Single-cell RNA sequencing in osteosarcoma: applications in diagnosis, prognosis, and treatment.

Osteosarcoma is the most common malignant bone tumor in children and adolescents, characterized by high heterogeneity and a complex tumor microenvironment (TME). Despite multimodal treatments, survival rates have stagnated, highlighting the need for new therapeutic options. Single-cell RNA sequencing (scRNA-seq) offers a powerful tool to dissect heterogeneity and uncover mechanisms of progression and immune evasion. A narrative literature review, guided by PRISMA principles, was conducted through October 2024 via PubMed and Scopus databases to assess scRNA-seq contributions to osteosarcomagenesis. A total of 107 studies were analyzed to highlight the identification of tumor subpopulations, signaling pathways, diagnostic and prognostic biomarkers, and therapeutic assessments. Our analysis highlights the critical role of scRNA-seq in revealing the complexity of the osteosarcoma TME. Studies identified distinct immune and non-immune cell subpopulations, with TXNIP+ and IFIT1+ macrophages, KAZALD1, EGFL7, TNFSF11, and TRAIL receptors emerging as potential therapeutic targets. scRNA-seq has elucidated mechanisms of tumor progression and metastasis, including CD24 expression, and enabled the discovery of immune and stromal biomarkers within the TME. It also revealed novel therapeutic strategies, such as targeting Tregs via CXCR4 inhibition, CAFs through LOX and SERPINE1 modulation, and MCL1 in metastatic niches. Additionally, it uncovered promising drug candidates-etoposide, mevastatin, oxfendazole, HDAC inhibitors, and TIGIT blockade-as well as immunotherapies like PD-1 inhibition and adoptive CD8+ T cell therapy. scRNA-seq has transformed insights into osteosarcoma by exposing key cellular dynamics and potential therapeutic targets. While technical challenges remain, it paves the way for more personalized and effective treatment strategies. However, the current findings are subject to limitations, including technical biases in single-cell protocols and the exclusion of non-English literature, which may affect generalizability.