Qingcheng Yang

Abstract Osteosarcoma is the most frequent primary bone tumor with poor prognosis. Through RNA-sequencing of 100,987 individual cells from 7 primary, 2 recurrent, and 2 lung metastatic osteosarcoma lesions, 11 major cell clusters are identified based on unbiased clustering of gene expression profiles and canonical markers. The transcriptomic properties, regulators and dynamics of osteosarcoma malignant cells together with their tumor microenvironment particularly stromal and immune cells are characterized. The transdifferentiation of malignant osteoblastic cells from malignant chondroblastic cells is revealed by analyses of inferred copy-number variation and trajectory. A proinflammatory FABP4 + macrophages infiltration is noticed in lung metastatic osteosarcoma lesions. Lower osteoclasts infiltration is observed in chondroblastic, recurrent and lung metastatic osteosarcoma lesions compared to primary osteoblastic osteosarcoma lesions. Importantly, TIGIT blockade enhances the cytotoxicity effects of the primary CD3 + T cells with high proportion of TIGIT + cells against osteosarcoma. These results present a single-cell atlas, explore intratumor heterogeneity, and provide potential therapeutic targets for osteosarcoma.

Disseminated tumor cells often fall into a long term of dormant stage, characterized by decreased proliferation but sustained survival, in distant organs before awakening for metastatic growth. However, the regulatory mechanism of metastatic dormancy and awakening is largely unknown. Here, we show that the epithelial-like and mesenchymal-like subpopulations of breast cancer stem-like cells (BCSCs) demonstrate different levels of dormancy and tumorigenicity in lungs. The long non-coding RNA (lncRNA) NR2F1-AS1 (NAS1) is up-regulated in the dormant mesenchymal-like BCSCs, and functionally promotes tumor dissemination but reduces proliferation in lungs. Mechanistically, NAS1 binds to NR2F1 mRNA and recruits the RNA-binding protein PTBP1 to promote internal ribosome entry site (IRES)-mediated NR2F1 translation, thus leading to suppression of ΔNp63 transcription by NR2F1. Furthermore, ΔNp63 downregulation results in epithelial-mesenchymal transition, reduced tumorigenicity and enhanced dormancy of cancer cells in lungs. Overall, the study links BCSC plasticity with metastatic dormancy, and reveals the lncRNA as an important regulator of both processes.

BACKGROUND: Hypoxia is a common feature of many solid cancers and linked to malignant transformation, metastases and treatment resistance. Hypoxia is known to induce hypoxia-inducible factor-1alpha (HIF-1alpha) expression. The aim of this study is to investigate the impact of overexpression of HIF-1alpha on prognosis and the relationship with clinicopathological characteristics in human osteosarcoma. METHODS: Immunochemistry with digital image analysis was used to determine the HIF-1alpha protein expression in histologic sections from 39 treated patients. RESULTS: According to our study, expression of HIF-1alpha protein were detected in 31 of 39 cases (79%), with signal concentrated primarily within the nuclei of tumor cell. In contrast, non-cancerous adjacent tissues showed no HIF-1alpha immunoreactivity. HIF-1alpha expression was significantly associated with surgical stage, percentage of dead cells and microvessel density (MVD). Surgical stage, percentage of dead cells and HIF-1alpha expression showed significant influence on overall survival (OS) and disease-free survival (DFS) in univariate analysis. In multivariate analysis, surgical stage (IIA versus IIB/III) and percentage of dead cells (<90% versus > or =90%) were significant for DFS and OS. Those patients with HIF-1alpha moderate/strong expression showed significantly shorter OS and DFS compared with HIF-1alpha negative/weak expression. CONCLUSIONS: Overexpression of HIF-1alpha is predictive of a poor outcome and might be a novel therapeutic target in human osteosarcoma.