In situ analysis of mTORC1/2 and cellular metabolism-related proteins in human Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare progressive cystic lung disease with features of a low-grade neoplasm. It is primarily caused by mutations in TSC1 or TSC2 genes. Sirolimus, an inhibitor of mTOR complex 1 (mTORC1), slows down disease progression in some, but not all patients. Hitherto, other potential therapeutic targets such as mTOR complex 2 (mTORC2) and various metabolic pathways have not been investigated in human LAM tissues. The aim of this study was to assess activities of mTORC1, mTORC2 and various metabolic pathways in human LAM tissues through analysis of protein expression. Immunohistochemical analysis of p-S6 (mTORC1 downstream protein), Rictor (mTORC2 scaffold protein) as well as GLUT1, GAPDH, ATPB, GLS, MCT1, ACSS2 and CPT1A (metabolic pathway markers) were performed on lung tissue from 11 patients with sporadic LAM. Immunoreactivity was assessed in LAM cells with bronchial smooth muscle cells as controls. Expression of p-S6, Rictor, GAPDH, GLS, MCT1, ACSS2 and CPT1A was significantly higher in LAM cells than in bronchial smooth muscle cells (P<.01). No significant differences were found between LAM cells and normal bronchial smooth muscle cells in GLUT1 and ATPB expression. The results are uniquely derived from human tissue and indicate that, in addition to mTORC1, mTORC2 may also play an important role in the pathobiology of LAM. Furthermore, glutaminolysis, acetate utilization and fatty acid β-oxidation appear to be the preferred bioenergetic pathways in LAM cells. mTORC2 and these preferred bioenergetic pathways appear worthy of further study as they may represent possible therapeutic targets in the treatment of LAM

Pulmonary Vein Stenosis Mimicking Nonspecific Interstitial Pneumonia

Pulmonary vein stenosis (PVS) is a known complication after catheter ablation of arrhythmias. Surprisingly, little information is available on its manifestations in the lung. We describe the case of a 39-year-old woman who presented from an outside hospital with worsening shortness of breath after catheter ablation of pulmonary veins for atrial fibrillation. After an initial diagnosis of pneumonia and its nonimprovement with antibiotics, a surgical lung biopsy was done and interpreted as nonspecific interstitial pneumonia (NSIP) with vascular changes consistent with pulmonary arterial hypertension. Later, she was admitted to our institution where a transthoracic echocardiogram (TTE) and subsequent computed tomography (CT) angiogram of the heart showed severe stenosis of all four pulmonary veins. The previous lung biopsy was rereviewed and reinterpreted as severe parenchymal congestion mimicking NSIP. Our case demonstrates that PVS is an underrecognized complication of catheter ablation, and increased awareness among both clinicians and pathologists is necessary to avoid misdiagnosis

Early restriction of peripheral and proximal cell lineages during formation of the lung

To establish the timing of lineage restriction among endodermal derivatives, we developed a method to label permanently subsets of lung precursor cells at defined times during development by using Cre recombinase to activate floxed alkaline phosphatase or green fluorescent protein genes under control of doxycycline-dependent surfactant protein C promoter. Extensive or complete labeling of peripheral lung, thyroid, and thymic epithelia, but not trachea, bronchi, or gastrointestinal tract occurred when mice were exposed to doxycycline from embryonic day (E) 4.5 to E6.5. Nonoverlapping cell lineages of conducting airways (trachea and bronchi), as distinct from those of peripheral airways (bronchioles, acini, and alveoli), were established well before formation of the definitive lung buds at E9–9.5. At E11.5, the labeled precursors of peripheral lung were restricted to relatively few cells along the bronchial tubes and clusters in bronchial tips and lateral buds. Thereafter, these cells underwent marked expansion to form the entire gas-exchange region in the lung. This study demonstrates early restriction of endodermal progenitor cells forming peripheral as compared with proximal airways, identifies distinct cell lineages in conducting airways, and distinguishes neuroepithelial and tracheal–bronchial gland cell lineages from those lining peripheral regions of the lung. This system for conditional gene addition or deletion is useful for the study of lung morphogenesis and gene function in vivo, and identifies progenitor cells that may serve as useful targets for cell or gene replacement for pulmonary disorders

Expression of mTORC1/2-related proteins in primary and brain metastatic lung adenocarcinoma

Brain metastases are common complications of adenocarcinomas of the lung and are associated with a poor prognosis. Although an increasing amount of data indicates that dysregulated activity of mammalian target of rapamycin (mTOR) can influence the metastatic potential of various tumors, the role of mTOR complexes in the development of brain metastases from adenocarcinomas of the lung is largely unknown. To estimate mTOR activity, we studied the expression of mTOR related proteins (mTORC1: p-mTOR, p-S6; mTORC2: p-mTOR, Rictor) in primary (n=67) and brain metastatic (n=67) lung adenocarcinomas, including 15 paired tissue samples, using immunohistochemistry and tissue microarrays. Correlation with clinicopathological parameters was also analyzed. Increased p-mTOR, p-S6 and Rictor expressions were observed in 34%, 33% and 37% of primary adenocarcinomas and in 79%, 70% and 66% of brain metastases, respectively. Expression of these markers was significantly higher in brain metastases as compared to primary carcinomas (P<.0001, P<.0001, P<.001). Rictor expression was significantly higher in primary ADCs of the paired cases with brain metastases as compared to primary ADCs without brain metastases (67% vs. 28%, P<.01). No other statistically significant correlations were found between mTOR activity and clinicopathological parameters. The increased mTORC1/C2 activity in a subset of pulmonary adenocarcinomas and the higher incidence of increased mTORC1/C2 activity in brain metastases suggest that the IHC panel for characterizing mTOR activity and its potential predictive and prognostic role warrants further investigations