CCL4 and osteosarcoma: Furthermore, the two CD8 + cytotoxic clusters demonstrated upregulation of NKG7, GZMB, GZMH, GZMK, CCL3, CCL4, and CCL5 (Fig. S6D), suggesting that chemotherapy amplified the cytotoxic function of CD8 + T cells, potentially enhancing their antitumor activity within the osteosarcoma tumor microenvironment.