Using whole-transcriptome sequencing and whole-exome sequencing with 37 metastatic breast cancer samples, the authors found that HER2 expression and taxane treatment correlated positively with a high expression of HAVCR2 (Tim-3), PDCD1 (PD-1), CD274 (PD-L1), CD276 (B7-H3), CTLA-4, indoleamine 2,3-dioxygenase 1(IDO1), and LAG-3 (78), supporting that HER2 expression and taxane treatment could regulate the expression of Tim-3 in breast cancer (Figure 2). This evidence concerns the gene IDO1 and breast cancer.