EDA2R reflects the acute brain response to cranial irradiation in liquid biopsies.

Background: Cranial radiotherapy is standard of care for high-grade brain tumors and metastases; however, it induces debilitating neurocognitive impairments in cancer survivors, especially children. As the numbers of pediatric brain cancer survivors continue improving, the numbers of individuals developing life-long neurocognitive sequalae are consequently expected to rise. Yet, there are no established biomarkers estimating the degree of the irradiation-induced brain injury at completion of radiotherapy to predict the severity of the expected neurocognitive complications. We aimed to identify sensitive biomarkers associated with brain response to irradiation that can be measured in easily accessible clinical materials, such as liquid biopsies.

Methods: Juvenile mice were subjected to cranial irradiation with 0.5, 1, 2, 4, and 8 Gy. Cerebrospinal fluid (CSF), plasma, and brains were collected at acute, subacute, and subchronic phases after irradiation, and processed for proteomic screens, and molecular and histological analyses.

Results: We found that the levels of ectodysplasin A2 receptor (EDA2R), member of tumor necrosis factor receptor superfamily, increased significantly in the CSF after cranial irradiation, even at lower irradiation doses. The levels of EDA2R were increased globally in the brain acutely after irradiation and decreased over time. EDA2R was predominantly expressed by neurons, and the temporal dynamics of EDA2R in the brain was reflected in the plasma samples.

Conclusions: We propose EDA2R as a promising potential biomarker reflecting irradiation-induced brain injury in liquid biopsies. The levels of EDA2R upon completion of radiotherapy may aid in predicting the severity of IR-induced neurocognitive sequalae at a very early stage after treatment.