Stromal SLIT2 impacts on pancreatic cancer-associated neural remodeling.

Pancreatic ductal adenocarcinoma (PDA) is a critical health issue in the field of cancer, with few therapeutic options. Evidence supports an implication of the intratumoral microenvironment (stroma) on PDA progression. However, its contribution to the role of neuroplastic changes within the pathophysiology and clinical course of PDA, through tumor recurrence and neuropathic pain, remains unknown, neglecting a putative, therapeutic window. Here, we report that the intratumoral microenvironment is a mediator of PDA-associated neural remodeling (PANR), and we highlight factors such as 'SLIT2' (an axon guidance molecule), which is expressed by cancer-associated fibroblasts (CAFs), that impact on neuroplastic changes in human PDA. We showed that 'CAF-secreted SLIT2' increases neurite outgrowth from dorsal root ganglia neurons as well as from Schwann cell migration/proliferation by modulating N-cadherin/ß-catenin signaling. Importantly, SLIT2/ROBO signaling inhibition disrupts this stromal/neural connection. Finally, we revealed that SLIT2 expression and CAFs are correlated with neural remodeling within human and mouse PDA. All together, our data demonstrate the implication of CAFs, through the secretion of axon guidance molecule, in PANR. Furthermore, it provides rationale to investigate the disruption of the stromal/neural compartment connection with SLIT2/ROBO inhibitors for the treatment of pancreatic cancer recurrence and pain.

Pancreatic tumours escape from translational control through 4E-BP1 loss.

The mRNA cap-binding protein eIF4E (eukaryotic translation initiation factor 4E) permits ribosome recruitment to capped mRNAs, and its phosphorylated form has an important role in cell transformation. The oncogenic function of eIF4E is, however, antagonised by the hypophosphorylated forms of the inhibitory eIF4E-binding proteins 1 and 2. eIF4E-binding protein 1 and 2 (4E-BP1 and 2) are two major targets of the protein kinase mTOR, and are essential for the antiproliferative effects of mTOR inhibitors. Herein, we report that pancreas expresses specifically and massively 4E-BP1 (4E-BP2 is nearly undetectable). However, 4E-BP1 expression is extinguished in more than half of the human pancreatic ductal adenocarcinomas (PDAC). 4E-BP1 shutoff is recapitulated in a mouse genetic model of PDAC, which is based on a pancreas-specific mutation of Kras, the more frequently mutated oncogene in human pancreatic tumours. 4E-BP1 downregulation enhances eIF4E phosphorylation and facilitates pancreatic cancer cell proliferation in vitro and tumour development in vivo. Furthermore, 4E-BP1 loss combined with the absence of 4E-BP2 renders eIF4E phosphorylation, protein synthesis and cell proliferation resistant to mTOR inhibition. However, proliferation can be better limited by a recently developed compound that mimics the function of 4E-BP1 and 2 independently of mTOR inhibition.

Dual roles of hemidesmosomal proteins in the pancreatic epithelium: the phosphoinositide 3-kinase decides.

Given the failure of chemo- and biotherapies to fight advanced pancreatic cancer, one major challenge is to identify critical events that initiate invasion. One priming step in epithelia carcinogenesis is the disruption of epithelial cell anchorage to the basement membrane which can be provided by hemidesmosomes (HDs). However, the existence of HDs in pancreatic ductal epithelium and their role in carcinogenesis remain unexplored. HDs have been explored in normal and cancer pancreatic cells, and patient samples. Unique cancer cell models where HD assembly can be pharmacologically manipulated by somatostatin/sst2 signaling have been then used to investigate the role and molecular mechanisms of dynamic HD during pancreatic carcinogenesis. We surprisingly report the presence of mature type-1 HDs comprising the integrin α6ß4 and bullous pemphigoid antigen BP180 in the human pancreatic ductal epithelium. Importantly, HDs are shown to disassemble during pancreatic carcinogenesis. HD breakdown requires phosphoinositide 3-kinase (PI3K)-dependent induction of the matrix-metalloprotease MMP-9, which cleaves BP180. Consequently, integrin α6ß4 delocalizes to the cell-leading edges where it paradoxically promotes cell migration and invasion through S100A4 activation. As S100A4 in turn stimulates MMP-9 expression, a vicious cycle maintains BP180 cleavage. Inactivation of this PI3K-MMP-9-S100A4 signaling loop conversely blocks BP180 cleavage, induces HD reassembly and inhibits cell invasion. We conclude that mature type-1 HDs are critical anchoring structures for the pancreatic ductal epithelium whose disruption, upon PI3K activation during carcinogenesis, provokes pancreatic cancer cell migration and invasion.

Anti-oncogenic potential of the eIF4E-binding proteins.

The eIF4E-binding proteins (4E-BPs) are inhibitors of protein synthesis that sequester the mRNA cap-binding protein eIF4E and consequently block cell growth and proliferation. In most tumors however, their inhibitory function is compromised by major oncogenic signaling pathways. Recently, thanks to the generation of mouse genetic models, considerable progress has been made in elucidating the involvement of 4E-BPs and their unique target, eIF4E, in the process of carcinogenesis. Increasing evidence indicates that an 'addiction' to protein synthesis emerges in cancer cells, highlighting the potential that 4E-BPs have as targets for therapeutics. In this review, we summarize the biochemical function, regulation and anti-oncogenic activity of the 4E-BPs.

Novel synergistic mechanism for sst2 somatostatin and TNFalpha receptors to induce apoptosis: crosstalk between NF-kappaB and JNK pathways.

Somatostatin is a multifunctional hormone that modulates cell proliferation, differentiation and apoptosis. Mechanisms for somatostatin-induced apoptosis are at present mostly unsolved. Therefore, we investigated whether somatostatin receptor subtype 2 (sst2) induces apoptosis in the nontransformed murine fibroblastic NIH3T3 cells. Somatostatin receptor subtype 2 expression induced an executioner caspase-mediated apoptosis through a tyrosine phosphatase SHP-1 (Src homology domain phosphatase-1)-dependent stimulation of nuclear factor kappa B (NF-kappaB) activity and subsequent inhibition of the mitogen-activated protein kinase JNK. Tumor necrosis factor alpha (TNFalpha) stimulated both NF-kappaB and c-Jun NH2-terminal kinase (JNK) activities, which had opposite action on cell survival. Importantly, sst2 sensitized NIH3T3 cells to TNFalpha-induced apoptosis by (1) upregulating TNFalpha receptor protein expression, and sensitizing to TNFalpha-induced caspase-8 activation; (2) enhancing TNFalpha-mediated activation of NF-kappaB, resulting in JNK inhibition and subsequent executioner caspase activation and cell death. We have here unraveled a novel signaling mechanism for a G protein-coupled receptor, which directly triggers apoptosis and crosstalks with a death receptor to enhance death ligand-induced apoptosis.

Physiology of somatostatin receptors.

Since its discovery three decades ago as an inhibitor of GH release from the pituitary gland, somatostatin has attracted much attention because of its functional role in the regulation of a wide variety of physiological functions in the brain, pituitary, pancreas, gastrointestinal tract, adrenals, thyroid, kidney and immune system. Its actions include inhibition of endocrine and exocrine secretions, modulation of neurotransmission, motor and cognitive functions, inhibition of intestinal motility, absorption of nutrients and ions and vascular contractility. In addition, the peptide controls the proliferation of normal and tumor cells. Its action is mediated by a family of G protein-coupled receptors [somatostatin receptor (SSTR)1-SSTR5] that are widely distributed in normal and cancer cells. Direct antitumor activities, mediated through SSTR expressed in tumor cells, include blockade of autocrine/paracrine growth-promoting hormone and growth factor production, inhibition of growth factor-mediated mitogenic signals and induction of apoptosis. Indirect antitumor effects include inhibition of growth-promoting hormone and growth factor secretion, and antiangiogenic actions. Many human tumors express more than one SSTR subtype, with SSTR2 being predominant. These receptors represent the molecular basis for the clinical use of somatostatin analogs in the treatment of endocrine tumors and their in vivo localization. This review covers the present knowledge in SSTR biology and signaling.

Somatostatin receptors and regulation of cell proliferation.

Somatostatin is an inhibitory neuropeptide, which acts on various targets throughout the body to regulate a variety of physiological functions including inhibition of endocrine and exocrine secretions, modulation of neurotransmission, motor and cognitive functions, inhibition of intestinal motility, absorption of nutrients and ions, vascular contractility and inhibition of normal and tumour cell proliferation. It exerts its effects through interaction with five somatostatin receptors (sst1-sst5), which belong to the family of G-protein-coupled receptors with seven transmembrane spanning domains and are variably expressed in a variety of tumours such as gastroenteropancreatic tumours, pituitary tumours, and carcinoid tumours. This review covers the present knowledge regarding the molecular mechanisms involved in somatostatin antineoplastic activity. Evidence that sst2 receptor acts as a tumour suppressor is also discussed.

[Value of thoracic CT in the management of severe hemoptysis]. / Hémoptysies sévères: apport de la tomodensitométrie thoracique.

PURPOSE: To assess the value of thoracic CT in the management of patients with severe hemoptysis. PATIENTS AND METHODS: Between January 1997 and January 2001, 62 patients were investigated for severe hemoptysis (>300 ml/24H). The protocol, performed before angiography and embolization, included bronchial fiberoptic examination (BFE) followed by thoracic spiral CT-angiography. Data recorded at CT and BFE were the presence and location of bleeding, the etiology of hemoptysis and the therapeutic modality. RESULTS: Nine patients with life-threatening hemoptysis directly underwent bronchial embolization. CT was available in the 53 remaining patients. No abnormality was found in 4 patients. CT assessed the presence (n=49) and the location (n=38) of the bleeding. The etiology was determined in 49 patients. BFE was feasible in 38/53 patients. BFE assessed the presence (n=38) and location (n=15) of the bleeding. The etiology was determined in 12 cases of bronchial tumour. The available findings of CT and BFE for the presence and the location of the bleeding were concordant. Comparing fiberoptic examination and thoracic CT, the percentages of localized bleedings (39% and 72%) and demonstrated etiologies (32% and 92%), were significantly different (p<0,005 and p<0.0001 respectively). CONCLUSION: Although retrospective and limited by the small number of cases, our study provides arguments to perform thoracic CT before bronchial fiberoptic examination for the management of severe hemoptysis.

[Intracranial primary epidermoid carcinoma]. / Carcinome épidermoïde primitif intracrânien.

We report a case of intracranial primitive epidermoid carcinoma localized in the right temporal fossa in a 40-year-old man. The patient was submitted to surgical removal of his tumor and radiotherapy. Unfortunately, the survival time was six weeks after the operation. Clinical, radiological, anatomopathological features and the interest of the radiotherapy are discussed.

cAMP neuropeptide agonists induce pituitary suppressor of cytokine signaling-3: novel negative feedback mechanism for corticotroph cytokine action.

The hypothalamo-pituitary-adrenal (HPA) axis maintains a homeostatic response to stress, infection, or neoplasia. Inflammatory cytokines, including leukemia inhibitory factor (LIF), stimulate the HPA axis either directly at the pituitary corticotroph, or indirectly through induction of CRH or sympathetic noradrenergic neurons, and mediate the immuno-neuroendocrine interface. Unrestrained HPA axis activation leads, however, to immunosuppression. Because suppressor of cytokine signaling-3 (SOCS-3) is a potent inhibitor of LIF-activated HPA axis, and dynamic interactions between hypothalamus-derived cAMP-inducing neuropeptides and proinflammatory cytokines occur at the corticotroph level, we investigated SOCS-3 expression in response to peptides that stimulate cAMP including CRH, pituitary adenylate cyclase-activating polypeptide, and epinephrine. (Bu)2cAMP mediates induction of SOCS-3 promoter activity (6.7-fold +/- 0.5, P < 0.001) and SOCS-3 gene expression (4-fold +/- 0.8, P < 0.005) in a PKA-dependent manner. LIF and cAMP-inducing agents are additive on SOCS-3 promoter activity (22-fold +/- 2.6, LIF + (Bu)2cAMP vs. 7.3-fold +/- 0.6, LIF alone, P < 0.05) and on SOCS-3 transcription (11.3-fold +/- 2.1, LIF + (Bu)2cAMP vs. 9.3-fold +/- 1, LIF alone, P < 0.05), suggesting alternate pathways for LIF and cAMP-mediated corticotroph signaling. Similarly, LIF and CRH or pituitary adenylate cyclase-activating polypeptide are additive for SOCS-3 promoter activity and transcription (P < 0.05). Whereas signal transducer and activator of transcription 3 binding to the SOCS-3 promoter mediates LIF action, several SOCS-3 promoter regions containing cAMP-responsive elements are required for cAMP-PKA effect. Thus, both classes of POMC-inducing agents, cytokines as well as cAMP-inducing central peptides, regulate SOCS-3, providing a further level of negative HPA axis control during inflammation. These results indicate a sensitive intracellular autoregulation of corticotroph function.

Reversible amiodarone-induced lung disease: HRCT findings.

The aim of this study was to describe thoracic high-resolution computed tomography (HRCT) findings of reversible amiodarone-induced lung disease (AILD). The thoracic HRCT of 20 symptomatic patients who were considered as having reversible AILD by the medical staff of our institution were retrospectively reviewed. The patient-selection criteria used were the development of new respiratory symptoms while receiving amiodarone, the exclusion of other respiratory and cardiac diseases, and the decrease of both respiratory symptoms and radiological abnormalities after cessation of amiodarone and corticotherapy. The CT data recorded were those usually sought infiltrative lung diseases. The radiological findings using chest film (n=20) and HRCT (n=4) follow-up was noted. All patients had ground-glass opacities, associated with consolidations (n=4), thin intralobular reticulations (n=5), or both (n=11), with a subpleural (n=18) or central (n=2) location. Eight patients had high-density areas and 13 had pleural thickening (n=13). Bronchial abnormalities included dilation (n=16) and wall thickening (n=19). After therapeutic management, the radiological follow-up showed complete (n=17) or incomplete (n=3) improvement. Ground-glass opacities associated with thin intralobular reticulations and/or subpleural consolidations and bronchial abnormalities are common HRCT findings in reversible AILD.

Antiproliferative effect of somatostatin and analogs.

Over the past decade, antiproliferative effects of somatostatin and analogs have been reported in many somatostatin receptor-positive normal and tumor cell types. Regarding the molecular mechanisms involved, somatostatin or analogs mediate their action through both indirect and direct effects. Somatostatin acts through five somatostatin receptors (SSTR1-5) which are variably expressed in normal and tumor cells. These receptors regulate a variety of signal transduction pathways including inhibition of adenylate cyclase, regulation of ion channels, regulation of serine/threonine and tyrosine kinases and phosphatases. This review focuses on recent advances in biological mechanisms involved in the antineoplastic activity of somatostatin and analogs.

Direct regulation of pituitary proopiomelanocortin by STAT3 provides a novel mechanism for immuno-neuroendocrine interfacing.

Neuroendocrine ACTH secretion responds to peripheral inflammatory and stress signals. We previously demonstrated that the proinflammatory cytokine, leukemia inhibitory factor (LIF), affects the hypothalamo-pituitary-adrenal axis (HPA) by stimulating in vitro and in vivo pituitary proopiomelanocortin (POMC) gene expression and ACTH secretion and by potentiating the action of hypothalamic corticotropin releasing hormone (CRH). Whereas pathways shown thus far to regulate POMC expression exclusively involve cAMP or calcium, we here describe a direct and indirect STAT3-dependent regulation of POMC transcription by LIF. Using progressive 5'-deletions of POMC promoter, we identified a LIF-responsive -407/-301 region that contains two juxtaposed sequences within -399/-379 related to a STAT3 DNA-binding motif. Each sequence within -399/-379 separately corresponds to a low-affinity and direct binding site for STAT3, but, in combination, these sequences bind STAT3 cooperatively and with high affinity. Moreover, LIF-activated STAT3 indirectly mediates LIF corticotroph action by inducing and potentiating CRH-induced c-fos and JunB expression and binding to the POMC AP-1 element. We therefore conclude that both a direct and indirect route mediate LIF-induced STAT3 activation of POMC transcription. Demonstration of STAT3-dependent regulation of the POMC gene represents a powerful mechanism for immuno-neuroendocrine interfacing and implies a direct stimulation of ACTH secretion by inflammatory and stress-derived STAT3-inducing cytokines.

Signal transduction of somatostatin receptors negatively controlling cell proliferation.

Somatostatin acts as an inhibitory peptide of various secretory and proliferative responses. Its effects are mediated by a family of G-protein-coupled receptors (sst1-5) that can couple to diverse signal transduction pathways such as inhibition of adenylate cyclase and guanylate cyclase, modulation of ionic conductance channels, and protein dephosphorylation. The five receptors bind the natural peptide with high affinity but only sst2, sst5 and sst3 bind the short synthetic analogues. Somatostatin negatively regulates the growth of various normal and tumour cells. This effect is mediated indirectly through inhibition of secretion of growth-promoting factors, angiogenesis and modulation of the immune system. Somatostatin can also act directly through sst receptors present on target cells. The five receptors are expressed in various normal and tumour cells, the expression of each receptor being receptor subtype and cell type specific. According to the receptor subtypes, distinct signal transduction pathways are involved in the antiproliferative action of somatostatin. Sst1, 4 and 5 modulate the MAP kinase pathway and induce G1 cell cycle arrest. Sst3 and sst2 promote apoptosis by p53-dependent and -independent mechanisms, respectively.

[Interventional radiology of the thorax]. / Radiologie interventionnelle du thorax.

Interventional radiology of the thorax includes a wide variety of diagnostic and/or therapeutic procedures. Transthoracic needle biopsy is a widely used technique. Generall, computed tomography is used to guide the puncture, less commonly fluoroscopy or in exceptional cases ultrasound. Targets include parenchymatous, pleural and mediastinal lesions. The biopsy specimen is used for cytology, histology, bacteriology, mycology and parasitology studies. Needle biopsy is also the first step in more complex procedures: drainage of thoracic collections, inserting harpoons, thoracic sympatholysis, palliative treatment of aspergillomas. Bronchial arteriography with embolization is an effective emergency symptomatic treatment for severe hemoptysis. Endovascular vaso-occlusion procedures can be used for rare arteriovenous pulmonary fistulas. Superior vena cava obstruction can be treated, usually in a palliative procedure, by installing an endovascular endoprosthesis.

SOCS proteins: modulators of neuroimmunoendocrine functions. Impact on corticotroph LIF signaling.

Several members of the newly characterized family of suppressor of cytokine signaling (SOCS) proteins-such as SOCS-1, SOCS-3, and CIS-act as negative regulators of the cytokine-induced Jak-STAT signaling cascade. The expression of SOCS proteins is stimulated by a variety of cytokines and hormones in a tissue-specific manner. This article reviews our current understanding of SOCS proteins and their role as modulators of neuroimmunoendocrine functions, for example, in signaling of leptin, growth hormone, and prolactin, specially focusing on the impact of SOCS proteins on corticotroph leukemia inhibitory factor (LIF) signaling. LIF, a member of the gp130 sharing cytokine family, modulates pituitary development, POMC gene expression, and ACTH secretion. Current data on the negative autoregulatory function of the suppressor of cytokine signaling, SOCS-3, in LIF-induced POMC gene expression and ACTH secretion are extensively discussed.

Inhibitory roles for SHP-1 and SOCS-3 following pituitary proopiomelanocortin induction by leukemia inhibitory factor.

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine that stimulates the hypothalamo-pituitary-adrenal (HPA) axis through JAK-STAT activation. We show here that LIF-induced JAK2 and STAT3 tyrosine phosphorylation is transient, disappearing within 20 and 40 minutes, respectively. LIF activates the SH2 domain-containing tyrosine phosphatase, SHP-1, with maximal stimulation observed at 30 minutes. SHP-1 is constitutively associated with JAK2, and LIF induces recruitment of phosphorylated STAT3 to this complex. Overexpression of wild-type or dominant negative forms of SHP-1 shows decreased or increased LIF-induced proopiomelanocortin (POMC) promoter activity, respectively. LIF-induced JAK2 and STAT3 dephosphorylation is delayed until after 60 minutes in cells that overexpress the mutant SHP-1. In addition, SOCS-3, a negative regulator of LIF signaling, binds to JAK2 after 60 minutes of LIF stimulation, after which the complex is degraded by the proteasome. SOCS-3 overexpression blocks LIF-induced JAK2 tyrosine phosphorylation, confirming a role for SOCS-3 in deactivating JAK2 by direct association. Using SOCS-3 fusion proteins, we also define regions of the SOCS-3 protein that are critical for inhibition of LIF-induced POMC promoter activity. Corticotrophic signaling by LIF is thus subject to 2 forms of negative autoregulation: dephosphorylation of JAK2 and STAT3 by the SHP-1 tyrosine phosphatase, and SOCS-3-dependent inactivation of JAK2.

Autoregulation of pituitary corticotroph SOCS-3 expression: characterization of the murine SOCS-3 promoter.

Pituitary corticotroph SOCS-3 is a novel intracellular regulator of leukemia inhibitory factor (LIF)-mediated proopiomelanocortin gene expression and adrenocorticotropic hormone (ACTH) secretion, inhibiting LIF-activated Janus kinase-signal transducers and activators of transcription (STAT) signaling in a negative autoregulatory loop. We now demonstrate in corticotroph AtT-20 cells that LIF-stimulated endogenous SOCS-3 mRNA expression is blocked in stable transfectants of SOCS-3 wild type or in dominant negative STAT-3 mutants, respectively. We characterized approximately 3.8-kb genomic 5' sequence of murine SOCS-3, including approximately 2.9-kb sequence upstream of the transcription start site (+1), which was determined by 5' rapid amplification of cDNA ends and RNase protection assay. Different 5' constructs were cloned into the pGL3Basic vector, and luciferase activity was assayed in transiently transfected ACTH-secreting corticotroph AtT-20 cells. A STAT-1/STAT-3 binding element, located at nucleotides -72 to -64, was essential for LIF stimulation of SOCS-3 promoter activity. LIF induced 10-fold increased luciferase activity in a wild-type construct spanning -2757 to +929 bases. However, deletion or point mutation of the STAT-1/STAT-3 binding element abrogated LIF action (2- to 3-fold). Electrophoretic mobility-shift assay analysis confirmed specific binding of STAT-1 and STAT-3 to this region. These results characterize the genomic 5' region of murine SOCS-3 and identify an important STAT-1/STAT-3 binding element therein. Thus, LIF-stimulated SOCS-3 gene expression is at least in part mediated by STAT-3 and STAT-1. The cytokine inhibitor SOCS-3 acts in a negative loop to autoregulate its own gene expression, thus limiting its accumulation in the corticotroph cell. These results demonstrate a mechanism for corticotroph plasticity with rapid "on" and "off" ACTH induction in response to neuro-immuno-endocrine stimuli, such as LIF.