Proteins Point the Way to Precision Treatments for Medulloblastoma in Children

Proteins Point the Way to Precision Treatments for Medulloblastoma in Children
Computer artwork representing brain cancer, with a cancer cell between two halves of a human brain.

A discovery of unique proteins in a patient’s individual tumor cells has allowed researchers at Children’s National Hospital to generate personalized T cells to target and kill tumors, according to a preclinical study published in Nature Communications.

This effort is reportedly the first to create a new workflow for neoantigen identification that incorporates both genetic sequencing and protein identification to create a personalized treatment for medulloblastoma in children, a common malignant brain tumor. Given these findings, the researchers are now designing a Phase I clinical trial slated to open in 12–18 months.

“Neoantigen discovery in pediatric brain tumors is hampered by their low mutational burden and scant tissue availability. Here we develop a proteogenomic approach combining tumor DNA/RNA sequencing and mass spectrometry proteomics to identify tumor-restricted (neoantigen) peptides arising from multiple genomic aberrations to generate a highly target-specific, autologous, personalized T cell immunotherapy,” write the investigators.

“Our data indicate that aberrant splice junctions are the primary source of neoantigens in medulloblastoma, a common pediatric brain tumor. Proteogenomically identified tumor-specific peptides are immunogenic and generate MHC II-based T cell responses. Moreover, polyclonal and polyfunctional T cells specific for tumor-specific peptides effectively eliminate tumor cells in vitro. Targeting tumor-specific antigens obviates the issue of central immune tolerance while potentially providing a safety margin favoring combination with other immune-activating therapies.

“These findings demonstrate the proteogenomic discovery of immunogenic tumor-specific peptides and lay the groundwork for personalized targeted T cell therapies for children with brain tumors.”

“This work is an incredibly exciting advancement in personalized medicine. It will allow us to treat patients with a novel T cell therapy that is developed for each individual patient to specifically attack and kill their tumor,” said Catherine Bollard, MD, director of the Center for Cancer and Immunology Research at Children’s National and co-senior author on the paper. “This treatment will offer a potential option for children with hard-to-treat brain tumors for which all other therapeutic options have been exhausted.”

First, the researchers sequenced the DNA of small tissue samples while studying its complete set of proteins that influence cancer biology—also named a “low-input proteogenomic approach” by the authors. After analyzing the empirical data, which shies away from the commonly used predictive models, the researchers developed a T cell immunotherapy that targets the tumor’s unique proteins and allows the T cells to distinguish between healthy cells and tumor cells.

This means that Rivero-Hinojosa et al. managed to merge two research fields, proteogenomics and immunotherapy, and lay the groundwork for personalized, targeted T cell therapies to treat children with brain tumors.

“Neoantigen discovery techniques have either been dependent upon in silico prediction algorithms or have required a significant amount of tumor tissue, making them inappropriate for most brain tumors,” noted Brian Rood, MD, medical director of Neuro-oncology and the Brain Tumor Institute at Children’s National. “This neoantigen identification pipeline creates a new opportunity to expand the repertoire of T cell-based immunotherapies.”

“We developed a new filtering pipeline to remove non-annotated normal peptides. Targeting antigens that are completely specific to the tumor, and expressed nowhere else in the body, will potentially increase the strength of tumor antigen-specific T cell products while decreasing the toxicity,” added Samuel Rivero-Hinojosa, PhD, staff scientist at Children’s National and first author of the study.

Once the experts identified these unique peptides, they used them to select and expand T cells, which showed specificity for the tumor specific neoantigens and the ability to kill tumor cells. The next step is to conduct a clinical trial in which a patient’s own T cells are trained to recognize their tumor’s unique neoantigens and then reinfused back into the patient.

From an immunotherapy standpoint, tumor specificity is important because when clinicians treat patients with T cell therapies, they want to make sure that the T cells directly target and kill the tumor and will not cause devastating harm to healthy cells. This paper demonstrated that it may be possible to create a better efficacy and safety margin with this new technique.