Further studies are needed to identify which DRG2 form regulates PD-L1 endosomal trafficking and to evaluate the correlation between DRG2 expression and the response to PD-1/PD-L1 ICIs in PD-L1 IHC-positive patients across various cancer types, including melanoma, breast cancer, cervical cancer, and others. This evidence concerns the gene DRG2 and breast cancer.