Immunobiology of paediatric intracranial tumours. A preliminary report

Immunotherapy for Medulloblastoma: Current Perspectives

Background

Immune-mediated therapies have transformed the treatment of metastatic melanoma and renal, bladder, and both small and non-small cell lung carcinomas. However, immunotherapy is yet to demonstrate dramatic results in brain tumors like medulloblastoma for a variety of reasons. Recent pre-clinical and early phase human trials provide encouraging results that may overcome the challenges of central nervous system (CNS) tumors, which include the intrinsic immunosuppressive properties of these cancers, a lack of antigen targets, antigenic variability, and the immune-restrictive site of the CNS. These studies highlight the growing potential of immunotherapy to treat patients with medulloblastoma, a disease that is a frequent cause of morbidity and mortality to children and young adults.

Methods

We conducted an inclusive review of the PubMed-indexed literature and studies listed in clinicaltrials.gov using combinations of the keywords medulloblastoma, immunotherapy, CNS tumors, brain tumors, vaccines, oncolytic virus, natural killer, and CAR T to identify trials evaluating immunotherapy in preclinical experiments or in patients with medulloblastoma. Given a limited number of investigations using immunotherapy to treat patients with medulloblastoma, 24 studies were selected for final analysis and manuscript citation.

Results

This review presents results from pre-clinical studies in medulloblastoma cell lines, animal models, and the limited trials involving human patients.

Conclusion

From our review, we suggest that cancer vaccines, oncolytic viral therapy, natural killer cells, and CAR T therapy hold promise against the innate immunosuppressive properties of medulloblastoma in order to prolong survival. There is an unmet need for immunotherapy regimens that target overexpressed antigens in medulloblastoma tumors. We advocate for more combination treatment clinical trials using conventional surgical and radiochemotherapy approaches in the near-term clinical development.

Progress from clinical trials and emerging non-conventional therapies for the treatment of Medulloblastomas

Medulloblastomas are highly aggressive tumors of the cerebellum with an embryonal origin. Despite current treatment modalities which include a combination of surgery, chemotherapy and/or radiation, challenges still exist to effectively treat some patients, especially those within the younger age group. In an effort to find improved therapies, ongoing research led by world-wide teams have explored non-conventional therapeutic strategies, as well as examined the efficacy of several drugs in clinical trials among patients with Medulloblastomas. We outline in this article, recent advances on the efficacy and toxicity of numerous therapeutic agents including those that are DNA damaging agents, microtubules binding compounds, and those that are inhibitors of Topoisomerase and of the Notch and Hedgehog signaling pathway, which were assessed in recent Phase I and II clinical trials. Among these clinical trials, it is unfortunate that the outcomes were dismal with the majority of the patients with Medulloblastomas still succumbing to relapse after conventional therapies. Furthermore, it is yet to be established clearly the clinical efficacy of non-conventional therapies such as immunotherapy and gene therapy. Moreover, there is growing interest in proton therapy as a potential replacement for photon therapy, while high dose chemotherapy and autologous stem cell rescue may improve therapeutic efficacies. However, further research is needed to resolve the inherent toxicity from these novel therapeutic methods. In conclusion, novel therapies based on a better understanding of the biology of Medulloblastomas are pivotal in improving non-conventional therapies in the treatment of this deadly disease.

Medulloblasoma: challenges for effective immunotherapy

For medulloblastoma patients, the current therapeutic paradigm of surgery followed by radiation and chemotherapy can lead to long-term remission. However, the sequelae of treatment can be very debilitating, particularly in young children. Immunotherapy is an attractive treatment approach to optimize the targeting of tumor cells while sparing the vulnerable surrounding brain that is still developing in children. Understanding the relationship between medulloblastoma and the immune system is critical to develop effective immunologic-based treatment strategies for these patients. This review focuses on current knowledge of tumor immunology and the factors that contribute to the lack of immune system recognition of these tumors. The specificity of tumor antigens present in medulloblastoma is also discussed along with a summary of early clinical immunotherapy results.

Immunological monitoring of patients affected by anaplastic glioma concerning in effects of surgery, radio-, and chemotherapy. A preliminary report

The authors studied 24 patients affected by anaplastic gliomas, as regards immunology. In all of them the authors evaluated the lymphocyte subpopulation (B and T), firstly by simple lymphocyte count, secondly by studying the rosettes E-total and EAC, thirdly by stimulating the lymphocytes with mitogens phyto-haemoagglutinin-P (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM), and lastly by counting the release of Cr51 in Chang liver cells culture in order to obtain antibody dependent cellular cytotoxicity (ADCC). The parameters were also evaluated after surgery and during conventional radio-chemotherapy with BCNU. Whereas the so-called B-pool seems to be unaffected, the preliminary results show that the T-pool (identified by the E-t rosettes and by responses to PHA, PWM, and ConA) is depressed to a statistically significant degree, if compared with a control group. This depression seems to be related to the tumoral mass, and it is not increased by radio-chemotherapy. In addition, ADCC also seems to be depressed in our glioma patients in comparison with a control group and witha group of bladder cancer patients.

The utilization of native glioma antigens in the assessment of cellular and humoral immune responses in malignant glioma patients

Cellular and humoral components of the immune response have been studied preoperatively, concurrently, and serially in patients with malignant glial neoplasms. In order to assess titres of circulating antibodies to tumour cell constituents an indirect immunofluorescent technique was applied to single cell suspensions and snap frozen cell smears. In an allogeneic system, 49% of 47 test and 7% of 124 control sera gave a positive response to cytoplasmic components. The leucocyte adherence inhibition assay was applied to study 39 test and 64 control patients. Significant non-adherence of leukocytes was observed in 77% of test cases. Control parameters indicated specificity of the response. Simultaneous assessment in 28 test patients yielded a positive response for one or both assays in 89% of cases..