In our first attempt to investigate whether we can detect circulating miRNAs in sera of human BC (HER2+, TNBC), cell line-transplanted mice (JIMT-1- and MDA-MB-231-transplanted HTM, see Table 1) under different treatment regimens (with and without irradiation and/or without anti-PD-L1 treatment), we analyzed circulating miRNAs in mice sera, as well as miRNAs from the exosomal fraction of sera, and compared the results to untreated controls and an NSG control (see Table 1). This evidence concerns the gene CD274 and breast cancer.