Because these cells share a number of distinctive neuronal characteristics such as dense core secretion granules containing peptides and biogenic amines and some antigens with nerve elements the term “neuroendocrine” is used to connote such cell types. Release of hormones from neuroendocrine cells is a highly regulated process that requires adjustments to maintain internal balance throughout life to perform key functions in humans such as growth, reproduction, lactation, response to stress and metabolism.
Cell proliferation and differentiation towards neuroendocrine phenotypes capable of hormonal secretion are tightly regulated by hypothalamic factors, hormones, growth factors, transcription factors etc. A defect in this regulation during embryogenesis or life leads to hormonal deficiencies or hormonal hypersecretion inducing opposite pathologies, like the canonical examples of dwarfism and gigantism. Our team results from the merging of two previously distinct teams within the CRN2M (CNRS UMR 7286) sharing a common interest for the field of Neuroendocrinology and sharing common projects from several years (see below). One team was involved in the “role of transcription factors in pituitary pathophysiology” led by Thierry Brue and the other one focused on “signaling in neuroendocrine tumours” led by Anne Barlier. Both teams have already been working for a number of years in strong collaboration within AP-HM and the reference center for rare pituitary diseases ‘DEFHY” (coordinator: Th. Brue).
Our main objectives are to identify key factors (from receptors to transcription factors) involved in differentiation and proliferation mechanisms of neuroendocrine cells and to improve our understanding of the physiological molecular pathways and their abnormalities involved in hormone deficiencies or neuroendocrine hypersecretion and proliferation syndromes in order to identify new therapeutic strategies.
For several years, we have used gene or protein candidate strategies. However, up to now, only 10% of patients with pituitary deficiencies have an identified genetic etiology, and the treatment of neuroendocrine tumors (NET) remains highly challenging.
To increase the rate of identification of genetic causes, we have developed over the last 2 years high-throughput genomic analysis, from gene panels using new generation sequencing to comparative hybridization (CGH) and whole exome studies. These strategies are used for both pituitary deficiencies (GenHypopit network, coordinator T. Brue) and hereditary neuroendocrine tumors (TENGEN network, coordinator A Barlier) in collaboration with AP-HM Molecular Biology Laboratory led by A Barlier.
These large scale genomic technologies will allow identification of new genomic abnormalities. However, pathologies of the neuroendocrine system are rare diseases and relevant cellular models are lacking. Human cells are poorly available due to their localization while murine models display a number of discrepancies with human neuroendocrine physiology and pathology. Therefore our experimental strategy is to develop human cellular models from induced pluripotent stem cells(iPS) differentiated into neuroendocrine cells of interest such as pituitary cells (in collaboration with E. Nivet, CNRS).
Endocrinology is a field of medicine that develops physiological therapy through hormonal replacement. However, albeit hormonal secretion is highly regulated by numerous factors, current therapeutic hormonal replacements poorly mimic physiological hormone secretion, resulting in altered quality of life. Our most challenging project will be to establish a proof of concept in a mouse model by using iPS to rescue pituitary deficiencies in conditions closer to physiology. To progress in the treatment of NET, we are also using a high-throughput proteomics analysis to decipher signaling modules involved in therapeutic resistance. These proteomic data will be integrated into computer-generated mathematical models to identify important signalling modules for NET tumoural biology (in collaboration with A Baudot, N. Levy’s team). In parallel, we will continue our drug screening strategy in collaboration with pharmacological companies on human primary culture of tumours, the neurosurgery (Pr H Dufour) and the neuropathology (Pr Figarella-Branger) departments from APHM.
Overall the ultimate goal of our research is to develop new therapeutic strategies for neuroendocrine diseases based on a better understanding of their mechanisms, which accounts for the presentation of our results and projects in 2 parts, focusing on mechanisms and therapies respectively.
We have thus developed the conditions to achieve significant results in the elucidation of the molecular mechanisms leading to pituitary deficiency and tumors in humans and to open new therapeutic strategies for such diseases. More particularly, the availability of a unique collection of genomic DNA samples and neuroendocrine tumors with well characterized phenotype, our genomic data bases, clinical expertise on pituitary diseases and their treatments through CRMR DEFHY and our strong international collaborations (T. Brue, President-elect of the European NeuroEndocrine Association) in that field of rare diseases are major strengths of our projects. Our significant evolutions in the following years will be to move from gene or protein candidates to large scale studies at genomic and proteomic levels, and in the reprogramming iPS in pituitary cells to obtain relevant cellular models of human pituitary diseases.
1- Description of a new syndrome: DAVID syndrome associating CPHD and variable immune deficiency; identification of the causative gene: NFKB2 (Quentien JCEM 2012, Brue BMC Med Genetics, 2014)
2- Genhypopit international database including 1143 index cases carrying with combined pituitary hormone deficiency, with well characterized phenotypes allowing to progress in the phenotype description and genetic causes (Reynaud, manuscript in preparation).
3- Characterization of Pit-1 transcription factor targets and roles in dwarfism and gigantism (Dose dependent Pit-1 switching in somatolactotroph cells, from cell maintenance to cell death induction (Herman, Mol Endoc, 2012; Roche Gene Therapy, 2012; Jullien PlosOne, 2015)
4- Characterization of activation levels of Pi3K/AkT/mTor pathway in neuroendocrine tumors suggesting for the first time the lack of benefits of a combined treatment with everolimus and Somatostatin agonists (in contrast to the usual response observed in other tumors) (Mohamed ERC 2014 and Oncotarget in revision)
5- Identification of GH autocrine loop enhancing GH oversecretion in somatotroph tumoral cells (Cuny, ERC 2016)
1- Rochette C, Jullien N, Saveanu A, Caldagues E, Bergada I, Braslavsky D, Pfeifer M, Reynaud R, Herman JP, Barlier A, Brue T, Enjalbert A, Castinetti F. Identifying the Deleterious Effect of Rare LHX4 Allelic Variants, a Challenging Issue. PLoS One. 2015 May 8;10(5):e0126648. doi: 10.1371/journal.pone.0126648. eCollection 2015. PubMed PMID: 25955177; PubMed Central PMCID: PMC4425544.
2- - Mohamed A, Blanchard MP, Albertelli M, Barbieri F, Brue T, Niccoli P, Delpero JR, Monges G, Garcia S, Ferone D, Florio T, Enjalbert A, Moutardier V, Schonbrunn A, Gerard C, Barlier A, Saveanu A. Pasireotide and octreotide antiproliferative effects and sst2 trafficking in human pancreatic neuroendocrine tumor cultures. Endocr Relat Cancer. 2014 Oct;21(5):691-704. doi: 10.1530/ERC-14-0086. Epub 2014 Jul 10. PubMed PMID: 25012983.
3- Cuny T, Zeiller C, Bidlingmaier M, Defilles C, Roche C, Blanchard MP, Theodoropoulou M, Graillon T, Pertuit M, Figarella-Branger D, Enjalbert A, Brue T, Barlier A. In vitro impact of Pegvisomant on GH-secreting pituitary adenoma cells. Endocr Relat Cancer. 2016 Jun 7. pii: ERC-16-0140. [Epub ahead of print] PubMed PMID: 27267119.
4- Quentien MH, Delemer B, Papadimitriou DT, Souchon PF, Jaussaud R, Pagnier A, Munzer M, Jullien N, Reynaud R, Galon-Faure N, Enjalbert A, Barlier A, Brue T. Deficit in anterior pituitary function and variable immune deficiency (DAVID) in children presenting with adrenocorticotropin deficiency and severe infections. J Clin Endocrinol Metab. 2012 Jan;97(1):E121-8. doi: 10.1210/jc.2011-0407. Epub 2011 Oct 19. PubMed PMID: 22013103.
5- Couture C, Saveanu A, Barlier A, Carel JC, Fassnacht M, Flück CE, Houang M, Maes M, Phan-Hug F, Enjalbert A, Drouin J, Brue T, Vallette S. Phenotypic homogeneity and genotypic variability in a large series of congenital isolated ACTH-deficiency patients with TPIT gene mutations. J Clin Endocrinol Metab. 2012 Mar;97(3):E486-95. doi: 10.1210/jc.2011-1659. Epub 2011 Dec 14. PubMed PMID: 22170728.