CTLA4 and melanoma: At present, immune checkpoint inhibitors (ICIs) are the most widely used in cancer immunotherapy, and anti-CTLA4-PD-1 dual immunotherapy has successfully treated a group of tumors including melanoma [37], so we selected the common ICIs—PD-1, PD-L1, and CTLA4, to explore the role of SLC25s in cancer immunotherapy.