In recent studies, it was reported that metformin, a biguanide anti‐diabetic drug for the type II diabetes, can selectively reduce the number of BCSCs and suppress tumour development.21 Moreover, the expression of PD‐L1 in tumour cells can be effectively inhibited by metformin.16 These findings imply that metformin may exert its antitumour effects through regulating immune‐related genes and signalling pathways. Here, CD274 is linked to neoplasm.