Integrated analysis of single-cell and bulk RNA sequencing data reveals an immunostimulatory microenvironment in tumor thrombus of osteosarcoma

Abstract

Tumor thrombus of bone sarcomas represents a unique reservoir for various types of cancer and immune cells, however, the investigation of tumor thrombus at a single-cell level is very limited. And it is still an open question to identify the thrombus-specific tumor microenvironment that is associated with the tumor-adaptive immune response. Here, by analyzing bulk tissue and single-cell level transcriptome from the paired thrombus and primary tumor samples of osteosarcoma (OS) patients, we define the immunostimulatory microenvironment in tumor thrombus of OS with a higher proportion of tumor-associated macrophages with M1-like states (TAM-M1) and TAM-M1 with high expression of CCL4. OS tumor thrombus is found to have upregulated IFN-γ and TGF-β signalings that are related to immune surveillance of circulating tumor cells in blood circulation. Further multiplexed immunofluorescence staining of the CD3/CD4/CD8A/CD68/CCL4 markers validates the immune-activated state in the tumor thrombus samples. Our study first reports the transcriptome differences at a single-cell level between tumor thrombus and primary tumor in sarcoma.

Advancements in osteosarcoma management: integrating immune microenvironment insights with immunotherapeutic strategies

“…Pahl et al observed that M1 macrophages, activated by LPS and IFN-γ, effectively suppress osteosarcoma cell proliferation, demonstrating an advantageous role in osteosarcoma immunotherapy ( Pahl et al, 2014 ). Furthermore, Ji et al confirmed that osteosarcoma tumor thrombi contain a substantial proportion of M1-like macrophages (TAM-M1), exhibiting an immunostimulatory state, positively influencing the activation of anti-tumor immune responses ( Ji et al, 2023 ). Simultaneously, according to Gong et al, MPIRx nanoparticles prompt a specific mechanism causing macrophage polarization towards the M1 phenotype, thereby augmenting macrophage phagocytic function against osteosarcoma cells and contributing to an anti-tumor effect ( Gong et al, 2023 ).…”

Exploratory study of an anti-PD-L1/TGF-β antibody, TQB2858, in patients with refractory or recurrent osteosarcoma and alveolar soft part sarcoma: a report from Chinese sarcoma study group (TQB2858-Ib-02)

“…Preclinical research has shown that osteosarcoma cells educate these MSCs by secreting TGF-βcontaining extracellular vesicles that drive the formation of metastatic foci within the lungs [12]. Ji et al [13] also revealed that elevated IFN-γ signaling indicates the antitumor immune response in metastatic osteosarcoma thrombus by paired samples single-cell and bulk RNA sequencing data. Liu et al [14] used a comprehensive landscape of TGF-β-related signatures to predict prognosis, immune characteristics, and therapeutic response for osteosarcoma.…”