Recently, Liu et al. demonstrated that the disruption of the glutamic acid–cystine metabolic balance can lead to elevated PD-L1 levels in melanoma via the transcription factors IRF4 and EGR1, promote PD-L1-containing exosomes release, induce M2 macrophage polarization, and reduce PD-1/PD-L1 inhibitor efficacy [129]. Here, CD274 is linked to melanoma.