CTLA4 and breast cancer: Since our previous data have shown that CTLA-4 and PD-L1 ICs are expressed at satisfactory levels on MDA-MB-231 and BT-549 TNBC cells [40], we investigated whether these targets were also expressed on a malignant non-TNBC subtype of breast cancer, such as the BT-474 cell line, which could represent a good model for highlighting differences among different breast cancer subtypes for the emerging anti-cancer drugs [41].