RAB27A and nonpapillary renal cell carcinoma: Given that CD63 is a hallmark protein for exosomes [21], we examined colocalization between PD-L2 and CD63, and found that the colocalization was higher in WT cells than in PD-L2 KO cells, while colocalization was lower in WT cells than in Rab27a KD cells (Fig. 1H), supporting that PD-L2 is secreted via exosomes in ccRCC cells.