Expression of aberrant beta-catenin and impaired p63 in craniopharyngiomas

Adamantinomatous craniopharyngioma cyst fluid can trigger inflammatory activation of microglia to damage the hypothalamic neurons by inducing the production of β-amyloid

INTRODUCTION

The mechanism by which adamantinomatous craniopharyngioma (ACP) damages the hypothalamus is still unclear. Cyst fluid rich in lipids and inflammatory factors is a characteristic pathological manifestation of ACP and may play a very important role in hypothalamic injury caused by tumors.

OBJECTIVE

The objective of this study was to construct a reliable animal model of ACP cyst fluid-induced hypothalamic injury and explore the specific mechanism of hypothalamic injury caused by cyst fluid.

METHODS

An animal model was established by injecting human ACP cyst fluid into the bilateral hypothalamus of mice. ScRNA-seq was performed on the mice hypothalamus and on an ACP sample to obtain a complete gene expression profile for analysis. Data verification was performed through pathological means.

RESULTS

ACP cystic fluid caused growth retardation and an increased obesity index in mice, affected the expression of the Npy, Fgfr2, Rnpc3, Sst, and Pcsk1n genes that regulate growth and energy metabolism in hypothalamic neurons, and enhanced the cellular interaction of Agrp-Mc3r. ACP cystic fluid significantly caused inflammatory activation of hypothalamic microglia. The cellular interaction of CD74-APP is significantly strengthened between inflammatory activated microglia and hypothalamic neurons. Beta-amyloid, a marker of neurodegenerative diseases, was deposited in the ACP tumor tissues and in the hypothalamus of mice injected with ACP cyst fluid.

CONCLUSION

In this study, a novel animal model of ACP cystic fluid-hypothalamic injury was established. For the first time, it was found that ACP cystic fluid can trigger inflammatory activation of microglia to damage the hypothalamus, which may be related to the upregulation of the CD74-APP interaction and deposition of β-amyloid, implying that there may be a similar mechanism between ACP cystic fluid damage to the hypothalamus and neurodegenerative diseases.

Current Advances in the Management of Adult Craniopharyngiomas

Craniopharyngiomas (CPs) are slow growing, histologically benign intracranial tumors located in the sellar–suprasellar region. Although known to have low mortality, their location and relationship to the adjacent neural structures results in patients having significant neurologic, endocrine, and visual comorbidities. The invasive nature of this tumor makes complete resection a challenge and contributes to its recurrence. Additionally, these tumors are bimodally distributed, being treated with surgery, and are followed by other adjuncts, such as focused radiation therapy, e.g., Gamma knife. Advances in surgical techniques, imaging tools, and instrumentations have resulted in the evolution of surgery using endoscopic techniques, with residual components being treated by radiotherapy to target the residual tumor. Advances in molecular biology have elucidated the main pathways involved in tumor development and recurrence, but presently, no other treatments are offered to patients, besides surgery, radiation, and endocrine management, as the disease and tumor evolve. We review the contemporary management of these tumors, from the evolution of surgical treatments, utilizing standard open microscopic approaches to the more recent endoscopic surgery, and discuss the current recommendations for care of these patients. We discuss the developments in radiation therapy, such as radiosurgery, being used as treatment strategies for craniopharyngioma, highlighting their beneficial effects on tumor resections while decreasing the rates of adverse outcomes. We also outline the recent chemotherapy modalities, which help control tumor growth, and the immune landscape on craniopharyngiomas that allow the development of novel immunotherapies.

[The 2017 WHO classification of pituitary tumors]

The 2017 WHO classification of pituitary tumors is still based on structural analyses and expression of various pituitary hormones. Three innovations have to be considered: (1) The expression of pituitary transcription factors Pit‑1, T‑Pit and SF‑1. (2) The term "atypical adenoma" was replaced by "aggressive adenoma". (3) The three tumor types of the neurohypophysis (pituicytoma, spindle cell oncocytoma, granular cell tumor) are defined by their common expression of TTF‑1. Craniophyryngiomas are identified as adamantinomatous type by focal nuclear expression of β‑catenin or as papillary type by demonstration of BRAF V600E mutation. Further primary tumors of the pituitary are extremely rare. These and also the other tumors of the sellar region can be structurally very similar to pituitary adenomas but can be-nearly without exception-differentiated by immunocytochemistry.

Ki67 as a prognostic factor of craniopharyngioma's recurrence in paediatric population

PURPOSE

Craniopharyngioma is one of the most frequent benign tumours of the central nervous system in the paediatric population. Although it is a benign tumour according to the WHO classification, it significantly deteriorates the patient's quality of life. The aim of this study is to assess if proliferation index Ki67 can be a useful marker of the risk of craniopharyngioma's recurrence.

METHODS

Expression of Ki67 was examined in 85 specimens of primary craniopharyngioma and in 11 specimens of the recurring tumour. In all the cases, adamantinomatous type of craniopharyngioma was diagnosed. Values of Ki67 expression were compared between patients with and without recurrence, between patients with progression and relapse and between primary and recurrent tumours.

RESULTS

No statistically significant differences were found between proliferation index Ki67 values in tumours with recurrence and without (median values 2.5% and 3%, respectively, p = 0.69). The median value of proliferation index Ki67 in progression group was 1% and in the relapse group 4%; no statistical significance between those groups was found (p = 0.067). The median value of proliferation index Ki67 in primary tumours was 3% (0-20%) and in recurrent tumours it was 5% (0-14%). Despite the lack of statistical significance (p = 0.61), a tendency towards higher values of Ki67 in recurring tumours in comparison with primary tumours was shown.

CONCLUSIONS

Proliferation index Ki67 is not a reliable prognostic factor of craniopharyngioma's recurrence.

Can tissue biomarkers reliably predict the biological behavior of craniopharyngiomas? A comprehensive overview

BACKGROUND

The growing interest in the molecular and genetic alterations of craniopharyngiomas (CPs) is embodied in recent studies revealing insights into the CP tumorigenesis and identifying novel molecular pathways amenable of targeted therapies. The actual impact of this new information, however, remains inconclusive.

METHODS

We present a comprehensive review of the accumulated knowledge on molecular biology of CPs and a critical analysis on the strengths and weaknesses of the studies focused on CP molecular/genetic alterations published to date.

RESULTS

A thorough analysis of the alterations of β-catenin/CTNNB1 and BRAF genes investigated in 1123 CP cases included in 27 studies, showed that, on average, CTNNB1 mutations were present in two-thirds of adamantinomatous CPs and BRAF mutations in 90% of papillary CPs. Their role as oncogenic drivers has not been well established. Although rare, coexistence of both mutations may occur. The involvement of pituitary stem cells in human CP tumorigenesis is still uncertain. Expression of stem markers in human CP samples predominantly occurred along the CP border in contact with brain tissue. Finally, none of the various molecular alterations which have been proposed as markers for CP recurrence can be used today as reliable predictors of the CP behavior.

CONCLUSIONS

The isolated evaluation of CPs' molecular or genetic profiles that do not take into consideration fundamental pathological and therapeutic factors, specifically the tumor topography and the degree of tumor removal, may actually generate confusion regarding the reliability of some biomarkers to predict the CP biological behavior.

Tumour compartment transcriptomics demonstrates the activation of inflammatory and odontogenic programmes in human adamantinomatous craniopharyngioma and identifies the MAPK/ERK pathway as a novel therapeutic target

Adamantinomatous craniopharyngiomas (ACPs) are clinically challenging tumours, the majority of which have activating mutations in CTNNB1. They are histologically complex, showing cystic and solid components, the latter comprised of different morphological cell types (e.g. β-catenin-accumulating cluster cells and palisading epithelium), surrounded by a florid glial reaction with immune cells. Here, we have carried out RNA sequencing on 18 ACP samples and integrated these data with an existing ACP transcriptomic dataset. No studies so far have examined the patterns of gene expression within the different cellular compartments of the tumour. To achieve this goal, we have combined laser capture microdissection with computational analyses to reveal groups of genes that are associated with either epithelial tumour cells (clusters and palisading epithelium), glial tissue or immune infiltrate. We use these human ACP molecular signatures and RNA-Seq data from two ACP mouse models to reveal that cell clusters are molecularly analogous to the enamel knot, a critical signalling centre controlling normal tooth morphogenesis. Supporting this finding, we show that human cluster cells express high levels of several members of the FGF, TGFB and BMP families of secreted factors, which signal to neighbouring cells as evidenced by immunostaining against the phosphorylated proteins pERK1/2, pSMAD3 and pSMAD1/5/9 in both human and mouse ACP. We reveal that inhibiting the MAPK/ERK pathway with trametinib, a clinically approved MEK inhibitor, results in reduced proliferation and increased apoptosis in explant cultures of human and mouse ACP. Finally, we analyse a prominent molecular signature in the glial reactive tissue to characterise the inflammatory microenvironment and uncover the activation of inflammasomes in human ACP. We validate these results by immunostaining against immune cell markers, cytokine ELISA and proteome analysis in both solid tumour and cystic fluid from ACP patients. Our data support a new molecular paradigm for understanding ACP tumorigenesis as an aberrant mimic of natural tooth development and opens new therapeutic opportunities by revealing the activation of the MAPK/ERK and inflammasome pathways in human ACP.

Potential evolution of neurosurgical treatment paradigms for craniopharyngioma based on genomic and transcriptomic characteristics

The recent genomic and transcriptomic characterization of human craniopharyngiomas has provided important insights into the pathogenesis of these tumors and supports that these tumor types are distinct entities. Critically, the insights provided by these data offer the potential for the introduction of novel therapies and surgical treatment paradigms for these tumors, which are associated with high morbidity rates and morbid conditions. Mutations in the CTNNB1 gene are primary drivers of adamantinomatous craniopharyngioma (ACP) and lead to the accumulation of β-catenin protein in a subset of the nuclei within the neoplastic epithelium of these tumors. Dysregulation of epidermal growth factor receptor (EGFR) and of sonic hedgehog (SHH) signaling in ACP suggest that paracrine oncogenic mechanisms may underlie ACP growth and implicate these signaling pathways as potential targets for therapeutic intervention using directed therapies. Recent work shows that ACP cells have primary cilia, further supporting the potential importance of SHH signaling in the pathogenesis of these tumors. While further preclinical data are needed, directed therapies could defer, or replace, the need for radiation therapy and/or allow for less aggressive surgical interventions. Furthermore, the prospect for reliable control of cystic disease without the need for surgery now exists. Studies of papillary craniopharyngioma (PCP) are more clinically advanced than those for ACP. The vast majority of PCPs harbor the BRAF^v600e mutation. There are now 2 reports of patients with PCP that had dramatic therapeutic responses to targeted agents. Ongoing clinical and research studies promise to not only advance our understanding of these challenging tumors but to offer new approaches for patient management.

Molecular pathology of adamantinomatous craniopharyngioma: review and opportunities for practice

Since the first identification of CTNNB1 mutations in adamantinomatous craniopharyngioma (ACP), much has been learned about the molecular pathways and processes that are disrupted in ACP pathogenesis. To date this understanding has not translated into tangible patient benefit.

The recent development of novel techniques and a range of preclinical models now provides an opportunity to begin to support treatment decisions and develop new therapeutics based on molecular pathology.

In this review the authors summarize many of the key findings and pathways implicated in ACP pathogenesis and discuss the challenges that need to be tackled to translate these basic science findings for the benefit of patients.

60 YEARS OF NEUROENDOCRINOLOGY: Biology of human craniopharyngioma: lessons from mouse models

Adamantinomatous craniopharyngiomas (ACP) are clinically relevant tumours that are associated with high morbidity, poor quality of life and occasional mortality. Human and mouse studies have provided important insights into the biology of these aggressive tumours, and we are starting to understand why, how and when these tumours develop in humans. Mutations in β-catenin that result in the over-activation of the WNT/β-catenin signalling pathway are critical drivers of most, perhaps of all, human ACPs. Mouse studies have shown that only pituitary embryonic precursors or adult stem cells are able to generate tumours when targeted with oncogenic β-catenin, which suggests that the cell context is critical in order for mutant β-catenin to exert its oncogenic effect. Interestingly, mutant stem cells do not generate the bulk of the tumour cells; instead, they induce tumours in a paracrine manner. Combining basic studies in mice and humans will provide further insights into the biology of these neoplasms and will reveal pathogenic pathways that could be targeted with specific inhibitors for the benefit of patients. These benign tumours may additionally represent a unique model for investigating the early steps that lead to oncogenesis.

Identification of targets for rational pharmacological therapy in childhood craniopharyngioma

Introduction

Pediatric adamantinomatous craniopharyngioma (ACP) is a histologically benign but clinically aggressive brain tumor that arises from the sellar/suprasellar region. Despite a high survival rate with current surgical and radiation therapy (75–95 % at 10 years), ACP is associated with debilitating visual, endocrine, neurocognitive and psychological morbidity, resulting in excheptionally poor quality of life for survivors. Identification of an effective pharmacological therapy could drastically decrease morbidity and improve long term outcomes for children with ACP.

Results

Using mRNA microarray gene expression analysis of 15 ACP patient samples, we have found several pharmaceutical targets that are significantly and consistently overexpressed in our panel of ACP relative to other pediatric brain tumors, pituitary tumors, normal pituitary and normal brain tissue. Among the most highly expressed are several targets of the kinase inhibitor dasatinib – LCK, EPHA2 and SRC; EGFR pathway targets – AREG, EGFR and ERBB3; and other potentially actionable cancer targets – SHH, MMP9 and MMP12. We confirm by western blot that a subset of these targets is highly expressed in ACP primary tumor samples.

Conclusions

We report here the first published transcriptome for ACP and the identification of targets for rational therapy. Experimental drugs targeting each of these gene products are currently being tested clinically and pre-clinically for the treatment of other tumor types. This study provides a rationale for further pre-clinical and clinical studies of novel pharmacological treatments for ACP. Development of mouse and cell culture models for ACP will further enable the translation of these targets from the lab to the clinic, potentially ushering in a new era in the treatment of ACP.

The Wnt signalling cascade and the adherens junction complex in craniopharyngioma tumorigenesis

Craniopharyngiomas are epithelial, sellar tumours with adamantinomatous (aCP) and papillary (pCP) subtypes. The aCP type usually occurs during childhood and pCP in middle-aged adults; aCPs often contain mutations in CTNNB1, encoding β-catenin, a component of the adherens junction and a mediator of Wnt signalling. No such mutational event has been associated with pCPs, where the BRAF gene appears to be more important. In a large series of 95 craniopharyngiomas, we show that the aCP subtype harbours mutations in CTNNB1 in 52 % of cases, while the pCP subtype does not, with agreement between immunohistochemistry and sequencing methods in the majority of cases. When present, the CTNNB1 mutation is found throughout the aCP tumour, while translocation of β-catenin from membrane to cytosol and nucleus is restricted to small cell clusters near the invading tumour front. We observed translocated β-catenin in 100 % of aCPs, occurring not only in cell clusters but also in individual cells scattered throughout the tumour. We characterised the adherens junction involving α-catenin, β-catenin, γ-catenin, p120 and E-cadherin (cytosolic and membranous components). Although suggested to be important in other sellar mass tumourigenesis pathways, there was no disruption of the adherens junction in these tumours, indicating that a loss of junctional integrity is not associated with β-catenin translocation or mutation. We conclude that mutations in CTNNB1 underlie tumourigenesis in the majority of aCPs, which are distinct morphologically and at the molecular level from pCPs.

Disease control after reduced volume conformal and intensity modulated radiation therapy for childhood craniopharyngioma

PURPOSE

To estimate the rate of disease control after conformal radiation therapy using reduced clinical target volume (CTV) margins and to determine factors that predict for tumor progression.

METHODS AND MATERIALS

Eighty-eight children (median age, 8.5 years; range, 3.2-17.6 years) received conformal or intensity modulated radiation therapy between 1998 and 2009. The study group included those prospectively treated from 1998 to 2003, using a 10-mm CTV, defined as the margin surrounding the solid and cystic tumor targeted to receive the prescription dose of 54 Gy. The CTV margin was subsequently reduced after 2003, yielding 2 groups of patients: those treated with a CTV margin greater than 5 mm (n=26) and those treated with a CTV margin less than or equal to 5 mm (n=62). Disease progression was estimated on the basis of additional variables including sex, race, extent of resection, tumor interventions, target volume margins, and frequency of weekly surveillance magnetic resonance (MR) imaging during radiation therapy. Median follow-up was 5 years.

RESULTS

There was no difference between progression-free survival rates based on CTV margins (>5 mm vs ≤5 mm) at 5 years (88.1% ± 6.3% vs 96.2% ± 4.4% [P=.6386]). There were no differences based on planning target volume (PTV) margins (or combined CTV plus PTV margins). The PTV was systematically reduced from 5 to 3 mm during the time period of the study. Factors predictive of superior progression-free survival included Caucasian race (P=.0175), no requirement for cerebrospinal fluid shunting (P=.0066), and number of surveillance imaging studies during treatment (P=.0216). Patients whose treatment protocol included a higher number of weekly surveillance MR imaging evaluations had a lower rate of tumor progression.

CONCLUSIONS

These results suggest that targeted volume reductions for radiation therapy using smaller margins are feasible and safe but require careful monitoring. We are currently investigating the differences in outcome based on host factors to explain the results.