Integrated multi-omics profiling reveals a clinically relevant molecular feature and potential therapeutic target on phyllodes tumors of breast

Phyllodes tumors (PTs) has an increased risk of local relapse and distant metastases. Molecular features correlating to histologic grade and aggressive behavior of PTs are poorly characterized. Here, whole exome sequencing (WES) was performed to explore genetic mutations in 61 samples of fibroepithelial breast tumors, including 16 fibroadenomas (FAs), 18 benign PTs, 19 borderline PTs, and 8 malignant PTs. Our work clearly shows that FA, benign PT, borderline PT, and malignant PT are independent entities at the genomic level. They may exist as hidden sub-clones carrying specific genetic alterations. Malignant PT-specific mutations present a multi-gene co-mutational pattern suggesting a synergistic effect of co-mutated genes in processes associated with malignant behavior. Moreover, we made a combined genomic and transcriptomic analysis, which presented a mutated gene-based interaction with expression profiles. We found that EGFR mutations (c.710C > T, c.758A > G, c.1295A > G, and c.2156G > C) serve as a hub of interaction network in borderline PTs, which suggests EGFR tyrosine kinase inhibitors (EGFRi) might be effective for borderline PTs. We found TP53 mutations (c.730G > T, c.844C > T, and c.1019delA) serves as a hub event of molecular changes of malignant PTs. Thus, our study based on the omics platforms of genome and transcriptome provides a better understanding of relapse process and the potential targeted therapy in PTs, which is pivotal in improving molecular-guided patient selection and designing clinically relevant combination strategies.