Dissecting the tumor microenvironment in primary breast angiosarcoma: insights from single-cell RNA sequencing.

BACKGROUND: Angiosarcoma, a rare and highly aggressive malignancy originating from vascular endothelial cells, is characterized by its rapid progression, high invasiveness, and poor prognosis. Due to the limited understanding of its tumor microenvironment (TME) and the absence of effective treatments, further research is essential to elucidate its pathogenic mechanisms and improve therapeutic strategies. OBJECTIVE: This study aims to characterize the cellular heterogeneity and unique TME of primary breast angiosarcoma using single-cell RNA sequencing (scRNA-seq), to identify potential therapeutic targets and improve clinical outcomes. METHODS: Tumor samples were obtained from a patient with bilateral primary breast angiosarcoma and two patients with invasive breast cancer. Single-cell RNA sequencing (scRNA-seq) was conducted to capture the transcriptomic profiles of individual cells within the tumor samples. Following stringent quality control, a total of 31,771 cells were analyzed using comprehensive bioinformatics approaches. Cell populations were identified and classified into distinct cell types, and differential gene expression analysis was performed to explore key signaling pathways. Functional enrichment analysis was used to identify pathways related to tumor progression and immune evasion. Additionally, cell-cell communication networks were mapped to understand interactions within the TME, with a focus on pathways that may serve as therapeutic targets. RESULTS: The scRNA-seq analysis revealed significant differences in the distribution of perivascular cells, fibroblasts, T cells, endothelial cells, and myeloid cells in breast angiosarcoma compared to invasive breast cancer. Key pathways enriched in angiosarcoma samples included growth factor binding, platelet-derived growth factor binding, and ribosome biogenesis, with abnormal expression of several ribosomal proteins. Notably, genes such as FAT4, KDR, FN1, and KIT were highly expressed in angiosarcoma endothelial cells, correlating with poor prognosis. Cell communication analysis highlighted the CXCL12-CXCR4 axis as a crucial mediator of the TME in angiosarcoma. CONCLUSION: This study provides critical insights into the TME of primary breast angiosarcoma, highlighting potential molecular targets and pathways for therapeutic intervention. These findings may inform the development of more effective treatment strategies for this rare and challenging tumor type.