. HMB45 showed strong but usually focal staining in every case compared with A103, which was very focally expressed (39%) or negative. β-catenin showed strong, diffuse cytoplasmic and membranous (non-nuclear) reactivity in 100% of cases. At the last clinic visit, all 19 patients had no manifestations of pulmonary LAM. In an absence of signs of symptoms of extranodal LAM, patients with incidentally discovered nodal LAM smaller than 10 mm are not at risk of developing pulmonary LAM.

[Pulmonary lymphangioleiomyomatosis: From pathogenesis to management]

INTRODUCTION

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease affecting mainly young women.

BACKGROUND

The respiratory manifestations are characterized by a progressive cystic destruction of the lung parenchyma. Extrapulmonary involvement includes benign renal tumours called angiomyolipomas and abdominal lymphatic masses called lymphangioleiomyomas. At the pathological level, the cellular proliferation found in LAM is in part due to the presence of mutations in the tumour suppressor genes TSC1 and TSC2 (Tuberous Sclerosis Complex). These mutations lead to the activation of the mTOR pathway, which is currently the main therapeutic target. mTOR inhibitors such as sirolimus or everolimus have shown a beneficial effect on the decline in pulmonary function and a reduction of angiomyolipoma size, but are necessary in only some patients.

PERSPECTIVES

LAM cells have migratory properties mediated by the formation of new lymphatic vessels. They are also able to secrete metalloproteases, which enhance their invasiveness. Moreover, the expression of estrogen and progesterone receptors by LAM cells suggests a possible role for sex hormones in the pathogenesis of the disease.

CONCLUSION

A better understanding of mTOR-independent mechanisms would allow the development of novel therapeutic approaches.

A Model of Lymphangioleiomyomatosis in a Three-Dimensional Culture System

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a tumor consisting of benign-looking neoplastic cells, but its wretched clinical outcome often resembles a malignant disease. LAM cell clusters (LCCs), unique microstructures commonly found in LAM-associated chylous effusion, are aggregates of LAM cells rimmed by lymphatic endothelium. LCCs seem to be crucial participants in the dissemination and progression of LAM.

METHODS AND RESULTS

LCCs isolated from LAM-associated chylous effusion were embedded in a three-dimensional (3-D) culture gels, and then placed in a humidified CO2 incubator. During serial observations of their morphological changes, we found tube formations with lymphatic endothelial cells when LCCs settled side by side in 3-D gels. On the other hand, when LCCs were embedded separately enough to be isolated at their initial sites of settlement in the gels, each of LCCs gradually broke down, leaving a "cyst-like" hole after 7 days at the site where LCCs initially resided. Finally, we demonstrated that "cyst-like" hole formation in 3-D gels was inhibited with treatment with doxycycline or recombinant human VEGF receptor-3.

CONCLUSIONS

We consider that our observation of this sequence in vitro illustrates how LCCs behave in vivo while enacting their important role in the progression of LAM. Our results indicate that the 3-D gel culture system for LCCs is a useful tool for exploring the effects of new therapeutic drugs under conditions when LCCs are constantly available.

Bronchial involvement in advanced stage lymphangioleiomyomatosis: histopathologic and molecular analyses

Lymphangioleiomyomatosis (LAM), a rare progressive disease that almost exclusively affects women, is characterized by pulmonary cysts and neoplastic proliferation of smooth muscle-like cells (LAM cells). Airflow obstruction is a physiologic consequence that is commonly observed in LAM and has been attributed to narrowing of peripheral airways. However, histopathologic examinations of the entire airway have been precluded by the limited availability of such specimens. Here, we used explanted lung tissues from 30 LAM patients for a thorough histologic analysis with a special emphasis on the bronchi. We found bronchial involvement by LAM cells and lymphatics in all patients examined. Furthermore, a moderate to severe degree of chronic inflammation (73%), goblet cell hyperplasia (97%), squamous cell metaplasia (83%) of the epithelium, and thickening of basal lamina (93%) were identified in the bronchi. Because LAM cells are transformed by the functional loss of the TSC genes leading to a hyperactivated mammalian target of rapamycin complex 1 (mTORC1) signaling pathway, we confirmed the expression of phospho-p70S6K, phospho-S6, phospho-4E-BP1, and vascular endothelial growth factor (VEGF)-D in LAM cells from all of the patients examined. In contrast, no protein expression of hypoxia-inducible factor 1α, a downstream molecule indicative of mTORC1 activation and leading to VEGF production, was detected in any patient. Our study indicates that late-stage LAM patients commonly have bronchi involved by the proliferation of both LAM cells and lymphatics and that chronic inflammation complicated their disease. Furthermore, the up-regulation of hypoxia-inducible factor 1α, a common event in mTORC1-driven tumor cells, does not occur in LAM cells and plays no role in VEGF-D expression in LAM cells.

Detection of low-prevalence somatic TSC2 mutations in sporadic pulmonary lymphangioleiomyomatosis tissues by deep sequencing

Lymphangioleiomyomatosis (LAM) (MIM #606690) is a rare lung disorder leading to respiratory failure associated with progressive cystic destruction due to the proliferation and infiltration of abnormal smooth muscle-like cells (LAM cells). LAM can occur alone (sporadic LAM, S-LAM) or combined with tuberous sclerosis complex (TSC-LAM). TSC is caused by a germline heterozygous mutation in either TSC1 or TSC2, and TSC-LAM is thought to occur as a result of a somatic mutation (second hit) in addition to a germline mutation in TSC1 or TSC2 (first hit). S-LAM is also thought to occur under the two-hit model involving a somatic mutation and/or loss of heterozygosity in TSC2. To identify TSC1 or TSC2 changes in S-LAM patients, the two genes were analyzed by deep next-generation sequencing (NGS) using genomic DNA from blood leukocytes (n = 9), LAM tissue from lung (n = 7), LAM cultured cells (n = 4), or LAM cell clusters (n = 1). We identified nine somatic mutations in six of nine S-LAM patients (67 %) with mutant allele frequencies of 1.7-46.2 %. Three of these six patients (50 %) showed two different TSC2 mutations with allele frequencies of 1.7-28.7 %. Furthermore, at least five mutations with low prevalence (<20 % of allele frequency) were confirmed by droplet digital PCR. As LAM tissues are likely to be composed of heterogeneous cell populations, mutant allele frequencies can be low. Our results confirm the consistent finding of TSC2 mutations in LAM samples, and highlight the benefit of laser capture microdissection and in-depth allele analyses for detection, such as NGS.

Pharmacological targeting of VEGFR signaling with axitinib inhibits Tsc2-null lesion growth in the mouse model of lymphangioleiomyomatosis

Pulmonary lymphangioleiomyomatosis (LAM), a rare progressive lung disease associated with mutations of the tuberous sclerosis complex 2 (Tsc2) tumor suppressor gene, manifests by neoplastic growth of LAM cells, induction of cystic lung destruction, and respiratory failure. LAM severity correlates with upregulation in serum of the prolymphangiogenic vascular endothelial growth factor D (VEGF-D) that distinguishes LAM from other cystic diseases. The goals of our study was to determine whether Tsc2 deficiency upregulates VEGF-D, and whether axitinib, the Food and Drug Administration-approved small-molecule inhibitor of VEGF receptor (VEGFR) signaling, will reduce Tsc2-null lung lesion growth in a mouse model of LAM. Our data demonstrate upregulation of VEGF-D in the serum and lung lining in mice with Tsc2-null lesions. Progressive growth of Tsc2-null lesions induces recruitment and activation of inflammatory cells and increased nitric oxide production. Recruited cells isolated from the lung lining of mice with Tsc2-null lesions demonstrate upregulated expression of provasculogenic Vegfa, prolymphangiogenic Figf, and proinflammatory Nos2, Il6, and Ccl2 genes. Importantly, axitinib is an effective inhibitor of Tsc2-null lesion growth and inflammatory cell recruitment, which correlates with reduced VEGF-D levels in serum and lung lining. Our data demonstrate that pharmacological inhibition of VEGFR signaling with axitinib inhibits Tsc2-null lesion growth, attenuates recruitment and activation of inflammatory cells, and reduces VEGF-D levels systemically and in the lung lining. Our study suggests a potential therapeutic benefit of inhibition of VEGFR signaling for treatment of LAM.