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). The gene discussed is CXCR6; the disease is cancer.