Characterization of the malignant cells and microenvironment of infantile fibrosarcoma via single-cell RNA sequencing.

Background:Infantile fibrosarcoma (IFS) is the most prevalent soft tissue sarcoma in children under 1 year old and is known for its rapid growth. The tumor lacks specific immunohistochemical tumor marker and a general view of tumor microenvironment (TME). Its primary therapeutic intervention places patients at a risk of disability or mutilation. This study aimed to elucidate the universal transcriptional characteristics of IFS and explore novel targets for diagnosis and therapy using single-cell RNA sequencing (scRNA-seq). Methods:Fresh tissue samples of IFS for scRNA-seq were collected from four patients before other treatments were administered. We conducted cell clustering, inferring copy number variation from scRNA-seq (InferCNV) analysis, gene differential expression analysis, cell function evaluation, Pearson correlation analysis, and cell-cell and ligand-receptor interaction analysis to investigate the distinct ecosystem of IFS. Results:According to the single-cell resolution data, we depicted the cell atlas of IFS, which comprised 14 cell populations. Through comparison with normal cells, the malignant cells were distinguished, and potential novel markers (POSTN, IGFBP2 and CTHRC1) were identified. We also found four various functional malignant cell subtypes, three of which exhibited cancer stem cells (CSCs) phenotypes, and investigated the interplay between these subtypes and nonmalignant cells in the TME of IFS. Endothelial cells and macrophages were found to dominate the cell-cell communication landscape within the microenvironment, promoting tumorigenesis via multiple receptor-ligand interactions. Conclusions:This study provides a comprehensive characterization of the tumor transcriptome and TME of IFS at the cellular level, offering valuable insights for clinically significant advancements in the immunohistochemical diagnosis and treatment of IFS.