Single-cell transcriptional profiling reveals heterogeneity and developmental trajectories of Ewing sarcoma

Ewing sarcoma (EwS) is an aggressive malignant neoplasm composed of small round cells. The heterogeneity and developmental trajectories of EwS are uncertain.

Single-cell RNA sequencing was performed on 4 EwS tumor tissue samples, and 3 transcriptional atlases were generated. K-nearest neighbor algorithm was used to predict the origin of tumor cells at single-cell resolution. Monocle2 package was used to perform pseudotime trajectory analysis in tumor cells. Differentially expressed genes were compared against those in all other clusters via the FindMarkers function, and then they were subjected to GO analysis using clusterProfiler package.

Combined with the results of k-nearest neighbor algorithm and pseudotime trajectory analysis in tumor cells, we thought meningeal EwS originated from neural crest cells during epithelial to mesenchymal transition and simulated the process of neural crest cell lineage differentiation. But for perirenal EwS and spinal EwS, we hypothesized that after the neural crest cell lineage mutated into them, the tumor cells did not maintain the differentiation trajectory of neural crest cell lineage, and the development trajectory of tumor cells became chaotic. GO analysis results showed that interferon signaling pathway-related biological processes play an essential role in the tumorigenesis and tumor progression process of EwS, and among these biological processes genes, JAK1 gene up-regulated most significantly and highly expressed in all tumor cells. Ruxolitinib was used to explore the function of JAK1. Targeting JAK1 can promote apoptosis of EwS tumor cells, inhibit the migration and invasion of EwS tumor cells, and inhibit cell proliferation by inducing cell cycle S phase arrest.

EwS was derived from neural crest cell lineage with variable developmental timing of oncogenic conversion, and the JAK1 might be a candidate for therapeutic targets of EwS.