CCL21 and hepatocellular carcinoma: Both breast and melanoma cancer cells express high levels of CXCR4 and CCR7 receptors, which enables them to migrate to the lungs in response to CXCL12 and CCL21 ligands.254 Exosomes released from CD103+ CSCs are enriched for miR-15b-3p, promoting the colonization and growth of clear cell renal cell carcinoma (CCRCC) cells in the lung and accelerating metastasis.255 EVs released by hepatocellular carcinoma (HCC) cells contain nidogen 1, which enhances angiogenesis and activates fibroblasts in the lungs, thereby contributing to the survival and proliferation of tumor cells.256