Medulloblastoma initiation and spread: Where neurodevelopment, microenvironment and cancer cross pathways

Complement C3a activates astrocytes to promote medulloblastoma progression through TNF-α

Background

Medulloblastoma (MB) is the most common malignant brain tumor in children. Approximately one-third of MB patients remain incurable. Understanding the molecular mechanism of MB tumorigenesis is, therefore, critical for developing specific and effective treatment strategies. Our previous work demonstrated that astrocytes constitute the tumor microenvironment (TME) of MB and play an indispensable role in MB progression. However, the underlying mechanisms by which astrocytes are regulated and activated to promote MB remain elusive.

Methods

By taking advantage of Math1-Cre/Ptch1^loxp/loxp mice, which spontaneously develop MB, primary MB cells and astrocytes were isolated and then subjected to administration and coculture in vitro. Immunohistochemistry was utilized to determine the presence of C3a in MB sections. MB cell proliferation was evaluated by immunofluorescent staining. GFAP and cytokine expression levels in C3a-stimulated astrocytes were assessed by immunofluorescent staining, western blotting, q-PCR and ELISA. C3a receptor and TNF-α receptor expression was determined by PCR and immunofluorescent staining. p38 MAPK pathway activation was detected by western blotting. Transplanted MB mice were treated with a C3a receptor antagonist or TNF-α receptor antagonist to investigate their role in MB progression in vivo.

Results

We found that complement C3a, a fragment released from intact complement C3 following complement activation, was enriched in both human and murine MB tumor tissue, and its receptor was highly expressed on tumor-associated astrocytes (TAAs). We demonstrated that C3a activated astrocytes and promoted MB cell proliferation via the p38 MAPK pathway. Moreover, we discovered that C3a upregulated the production of proinflammatory cytokines, such as IL-6 and TNF-α in astrocytes. Application of the conditioned medium of C3a-stimulated astrocytes promoted MB cell proliferation, which was abolished by preincubation with a TNF-α receptor antagonist, indicating a TNF-α-dependent event. Indeed, we further demonstrated that administration of a selective C3a receptor or TNF-α receptor antagonist to mice subcutaneously transplanted with MB suppressed tumor progression in vivo.

Conclusions

C3a was released during MB development. C3a triggered astrocyte activation and TNF-α production via the p38 pathway, which promoted MB cell proliferation. Our findings revealed the novel role of C3a-mediated TNF-α production by astrocytes in MB progression. These findings imply that targeting C3a and TNF-α may represent a potential novel therapeutic approach for human MB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02516-9.

STAT3 inhibitor in combination with irradiation significantly inhibits cell viability, cell migration, invasion and tumorsphere growth of human medulloblastoma cells

Persistent activation of signal transducer and activator of transcription 3 (STAT3) is frequently reported in cancers and plays important roles in tumor progression. Therefore, directly targeting persistent STAT3 signaling is an attractive cancer therapeutic strategy. The aim of this study is to test the inhibitory efficacy of novel STAT3 small molecule inhibitors, LLY17 and LLL12B, in combination with irradiation in human medulloblastoma cells. Both LLY17 and LLL12B inhibit the IL-6-induced and persistent STAT3 phosphorylation in human medulloblastoma cells. Irradiation using 4 Gy alone exhibits some inhibitory effects on medulloblastoma cell viability, and these effects are further enhanced by combining with either STAT3 inhibitor. Irradiation alone also shows certain inhibitory effects on medulloblastoma cell migration and invasion and the combination of LLY17 or LLL12B with irradiation further demonstrates greater inhibitory effects than monotherapy. STAT3 inhibitor alone or irradiation alone exhibits some suppression of medulloblastoma tumorsphere growth, and the combination of LLY17 or LLL12B and irradiation exhibits greater suppression of tumorsphere growth than monotherapy. Combining either STAT3 inhibitor with irradiation reduces the expression of STAT3 downstream targets, Cyclin D1 and Survivin, and induces apoptosis in medulloblastoma cells. These results support that combination of a potent STAT3 inhibitor such as LLY17 or LLL12B with irradiation is an effective and novel therapeutic approach for medulloblastoma.

Construction and Validation of a 13-Gene Signature for Prognosis Prediction in Medulloblastoma

Background: Recent studies have identified several molecular subgroups of medulloblastoma associated with distinct clinical outcomes; however, no robust gene signature has been established for prognosis prediction. Our objective was to construct a robust gene signature-based model to predict the prognosis of patients with medulloblastoma.

Methods: Expression data of medulloblastomas were acquired from the Gene Expression Omnibus (GSE85217, n = 763; GSE37418, n = 76). To identify genes associated with overall survival (OS), we performed univariate survival analysis and least absolute shrinkage and selection operator (LASSO) Cox regression. A risk score model was constructed based on selected genes and was validated using multiple datasets. Differentially expressed genes (DEGs) between the risk groups were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and protein–protein interaction (PPI) analyses were performed. Network modules and hub genes were identified using Cytoscape. Furthermore, tumor microenvironment (TME) was evaluated using ESTIMATE algorithm. Tumor-infiltrating immune cells (TIICs) were inferred using CIBERSORTx.

Results: A 13-gene model was constructed and validated. Patients classified as high-risk group had significantly worse OS than those as low-risk group (Training set: p < 0.0001; Validation set 1: p < 0.0001; Validation set 2: p = 0.00052). The area under the curve (AUC) of the receiver operating characteristic (ROC) analysis indicated a good performance in predicting 1-, 3-, and 5-year OS in all datasets. Multivariate analysis integrating clinical factors demonstrated that the risk score was an independent predictor for the OS (validation set 1: p = 0.001, validation set 2: p = 0.004). We then identified 265 DEGs between risk groups and PPI analysis predicted modules that were highly related to central nervous system and embryonic development. The risk score was significantly correlated with programmed death-ligand 1 (PD-L1) expression (p < 0.001), as well as immune score (p = 0.035), stromal score (p = 0.010), and tumor purity (p = 0.010) in Group 4 medulloblastomas. Correlations between the 13-gene signature and the TIICs in Sonic hedgehog and Group 4 medulloblastomas were revealed.

Conclusion: Our study constructed and validated a robust 13-gene signature model estimating the prognosis of medulloblastoma patients. We also revealed genes and pathways that may be related to the development and prognosis of medulloblastoma, which might provide candidate targets for future investigation.

CTGF expression is indicative of better survival rates in patients with medulloblastoma

Medulloblastoma (MB) is the most frequent malignant brain tumor in children and it is subgrouped into 4 entities (SHH, WNT, Group 3, and Group 4). Molecular pathways involved in these different subgroups still are evolving and can be of clinical relevance to therapy. The YAP1-CTGF axis is known to regulate cell proliferation, differentiation, and cell death; however, its role in MB is poorly explored. We aimed to investigate the role of YAP1 gene in the MB SHH cell line DAOY and evaluate cell proliferation, doubling time and 3D spheroids invasion and its consequence on CTGF regulation. We assessed CTGF expression from 22 children with MB. Lastly, we validated our findings through in silico analysis in large cohorts dataset of patients. We observed an increased invasion rate of DAOY cells and CTGF downregulation under YAP1 knockdown (p < 0.0001). Additionally CTGF is overexpressed in MB with extensive nodularity subtype and an indicative of higher survival rates in pediatric MB (p < 0.05). Interestingly, no difference of CTGF expression was observed between molecular subgroups. These results provide new evidence ofCTGF as a potential prognostic marker for MB, corroborating to the role of YAP1 in restricting MB cell.

Genetic ablation of Gpr37l1 delays tumor occurrence in Ptch1+/- mouse models of medulloblastoma

The G-protein coupled receptor 37-like 1 (Gpr37l1) is specifically expressed in most astrocytic glial cells, including cerebellar Bergmann astrocytes and interacts with patched 1 (Ptch1), a co-receptor of the sonic hedgehog (Shh)-smoothened (Smo) signaling complex. Gpr37l1 null mutant mice exhibit precocious post-natal cerebellar development, with altered Shh-Smo mitogenic cascade and premature down-regulation of granule cell precursor (GCP) proliferation. Gpr37l1 expression is downregulated in medulloblastoma (MB) and upregulated in glioma and glioblastoma tumors. Shh-associated MBs originate postnatally, from dysregulated hyperproliferation of GCPs in developing cerebellum's external granular layer (EGL), as shown in heterozygous Ptch1^+/- knock-out mouse strains that model human MB occurrence and progression. This study investigates cerebellar MB phenotypes in newly produced Gpr37l1, Ptch1 double mutant mice. Natural history analysis shows that Gpr37l1 genetic ablation, in Ptch1^+/- model animals, results in marked deferment of post-natal tumor occurrence and decreased incidence of more aggressive tumor types. It is also associated with the delayed and diminished presence of more severe types of hyperplastic lesions in Ptch1^+/- mice. Consistently, during early post-natal development Gpr37l1^-/-;Ptch1^+/- pups exhibit reduction in cerebellar GCP proliferation and EGL thickness and a precocious, sustained expression of wingless-type MMTV integration site member 3 (Wnt3), a specific inhibitor of Shh-induced neuronal mitogenesis, in comparison with Ptch1^+/- heterozygous single mutants. These findings highlight the specific involvement of Gpr37l1 in modulating postnatal cerebellar Shh-Ptch1-Smo mitogenic signaling in both normal and pathological conditions. The novel Gpr37l1^-/-;Ptch1^+/- mouse models may thus be instrumental in the detailed characterization of the initial phases of Shh-associated MB insurgence and development.

Nkx2-2as Suppression Contributes to the Pathogenesis of Sonic Hedgehog Medulloblastoma

Aberrant Hedgehog signaling and excessive activation of the Gli family of transcriptional activators are key drivers of medulloblastoma (MB), the most common human pediatric brain malignancy. MB originates mainly from cerebellar granule neuron progenitors (CGNP), but the mechanisms underlying CGNP transformation remain largely obscure. In this study, we found that suppression of the noncoding RNA Nkx2-2as promoted Sonic Hedgehog (Shh)-potentiated MB development. Nkx2-2as functioned as a competing endogenous RNA against miR-103 and miR-107, sequestering them and thereby derepressing their tumor suppressive targets BTG2 and LATS1 and impeding cell division and migration. We also found that Nkx2-2as tethered miR-548m and abrogated its LATS2 targeting activity. Shh signaling impaired Nkx2-2as expression by upregulating the transcriptional repressor FoxD1. In clinical specimens of Shh-subgroup MB, we validated coordinated expression of the aforementioned proteins. Notably, exogenous expression of Nkx2-2as suppressed tumorigenesis and prolonged animal survival in MB mouse models. Our findings illuminate the role of noncoding RNAs in Hedgehog signaling and MB occurrence, with implications for identifying candidate therapeutic targets for MB treatment.Significance: These findings illuminate the role of noncoding RNAs in Hedgehog signaling and an interplay between the Hedgehog and Hippo pathways in medulloblastoma pathogenesis. Cancer Res; 78(4); 962-73. ©2017 AACR.

An Unusual Combination of Mirror-Image Dextrocardia with Familial Medulloblastoma: Is There a Histogenetic Relationship?

BACKGROUND

The occurrence of medulloblastoma in the absence of hereditary syndromes is rare. Dextrocardia with situs inversus is also called mirror-image dextrocardia. A combination of mirror-image dextrocardia with medulloblastoma has not been reported previously. To the best of our knowledge, this is the first report of this rare combination in a family with medulloblastoma.

METHODS

The clinical manifestation, radiographic characteristics, treatment, and outcomes of 3 medulloblastoma cases in 2 cousins and their maternal uncle was described. Tumor samples of the 2 cousins were first examined for histologic subtypes. Total RNA of their tumors was extracted from formalin-fixed and paraffin-embedded samples. Then, expression of 22 subgroup-specific genes and 3 housekeeping genes was analyzed by the NanoString nCounter Analysis System. The posttest data were normalized by NanoStringNorm package for molecular subgroup prediction.

RESULTS

The proband remains tumor free and alive up to the latest follow-up. His cousin, who had combined mirror-image dextrocardia with situs inversus, died of anoxia after surgery and his uncle died of tumor 2.5 years after surgery. Medulloblastoma of the 2 cousins was classified as classic and molecular group 4 subtype.

CONCLUSIONS

The same classic and molecular group 4 subtype of the 2 cousins may suggest a similar genetic predisposition. Involvement of the Otx2 gene dysfunction in both group 4 subtype medulloblastoma and mirror-image dextrocardia with situs inversus points to a possible mechanism that dysfunction of a shared signaling pathway such as Otx2 might be the underlying cause of these 2 conditions in this family.

Medulloblastoma with Atypical Dynamic Imaging Changes: Case Report with Literature Review

OBJECTIVE

We analyzed a case of medulloblastoma with atypical dynamic imaging changes retrospectively to summarize the atypical magnetic resonance imaging (MRI) features of medulloblastoma by reviewing the literature.

METHODS

An atypical case of medulloblastoma in the cerebellar hemisphere confirmed by pathology was analyzed retrospectively, and the literature about it was reviewed.

RESULTS

The radiologic findings of the patient were based on 3 examinations. The first examination showed that the cortex of the bilateral cerebellar hemisphere had diffuse nodular thickening, with a high signal on diffusion-weighted imaging and significant enhancement. Contrast enhancement MRI 1 year later showed the signal of cerebellar hemisphere returned to normal but revealed an enhanced nodule. A reexamination 6 months later showed an irregular mass with a high-density shadow in the cerebellar vermis on CT scan. The T2-weighted image revealed multiple degenerative cysts, and the mass had significant enhancement.

CONCLUSION

The radiologic characteristics of atypical medulloblastomas vary in adults and children. Understanding the radiologic characteristics of medulloblastomas, such as MRI features, age of onset, and location of atypical medulloblastomas, can help improve the diagnosis of medulloblastomas.

Proteomic profiling of isogenic primary and metastatic medulloblastoma cell lines reveals differential expression of key metastatic factors

Medulloblastoma is the most common malignant brain tumor in children. Around 30% of medulloblastoma patients are diagnosed with metastasis, which often results in a poor prognosis. Unfortunately, molecular mechanisms of medulloblastoma metastasis remain largely unknown. In this study, we employed the recently developed deep proteome analysis approach to quantitatively profile the expression of >10,000 proteins from CHLA-01-MED and CHLA-01R-MED isogenic cell lines derived from the primary and metastatic tumor of the same patient diagnosed with a group IV medulloblastoma. Using statistical analysis, we identified ~1400 significantly altered proteins between the primary and metastatic cell lines including known factors such as placental growth factor (PLGF), LIM homeobox 1 (LHX1) and prominim 1 (PROM1), as well as the negative regulator secreted protein acidic and cysteine rich (SPARC). Additional transwell experiments and immunohistochemical analysis of clinical medulloblastoma samples implicated yes-associated protein 1 (YAP1) as a potential key factor contributing to metastasis. Taken together, our data broadly defines the metastasis-relevant regulated proteome and provides a precious resource for further investigating potential mechanisms of medulloblastoma metastasis.

SIGNIFICANCE

This study represented the first deep proteome analysis of metastatic medulloblastomas and provided a valuable candidate list of altered proteins in metastatic medulloblastomas. The primary data suggested YAP1 as a potential driver for the metastasis of medulloblastoma. These results open up numerous avenues for further investigating the underlying mechanisms of medulloblastoma metastasis and improving the prognosis of medulloblastoma patients.