While CXCL16 can exist as either secreted or trans-membrane bound forms, only the soluble form is known to function as a chemotactic ligand for CXCR6-expressing cancer and immune cells.19–21 Production of the secreted form of CXCL16 was analyzed via ELISA from each representative CAF population (Fig. 3d). This evidence concerns the gene CXCL16 and cancer.