Researchers at Children’s Hospital of Philadelphia (CHOP) have identified small fragments of messenger RNA, known as microexons, that are missing in pediatric high-grade glioma tumors but present in normal brain tissue. The study, published in Cell Reports, suggests these absent RNA fragments could make difficult-to-treat tumors more responsive to immunotherapy.
The team found that previous RNA sequencing efforts did not account for microexons—very short exons involved in alternative splicing. This process allows a single gene to produce multiple proteins by rearranging exons. In glioma cells, many microexons fail to be included in messenger RNAs encoding key surface proteins such as NRCAM, a neuronal cell adhesion molecule needed for synapse formation in normal brain cells. In pediatric high-grade gliomas, two NRCAM microexons were consistently skipped, resulting in a distinct protein structure with an unknown function.
When the researchers examined these microexons further, they discovered that the shortened version of NRCAM created by skipping microexons was essential for cancer cell migration and invasion in laboratory studies and tumor growth in mouse models. The glioma-specific version of NRCAM may serve as a promising immunotherapy target because it is unlikely that tumors could easily evade therapies directed against it.
“While microexons may be small, the effects they have on the overall protein structure are quite profound,” said Andrei Thomas-Tikhonenko, PhD, chief of the Division of Cancer Pathobiology at CHOP and Professor in the Department of Pathology and Laboratory Medicine at the Perelman School of Medicine of the University of Pennsylvania. “Because the skipping of NRCAM microexons profoundly changes protein conformation, we were able to develop a mouse monoclonal antibody against the glioma-specific version of NRCAM. When mixed with glioma cells, the antibody worked like a highlighter, ‘painting’ glioma cells and marking them for killing by T cells armed with an immune receptor for mouse antibodies.”
“In addition to developing these immune receptors clinically, we are actively using our proof-of-principle experiments to design traditional CAR T cell-based immunotherapeutics that selectively target glioma cells,” said Priyanka Sehgal, PhD, first author and research scientist at CHOP. “This could also change the way we find new targets in other solid tumors.”
Researchers plan to expand preclinical work and identify forms of immunotherapy suitable for clinical trials. They also noted that similar mechanisms may be present in other cancers such as glioblastoma multiforme and neuroendocrine tumors, which could potentially benefit from NRCAM-directed therapies.
Funding for this study came from several organizations including CureSearch for Children’s Cancer Foundation Acceleration Initiative and various National Institutes of Health grants. Additional support was provided by groups such as the Children’s Brain Tumor Network and the Chad Tough Foundation.
The full study is available online: Sehgal et al., “NRCAM variant defined by microexon skipping is a targetable cell surface proteoform in high-grade gliomas.” Cell Rep. Online August 7, 2025. DOI: 10.1016/j.celrep.2025.116099.
