Thoracoscopic lobectomy for type I pleuropulmonary blastoma in an infant

Pleuropulmonary blastoma (PPB) is a rare, aggressive, intrathoracic mesenchymal neoplasm associated with cystic lung lesions. The authors describe an 8-month-old male who underwent thoracoscopic left upper lobectomy for a cystic lung lesion initially diagnosed as congenital pulmonary airway malformation. Pathology revealed type I PPB.

Pulmonary arteriole gene expression signature in idiopathic pulmonary fibrosis

A third of patients with idiopathic pulmonary fibrosis (IPF) develop pulmonary hypertension (PH-IPF), which is associated with increased mortality. Whether an altered gene expression profile in the pulmonary vasculature precedes the clinical onset of PH-IPF is unknown. We compared gene expression in the pulmonary vasculature of IPF patients with and without PH with controls. Pulmonary arterioles were isolated using laser capture microdissection from 16 IPF patients: eight with PH (PH-IPF) and eight with no PH (NPH-IPF), and seven controls. Probe was prepared from extracted RNA, and hybridised to Affymetrix Hu133 2.0 Plus genechips. Biometric Research Branch array tools and Ingenuity Pathway Analysis software were used for analysis of the microarray data. Univariate analysis revealed 255 genes that distinguished IPF arterioles from controls (p<0.001). Mediators of vascular smooth muscle and endothelial cell proliferation, Wnt signalling and apoptosis were differentially expressed in IPF arterioles. Unsupervised and supervised clustering analyses revealed similar gene expression in PH-IPF and NPH-IPF arterioles. The pulmonary arteriolar gene expression profile is similar in IPF patients with and without coexistent PH. Pathways involved in vascular proliferation and aberrant apoptosis, which may contribute to pulmonary vascular remodelling, are activated in IPF patients.

Abstract LB-46: C/EBPα acts as tumor suppressor in lung cancer by inhibiting the proto-oncogene Bmi-1

C/EBPα gene expression is frequently lost in non-small cell lung cancer, suggesting it acts as a tumor suppressor. Here, we generated an inducible lung-specific mouse model of C/EBPα deletion (C/EBPαLung-Δ mice) that develops lung adenocarcinomas. We observed that C/EBPα excision results in upregulation of Bmi-1, and that tumor initiation strictly depends on Bmi-1 gene dosage, as C/EBPαLung-Δ mice carrying only one functional Bmi-1 allele escape tumorigenesis. Accordingly, C/EBPα negative human adenocarcinomas show elevated Bmi-1 expression, in line with our observation that C/EBPα acts as tumor suppressor in lung cells by directly inhibiting Bmi-1 transcription. Furthermore, pharmacological inhibition of Bmi-1 impairs the ability of C/EBPα null adenocarcinoma cells to form tumors in xenografts. Overall, we have identified Bmi-1 as a critical therapeutic target in those patients carrying abnormal C/EBPα function.

Citation Format: Elena Levantini, Daniela S. Basseres, Wen Cai Zhang, Robert S. Welner, Meritxell Alberich-Jorda’, Kol Jia Yong, Bhavin M. Thakkar, Junyan Zhang, Chiara Battelli, Christopher J. Hetherington, Min Ye, Karen O'Brien, Maria Cristina Magli, Marie Loh, Min En Nga, Yin Huei Pang, Alain C. Borczuk, Lyuba Varticovski, Olivier Kocher, Pu Zhang, Ross A. Soo, Bing Lim, Balazs Halmos, Daniel G. Tenen. C/EBPα acts as tumor suppressor in lung cancer by inhibiting the proto-oncogene Bmi-1. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-46. doi:10.1158/1538-7445.AM2013-LB-46

Neoplastic and nonneoplastic benign mass lesions of the lung

While most lung neoplasms are malignant, a subset of true neoplasms are benign, the most common of which are pulmonary hamartomas. In addition, a substantial proportion of lung mass lesions are nonneoplastic; granulomas are among the commonly encountered nonneoplastic masses. There is also a group of relatively rare, mainly inflammatory and fibrous tumor-like lesions that are encountered on core biopsy and excisions of lung tissue.

Guidelines for pathologic diagnosis of malignant mesothelioma: 2012 update of the consensus statement from the International Mesothelioma Interest Group

CONTEXT

Malignant mesothelioma (MM) is an uncommon tumor that can be difficult to diagnose.

OBJECTIVE

To provide updated practical guidelines for the pathologic diagnosis of MM.

DATA SOURCES

Pathologists involved in the International Mesothelioma Interest Group and others with an interest in the field contributed to this update. Reference material includes peer-reviewed publications and textbooks.

CONCLUSIONS

There was consensus opinion regarding (1) distinction of benign from malignant mesothelial proliferations (both epithelioid and spindle cell lesions), (2) cytologic diagnosis of MM, (3) key histologic features of pleural and peritoneal MM, (4) use of histochemical and immunohistochemical stains in the diagnosis and differential diagnosis of MM, (5) differentiation of epithelioid MM from various carcinomas (lung, breast, ovarian, and colonic adenocarcinomas, and squamous cell and renal cell carcinomas), (6) diagnosis of sarcomatoid mesothelioma, (7) use of molecular markers in the diagnosis of MM, (8) electron microscopy in the diagnosis of MM, and (9) some caveats and pitfalls in the diagnosis of MM. Immunohistochemical panels are integral to the diagnosis of MM, but the exact makeup of panels used is dependent on the differential diagnosis and on the antibodies available in a given laboratory. Immunohistochemical panels should contain both positive and negative markers. It is recommended that immunohistochemical markers have either sensitivity or specificity greater than 80% for the lesions in question. Interpretation of positivity generally should take into account the localization of the stain (eg, nuclear versus cytoplasmic) and the percentage of cells staining (>10% is suggested for cytoplasmic membranous markers). These guidelines are meant to be a practical reference for the pathologist.

Utility of Glucose Transporter 1 in the Distinction of Benign and Malignant Thoracic and Abdominal Mesothelial Lesions

Context.—Malignant mesothelioma, of either peritoneum or pleura, is an uncommon cancer. The diagnosis is often difficult to make, in part because of the overlapping morphology of reactive and malignant mesothelial cells. Glucose transporter 1 (GLUT-1) is a glucose transporter typically found on erythrocytes, which is aberrantly expressed in various carcinomas. It has recently been reported as specific and sensitive in discriminating malignant pleural mesothelioma from reactive hyperplasia. The application of GLUT-1 staining in peritoneal mesothelioma has not been fully explored.

Objective.—To determine if GLUT-1 staining is helpful in distinguishing abdominal mesotheliomas from benign, reactive mesothelial lesions and to further study its utility in the thorax.

Design.—Tissue microarrays containing 135 abdominal malignant mesotheliomas and 30 malignant pleural mesotheliomas were stained with an antibody to GLUT-1, as were 56 reactive mesothelial lesions.

Results.—The overall sensitivity and specificity for GLUT-1 in mesothelioma was 53% and 98%, respectively. The sensitivity in epithelioid malignant mesothelioma was 49% and in sarcomatoid/biphasic malignant mesothelioma, 66%. In the thorax, the sensitivity was 50% and in the abdomen it was 54%. The positive predictive value of GLUT-1 immunoreactivity was 98% and the negative predictive value was 40%.

Conclusion.—Glucose transporter 1 staining of thoracic mesotheliomas showed high specificity but lower sensitivity than previously reported. Abdominal malignant mesotheliomas showed similar results. Because of low sensitivity, only positive staining is informative. In both sites, the utility of the stain was limited by nonspecific staining (eg, in necrotic areas) as well as bright labeling of erythrocytes and occasional lymphoid elements. Despite these limitations, GLUT-1 can help differentiate malignant mesothelioma from reactive benign mesothelium.

In situ distribution of metallic platinum in tumor tissues after intraperitoneal platinum chemotherapy assessed by digital synchrotron-abetted x-ray fluorescence microscopy

e13067

Background: Hyperthermic intraoperative intraperitoneal chemotherapy (HIPEC) and catheter-administered intraperitoneal chemotherapy (CAIPEC) are used to treat peritoneal surface-spreading malignancies, including Malignant Peritoneal Mesothelioma (MPM), to maximize local drug concentrations. Previous HIPEC studies showed tissue penetration of cisplatin ~5mm from the peritoneal surface; biodistribution of CAIPEC has not been reported. Methods: Our protocol for MPM includes initial debulking surgery with HIPEC (41°C over 1 hour, drug is then removed), 6 cycles of CAIPEC (room temperature, indefinite dwell-time), and a second debulking surgery with HIPEC. To compare tissue drug penetrations in HIPEC versus CAIPEC, on an IRB-approved protocol we collected peritoneal tissue from 6 MPM patients receiving HIPEC at initial (n=2; both cisplatin) or second surgery (n=4; 2 cisplatin and 2 oxaliplatin) for digital image localization of in situ Pt by synchrotron-abetted (Brookhaven National Laboratory, Upton NY) x-ray fluorescence microscopy at a resolution of 10 microns. Results: Overall Pt levels were highest at second surgery post-HIPEC (median=26.1ppm, range: 2.2-113.4), lowest at initial surgery post-HIPEC (median=5.2ppm, range=4.7-5.8), and intermediate at second surgery pre-HIPEC (median=16.0ppm, range=5.6-21.8). Every sample had higher Pt at the peritoneal surface; also highest at second surgery post-HIPEC (median=40.4ppm, range=4.4-219.7), lowest at initial surgery post-HIPEC (median=11.3ppm, range=8.4-14.2), and intermediate at second surgery pre-HIPEC (median=25.9ppm, range=8.4-29.9). At second surgery, each sample’s overall Pt level was higher than contemporaneous plasma Pt, pre-HIPEC (median=0.27ppm, range=0.08-0.33) and post-HIPEC (median=1.86ppm, range=0.84-2.87). Conclusions: Both CAIPEC and HIPEC effect tissue drug accumulation, greatest at the peritoneal surface. The proportion of peritoneal surface Pt was lowest in second surgery pre-HIPEC samples, suggesting more homogeneous and/or extensive drug distribution in CAIPEC than HIPEC, likely due to longer dwell-time.

Validation of interobserver agreement in lung cancer assessment: hematoxylin-eosin diagnostic reproducibility for non-small cell lung cancer: the 2004 World Health Organization classification and therapeutically relevant subsets

CONTEXT

Precise subtype diagnosis of non-small cell lung carcinoma is increasingly relevant, based on the availability of subtype-specific therapies, such as bevacizumab and pemetrexed, and based on the subtype-specific prevalence of activating epidermal growth factor receptor mutations.

OBJECTIVES

To establish a baseline measure of interobserver reproducibility for non-small cell lung carcinoma diagnoses with hematoxylin-eosin for the current 2004 World Health Organization classification, to estimate interobserver reproducibility for the therapeutically relevant squamous/nonsquamous subsets, and to examine characteristics that improve interobserver reproducibility.

DESIGN

Primary, resected lung cancer specimens were converted to digital (virtual) slides. Based on a single hematoxylin-eosin virtual slide, pathologists were asked to assign a diagnosis using the 2004 World Health Organization classification. Kappa statistics were calculated for each pathologist-pair for each slide and were summarized by classification scheme, pulmonary pathology expertise, diagnostic confidence, and neoplastic grade.

RESULTS

The 12 pulmonary pathology experts and the 12 community pathologists each independently diagnosed 48 to 96 single hematoxylin-eosin digital slides derived from 96 cases of non-small cell lung carcinoma resection. Overall agreement improved with simplification from the comprehensive 44 World Health Organization diagnoses (κ  =  0.25) to their 10 major header subtypes (κ  =  0.48) and improved again with simplification into the therapeutically relevant squamous/nonsquamous dichotomy (κ  =  0.55). Multivariate analysis showed that higher diagnostic agreement was associated with better differentiation, better slide quality, higher diagnostic confidence, similar years of pathology experience, and pulmonary pathology expertise.

CONCLUSIONS

These data define the baseline diagnostic agreement for hematoxylin-eosin diagnosis of non-small cell lung carcinoma, allowing future studies to test for improved diagnostic agreement with reflex ancillary tests.

Assessment of invasion in lung adenocarcinoma classification, including adenocarcinoma in situ and minimally invasive adenocarcinoma

Classification of adenocarcinoma has undergone recent evaluation to better align histological classification with clinical outcomes. One terminology, in particular, that of bronchioloalveolar carcinoma (BAC), has been debated for many decades. Although initial discussion surrounded the cell-of-origin of this tumor, more recent confusion has been generated from the use of this term both as a pattern of growth within an otherwise invasive adenocarcinoma and as a term for a pre-invasive tumor synonymous with adenocarcinoma in situ. As a result, adenocarcinomas with quite different radiology, gross morphology and metastatic potential have been associated with the BAC term. Focusing on invasion and using an illustrative case, we will explore the current recommendations that incorporate assessment of invasion to clarify the confusion caused by the different uses of the historical term 'BAC'.

Pleomorphic (spindle and squamous cell) carcinoma arising in a peripheral mixed squamous and glandular papilloma in a 70-year-old man

Solitary papillomas of the bronchial tree are rare, particularly in the distal airways. When encountered, solitary papillomas are not frequently found to undergo malignant transformation. When this does happen, it is usually a squamous cell carcinoma arising in a human papillomavirus-associated squamous papilloma (usually in a central airway). Here we report a unique case of pleomorphic (spindle and squamous cell) carcinoma arising in a mixed glandular and squamous papilloma without human papillomavirus association.

Progression of human bronchioloalveolar carcinoma to invasive adenocarcinoma is modeled in a transgenic mouse model of K-ras-induced lung cancer by loss of the TGF-β type II receptor

Clinical investigations have suggested that repression of the TGF-β type II receptor (TβRII) may be an important step in progression of lung adenocarcinoma from an indolent in situ state to a frank invasive carcinoma. To test this hypothesis, we compared the effects of deleting the murine homolog of this receptor (Tgfbr2) in a mouse model of mutant K-ras-induced lung carcinoma, which normally induces the formation of multifocal tumors of low invasive potential. In this model, loss of Tgfbr2 induced a highly invasive phenotype associated with lymph node metastasis and reduced survival. Tumor-associated stromal cells displayed an immunosuppressive profile marked by increased numbers of B and T cells. Moreover, tumor stromal cell profiling revealed a developmental TGF-β response profile that associated with a collagenized extracellular matrix and increased invasion of TGF-β nonresponsive tumor cells. Together, these results suggest that our KrasTgfbr2(-/-) mouse model of invasive lung carcinoma mirrors the genomic response and clinical progression of human lung adenocarcinoma, recapitulating changes in lung stromal pathways that occur in the tumor microenvironment during malignant progression in this disease.

Do all lung adenocarcinomas follow a stepwise progression?

Similar to the adenoma-carcinoma sequence of colorectal cancer, lung adenocarcinoma is thought to follow a linear multistep progression, in which a precursor lesion progresses to adenocarcinoma in situ, which is followed by invasive adenocarcinoma. However, lung adenocarcinoma can no longer be considered as a single type of tumor but rather a group of distinct subsets of tumors that arise from different molecular pathways. Consistent with this concept, recent findings revealed that this linear progression might not occur in all lung adenocarcinomas. First, according to the molecular classification based on expression profiling, lung cancer can be divided into at least two subsets; precancerous and in situ lesions share characteristics of molecular expression and clinical features with only one of the two subsets, suggesting that the linear progression is only applicable to the subset in the molecular classification. Second, when EGFR and KRAS were examined based on the progression steps, the mutation rate of KRAS was disproportionally distributed; however, according to the progression schema, gene alterations should be evenly accumulated along the entire progression. Third, by means of comparative genomic hybridization analysis, some adenocarcinoma in situ revealed gene alterations discontinuous to invasive adenocarcinoma. Finally, there were some clinical observations that support that some lesions escape from the progression. In this review, we hypothesize a novel scenario for the progression of lung adenocarcinoma, which does not support a linear progression schema.

Revolution in lung cancer: new challenges for the surgical pathologist

CONTEXT

Traditionally, lung cancer has been viewed as an aggressive, relentlessly progressive disease with few treatment options and poor survival. The traditional role of the pathologist has been primarily to differentiate small cell carcinoma from non-small cell carcinoma on biopsy and cytology specimens and to stage non-small cell carcinomas that underwent resection. In recent years, our concepts of lung cancer have undergone a revolution, including (1) the advent of successful, new, molecular-targeted therapies for lung cancer, many of which are associated with specific histologic cell types and subtypes; (2) new observations on the natural history of lung cancer derived from ongoing high-resolution computed tomography screening studies and recent histologic findings; and (3) proposals to revise the classification of lung cancers, particularly adenocarcinomas, in part because of the first 2 developments.

OBJECTIVE

To summarize the important, new developments in lung cancer, emphasizing the role of the surgical pathologist in personalized care for patients with lung cancer.

DATA SOURCES

Information about the new developments in lung cancer was obtained from the peer-review medical literature and the authors' experiences.

CONCLUSIONS

For decades, we have perceived lung cancer as a relentlessly aggressive and mostly incurable disease for which the surgical pathologist had a limited role. Today, surgical pathologists have an important and expanding role in the diagnosis and treatment of lung cancer, and it is essential to keep informed of new advances.

Revolution in lung cancer: new challenges for the surgical pathologist

CONTEXT

Traditionally, lung cancer has been viewed as an aggressive, relentlessly progressive disease with few treatment options and poor survival. The traditional role of the pathologist has been primarily to differentiate small cell carcinoma from non-small cell carcinoma on biopsy and cytology specimens and to stage non-small cell carcinomas that underwent resection. In recent years, our concepts of lung cancer have undergone a revolution, including (1) the advent of successful, new, molecular-targeted therapies for lung cancer, many of which are associated with specific histologic cell types and subtypes; (2) new observations on the natural history of lung cancer derived from ongoing high-resolution computed tomography screening studies and recent histologic findings; and (3) proposals to revise the classification of lung cancers, particularly adenocarcinomas, in part because of the first 2 developments.

OBJECTIVE

To summarize the important, new developments in lung cancer, emphasizing the role of the surgical pathologist in personalized care for patients with lung cancer.

DATA SOURCES

Information about the new developments in lung cancer was obtained from the peer-review medical literature and the authors' experiences.

CONCLUSIONS

For decades, we have perceived lung cancer as a relentlessly aggressive and mostly incurable disease for which the surgical pathologist had a limited role. Today, surgical pathologists have an important and expanding role in the diagnosis and treatment of lung cancer, and it is essential to keep informed of new advances.

A molecular profile of focal segmental glomerulosclerosis from formalin-fixed, paraffin-embedded tissue

Focal segmental glomerulosclerosis (FSGS) is a common form of idiopathic nephrotic syndrome defined by the characteristic lesions of focal glomerular sclerosis and foot process effacement; however, its etiology and pathogenesis are unknown. We used mRNA isolated from laser-captured glomeruli from archived formalin-fixed, paraffin-embedded renal biopsies, until recently considered an unsuitable source of mRNA for microarray analysis, to investigate the glomerular gene expression profiles of patients with primary classic FSGS, collapsing FSGS (COLL), minimal change disease (MCD), and normal controls (Normal). Amplified mRNA was hybridized to an Affymetrix Human X3P array. Unsupervised (unbiased) hierarchical clustering revealed two distinct clusters delineating FSGS and COLL from Normal and MCD. Class comparison analysis of FSGS + COLL combined versus Normal + MCD revealed 316 significantly differentially regulated genes (134 up-regulated, 182 down-regulated). Among the differentially regulated genes were those known to be part of the slit diaphragm junctional complex and those previously described in the dysregulated podocyte phenotype. Analysis based on Gene Ontology categories revealed overrepresented biological processes of development, differentiation and morphogenesis, cell motility and migration, cytoskeleton organization, and signal transduction. Transcription factors associated with developmental processes were heavily overrepresented, indicating the importance of reactivation of developmental programs in the pathogenesis of FSGS. Our findings reveal novel insights into the molecular pathogenesis of glomerular injury and structural degeneration in FSGS.

Computer-aided diagnosis of pulmonary nodules using a two-step approach for feature selection and classifier ensemble construction

OBJECTIVE

Accurate classification methods are critical in computer-aided diagnosis (CADx) and other clinical decision support systems. Previous research has reported on methods for combining genetic algorithm (GA) feature selection with ensemble classifier systems in an effort to increase classification accuracy. In this study, we describe a CADx system for pulmonary nodules using a two-step supervised learning system combining a GA with the random subspace method (RSM), with the aim of exploring algorithm design parameters and demonstrating improved classification performance over either the GA or RSM-based ensembles alone.

METHODS AND MATERIALS

We used a retrospective database of 125 pulmonary nodules (63 benign; 62 malignant) with CT volumes and clinical history. A total of 216 features were derived from the segmented image data and clinical history. Ensemble classifiers using RSM or GA-based feature selection were constructed and tested via leave-one-out validation with feature selection and classifier training executed within each iteration. We further tested a two-step approach using a GA ensemble to first assess the relevance of the features, and then using this information to control feature selection during a subsequent RSM step. The base classification was performed using linear discriminant analysis (LDA).

RESULTS

The RSM classifier alone achieved a maximum leave-one-out Az of 0.866 (95% confidence interval: 0.794-0.919) at a subset size of s=36 features. The GA ensemble yielded an Az of 0.851 (0.775-0.907). The proposed two-step algorithm produced a maximum Az value of 0.889 (0.823-0.936) when the GA ensemble was used to completely remove less relevant features from the second RSM step, with similar results obtained when the GA-LDA results were used to reduce but not eliminate the occurrence of certain features. After accounting for correlations in the data, the leave-one-out Az in the two-step method was significantly higher than in the RSM and the GA-LDA.

CONCLUSIONS

We have developed a CADx system for evaluation of pulmonary nodule based on a two-step feature selection and ensemble classifier algorithm. We have shown that by combining classifier ensemble algorithms in this two-step manner, it is possible to predict the malignancy for solitary pulmonary nodules with a performance exceeding that of either of the individual steps.

A postinfluenza model of Staphylococcus aureus pneumonia

BACKGROUND

Postinfluenza Staphylococcus aureus pneumonias are increasingly recognized as a major form of life-threatening infections.

METHODS

A mouse model of postinfluenza S. aureus pneumonia was developed. Mice were intranasally infected with bacteria alone or bacteria plus virus. Infection was assessed by mouse survival, lung histopathology, bacterial density in the lungs, and cellular response to infection.

RESULTS

Mice infected with both influenza virus and S. aureus showed higher mortality, greater lung parenchymal damage, and greater bacterial density at metastatic tissue sites than mice infected with only S. aureus. At 4 h, more polymorphonuclear leukocytes and fewer CD11c(+) cells were found in lung samples from mice infected with virus and bacteria than in those from mice infected with bacteria. alpha-Hemolysin and protein A were maximally expressed 4 h after infection, and Panton-Valentine leukocidin was maximally expressed 72 h after infection, with higher levels of alpha-hemolysin expression in mice infected with bacteria alone. Interferon gamma expression was higher in tissue collected from mice infected with virus plus bacteria than in those from bacteria-infected mice.

CONCLUSIONS

The results from this model demonstrate diverse effects caused by antecedent influenza virus infection, which have a profound influence on the morbidity and mortality associated with S. aureus pneumonia.

Dual specificity phosphatase 6 (DUSP6) is an ETS-regulated negative feedback mediator of oncogenic ERK signaling in lung cancer cells

Mitogen-activated protein kinase (MAPK) pathway signaling plays an important role in the majority of non-small-cell lung cancers (NSCLCs). In a prior microarray analysis of epidermal growth factor receptor (EGFR) inhibition in NSCLC cell lines, we noted that several dual specificity phosphatases (DUSPs) were among the most highly and immediately regulated genes. DUSPs act as natural terminators of MAPK signal transduction and therefore, we hypothesized a tumor suppressive role via feedback mechanisms. In the current study, we focus on the assessment of DUSP6, a cytoplasmic DUSP with high specificity for extracellular signal-regulated kinase (ERK). We demonstrate that DUSP6 expression tracks in tandem with ERK inhibition and that regulation of DUSP6 is mediated at the promoter level by ETS1, a well-known nuclear target of activated ERK. Small interfering RNA knockdown in DUSP6-high H441 lung cancer cells significantly increased ERK activation and cellular proliferation, whereas plasmid-driven overexpression in DUSP6-low H1975 lung cancer cells significantly reduced ERK activation and cellular proliferation and promoted apoptosis. Also, DUSP6 overexpression synergized with EGFR inhibitor treatment in EGFR-mutant HCC827 cells. Our results indicate that DUSP6 expression is regulated by ERK signaling and that DUSP6 exerts antitumor effects via negative feedback regulation, pointing to an important feedback loop in NSCLC. Further studies assessing the tumor suppressive role of DUSP6 and strategies aimed at modulation of its activity are warranted.

Gene expression profiling of pulmonary fibrosis identifies Twist1 as an antiapoptotic molecular "rectifier" of growth factor signaling

Idiopathic pulmonary fibrosis (IPF) is a progressive and typically fatal lung disease. To gain insight into IPF pathogenesis, we performed gene expression profiling of IPF lungs. Twist1, a basic helix-loop-helix protein, was found among the most consistently and highly up-regulated genes and was expressed in nuclei of type II epithelial cells, macrophages, and fibroblasts in IPF lungs. We studied the function of Twist1 in fibroblasts further, because they are the major effector cells in this disease and persist despite an ambient proapoptotic environment. Twist1 was induced by the profibrotic growth factors (GFs) basic fibroblast growth factor, platelet-derived growth factor, and epidermal growth factor in primary rat lung fibroblasts (RLFs). Suppression of Twist1 expression resulted in decreased RLF accumulation due to increased apoptosis, whereas Twist1 overexpression protected RLFs against several apoptotic stimuli. Addition of platelet-derived growth factor in combination with other GFs led to an increase in proliferation. When Twist1 was depleted, GFs continued to act as mitogens but caused a marked increase in cell death. The increase in apoptosis under basal or growth factor-stimulated conditions was partly mediated by up-regulation of the proapoptotic Bcl-2 family members, Bim and PUMA. These findings indicate that Twist1 promotes survival and accumulation of fibroblasts by shaping their responsiveness to growth factor stimulation. We propose that Twist1 represents one of the factors that promotes pathogenic accumulation of fibroblasts in fibrotic lung disease.

Sarcoidosis-associated fibrosing mediastinitis with resultant pulmonary hypertension: a case report and review of the literature

Pulmonary hypertension, a common manifestation of advanced sarcoidosis, is thought to result from fibrosis with chronic hypoxia and destruction of small vessels, extrinsic compression of pulmonary arteries, or granulomatous vasculitis. We report a case of sarcoidosis-associated pulmonary hypertension due to fibrosing mediastinitis. Our patient presented with cough and dyspnea on exertion and was found to have pulmonary artery enlargement, pulmonary venous compression, and mediastinal soft tissue enhancement on magnetic resonance imaging. Pulmonary hypertension was confirmed by right heart catheterization and sarcoidosis was diagnosed by histologic examination of tissue obtained at mediastinoscopy. Treatment with steroids resulted in decreased pulmonary artery pressures as well as symptomatic improvement. While pulmonary hypertension is a common complication of sarcoidosis, fibrosing mediastinitis is an unusual etiology that should be considered by clinicians.