PDCD1 and breast cancer: Interestingly, the expression of these pro-cytotoxic transcripts in tumours is associated with the counter activation of suppressive mechanisms, such as the expression of IDO1, CTLA4, CD274 (PD-L1), PDCD1 (PD-1), and FOXP3.26 In a study27 centred on the TCGA data set, we found that breast cancers can be classified in four classes according to the ICR signature.