Intriguingly, moreover, the ARF6-AMAP1 pathway is also linked to the processes of intracellular recycling and cell surface expression of PD-L1 and carbonic anhydrase 9 (CA9), and hence may promote the onset of immune checkpoint (i.e., enhanced PD-L1 expression at the cell surface) and acidosis (i.e., enhanced CA9 expression at the cell surface), which both favor cancer immune evasion [7, 40]. Here, CA9 is linked to cancer.