Immunotherapy of pediatric brain tumor patients should include an immunoprevention strategy: a medical hypothesis paper

Recent advances and future of immunotherapy for glioblastoma

INTRODUCTION

Outcome for glioma (GBM) remains dismal despite advances in therapeutic interventions including chemotherapy, radiotherapy and surgical resection. The overall survival benefit observed with immunotherapies in cancers such as melanoma and prostate cancer has fuelled research into evaluating immunotherapies for GBM.

AREAS COVERED

Preclinical studies have brought a wealth of information for improving the prognosis of GBM and multiple clinical studies are evaluating a wide array of immunotherapies for GBM patients. This review highlights advances in the development of immunotherapeutic approaches. We discuss the strategies and outcomes of active and passive immunotherapies for GBM including vaccination strategies, gene therapy, check point blockade and adoptive T cell therapies. We also focus on immunoediting and tumor neoantigens that can impact the efficacy of immunotherapies.

EXPERT OPINION

Encouraging results have been observed with immunotherapeutic strategies; some clinical trials are reaching phase III. Significant progress has been made in unraveling the molecular and genetic heterogeneity of GBM and its implications to disease prognosis. There is now consensus related to the critical need to incorporate tumor heterogeneity into the design of therapeutic approaches. Recent data also indicates that an efficacious treatment strategy will need to be combinatorial and personalized to the tumor genetic signature.

Eosinophil Infiltrates in Pilocytic Astrocytomas of Children and Young Adults

Objective

Eosinophils may affect each stage of tumour development. Many studies have suggested that tumour-associated tissue eosinophilia (TATE) is associated with favourable prognosis in some malignant tumours. However, only a few studies exist on TATE in central nervous system (CNS) tumours. Our recent study exhibited eosinophils in atypical teratoid/rhabdoid tumours (AT/RTs), pediatric malignant CNS tumours with divergent differentiation. This study examines eosinophils in pilocytic astrocytomas (PAs).

Methods

The study included 44 consecutive cases of patients with PAs and no concurrent CNS inflammatory disease.

Results

We found eosinophils in 19 (43%) of 44 PAs (patient age range, 0.5-72 years). Eosinophils were intratumoural and clearly distinguishable. The density of eosinophils was rare to focally scattered. PAs containing eosinophils were located throughout the CNS. Furthermore, eosinophilic infiltration was identified in 18 (62%) of 29 pediatric (age range, 0.5-18 years) PAs but only 1 (7%) of 15 (p<0.001, significantly less) adult (age range, 20-72 years) PAs. Eosinophilic infiltration showed no significant differences between PAs with and without MRI cystic formation, surgical procedures, or PAs with and without leptomeningeal infiltration. In comparison, eosinophils were absent in 10 pediatric (age range, 0.5-15 years) ependymomas (or anaplastic ependymomas).

Conclusions

These results suggest that eosinophils are common in pediatric PAs but rare in adult PAs. This difference is probably related to the developing immune system and different tumour-specific antigens in children. TATE may play a functional role in the development of pediatric PAs, as well as some other pediatric CNS tumours such as AT/RTs.

Perspectives on the immunologic microenvironment of astrocytomas

Background

The microenvironment of astrocytomas includes infiltrative inflammatory cells that are dynamic in nature, possibly reflecting tumor biology. We evaluated the inflammatory cell infiltrate in astrocytic tumors aiming for a better understanding of their immunobiology.

Methods

Immunohistochemical expression of CD68, CD3, and CD20 was investigated in 21 glioblastomas, 21 anaplastic astrocytomas, 13 diffuse astrocytomas, and 18 pilocytic astrocytomas. The inflammatory infiltrate was classified based on microanatomic location as perivascular and intratumoral, and subsequently graded semiquantitatively.

Results

Perivascularly, CD68-positive infiltrate was noted in 71.4% of glioblastomas compared with 14.3% of anaplastic astrocytomas (P = 0.0001), 7.7% of diffuse astrocytomas (P = 0.0001), and 33.3% of pilocytic astrocytomas (P = 0.017). Intratumorally, 85.7% of glioblastomas exhibited CD68-positive infiltrate compared with 42.9% of anaplastic astrocytomas (P = 0.004), 38.5% of diffuse astrocytomas (P = 0.008), and 33.3% of pilocytic astrocytomas (P = 0.001). Among diffusely infiltrating astrocytomas, intratumoral CD3-positive infiltrate was only associated with glioblastoma. A CD20-positive infiltrate was only detected in the perivascular space of a single case of diffuse astrocytoma.

Conclusion

These data indicate a distinct immune profile in the glioblastoma microenvironment primarily related to the prevalence of macrophages. Thus, novel glioblastoma therapies should address this key CD68-positive population and its possible role in generating an antitumor immune response.

Cellular-based immunotherapies for patients with glioblastoma multiforme

Treatment of patients with glioblastoma multiforme (GBM) remains to be a challenge with a median survival of 14.6 months following diagnosis. Standard treatment options include surgery, radiation therapy, and systemic chemotherapy with temozolomide. Despite the fact that the brain constitutes an immunoprivileged site, recent observations after immunotherapies with lysate from autologous tumor cells pulsed on dendritic cells (DCs), peptides, protein, messenger RNA, and cytokines suggest an immunological and even clinical response from immunotherapies. Given this plethora of immunomodulatory therapies, this paper gives a structure overview of the state-of-the art in the field. Particular emphasis was also put on immunogenic antigens as potential targets for a more specific stimulation of the immune system against GBM.