CXCR4 and lung cancer: CXCL12 is additionally secreted by stromal fibroblasts, endothelial cells, and immune cells in lung cancer in such amounts that they form chemotactic gradients drawing CXCR4-expressing cancer cells to metastatic niches such as liver, brain, and bone marrow (Mir et al., 2023; Thapa et al., 2023).