Novel therapeutic approaches for pediatric diencephalic tumors: improving functional outcomes

Pediatric diencephalic tumors represent a histopathologically and molecularly diverse group of neoplasms arising in the central part of the brain and involving eloquent structures, including the hypothalamic-pituitary axis (HPA), optic pathway, thalamus, and pineal gland. Presenting symptoms can include significant neurological, endocrine, or visual manifestations which may be exacerbated by injudicious intervention. Upfront multidisciplinary assessment and coordinated management is crucial from the outset to ensure best short- and long-term functional outcomes. In this review we discuss the clinical and pathological features of the neoplastic entities arising in this location, and their management. We emphasize a clear move towards 'function preserving' diagnostic and therapeutic approaches with novel toxicity-sparing strategies, including targeted therapies.

Mapping glioma heterogeneity using multiparametric 18 F-choline PET/MRI in childhood and teenage-young adults

OBJECTIVE

The heterogeneity of post-treatment imaging remains a significant challenge in children and teenagers/young adults (TYA) diagnosed with glioma. The aim of this study was to evaluate the utility of 18 F-choline PET/MRI in determining intratumoural heterogeneity in paediatric and TYA gliomas.

METHODS

Twenty-six patients (mean age 16 years, range 8-22 years) with suspected glioma disease progression were evaluated with 18 F-choline PET/MRI. Relative cerebral blood volume (rCBV), apparent diffusion coefficient (ADC) and maximum standardised uptake values (SUV max ) in enhancing (enh) and non-enhancing (ne) tumour volumes and normal-appearing white matter (wm) were calculated (rCBV enh , rCBV ne , rCBV wm , ADC enh , ADC ne , ADC wm , SUV enh , SUV ne and SUV wm ).

RESULTS

Significantly higher SUV enh and SUV ne compared with SUV wm were observed [SUV enh 0.89 (0.23-1.90), SUV ne 0.36 (0.16-0.78) versus SUV wm 0.15 (0.04-1.19); P  < 0.001 and P  = 0.004, respectively]. Equivalent results were observed for ADV and rCBV (ADC enh , ADC ne : P  < 0.001 versus ADC wm ; rCBV enh , rCBV ne : P  < 0.001 versus rCBV wm ). The highest values for mean SUV max [0.89 (0.23-1.90)] and mean rCBV [2.1 (0.74-5.08)] were in the enhancing component, while the highest values for ADC [1780 mm 2 /s (863-2811)] were in the necrotic component.

CONCLUSION

18 F-choline PET/MRI is able map imaging heterogeneity in paediatric and TYA gliomas, detecting post-treatment enhancing, non-enhancing, and necrotic tumour components equivalent to ADC and DSC-derived rCBV. This offers potential in the response assessment of diffuse non-enhancing gliomas and in selected cases such as posterior fossa tumours where quantitative MRI is technically difficult.

Challenging the indiscriminate use of temozolomide in pediatric high-grade gliomas: A review of past, current, and emerging therapies

Pediatric high-grade gliomas (pHGG) constitute 8% to 12% of primary brain tumors in childhood. The most widely utilized treatment encompasses surgical resection followed by focal radiotherapy and temozolomide. However, experiences over past decades have not demonstrated improved outcomes. pHGG have been classified into different molecular subgroups defined by mutations in histone 3, IDH gene, MAPK pathway, and others, thereby providing a rationale for various targeted therapies. Additionally, immunotherapy and drug repurposing have also become attractive adjunctive treatments. This review focuses on past, present, and emerging treatments for pHGG integrating molecular research with the mainstream pediatric drug development in Europe and the United States to sketch a way forward in the development of novel therapeutic approaches. The implementation of randomized clinical trials with adaptive designs, underpinned by a robust biological rationale, and harnessing collaboration between the pharmaceutical industry, academia, regulators and patients/parents organizations will be essential to improve the outcomes for these children.

Multiparametric 18F-Choline PET/MR in childhood and teenage-young adult gliomas: assessment of suspected disease progression

Aim

Evaluation of post-treatment glioma burden remains a significant challenge in childhood, Teenage and Young Adults (TYA). Although amino acid PET impacts on glioma imaging, 18fluoro-Choline Positron Emission Tomography (ChoPET) is more widely available. The aim was to evaluate the utility of ChoPET/MRI for suspected disease progression in childhood and TYA gliomas.

Methods

27 consecutive patients with suspected glioma disease progression were evaluated with ChoPET/MR and 59 scans included. Relative cerebral blood volume (rCBV), ADC and SUVmax in enhancing (enh), non-enhancing (ne) tumour volumes and normal appearing white matter (wm) were calculated (rCBVenh, rCBVne, rCBVwm, ADCenh, ADCne, ADCwm, SUVenh, SUVne, SUVwm). Blinded nuclear medicine and neuroradiologist scored the images on tumour probability (1:unlikely-5:definitely). Receiver Operating Characteristic (ROC) analysis considering as gold standard histopathology or clinical follow-up was performed.

Results

Combined ChoPET/MR accuracy was 100% for residual tumour, conventional MR accuracy was 96.3% (91.7% <14years, 100% ≥15years) and ChoPET accuracy was 73.1% (66.7% <14years, 80.0% ≥15 years). Lack ack of agreement in 9/27 with ChoPET superior to MR in 1 case. Tumour component analysis demonstrated significantly higher SUVenh and SUVne than SUVwm (SUVenh: p<0.001,SUVne: p=0.003) equivalent to ADC (ADCenh, ADCnenh: p<0.001) and rCBV (rCBVenh, rCBVnenh: p<0,001).

Conclusions

Combined ChoPET/MR has 100% accuracy in TYA gliomas with suspected disease progression. ChoPET is able to detect enhancing and non-enhancing tumour but it is more reliable for evaluating enhancing disease >15 years. In selected cases where MRI is equivocal, a quantitative multi-modality ChoPET/MR better defines both enhancing and non-enhancing tumour for improved assessment of childhood and TYA gliomas.

FGFR1 Expression and Role in Migration in Low and High Grade Pediatric Gliomas

The heterogeneous and invasive nature of pediatric gliomas poses significant treatment challenges, highlighting the importance of identifying novel chemotherapeutic targets. Recently, recurrent Fibroblast growth factor receptor 1 (FGFR1) mutations in pediatric gliomas have been reported. Here, we explored the clinical relevance of FGFR1 expression, cell migration in low and high grade pediatric gliomas and the role of FGFR1 in cell migration/invasion as a potential chemotherapeutic target. A high density tissue microarray (TMA) was used to investigate associations between FGFR1 and activated phosphorylated FGFR1 (pFGFR1) expression and various clinicopathologic parameters. Expression of FGFR1 and pFGFR1 were measured by immunofluorescence and by immunohistochemistry (IHC) in 3D spheroids in five rare patient-derived pediatric low-grade glioma (pLGG) and two established high-grade glioma (pHGG) cell lines. Two-dimensional (2D) and three-dimensional (3D) migration assays were performed for migration and inhibitor studies with three FGFR1 inhibitors. High FGFR1 expression was associated with age, malignancy, tumor location and tumor grade among astrocytomas. Membranous pFGFR1 was associated with malignancy and tumor grade. All glioma cell lines exhibited varying levels of FGFR1 and pFGFR1 expression and migratory phenotypes. There were significant anti-migratory effects on the pHGG cell lines with inhibitor treatment and anti-migratory or pro-migratory responses to FGFR1 inhibition in the pLGGs. Our findings support further research to target FGFR1 signaling in pediatric gliomas.

Intravenous delivery of oncolytic reovirus to brain tumor patients immunologically primes for subsequent checkpoint blockade

Immune checkpoint inhibitors, including those targeting programmed cell death protein 1 (PD-1), are reshaping cancer therapeutic strategies. Evidence suggests, however, that tumor response and patient survival are determined by tumor programmed death ligand 1 (PD-L1) expression. We hypothesized that preconditioning of the tumor immune microenvironment using targeted, virus-mediated interferon (IFN) stimulation would up-regulate tumor PD-L1 protein expression and increase cytotoxic T cell infiltration, improving the efficacy of subsequent checkpoint blockade. Oncolytic viruses (OVs) represent a promising form of cancer immunotherapy. For brain tumors, almost all studies to date have used direct intralesional injection of OV, because of the largely untested belief that intravenous administration will not deliver virus to this site. We show, in a window-of-opportunity clinical study, that intravenous infusion of oncolytic human Orthoreovirus (referred to herein as reovirus) leads to infection of tumor cells subsequently resected as part of standard clinical care, both in high-grade glioma and in brain metastases, and increases cytotoxic T cell tumor infiltration relative to patients not treated with virus. We further show that reovirus up-regulates IFN-regulated gene expression, as well as the PD-1/PD-L1 axis in tumors, via an IFN-mediated mechanism. Finally, we show that addition of PD-1 blockade to reovirus enhances systemic therapy in a preclinical glioma model. These results support the development of combined systemic immunovirotherapy strategies for the treatment of both primary and secondary tumors in the brain.

Oncolytic Herpes Simplex Virus Inhibits Pediatric Brain Tumor Migration and Invasion

Pediatric high-grade glioma (pHGG) and diffuse intrinsic pontine glioma (DIPG) are invasive tumors with poor survival. Oncolytic virotherapy, initially devised as a direct cytotoxic treatment, is now also known to act via immune-mediated mechanisms. Here we investigate a previously unreported mechanism of action: the inhibition of migration and invasion in pediatric brain tumors. We evaluated the effect of oncolytic herpes simplex virus 1716 (HSV1716) on the migration and invasion of pHGG and DIPG both in vitro using 2D (scratch assay, live cell imaging) and 3D (spheroid invasion in collagen) assays and in vivo using an orthotopic xenograft model of DIPG invasion. HSV1716 inhibited migration and invasion in pHGG and DIPG cell lines. pHGG cells demonstrated reduced velocity and changed morphology in the presence of virus. HSV1716 altered pHGG cytoskeletal dynamics by stabilizing microtubules, inhibiting glycogen synthase kinase-3, and preventing localized clustering of adenomatous polyposis coli (APC) to the leading edge of cells. HSV1716 treatment also reduced tumor infiltration in a mouse orthotopic xenograft DIPG model. Our results demonstrate that HSV1716 targets the migration and invasion of pHGG and DIPG and indicates the potential of an oncolytic virus (OV) to be used as a novel anti-invasive treatment strategy for pediatric brain tumors.

Combination viroimmunotherapy with checkpoint inhibition to treat glioma, based on location-specific tumor profiling

BACKGROUND

Systemic delivery of a complementary cDNA library expressed from the vesicular stomatitis virus (VSV) treats tumors by vaccinating against a wide range of tumor associated antigens (TAAs). For subcutaneous B16 melanomas, therapy was achieved using a specific combination of self-TAAs (neuroblastoma-Ras, cytochrome c, and tyrosinase-related protein 1) expressed from VSV. However, for intracranial B16 tumors, a different combination was therapeutic (consisting of VSV-expressed hypoxia-inducible factor [HIF]-2α, Sox-10, c-Myc, and tyrosinase-related protein 1). Therefore, we tested the hypothesis that tumors of different histological types growing in the brain share a common immunogenic signature which can be exploited for immunotherapy.

METHODS

Syngeneic tumors, including GL261 gliomas, in the brains of immune competent mice were analyzed for their antigenic profiles or were treated with systemic viroimmunotherapy.

RESULTS

Several different histological types of tumors growing intracranially, as well as freshly resected human brain tumor explants, expressed a HIF-2α(Hi) phenotype imposed by brain-derived CD11b+ cells. This location-specific antigen expression was exploited therapeutically against intracranial GL261 gliomas using systemically delivered VSV expressing HIF-2α, Sox-10, and c-Myc. Viroimmunotherapy was enhanced by immune checkpoint inhibitors, associated with the de-repression of antitumor T-helper cell type 1 (Th1) interferon-γ and Th17 T cell responses.

CONCLUSIONS

Since different tumor types growing in the same location in the brain share a location-specific phenotype, we suggest that antigen-specific immunotherapies should be based upon expression of both histological type-specific tumor antigens and location-specific antigens. Our findings support clinical application of VSV-TAA therapy with checkpoint inhibition for aggressive brain tumors and highlight the importance of the intracranial microenvironment in sculpting a location-specific profile of tumor antigen expression.

Cell migration in paediatric glioma; characterisation and potential therapeutic targeting

BACKGROUND

Paediatric high grade glioma (pHGG) and diffuse intrinsic pontine glioma (DIPG) are highly aggressive brain tumours. Their invasive phenotype contributes to their limited therapeutic response, and novel treatments that block brain tumour invasion are needed.

METHODS

Here, we examine the migratory characteristics and treatment effect of small molecule glycogen synthase kinase-3 inhibitors, lithium chloride (LiCl) and the indirubin derivative 6-bromoindirubin-oxime (BIO), previously shown to inhibit the migration of adult glioma cells, on two pHGG cell lines (SF188 and KNS42) and one patient-derived DIPG line (HSJD-DIPG-007) using 2D (transwell membrane, immunofluorescence, live cell imaging) and 3D (migration on nanofibre plates and spheroid invasion in collagen) assays.

RESULTS

All lines were migratory, but there were differences in morphology and migration rates. Both LiCl and BIO reduced migration and instigated cytoskeletal rearrangement of stress fibres and focal adhesions when viewed by immunofluorescence. In the presence of drugs, loss of polarity and differences in cellular movement were observed by live cell imaging.

CONCLUSIONS

Ours is the first study to demonstrate that it is possible to pharmacologically target migration of paediatric glioma in vitro using LiCl and BIO, and we conclude that these agents and their derivatives warrant further preclinical investigation as potential anti-migratory therapeutics for these devastating tumours.