Comprehensive genomic and clinical analyses identify APOBEC mutational signatures as a brain metastasis risk factor in lung adenocarcinoma patients

Background Lung adenocarcinoma is the most common source of brain metastasis (BM), resulting in significant morbidity and mortality. We aimed to identify patients with high BM risk who possibly benefit from brain-penetrant drugs, prophylactic cranial irradiation, or close brain magnetic resonance imaging surveillance. Methods Metastatic lung adenocarcinoma patients with extracranial tumor samples profiled by a next-generation sequencing panel targeting 425 tumor-related genes were retrospectively enrolled between February 2008 and July 2021. We compared BM and non-BM patients’ genomic and clinical features and studied their associations with BM risk. Two external cohorts were used for result validation and molecular mechanisms investigation, respectively. Results We included 174 eligible patients, including 90 having developed BM by the end of follow-up. Age≤60, EGFR activating mutations, and high-level apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC) mutational signatures were associated with elevated BM risk. Similar findings in BM-free survival were obtained by fitting Fine-Gray subdistribution hazard models addressing competing risks. Increased BM risk related to APOBEC mutational signatures was validated in an external cohort (N = 440). RNA sequencing data analyses performed in another external cohort (N = 230) revealed that expressions of metastasis-related pathways such as transforming growth factor (TGF)β and epithelial-mesenchymal transition (EMT) were upregulated in the patients with high-level APOBEC mutational signatures. Conclusion APOBEC mutational signatures related to upregulated TGFβ and EMT, could serve as an independent risk factor for BM and BM-free survival in metastatic lung adenocarcinoma patients. Further investigations are warranted to tailor personalized treatments to improve the susceptible patient's outcomes.