Clinical insights into small cell lung cancer: Tumor heterogeneity, diagnosis, therapy, and future directions.

Small cell lung cancer (SCLC) is characterized by rapid growth and high metastatic capacity. It has strong epidemiologic and biologic links to tobacco carcinogens. Although the majority of SCLCs exhibit neuroendocrine features, an important subset of tumors lacks these properties. Genomic profiling of SCLC reveals genetic instability, almost universal inactivation of the tumor suppressor genes TP53 and RB1, and a high mutation burden. Because of early metastasis, only a small fraction of patients are amenable to curative-intent lung resection, and these individuals require adjuvant platinum-etoposide chemotherapy. Therefore, the vast majority of patients are currently being treated with chemoradiation with or without immunotherapy. In patients with disease confined to the chest, standard therapy includes thoracic radiotherapy and concurrent platinum-etoposide chemotherapy. Patients with metastatic (extensive-stage) disease are treated with a combination of platinum-etoposide chemotherapy plus immunotherapy with an anti-programmed death-ligand 1 monoclonal antibody. Although SCLC is initially very responsive to platinum-based chemotherapy, these responses are transient because of the development of drug resistance. In recent years, the authors have witnessed an accelerating pace of biologic insights into the disease, leading to the redefinition of the SCLC classification scheme. This emerging knowledge of SCLC molecular subtypes has the potential to define unique therapeutic vulnerabilities. Synthesizing these new discoveries with the current knowledge of SCLC biology and clinical management may lead to unprecedented advances in SCLC patient care. Here, the authors present an overview of multimodal clinical approaches in SCLC, with a special focus on illuminating how recent advancements in SCLC research could accelerate clinical development.

RANK rewires energy homeostasis in lung cancer cells and drives primary lung cancer.

Lung cancer is the leading cause of cancer deaths. Besides smoking, epidemiological studies have linked female sex hormones to lung cancer in women; however, the underlying mechanisms remain unclear. Here we report that the receptor activator of nuclear factor-kB (RANK), the key regulator of osteoclastogenesis, is frequently expressed in primary lung tumors, an active RANK pathway correlates with decreased survival, and pharmacologic RANK inhibition reduces tumor growth in patient-derived lung cancer xenografts. Clonal genetic inactivation of KRasG12D in mouse lung epithelial cells markedly impairs the progression of KRasG12D -driven lung cancer, resulting in a significant survival advantage. Mechanistically, RANK rewires energy homeostasis in human and murine lung cancer cells and promotes expansion of lung cancer stem-like cells, which is blocked by inhibiting mitochondrial respiration. Our data also indicate survival differences in KRasG12D -driven lung cancer between male and female mice, and we show that female sex hormones can promote lung cancer progression via the RANK pathway. These data uncover a direct role for RANK in lung cancer and may explain why female sex hormones accelerate lung cancer development. Inhibition of RANK using the approved drug denosumab may be a therapeutic drug candidate for primary lung cancer.

Pathologic diagnosis of lung cancer - recent developments.

PURPOSE OF REVIEW: Diagnosis of lung cancer has previously been based on the evaluation of resection specimen. However, approximately 80% of lung cancers are diagnosed in stage IV. Targeted therapy has changed the practice of pathology. Diagnosis is usually based on small biopsies or even needle aspirations. Subtyping is important, as a molecular classification has to be added. RECENT FINDINGS: Molecular analysis has to be done in adenocarcinomas and on some of the rarer carcinoma types. Molecular analysis of squamous cell carcinomas should be done in never or former smokers, as they might present with targetable oncogenes. The same applies for adenosquamous carcinomas. Both high-grade neuroendocrine carcinomas should be subtyped. These subtypes might become relevant for new treatment options, currently investigated. Subtyping is done by immunohistochemistry with antibodies for ASCL1, NeuroD1, and POU2F3. In carcinoids, molecular investigation can better define cases with a higher risk of recurrence and metastasis. SUMMARY: Diagnosis of lung cancer is most often done on small biopsies or cytological preparations. Only a minimal number of tissues or cellular material is used for diagnosis. A considerable portion is reserved for molecular analysis. Molecular investigation is important in adenocarcinomas, but also for other rare tumor types.

Expression patterns and prognostic relevance of subtype-specific transcription factors in surgically resected small-cell lung cancer: an international multicenter study.

The tissue distribution and prognostic relevance of subtype-specific proteins (ASCL1, NEUROD1, POU2F3, YAP1) present an evolving area of research in small-cell lung cancer (SCLC). The expression of subtype-specific transcription factors and P53 and RB1 proteins were measured by immunohistochemistry (IHC) in 386 surgically resected SCLC samples. Correlations between subtype-specific proteins and in vitro efficacy of various therapeutic agents were investigated by proteomics and cell viability assays in 26 human SCLC cell lines. Besides SCLC-A (ASCL1-dominant), SCLC-AN (combined ASCL1/NEUROD1), SCLC-N (NEUROD1-dominant), and SCLC-P (POU2F3-dominant), IHC and cluster analyses identified a quadruple-negative SCLC subtype (SCLC-QN). No unique YAP1-subtype was found. The highest overall survival rates were associated with non-neuroendocrine subtypes (SCLC-P and SCLC-QN) and the lowest with neuroendocrine subtypes (SCLC-A, SCLC-N, SCLC-AN). In univariate analyses, high ASCL1 expression was associated with poor prognosis and high POU2F3 expression with good prognosis. Notably, high ASCL1 expression influenced survival outcomes independently of other variables in a multivariate model. High POU2F3 and YAP1 protein abundances correlated with sensitivity and resistance to standard-of-care chemotherapeutics, respectively. Specific correlation patterns were also found between the efficacy of targeted agents and subtype-specific protein abundances. In conclusion, we investigated the clinicopathological relevance of SCLC molecular subtypes in a large cohort of surgically resected specimens. Differential IHC expression of ASCL1, NEUROD1, and POU2F3 defines SCLC subtypes. No YAP1-subtype can be distinguished by IHC. High POU2F3 expression is associated with improved survival in a univariate analysis, whereas elevated ASCL1 expression is an independent negative prognosticator. Proteomic and cell viability assays of human SCLC cell lines revealed distinct vulnerability profiles defined by transcription regulators. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Lung fibrosis in autoimmune diseases and hypersensitivity: how to separate these from idiopathic pulmonary fibrosis.

Lung involvement in autoimmune diseases (AID) is uncommon, but may precede other organ manifestations. A diagnostic problem is chronicity presenting with lung fibrosis. A new category of interstitial pneumonia with autoimmune features for patients with clinical symptoms of AID and presenting with usual interstitial pneumonia (UIP) enables antifibrotic treatment for these patients. Hypersensitivity pneumonia (HP) and other forms of lung fibrosis were not included into this category. As these diseases based on adverse immune reactions often present with unspecific clinical symptoms, a specified pathological diagnosis will assist the clinical evaluation. We aimed to establish etiology-relevant differences of patterns associated with AID or HP combined with lung fibrosis. We retrospectively evaluated 51 cases of AID, and 29 cases of HP with lung fibrosis, and compared these to 24 cases of idiopathic pulmonary fibrosis (UIP/IPF). Subacute AID and HP most often presented with organizing pneumonia (OP), whereas chronicity was associated with UIP. Unspecified fibrosis was seen in a few cases, whereas NSIP pattern was rare. In 9 cases, the underlying etiology could not be defined. Statistically significant features differentiating chronic AID or HP from UIP/IPF are lymphocytic infiltrations into myofibroblastic/fibroblastic foci. Other features significantly associated with AID and HP were granulomas, isolated Langhans giant cells, and protein deposits, but seen in only a minority of cases. A combination of UIP with one of these features enabled a specific etiology-based diagnosis. Besides the antifibrotic drug regimen, additional therapies might be considered.

JAK-STAT inhibition impairs K-RAS-driven lung adenocarcinoma progression.

Oncogenic K-RAS has been difficult to target and currently there is no K-RAS-based targeted therapy available for patients suffering from K-RAS-driven lung adenocarcinoma (AC). Alternatively, targeting K-RAS-downstream effectors, K-RAS-cooperating signaling pathways or cancer hallmarks, such as tumor-promoting inflammation, has been shown to be a promising therapeutic strategy. Since the JAK-STAT pathway is considered to be a central player in inflammation-mediated tumorigenesis, we investigated here the implication of JAK-STAT signaling and the therapeutic potential of JAK1/2 inhibition in K-RAS-driven lung AC. Our data showed that JAK1 and JAK2 are activated in human lung AC and that increased activation of JAK-STAT signaling correlated with disease progression and K-RAS activity in human lung AC. Accordingly, administration of the JAK1/2 selective tyrosine kinase inhibitor ruxolitinib reduced proliferation of tumor cells and effectively reduced tumor progression in immunodeficient and immunocompetent mouse models of K-RAS-driven lung AC. Notably, JAK1/2 inhibition led to the establishment of an antitumorigenic tumor microenvironment, characterized by decreased levels of tumor-promoting chemokines and cytokines and reduced numbers of infiltrating myeloid derived suppressor cells, thereby impairing tumor growth. Taken together, we identified JAK1/2 inhibition as promising therapy for K-RAS-driven lung AC.

Bulk tumour cell migration in lung carcinomas might be more common than epithelial-mesenchymal transition and be differently regulated.

BACKGROUND: Epithelial-to-mesenchymal transition (EMT) is one mechanism of carcinoma migration, while complex tumour migration or bulk migration is another - best demontrated by tumour cells invading blood vessels. METHODS: Thirty cases of non-small cell lung carcinomas were used for identifying genes responsible for bulk cell migration, 232 squamous cell and adenocarcinomas to identify bulk migration rates. Genes expressed differently in the primary tumour and in the invasion front were regarded as relevant in migration and further validated in 528 NSCLC cases represented on tissue microarrays (TMAs) and metastasis TMAs. RESULTS: Markers relevant for bulk cancer cell migration were regulated differently when compared with EMT: Twist expressed in primary tumour, invasion front, and metastasis was not associated with TGFß1 and canonical Wnt, as Slug, Snail, and Smads were negative and ß-Catenin expressed membraneously. In the majority of tumours, E-Cadherin was downregulated at the invasive front, but not absent, but, coexpressed with N-Cadherin. Vimentin was coexpressed with cytokeratins at the invasion site in few cases, whereas fascin expression was seen in a majority. Expression of ERK1/2 was downregulated, PLCγ was only expressed at the invasive front and in metastasis. Brk and Mad, genes identified in Drosophila border cell migration, might be important for bulk migration and metastasis, together with invadipodia proteins Tks5 and Rab40B, which were only upregulated at the invasive front and in metastasis. CXCR1 was expressed equally in all carcinomas, as opposed to CXCR2 and 4, which were only expressed in few tumours. CONCLUSION: Bulk cancer cell migration seems predominant in AC and SCC. Twist, vimentin, fascin, Mad, Brk, Tsk5, Rab40B, ERK1/2 and PLCγ are associated with bulk cancer cell migration. This type of migration requires an orchestrated activation of proteins to keep the cells bound to each other and to coordinate movement. This hypothesis needs to be proven experimentally.

Progression and metastasis of lung cancer.

Metastasis in lung cancer is a multifaceted process. In this review, we will dissect the process in several isolated steps such as angiogenesis, hypoxia, circulation, and establishment of a metastatic focus. In reality, several of these processes overlap and occur even simultaneously, but such a presentation would be unreadable. Metastasis requires cell migration toward higher oxygen tension, which is based on changing the structure of the cell (epithelial-mesenchymal transition), orientation within the stroma and stroma interaction, and communication with the immune system to avoid attack. Once in the blood stream, cells have to survive trapping by the coagulation system, to survive shear stress in small blood vessels, and to find the right location for extravasation. Once outside in the metastatic locus, tumor cells have to learn the communication with the "foreign" stroma cells to establish vascular supply and again express molecules, which induce immune tolerance.

Epigenetic down-regulation of integrin α7 increases migratory potential and confers poor prognosis in malignant pleural mesothelioma.

Malignant pleural mesothelioma (MPM) is a devastating malignancy characterized by invasive growth and rapid recurrence. The identification and inhibition of molecular components leading to this migratory and invasive phenotype are thus essential. Accordingly, a genome-wide expression array analysis was performed on MPM cell lines and a set of 139 genes was identified as differentially expressed in cells with high versus low migratory activity. Reduced expression of the novel tumour suppressor integrin α7 (ITGA7) was found in highly motile cells. A significant negative correlation was observed between ITGA7 transcript levels and average displacement of cells. Forced overexpression of ITGA7 in MPM cells with low endogenous ITGA7 expression inhibited cell motility, providing direct evidence for the regulatory role of ITGA7 in MPM cell migration. MPM cells showed decreased ITGA7 expressions at both transcription and protein levels when compared to non-malignant mesothelial cells. The majority of MPM cell cultures displayed hypermethylation of the ITGA7 promoter when compared to mesothelial cultures. A statistically significant negative correlation between ITGA7 methylation and ITGA7 expression was also observed in MPM cells. While normal human pleura samples unambiguously expressed ITGA7, a varying level of expression was found in a panel of 200 human MPM samples. In multivariate analysis, ITGA7 expression was found to be an independent prognostic factor. Although there was no correlation between histological subtypes and ITGA7 expression, importantly, patients with high tumour cell ITGA7 expression had an increased median overall survival compared to the low- or no-expression groups (463 versus 278 days). In conclusion, our data suggest that ITGA7 is an epigenetically regulated tumour suppressor gene and a prognostic factor in human MPM.

Clinical Manifestations of Respiratory Bronchiolitis as an Incidental Finding in Surgical Lung Biopsies: A Retrospective Analysis of a Large Austrian Registry.

BACKGROUND: While respiratory bronchiolitis (RB) is a frequent histopathological finding in smoker's lungs, RB-associated interstitial lung disease (RB-ILD) remains a rare disease. OBJECTIVES: We analyzed how the histological finding of RB was associated with clinical information in a series of 684 consecutive surgical lung biopsies. METHODS: Retrospective analysis with delineation of clinical manifestations, smoking habits, pulmonary function test, and blood gas analysis in patients with RB in surgical lung biopsy. In 240 of these biopsies, RB was diagnosed, and in 146 of these cases a full clinical dataset was available. RESULTS: The final diagnosis of these 146 patients was consistent with RB-ILD (n = 18), pulmonary Langerhans cell histiocytosis (n = 7), various ILD (n = 9), spontaneous pneumothorax (n = 43), traumatic pneumothorax (n = 5), lung cancer (n = 41), various benign lung tumors (n = 8), and chronic pulmonary effusion (n = 15). Smoking history was positive in 93% of patients, 72% revealed centrilobular emphysema in their biopsy, and 58% described dyspnea as the main symptom. Amongst these diagnoses there were significant differences in age and smoking habits, but only small distinctions in pulmonary function test and blood gas analysis. Out of the patients with RB-ILD, 17% developed lung cancer in the later course. CONCLUSION: RB is strongly related to smoking, emphysema, and dyspnea and frequently associated with lung cancer. RB-ILD is a rare disease that may represent a considerable risk for lung cancer. Pulmonary function testing and blood gas analysis do not differ between RB-associated diseases. The finding of RB should prompt further diagnostic workup, and in case of RB-ILD, entail regular screening for lung cancer.

A mouse model to identify cooperating signaling pathways in cancer.

We here establish a mouse cancer model called Multi-Hit that allows for the evaluation of oncogene cooperativities in tumor development. The model is based on the stochastic expression of oncogene combinations ('hits') that are mediated by Cre in a given tissue. Cells with cooperating hits are positively selected and give rise to tumors. We used this approach to evaluate the requirement of Ras downstream effector pathways in tumorigenesis.

Severe primary pulmonary lymphangiectasis in a premature infant: management and follow up to early childhood.

Primary pulmonary lymphangiectasis (PPL) is a rare congenital developmental abnormality of the lung with a generally poor prognosis. Only a limited number of patients with neonatal-onset PPL have been reported to survive. We present the case of a male preterm infant (gestational age 34 weeks 6 days) with histologically confirmed PPL, complicated by hydrops fetalis, bilateral hydrothorax (treated in utero with pleuro-amniotic shunts), and immediate respiratory distress at birth. He survived after extensive neonatal intensive care therapy and was discharged home at the age of 7 months. At last follow up he was 3 years 7 months old, still requiring assisted ventilation via tracheostomy, having recurrent episodes of wheezing and had mild global developmental delay. This case demonstrates that survival beyond the neonatal period is possible even with severe PPL but long-term morbidity may be relevant, and multidisciplinary management and close follow up are essential.

Hypoxia increases membrane metallo-endopeptidase expression in a novel lung cancer ex vivo model - role of tumor stroma cells.

BACKGROUND: Hypoxia-induced genes are potential targets in cancer therapy. Responses to hypoxia have been extensively studied in vitro, however, they may differ in vivo due to the specific tumor microenvironment. In this study gene expression profiles were obtained from fresh human lung cancer tissue fragments cultured ex vivo under different oxygen concentrations in order to study responses to hypoxia in a model that mimics human lung cancer in vivo. METHODS: Non-small cell lung cancer (NSCLC) fragments from altogether 70 patients were maintained ex vivo in normoxia or hypoxia in short-term culture. Viability, apoptosis rates and tissue hypoxia were assessed. Gene expression profiles were studied using Affymetrix GeneChip 1.0 ST microarrays. RESULTS: Apoptosis rates were comparable in normoxia and hypoxia despite different oxygenation levels, suggesting adaptation of tumor cells to hypoxia. Gene expression profiles in hypoxic compared to normoxic fragments largely overlapped with published hypoxia-signatures. While most of these genes were up-regulated by hypoxia also in NSCLC cell lines, membrane metallo-endopeptidase (MME, neprilysin, CD10) expression was not increased in hypoxia in NSCLC cell lines, but in carcinoma-associated fibroblasts isolated from non-small cell lung cancers. High MME expression was significantly associated with poor overall survival in 342 NSCLC patients in a meta-analysis of published microarray datasets. CONCLUSIONS: The novel ex vivo model allowed for the first time to analyze hypoxia-regulated gene expression in preserved human lung cancer tissue. Gene expression profiles in human hypoxic lung cancer tissue overlapped with hypoxia-signatures from cancer cell lines, however, the elastase MME was identified as a novel hypoxia-induced gene in lung cancer. Due to the lack of hypoxia effects on MME expression in NSCLC cell lines in contrast to carcinoma-associated fibroblasts, a direct up-regulation of stroma fibroblast MME expression under hypoxia might contribute to enhanced aggressiveness of hypoxic cancers.

The cGAS-STING pathway drives inflammation in Usual Interstitial Pneumonia, phagocytosis could prevent inflammation but is inhibited by the don't eat me signal CD47.

BACKGROUND: Usual Interstitial Pneumonia (UIP) a fibrosing pneumonia is associated with idiopathic pulmonary fibrosis, chronic autoimmune disease (AID), or hypersensitivity pneumonia. Oxygen radicals, due to tobacco smoke, can damage DNA and might upregulate PARP1. Cytosolic DNA from dying pneumocytes activate cytosolic GMP-AMP-synthase-stimulator of interferon genes (cGAS-STING) pathway and TREX1. Prolonged inflammation induces senescence, which might be inhibited by phagocytosis, eliminating nuclear debris. We aimed to evaluate activation of cGAS-STING-TREX1 pathway in UIP, and if phagocytosis and anti-phagocytosis might counteract inflammation. METHODS: 44 cases of UIP with IPF or AID were studied for the expression of cGAS, pSTING, TREX1 and PARP1. LAMP1 and Rab7 expression served as phagocytosis markers. CD47 protecting phagocytosis and p16 to identify senescent cells were also studied. RESULTS: Epithelial cells in remodeled areas and macrophages expressed cGAS-pSTING, TREX1; epithelia but not macrophages stained for PARP1. Myofibroblasts, endothelia, and bronchial/bronchiolar epithelial cells were all negative except early myofibroblastic foci expressing cGAS. Type II pneumocytes expressed cGAS and PARP1, but less pSTING. TREX1 although expressed was not activated. Macrophages and many regenerating epithelial cells expressed LAMP1 and Rab7. CD47, the 'don't-eat-me-signal', was expressed by macrophages and epithelial cells including senescence cells within the remodeled areas. CONCLUSIONS: The cGAS-STING pathway is activated in macrophages and epithelial cells within remodeled areas. LikelyTREX1 because not activated cannot sufficiently degrade DNA fragments. PARP1 activation points to smoking-induced oxygen radical release, prolonging inflammation and leading to fibrosis. By expressing CD47 epithelial cells within remodeled areas protect themselves from being eliminated by phagocytosis.

Pathological and imaging features of pulmonary invasive mucinous adenocarcinoma-a retrospective cohort study.

Background: Pulmonary invasive mucinous adenocarcinoma (IMA) is a rare subtype of lung cancer which is easily misdiagnosed as inflammatory nodules, tuberculosis, pulmonary diffuse lesions, or hamartomas due to the lack of clinical specificity. This study aims to identify the pathological and imaging characteristics of IMA, which will favor to improve the diagnostic and therapeutic efficacy. Methods: A retrospective study was conducted by enrolling patients histopathologically diagnosed with pulmonary IMA in the current study between January 2014 and December 2021. The clinical pathological and radiological data were collected for analysis to evaluate the radiological patterns and pathological and molecular characteristics of IMA. Results: A total of 136 patients were included in the study, of whom 58 were male and 78 were female. The patients had an average age of 63.0±9.7 years. The tumors were classified into the following three pathological types: pure mucinous (76 cases) featured by only mucinous cells observed under the microscope; mixed mucinous (23 cases) featured as an attached-wall, papillary, acinar, and solid tumor cells with more than 10% mucinous cells.; and mucinous-absent (29 cases) featured with the absence of mucous cells, but still can detect more than 10% of mucin expresses. In terms of the morphological classification based on the CT scans, 88 (64.7%) cases were identified as the nodular type, 31 (22.8%) as the inflammatory type, 15 (11.1%) as the mass-like type, and two (1.5%) as the diffuse type. For the molecular features, patients afflicted with IMA showed much lower levels of thyroid transcription factor-1 (15%) than those with usual adenocarcinoma (over 80%). However, cytokeratin 20 was more common in IMA (50%) than the usual adenocarcinoma (about 5%). The K-RAS mutation was prevalent in 75% of IMA, which contrasted sharply to its occurrence in a mere 15% of the usual adenocarcinoma. Epidermal growth factor receptor mutations were rarer in IMA (less than 5%) than the usual adenocarcinoma (about 50%). Conclusions: The pathological and imaging features enrich our understanding of the disease's heterogeneity, which will contribute to more personalized diagnostic and therapeutic strategies.

Does subtyping of high-grade pulmonary neuroendocrine carcinomas have an impact on therapy selection?

Background: Small cell lung cancer (SCLC) and large cell neuroendocrine carcinomas (LCNEC) are characterized by a rapid progressive course. Therapy for SCLC has not much changed for decades, and in LCNEC controversies exist, favoring either SCLC-like or non-small cell lung cancer (NSCLC)-like therapy. Three subtypes of SCLC identified in cell cultures, namely ASCL1, NeuroD1, and POU2F3 have been confirmed by immunohistochemistry. The fourth type based on the expression of YAP1 was questioned, and another type, inflamed SCLC, was proposed. Methods: SCLC and LCNEC samples were investigated by immunohistochemistry for different subtypes. Additionally, immunohistochemical markers as potential tools to identify patients who might respond to targeted treatment were investigated. For validation a biopsy set was added. Results: ASCL1, NeuroD1, and POU2F3 were expressed in different percentages in SCLC and LCNEC. Similar percentages of expression were found in biopsies. ATOH was expressed in combination with one of the subtypes. YAP1 and TAZ were expressed in some SCLC and LCNEC cases. HES1 expression was seen in few cases. Predominantly stroma cells expressed programmed cell death ligand 1 (PD-L1). The dominant MYC protein was N-MYC. Aurora kinase A (AURKA) was expressed in the majority of both carcinomas, whereas fibroblast growth factor receptor 2 (FGFR2) in few. Conclusions: SCLC and LCNEC can be subtyped into ASCL1-, NeuroD1-, and POU2F3-positive types. AURKA expression and positivity for N-MYC protein was not associated with subtypes. AURKA and FGFR2 are both possible targets for inhibition in SCLC and LCNEC, but patients' selection should be based on expression of the enzyme. Combined chemo- and immunotherapy might be decided by PD-L1 staining of stroma cells.

Peroxisome proliferator-activated receptor-ß/δ, the acute signaling factor in prostacyclin-induced pulmonary vasodilation.

As powerful vasodilators, prostacyclin analogues are presently the mainstay in the treatment of severe pulmonary arterial hypertension. Although the hemodynamic effects of prostacyclin analogues are well known, the molecular mechanism of their acute effects on pulmonary vascular tone and systemic vascular tone remains poorly understood. Peroxisome proliferator-activated receptor-ß/δ (PPARß/δ) was previously identified as a putative receptor responsible for the modulation of target gene expression in response to prostacyclin analogues. The present study investigated the signaling pathway of prostacyclin in human pulmonary arterial smooth muscle cells (PASMCs), and sought to define the role of PPARß/δ in the acute vasodilating effect. In human PASMCs, prostacyclin rapidly activated TWIK-related acid-sensitive K channel 1 (TASK-1) and calcium-dependent potassium channels (K(Ca)). This pathway was mediated via the prostanoid I receptor-protein kinase A pathway. The silencing of PPARß/δ demonstrated that the downstream K(Ca) activation was exclusively dependent on PPARß/δ signaling, whereas the activation of TASK-1 was not. In addition, the PPARß/δ-induced activation of K(Ca) was independent of NO. The acute prostacyclin-induced K(Ca) activation is critically dependent on PPARß/δ as a rapid signaling factor. This accounts in part for the vasodilating effect of prostacyclin in pulmonary arteries, and provides insights into a new molecular explanation for the effects of prostanoids.

Chromosomal aberrations as detected by array comparative genomic hybridization in early low-grade intraepithelial neoplasias of the breast.

AIMS: Low-grade flat ductal intraepithelial neoplasia (DIN1a, flat epithelial atypia) is one of the earliest morphologically recognizable neoplastic lesions of the breast. Frequently, it occurs concomitantly with lobular intraepithelial neoplasia (LIN). We aimed to elucidate chromosomal aberrations in these early neoplastic breast lesions with the use of array comparative genomic hybridization analysis. METHODS AND RESULTS: Laser capture microdissection of 12 archival formalin-fixed, paraffin-embedded specimens harbouring foci of both DIN1a and LIN was performed. All analysed cases of DIN1a and LIN showed chromosomal gains and losses. The aberration encountered most often was loss of 16q, noted in seven DIN1a (70% of those successfully examined) and 10 LIN (91%) cases. The next most common alteration was a gain on 1q, noted in four DIN1a (40%) and seven LIN (64%) cases. CONCLUSIONS: The results show concurrent chromosomal aberrations of 1q gains and 16q losses in several cases with coexisting LIN and DIN1a. These aberrations are known to be common in low-grade invasive (ductal and lobular) carcinomas as well as in more advanced (conventional) types of low-grade ductal intraepithelial neoplasia (DIN) (low-grade ductal carcinoma in situ). Our results raise the possibility of similar molecular-genetic pathways in coexisting LIN and low-grade flat DIN.

Evaluation of formalin-free tissue fixation for RNA and microRNA studies.

FineFix, RCL-2 and HOPE, three formalin-free fixatives, were compared to the common used formalin fixed tissue samples of lung cancer and were evaluated for their effects on quality, quantity and integrity of RNA and microRNA. Two commercially available RNA extraction Kits (RNeasy FFPE by Qiagen and RecoverAll™ Nucleic Acid Isolation by Ambion) were tested and optimized in order to determine an extraction protocol for RNA as well as miRNA independent of the fixative. Two selected miRNAs were quantified via TaqMan MicroRNA assays. The optimized RNA extraction protocol for Qiagen's Kit leads to similar results for RNA quality and integrity for all fixatives. Highest RNA yield was obtained for formalin and the highest average miRNA ratio was found for FineFix. RNA fragments smaller than 500 bases were detected in FineFix, formalin and RCL2 fixed tissues; HOPE was the only fixative showing long fragments in one third of the samples. Our findings demonstrate that formalin-free fixatives are in general not superior for RNA studies. With our optimized RNA extraction protocol, there is no difficulty in extracting great amounts of RNA with high quality. According to the quality obtained, quantitative real-time PCR analysis can be performed without any negative impact. Similar results can be achieved for the tested fixatives and therefore no fixative seems to represent a new "gold-standard" for tissue fixation.

Development of pulmonary fibrosis through a pathway involving the transcription factor Fra-2/AP-1.

Studies using genetically modified mice have revealed fundamental functions of the transcription factor Fos/AP-1 in bone biology, inflammation, and cancer. However, the biological role of the Fos-related protein Fra-2 is not well defined in vivo. Here we report an unexpected profibrogenic function of Fra-2 in transgenic mice, in which ectopic expression of Fra-2 in various organs resulted in generalized fibrosis with predominant manifestation in the lung. The pulmonary phenotype was characterized by vascular remodeling and obliteration of pulmonary arteries, which coincided with expression of osteopontin, an AP-1 target gene involved in vascular remodeling and fibrogenesis. These alterations were followed by inflammation; release of profibrogenic factors, such as IL-4, insulin-like growth factor 1, and CXCL5; progressive fibrosis; and premature mortality. Genetic experiments and bone marrow reconstitutions suggested that fibrosis developed independently of B and T cells and was not mediated by autoimmunity despite the marked inflammation observed in transgenic lungs. Importantly, strong expression of Fra-2 was also observed in human samples of idiopathic and autoimmune-mediated pulmonary fibrosis. These findings indicate that Fra-2 expression is sufficient to cause pulmonary fibrosis in mice, possibly by linking vascular remodeling and fibrogenesis, and suggest that Fra-2 has to be considered a contributing pathogenic factor of pulmonary fibrosis in humans.