Immunosuppressive tumor microenvironment of osteosarcoma [scRNA-seq]

Osteosarcoma is the most common malignant bone tumor in children, characterized by a high degree of genomic instability, resulting in copy-number alterations and genomic rearrangements without disease-defining recurrent mutations. Clinical trials based on molecular characterization have failed to find new effective therapies or improve outcomes over the last 40 years. To better understand the immune microenvironment of osteosarcoma, we performed single-cell RNA sequencing on six tumor biopsy samples, combined with a previously-published cohort of six samples. Additional osteosarcoma samples were profiled using spatial transcriptomics for validation of discovered subtypes and to add spatial context. Analysis revealed immunosuppressive cells, including myeloid-derived suppressor cells (MDSCs), regulatory and exhausted T-cells, and LAMP3+ dendritic cells. Using cell-cell communication modeling, we identified robust interactions between MDSCs and other cells, leading to NF-κB upregulation and an immunosuppressive microenvironment, as well as interactions involving regulatory T-cells and osteosarcoma cells that promoted tumor progression and a proangiogenic niche. Primary, treatment-naïve pediatric osteosarcoma biopsies were gathered from six patients at Connecticut Children's Medical Center or Children's Hospital Colorado. Tissues were dissociated into individual cells for single-cell RNA sequencing. Data was combined with single-cell RNA sequencing of six additional treatment-naïve pediatric osteosarcoma biopsy samples previously described in Liu et al. (Front Oncol, 2021) downloaded from the Gene Expression Omnibus (GSE162454).

骨肉瘤是儿童群体中最常见的恶性骨肿瘤，其核心特征为基因组不稳定性极高，可引发拷贝数变异与基因组重排，但缺乏可明确界定疾病的复发性突变。近40年来，基于分子特征分型的临床试验均未能开发出新型有效治疗方案，亦未改善患者的临床结局。为深入解析骨肉瘤的免疫微环境，本研究对6份肿瘤活检样本开展了单细胞RNA测序（single-cell RNA sequencing），并结合了此前已发表的6份样本队列。此外，研究团队利用空间转录组学（spatial transcriptomics）对额外的骨肉瘤样本进行测序分析，以验证所发现的肿瘤亚型，并补充肿瘤的空间维度信息。分析结果显示存在多种免疫抑制细胞类群，包括髓系来源抑制细胞（myeloid-derived suppressor cells, MDSCs）、调节性T细胞与耗竭性T细胞，以及LAMP3阳性树突状细胞。通过细胞间通讯建模分析，本研究明确了髓系来源抑制细胞与其他细胞间的强相互作用，该作用可诱导NF-κB通路上调并形成免疫抑制微环境；同时还发现调节性T细胞与骨肉瘤细胞间的相互作用可促进肿瘤进展，并构建促血管生成的微环境龛。本研究的原发、未经治疗的儿童骨肉瘤活检样本，采集自康涅狄格儿童医院（Connecticut Children's Medical Center）与科罗拉多儿童医院（Children's Hospital Colorado）的6名患者。研究人员将组织样本解离为单个细胞，用于后续的单细胞RNA测序实验。本研究数据还整合了Liu等人（发表于《Front Oncol》, 2021）此前报道的6份未经治疗的儿童骨肉瘤活检样本的单细胞RNA测序数据，该数据集从基因表达综合数据库（Gene Expression Omnibus, GSE162454）下载获取。