Immunological fluctuations during intrathecal immunotherapy in three patients affected by CNS tumours disseminating via CSF

The Role of Immunotherapy in the Treatment of Rare Central Nervous System Tumors

Establishing novel therapies for rare central nervous system (CNS) tumors is arduous due to challenges in conducting clinical trials in rare tumors. Immunotherapy treatment has been a rapidly developing field and has demonstrated improvements in outcomes for multiple types of solid malignancies. In rare CNS tumors, the role of immunotherapy is being explored. In this article, we review the preclinical and clinical data of various immunotherapy modalities in select rare CNS tumors, including atypical meningioma, aggressive pituitary adenoma, pituitary carcinoma, ependymoma, embryonal tumor, atypical teratoid/rhabdoid tumor, and meningeal solitary fibrous tumor. Among these tumor types, some studies have shown promise; however, ongoing clinical trials will be critical for defining and optimizing the role of immunotherapy for these patients.

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.

History and current state of immunotherapy in glioma and brain metastasis

Malignant brain tumors such as glioblastoma (GBM) and brain metastasis have poor prognosis despite conventional therapies. Successful use of vaccines and checkpoint inhibitors in systemic malignancy has increased the hope that immune therapies could improve survival in patients with brain tumors. Manipulating the immune system to fight malignancy has a long history of both modest breakthroughs and pitfalls that should be considered when applying the current immunotherapy approaches to patients with brain tumors. Therapeutic vaccine trials for GBM date back to the mid 1900s and have taken many forms; from irradiated tumor lysate to cell transfer therapies and peptide vaccines. These therapies were generally well tolerated without significant autoimmune toxicity, however also did not demonstrate significant clinical benefit. In contrast, the newer checkpoint inhibitors have demonstrated durable benefit in some metastatic malignancies, accompanied by significant autoimmune toxicity. While this toxicity was not unexpected, it exceeded what was predicted from pre-clinical studies and in many ways was similar to the prior trials of immunostimulants. This review will discuss the history of these studies and demonstrate that the future use of immune therapy for brain tumors will likely need a personalized approach that balances autoimmune toxicity with the opportunity for significant survival benefit.

In vitro Natural Killer Cell Immunotherapy for Medulloblastoma

How the immune system attacks medulloblastoma (MB) tumors effectively is unclear, although natural killer (NK) cells play an important role in immune defense against tumor cells. Interactions between receptors on NK cells and ligands expressed by tumor cells are critical for tumor control by immunotherapy. In this study, we analyzed tumor samples from 54 MB patients for expression of major histocompatibility complex class I-related chains A (MICA) and UL16 binding protein (ULPB-2), which are ligands for the NK group 2 member D activatory receptor (NKG2D). The percentage of MICA and ULBP-2 positive cells was higher than 25% in 68% and 6% of MB patients, respectively. A moderate-high intensity of MICA cytoplasmic staining was observed in 46% MB patients and weak ULBP-2 staining was observed in 8% MB patients. No correlation between MICA/ULBP-2 expression and patient outcome was found. We observed that HTB-186, a MB cell line, was moderately resistant to NK cell cytotoxicity in vitro. Blocking MICA/ULBP-2 on HTB-186, and NKG2D receptor on NK cells increased resistance to NK cell lysis in vitro. However, HLA class I blocking on HTB-186 and overnight incubation with IL-15 stimulated NK cells efficiently killed tumor cells in vitro. We conclude that although NKG2D/MICA-ULBP-2 interactions have a role in NK cell cytotoxicity against MB, high expression of HLA class I can protect MB from NK cell cytotoxicity. Even so, our in vitro data indicate that if NK cells are appropriately stimulated, they may have the potential to target MB in vivo.

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.

[The role of chemotherapy in pediatric medulloblastoma]

Medulloblastoma is one of the most frequent brain tumors in childhood. The mortality of medulloblastoma decreased significantly during the last few decades, which was the result of the better surgical and radiotherapeutic methods and of the development of chemotherapy. The aim of this publication is the critical review of the present chemotherapeutic treatment. The new therapeutic trials based on the molecular genetic mechanism of these tumors are also mentioned.

Immunotherapeutic approaches for glioma

The development of effective immunotherapy strategies for glioma requires adequate understanding of the unique immunological microenvironment in the central nervous system (CNS) and CNS tumors. Although the CNS is often considered to be an immunologically privileged site and poses unique challenges for the delivery of effector cells and molecules, recent advances in technology and discoveries in CNS immunology suggest novel mechanisms that may significantly improve the efficacy of immunotherapy against gliomas. In this review, we first summarize recent advances in the CNS and CNS tumor immunology. We address factors that may promote immune escape of gliomas. We also review advances in passive and active immunotherapy strategies for glioma, with an emphasis on lessons learned from recent early-phase clinical trials. We also discuss novel immunotherapy strategies that have been recently tested in non-CNS tumors and show great potential for application to gliomas. Finally, we discuss how each of these promising strategies can be combined to achieve clinical benefit for patients with gliomas.

Cytomegalovirus induces interferon-stimulated gene expression and is attenuated by interferon in the developing brain

Cytomegalovirus (CMV) is considered the most common infectious agent causing permanent neurological dysfunction in the developing brain. We have previously shown that CMV infects developing brain cells more easily than it infects mature brain cells and that this preference is independent of the host B- and T-cell responses. In the present study, we examined the innate antiviral defenses against mouse (m) and human (h) CMVs in developing and mature brain and brain cells. mCMV infection induced interferon (IFN)-stimulated gene expression by 10- to 100-fold in both glia- and neuron-enriched cultures. Treatment of primary brain cultures with IFN-alpha, -beta, and -gamma or a synthetic RNA, poly(I:C), reduced the number of mCMV-infected cells, both in older cells and in fresh cultures from embryonic mouse brains. When a viral dose that killed almost all unprotected cells was used, IFN-protected cells had a natural appearance, and when they were tested with whole-cell patch clamp recording, they appeared physiologically normal with typical resting membrane potentials and action potentials. mCMV infection increased expression of representative IFN-stimulated genes (IFIT3, OAS, LMP2, TGTP, and USP18) in both neonatal and adult brains to similarly large degrees. The robust upregulation of gene expression in the neonatal brain was associated with a much higher degree of viral replication at this stage of development. In contrast to the case for downstream gene induction, CMV upregulated IFN-alpha/beta expression to a greater degree in the adult brain than in the neonatal brain. Similar to the case with cultured brain cells, IFN treatment of the developing brain in vivo depressed mCMV replication. In parallel work with cultured primary human brain cells, IFN and poly(I:C) treatment reduced hCMV infection and prevented virus-mediated cell death. These results suggest that coupling IFN administration with current treatments may reduce CMV infections in the developing brain.

Adoptive cellular immunotherapy for the treatment of malignant gliomas

The median survival for adults with recurrent primary malignant gliomas is 56 weeks following surgery, radiation, and chemotherapy. Generally, reoperation can extend the median survival an additional 26-32 weeks. We have developed an aggressive treatment program that utilizes low doses of interleukin-2 (IL-2) combined with ex vivo activated killer cells (LAK) infused via an indwelling catheter placed into the surgical resection cavity. Autologous leukocytes were collected during a standard 3-4 h, outpatient leukapheresis procedure, then activated ex vivo for 4-5 days with high doses of IL-2. The treatment protocol consisted of two 2-week cycles of therapy over a 6-week period. Patients with stable disease or objective response on follow-up MRI scans were retreated at 3-month intervals. Acute and cumulative IL-2-related toxicities were observed, but limited, and included fever, headache and transient neurologic irritation. Corticosteroid levels and usage were strictly controlled during immunotherapy, although higher doses were used intermittently to mitigate toxicity. Biologic changes included lymphocytic infiltration, regional eosinophilia, tumor necrosis, and the localized production of IL-2, IFN-gamma and IL-12, demonstrated by in situ hybridization and immunohistochemistry.

SUMMARY

IL-2 plus autogeneic LAK cells can be safely administered intracavitary to treat high grade primary brain tumors with limited toxicity within the central nervous system. Six out of 28 patients had long-term survival of greater than 2 years post-reoperation plus immunotherapy with 2 patients alive over 8 years. The presence of a marked regional eosinophilia appeared to correlate with increased survival and may be predictive of a biologic and therapeutic response. Regional adoptive immune therapy was well tolerated and should be considered an option for patients with high-grade tumors refractive to standard therapeutic approaches.

Treatment of refractory recurrent malignant glioma with adoptive cellular immunotherapy: a case report

We report the successful treatment of a patient with recurrent malignant glioma with adoptive cellular immunotherapy. The patient is a young adult with recurrent progressive disease refractory to aggressive multi-modality therapy including repetitive surgical resection, radiation, radiosurgery and chemotherapy. He received multiple courses of local administration of autologous lymphokine-activated killer (LAK) cells in combination with a low dose of interleukin-2 (IL-2) through an Ommaya reservoir-catheter system. The side-effects of this treatment were limited and manageable. The patient achieved a complete remission, as demonstrated by MRI and confirmed by glucose-positron emission tomography (PET) imaging 11 months after initiation of immune therapy. Twenty-six months later, the patient is still in remission with improving performance status. Adoptive cellular immunotherapy utilizing autologous LAK cells with low dose IL-2 appears to be a safe and effective therapy for a subset of patients with primary, recurrent or progressive malignant glioma following conventional therapy.

New aspects of immunotherapy of leptomeningeal metastasis

Immunotherapeutic approaches to leptomeningeal metastasis (LM) include the intrathecal application of cytokines such as interleukin-2 (IL-2) and interferon-alpha (IFN-alpha), and lymphokine-activated killer cells (LAK cells). Results in a rodent model of leptomeningeal gliomatosis with intrathecal IL-2 application are discouraging, but some clinical improvement and clearance of neoplastic cells from CSF have been seen in patients with LM from melanoma treated with intrathecal IL-2 alone, and in patients with LM from primary brain tumors and squamous cell carcinoma of the tongue treated with intrathecal LAK cells and IL-2. The neurotoxicity of this therapy, mainly increased intracranial pressure, has been considerable but generally manageable. However, IFN-alpha caused severe neurotoxicity in form of an only partly reversible progressive vegetative state in the majority of patients. Considering the small number of patients treated with IL-2 and LAK cells, its value for the treatment of LM could only be stated by further investigation. In future, the application of recently discovered cytokines such as Fas-ligand, the continuous paracrine cytokine release by genetically modified cells, or vaccination strategies using genetically modified tumor cells might offer new immunotherapeutic approaches in LM.

Intrathecal immunotherapy in CNS tumors disseminating via CSF: preliminary evaluation using different treatment schedules

Eight patients affected by central nervous system tumours disseminating via cerebrospinal fluid received rIL-2 immunotherapy according to three different protocols involving intrathecal administration followed or not by systemic infusion. Immunological monitoring included serial evaluation of CSF leukocytes, CSF and peripheral blood CD3-CD56+ cells, and NK activity. The most marked rise in CSF leukocyte levels was induced by daily intrathecal rIL2 administration, which also induced increased PB NK activity. Systemic rIL2 infusion following intrathecal treatment maintained a high percentage of CSF CD3-CD56+ cells, but not CSF leukocytes at high levels. Clinical conditions improved after treatment in two patients, worsened in one and remained substantially unchanged in the remaining five. The side effects of intrathecal rIL2 treatment included fever, confusion, and seizures, and there were marked interindividual variations in the immunological response.