Identification of novel pathways involved in the pathogenesis of human adamantinomatous craniopharyngioma

Abstract

Activating mutations in the gene encoding β-catenin have been identified in the paediatric form of human craniopharyngioma (adamantinomatous craniopharyngioma, ACP), a histologically benign but aggressive pituitary tumour accounting for up to 10% of paediatric intracranial tumours. Recently, we generated an ACP mouse model and revealed that, as in human ACP, nucleocytoplasmic accumulation of β-catenin (β-catnc) and over-activation of the Wnt/β-catenin pathway occurs only in a very small proportion of cells, which form clusters. Here, combining mouse genetics, fluorescence labelling and flow-sorting techniques, we have isolated these cells from tumorigenic mouse pituitaries and shown that the β-catnc cells are enriched for colony-forming cells when cultured in stem cell-promoting media, and have longer telomeres, indicating shared properties with normal pituitary progenitors/stem cells (PSCs). Global gene profiling analysis has revealed that these β-catnc cells express high levels of secreted mitogenic signals, such as members of the SHH, BMP and FGF family, in addition to several chemokines and their receptors, suggesting an important autocrine/paracrine role of these cells in the pathogenesis of ACP and a reciprocal communication with their environment. Finally, we highlight the clinical relevance of these findings by showing that these pathways are also up-regulated in the β-catnc cell clusters identified in human ACP. As well as providing further support to the concept that pituitary stem cells may play an important role in the oncogenesis of human ACP, our data reveal novel disease biomarkers and potential pharmacological targets for the treatment of these devastating childhood tumours.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-012-0957-9) contains supplementary material, which is available to authorized users.

The role of proto-oncogene GLI1 in pituitary adenoma formation and cell survival regulation

“…Such assumption is strengthened by the detection of a side population in human pituitary adenomas that could represent tumor-initiating cells due to the expression of multidrug transporters, oncogenes and components of several stem cell pathways (Vankelecom & Gremeaux 2010). Moreover, craniopharyngiomas arising from embryonic pituitary tissue were found to express the stem cell markers SOX2, SOX9, OCT4, KLF4 and b-catenin (Gaston-Massuet et al 2011, Andoniadou et al 2012, Garcia-Lavandeira et al 2012.…”

Pituitary Stem Cells During Normal Physiology and Disease

“…Through isolating the cluster cells and performing gene expression analyses, we identified that they expressed a vast array of growth factors, chemokines and cytokines including members of the TGF, FGF and PDGF families of growth factors among many others. These cells could therefore act as signalling centres, likely changing the microenvironment and facilitating tumorigenesis (Andoniadou et al 2012(Andoniadou et al , 2013). An observation that was indicative of the potential of these cluster cells was that actively proliferating cells, as marked by immunofluorescence of Ki67, were readily detected in close proximity to the cell clusters in both mouse and human ACP (Gaston-Massuet et al 2011).…”

“…In the adherent cultures, time-lapse imaging of singe cells plated at clonal density confirmed that they gave rise to single colonies that contained multiple EYFP-positive cells, demonstrating self-renewal. Withdrawal of growth factors and prolonged culture in differentiation conditions promoted the expression of markers of the three main pituitary lineages and the expression of differentiation markers, as detected by qPCR (Andoniadou et al 2012). Interestingly, only a small percentage of SOX2 + cells were able to form colonies (up to 5 % depending on age), possibly reflecting heterogeneity within this population in terms of their potential; alternatively, the culture requirements allowed for expansion of a restricted subset of cells, where more cell types could have self-renewal capacity.…”

“…Double SOX2/S100β are located along the marginal zone, the epithelium lining the remnants of Rathke's pouch lumen, and also in the parenchyma of the anterior pituitary, often in groups distributed amongst hormone-secreting cells. We isolated SOX2 cells expressing GFP from these two regions by microdissection, and demonstrated that their in vitro clonogenic potential did not differ between the two locations (Andoniadou et al 2012). Recent studies from rat have revealed that double-positive SOX2 + /S100β + cells may be further refined through in vivo expression of the gene Cxadr, which codes for coxsackievirus and adenovirus receptor (CAR; Chen et al 2013).…”

“…Our group utilised a knock-in mouse strain expressing enhanced yellow fluorescent protein (EYFP) from the SOX2 locus, allowing identification of SOX2-positive cells (Andoniadou et al 2012). We isolated SOX2-EYFP-positive and -negative populations separately and plated these under conditions promoting the clonogenic expansion of single cells as adherent colonies.…”