Programmed cell death
The relationship between CXCL9/CXCR3 and the PDL-1/PD-1 is an important area of research. Programmed cell death-1 (PD-1) is heavily expressed on T cells at the tumor site than on T cells present in the peripheral blood and anti-PD-1 therapy can inhibit “immune escape” and the immune activation. Peng et al. showed that anti-PD-1 could not only enhance T cell-mediated tumor regression but also increase the expression of IFN-γ but not CXCL9 by bone marrow–derived cells. Blockade of the PDL-1/PD-1 axis in T cells may trigger a positive feedback loop at the tumor site through the CXCL9/CXCR3 axis. Also using anti-CTLA4 antibody, this axis was significantly up-regulated in pretreatment melanoma lesions in patients with good clinical response after ipilimumab administration.