<p>Osteosarcoma (OS) is the most prevalent malignant tumor among adolescents, characterized by high recurrence rates and poor prognosis. Identifying novel prognostic biomarkers and therapeutic targets has become an urgent clinical need. We analyzed the GSE99671 dataset and identified TMED2, STC2, and GAL as high-risk genes for OS through LASSO regression and multivariate Cox proportional hazards modeling. Further examination of the expression levels of these genes in paired tumor and adjacent non-tumor tissue samples from OS patients ultimately pinpointed TMED2 as a key candidate gene. Preliminary analysis based on TCGA data suggested that TMED2 might influence osteosarcoma progression by regulating immune cell infiltration. Functional experiments demonstrated that shRNA-mediated knockdown of TMED2 significantly suppressed the proliferation, migration, and invasive capacity of osteosarcoma cells, while promoting the polarization of M0 macrophages toward the M1 phenotype. KEGG enrichment analysis indicated that TMED2’s function is closely associated with the MAPK signaling pathway, and Western blot experiments further validated TMED2’s role in activating this pathway. Mechanistic studies revealed that CKAP4 may serve as a downstream effector molecule of TMED2, with CKAP4 knockdown significantly affecting macrophage polarization and the activation status of the MAPK pathway. To further validate these findings, we established a xenograft mouse model, and the in vivo experimental results were consistent with those of the in vitro cell experiments, confirming that the TMED2/CKAP4 axis may promote osteosarcoma progression by regulating the MEK/ERK signaling pathway and macrophage polarization.</p>