Background Osteosarcoma (OS) patients with lung metastasis have poor prognoses, and effective therapeutic strategies for delaying or inhibiting the spread of lung metastasis from the primary OS site are lacking. Hence, it is critical to elucidate the underlying mechanisms of OS metastasis and to identify additional new effective treatment strategies for patients. Methods Differential expression and functional analyses were performed to identify key genes and relevant signaling pathways associated with OS lung metastasis. The expression of CCR9 in OS cell lines and tissues was measured by RT-qPCR, western blotting and immunohistochemistry. Cell migration and invasion were assessed by wound healing and Transwell Matrigel invasion assays, respectively. The regulatory relationship between CCR9 and the Wnt/β-catenin signaling pathway was further evaluated by rescue experiments. Results The expression of CCR9 was elevated in OS cell lines and patients with lung metastasis. CCR9 promoted MG63 and HOS cell migration and invasion by activating the Wnt/β-catenin signaling pathway. Furthermore, knockdown of CCR9 repressed epithelial–mesenchymal transition (EMT) by downregulating mesenchymal markers (N-cadherin and Vimentin) and EMT-associated transcription factors (twist and snail) and upregulating an epithelial marker (E-cadherin). Conclusions Our findings suggest that CCR9 promotes EMT by activating Wnt/β-catenin pathways to promote OS metastasis. CCR9 may be a promising therapeutic target to inhibit lung metastasis and serve as a novel prognostic marker for OS.

Background: Osteosarcoma (OS) is a type of primary malignant tumor, and increasing amounts of evidence show the clinical benefits of immunotherapy in treating OS. However, the lack of comprehensive studies on the complex OS immune microenvironment hinders the application of immunotherapy. Thus, we aimed to systematically study the immune characteristics of OS and identify novel biomarkers for OS treatment.Methods: We systematically studied the immune score and proportion of infiltrating immune cells in OS in the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) databases using the ESTIMATE and CIBERSORT algorithms. Differential expression and functional analyses were used to identify dysregulated genes and explore their functions. Survival and Cox regression analyses were applied to establish an immune-related prognostic signature. The expression of MAP3K15 was performed by qPCR assay and immunohistochemistry. We divided 48 patients into high expression and low expression groups according to MAP3K15 expression.Results: A total of 103 differentially expressed immune genes (DEIGs) were found in the TARGET-OS and GSE39058 databases, and these DEIGs were mainly enriched in leukocyte proliferation, leukocyte differentiation, osteoclast differentiation, natural killer (NK) cell-mediated cytotoxicity and the adaptive immune system. A predictive signature was constructed based on the survival analysis, with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.65. Moreover, we found that mitogen-activated protein kinase kinase kinase 15 (MAP3K15) can predict the prognosis of patients with OS and is closely related to CD4 T cells, M0 macrophages, and M1 macrophages. We found that patients with high MAP3K15 expression had a significantly poorer prognosis Conclusions: Our study found that MAP3K15, whose expression level is closely related to immune activity in tumors, was a critical immune-related biomarker and may provide a basis for OS immunotherapy. Clinical Trial RegistrationNot applicable.

Background: Osteosarcoma (OS) is a type of primary malignant tumor, and increasing evidence shows the clinical benefits of immunotherapy in treating OS. However, the lack of comprehensive studies on the complex OS immune microenvironment hinders the application of immunotherapy. Thus, this study aimed to systematically explore the immune characteristics of OS and identify novel biomarkers for OS treatment.Methods: We systematically studied the immune score and proportions of infiltrating immune cells in OS in the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) databases using the ESTIMATE and CIBERSORT algorithms. Differential expression and functional analyses were used to identify dysregulated genes and explore their functions.Survival and Cox regression analyses were applied to establish an immune-related prognostic signature.Additionally, qPCR and immunohistochemistry were performed to validate the results.Results: A total of 103 differentially expressed immune genes (DEIGs) were found in the TARGET-OS and GSE39058 databases, and these DEIGs were mainly enriched in leukocyte proliferation, leukocyte differentiation, osteoclast differentiation, natural killer (NK) cell-mediated cytotoxicity, and the adaptive immune system. A predictive signature was constructed based on the survival analysis, with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.65. Moreover, we found that mitogenactivated protein kinase kinase kinase 15 (MAP3K15) can predict the prognosis of patients with OS and is closely related to CD4 + T cells and macrophages. The OS patients with high MAP3K15 expression had a significantly poorer prognosis.Conclusions: Our study found that MAP3K15, whose expression level is closely related to immune activity in tumors, is a critical immune-related biomarker, and our findings may provide a basis for OS immunotherapy.

In this article [1], the annotation was wrong in Fig. 5B and in Fig. 6C, the figure of HOS cells treated by OE-CCR9 + XAV 939 at 0 h was wrong. The revised Figure 5 and its legend and Figure 6 are given below.