CXCR6 and melanoma: However, in these CXCL16-transfected melanoma cells, we did not observe any regulation of proliferation upon stimulation with recombinant CXCR6 (Figure 4A), nor could we detect less cleavage of poly(ADP ribose) polymerase (PARP, Figure 4B) after induction of apoptosis with 0.1 μg/mL camptothecin.