Validation of NPTX2 function in osteosarcoma. (A–C) Association of NPTX2 mRNA with CD8A, IFNG, and GZMB expression in osteosarcoma tissues (n = 35). (D) The knockdown efficacy of NPTX2 in HOS and SW1353 cells as determined by qPCR. (E and F) Cell proliferation was measured with the CCK8 assays in HOS and SW1353 cells transfected with siRNAs or NC. (G and H) Apoptosis of HOS cells and SW1353 cells after transfection with siRNAs or NC was detected by flow cytometric assay. (I and J) The expression of CCL4, CCL5, CXCL9, CXCL10, and CXCL13 as measured with qPCR in HOS‐NPTX2‐NC and HOS‐NPTX2‐siRNAs cells, or SW1353‐NPTX2‐NC and SW1353‐NPTX2‐siRNAs cells. (K and L) The expression of CCL4, and CXCL13 as quantified with ELISA assay. (M and N) Association of NPTX2 mRNA with CCL4 expression in the TCGA datasets and in osteosarcoma tissues from our patients (n = 35). (O and P) Association of CCL4 mRNA with CD8A expression in the TCGA datasets and osteosarcoma tissues from our patients (n = 35)