The molecular pathogenesis of craniopharyngiomas

Research from the last 20 years has provided important insights into the molecular pathogenesis of craniopharyngiomas (CPs). Besides the well-known clinical and histological differences between the subtypes of CPs, adamantinomatous (ACP) and papillary (PCP) craniopharyngiomas, other molecular differences have been identified, further elucidating pathways related to the origin and development of such tumors. The present minireview assesses current knowledge on embryogenesis and the genetic, epigenetic, transcriptomic, and signaling pathways involved in the ACP and PCP subtypes, revealing the similarities and differences in their profiles. ACP and PCP subtypes can be identified by the presence of mutations in CTNNB1 and BRAF genes, with prevalence around 60% and 90%, respectively. Therefore, β-catenin accumulates in the nucleus-cytoplasm of cell clusters in ACPs and, in PCPs, cell immunostaining with specific antibody against the V600E-mutated protein can be seen. Distinct patterns of DNA methylation further differentiate ACPs and PCPs. In addition, research on genetic and epigenetic changes and tumor microenvironment specificities have further clarified the development and progression of the disease. No relevant transcriptional differences in ACPs have emerged between children and adults. In conclusion, ACPs and PCPs present diverse genetic signatures and each subtype is associated with specific signaling pathways. A better understanding of the pathways related to the growth of such tumors is paramount for the development of novel targeted therapeutic agents.

Optic tract edema in craniopharyngioma as a predictor of BRAFV600E mutation presence

OBJECTIVE

the advent of BRAF inhibitors for preoperative treatment of craniopharyngioma has necessitated the identification of BRAFV600E status. Hence, we investigated predictors of BRAFV600E mutation in craniopharyngiomas.

METHODS

this retrospective study utilized data from 30 patients who were newly diagnosed with craniopharyngioma between 2011 and 2021. Magnetic resonance imaging (MRI) and computed tomography were performed within 1 week prior to surgery. Genetic analysis for BRAF mutation was performed using the Oncomine next-generation sequencing panel or Sanger sequencing. The relationship between BRAF mutation and demographic data, endocrinological function and tumour characteristics on imaging was assessed.

RESULTS

tumour tissue carried the BRAFV600E mutation in nine patients. There was no significant difference in age, sex, or presence of hormonal dysfunction amongst patients with and without the BRAFV600E mutation in the tumour. Most tumours with the BRAFV600E mutation were histologically categorized as papillary craniopharyngioma (P = 0.0005), and were solid (P = 0.0002) and supra-diaphragmatic (P = 0.0033) on MRI. BRAFV600E tumours were more frequently associated with optic tract edema than wild-type tumour s (55.6 vs. 0%, P = 0.0009) and all tumour s with optic tract edema carried the BRAFV600E mutation. Optic tract edema was not associated with tumour volume, cysts, or preoperative pituitary function.

CONCLUSIONS

in craniopharyngiomas, the presence of optic tract edema can predict the presence of BRAFV600E mutation with a positive predictive value of 100%. The finding should be verified in larger prospective cohorts and multivariate regression analysis.

The Challenging Management of Craniopharyngiomas in Adults: Time for a Reappraisal?

Simple Summary

Craniopharyngiomas (CPs) currently represent one of the most challenging diseases to deal with in the group of skull base tumors. Due to their location near, within, or surrounding the pituitary gland and stalk, CPs can be revealed by pituitary tumor syndrome and/or symptoms of hormonal deficiencies. Furthermore, surgery, which represents the first-line therapy, almost always results in hypopituitarism, diabetes insipidus and, in the case of hypothalamic involvement by the tumor, the occurrence of hypothalamic syndrome. The latter is characterized by intractable weight gain associated with severe morbid obesity, memory impairment, attention deficit, reduced impulse control and, eventually, increased risk of cardiovascular and metabolic disorders. Recent progress made in the understanding of the molecular pathways involved in CPs tumorigenesis paves the way for promising alternative therapeutic approaches and diagnostic procedures. Taken together, they lay the groundwork for new paradigms in the management of CPs in adults.

Abstract

Craniopharyngiomas (CPs) are rare tumors of the skull base, developing near the pituitary gland and hypothalamus and responsible for severe hormonal deficiencies and an overall increase in mortality rate. While surgery and radiotherapy represent the recommended first-line therapies for CPs, a new paradigm for treatment is currently emerging, as a consequence of accumulated knowledge concerning the molecular mechanisms involved in tumor growth, paving the way for anticipated use of targeted therapies. Significant clinical and basic research conducted in the field of CPs will undoubtedly constitute a real step forward for a better understanding of the behavior of these tumors and prevent associated complications. In this review, our aim is to summarize the multiple steps in the management of CPs in adults and emphasize the most recent studies that will contribute to advancing the diagnostic and therapeutic algorithms.

Targeted Therapy in the Management of Modern Craniopharyngiomas

BACKGROUND

The proximity of craniopharyngiomas (CPs) to critical neurovascular structures can lead to a host of neurologic and endocrine complications that lead to difficulty with surgical management. In this review, we examine the molecular and genetic markers implicated in CP, their involvement in tumorigenic pathways, and their impact on CP prognosis and treatment.

METHODS

We undertook a focused review of relevant articles, clinical trials, and molecular summaries regarding CP.

RESULTS

Genetic and immunological markers show variable expression in different types of CP. BRAF is implicated in tumorigenesis in papillary CP (pCP), whereas CTNNB1 and EGFR are often overexpressed in adamantinomatous CP (aCP) and VEGF is overexpressed in aCP and recurrent CP. Targeted treatment modalities inhibiting these pathways can shrink or halt progression of CP. In addition, EGFR inhibitors may sensitize tumors to radiation therapy. These drugs show promise in medical management and neoadjuvant therapy for CP. Immunotherapy, including anti-interleukin-6 (IL-6) drugs and interferon treatment, are also effective in managing tumor growth. Ongoing clinical trials in CP are limited but are testing BRAF/MET inhibitors and IL-6 monoclonal antibodies.

CONCLUSIONS

Genetic and immunological markers show variable expression in different subtypes of CP. Several current molecular treatments have shown some success in the management of this disease. Additional clinical trials and targeted therapies will be important to improve CP patient outcomes.

Non-Invasive Radiomics Approach Predict Invasiveness of Adamantinomatous Craniopharyngioma Before Surgery

Purpose

Craniopharyngiomas (CPs) are benign tumors, complete tumor resection is considered to be the optimal treatment. However, although histologically benign, the local invasiveness of CPs commonly contributes to incomplete resection and a poor prognosis. At present, some advocate less aggressive surgery combined with radiotherapy as a more reasonable and effective means of protecting hypothalamus function and preventing recurrence in patients with tight tumor adhesion to the hypothalamus. Hence, if a method can be developed to predict the invasiveness of CP preoperatively, it will help in the development of a more personalized surgical strategy. The aim of the study was to report a radiomics-clinical nomogram for the individualized preoperative prediction of the invasiveness of adamantinomatous CP (ACPs) before surgery.

Methods

In total, 1,874 radiomics features were extracted from whole tumors on contrast-enhanced T1-weighted images. A support vector machine trained a predictive model that was validated using receiver operating characteristic (ROC) analysis on an independent test set. Moreover, a nomogram was constructed incorporating clinical characteristics and the radiomics signature for individual prediction.

Results

Eleven features associated with the invasiveness of ACPs were selected by using the least absolute shrinkage and selection operator (LASSO) method. These features yielded area under the curve (AUC) values of 79.09 and 73.5% for the training and test sets, respectively. The nomogram incorporating peritumoral edema and the radiomics signature yielded good calibration in the training and test sets with the AUCs of 84.79 and 76.48%, respectively.

Conclusion

The developed model yields good performance, indicating that the invasiveness of APCs can be predicted using noninvasive radiological data. This reliable, noninvasive tool can help clinical decision making and improve patient prognosis.

Adamantinomatous Craniopharyngioma in an Adult: A Case Report with NGS Analysis

PURPOSE

Several recent studies have documented CTNNB1 and BRAF mutations which are mutually exclusive for adamantinomatous craniopharyngioma (ACP) and papillary craniopharyngioma (PCP) tumors. This discovery is helpful in the development of novel targeted therapies in successful clinical trials with BRAF mutations in PCP cases. However, no such targeted therapy is available yet for ACP. Here, we report novel mutations, which are not previously reported, in a case of an adult ACP using NGS analysis.

RESULTS

Patient DNA was sequenced using Ion PI v3 chip on Ion Proton. A total of 16 variants were identified in this tumor by NGS analysis, out of which four were missense mutations, seven were synonymous mutations, and five were intronic variants. In CTNNB1 gene a known missense mutation in c.101G>T; in TP53 a known missense mutation in c.215C>G; and two known missense variants in PIK3CA, viz., in c.1173A>G; in exon 7, and in c.3128T>C; in exon 21, were found, respectively. Seven synonymous mutations were detected in this tumor, viz., in IDH1 (rs11554137), in FGFR3 (rs7688609), in PDGFRA (rs1873778), in APC (COSM3760869), in EGFR (rs1050171), in MET (rs35775721), and in RET (rs1800861), respectively. Three known, intronic variants were found in genes, such as PIK3CA, KDR, and JAK3, respectively. Also, a 3'-UTR and a splice site acceptor site variant in CSF1R and FLT3 genes were found in this tumor. We have shown allele coverage, allele ratio, and p-value, for all these mutations. The p-values and Phred quality score were significantly high for these variants.

CONCLUSION

As reported in previous studies, in ACP tumors we found a CTNNB1 mutation by NGS analysis. The PIK3CA variants we detected were not known previously in ACP tumors. Finding the PIK3CA mutations in the ACP tumors may help develop targeted therapy for a subset of craniopharyngiomas with PIK3CA activating mutations. Clinical trials are in progress with specific PIK3CA inhibitors in advanced stages of many cancers.

High-resolution melting and immunohistochemical analysis efficiently detects mutually exclusive genetic alterations of adamantinomatous and papillary craniopharyngiomas

Craniopharyngioma consists of adamantinomatous and papillary subtypes. Recent genetic analysis has demonstrated that the two subtypes are different, not only in clinicopathological features, but also in molecular oncogenesis. Papillary craniopharyngioma (pCP) is characterized by a BRAF mutation, the V600E (Val 600 Glu) mutation. Adamantinomatous craniopharyngioma (aCP) can be distinguished by frequent β-catenin gene (CTNNB1) mutations. Although these genetic alterations can be a diagnostic molecular marker, the precise frequency of these mutations in clinical specimens remains unknown. In this study, we first evaluated BRAF V600E and CTNNB1 mutations in four and 14 cases of pCP and aCP, respectively, using high-resolution melting analysis followed by Sanger sequencing. The results showed that 100% (4/4) of pCP cases had BRAF V600E mutations, while 78% (11/14) of the aCP cases had CTNNB1 mutations, with these genetic alterations being subtype-specific and mutually exclusive. Second, we evaluated BRAF V600E and CTNNB1 mutations by immunohistochemical analysis (IHC). All pCP cases showed positive cytoplasmic staining with the BRAF V600E-mutant antibody (VE-1), whereas 86% (12/14) of aCP cases showed positive cytoplasmic and nuclear staining for CTNNB1, suggesting a CTNNB1 mutation. Only one case of wild-type CTNNB1 on the DNA analysis showed immunopositivity on IHC. We did not detect a coexistence of BRAF V600E and CTNNB1 mutations in any single tumor, which indicated that these genetic alterations were mutually exclusive. We also report our modified IHC protocol for VE-1 staining, and present the possibility that BRAF V600E mutations can be used as a diagnostic marker of pCP in the differentiation of Rathke cleft cyst with squamous metaplasia.

PROGRESSES IN THE UNDERSTANDING OF THE PATHOGENESIS OF CRANIOPHARYNGIOMAS

Craniopharyngiomas (CP) are rare, dysembryoplastic tumors of the hypothalamo-pituitary area. There are two very distinct pathological types: adamantinomatous (ACP) and papillary (PCP). ACP and PCP also have significant clinical differences, pointing to a different pathogenesis. This only began to be elucidated lately and indeed discovered specific, mutually exclusive mutations with pathogenetic role in ACP and PCP, respectively. The vast majority of ACP harbor an activating mutation of the CTNNB1 gene coding for β-catenin (member of the Wnt pathway). The mutation was proved to be pathogenetic in animal models and a tumorigenesis model has already been created. In contrast, in PCP, BRAF (gene coding for a main actor in the MAPkinase pathway) mutations have been found in the majority of cases. These findings can improve the differential diagnosis of intracranian tumors (by specifically designed immunohistochemistry-antibodies) and the design of molecules to inhibit the disordered intracellular pathways. Such molecules are already available and promising for the BRAF/MAPkinase pathway. In conclusion, extremely significant progresses have been made in revealing the complex process of tumorigenesis in CP and they are likely to solve in the foreseeable future many challenges we typically face in the clear positive diagnosis and optimal management of these rare tumors.

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

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-cat(nc)) 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-cat(nc) 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-cat(nc) 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-cat(nc) 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.