To explore the mechanism of MLN8237 promoting PD-L1 expression, we screened JAK/STAT, PI3K/AKT and MAPK/ERK signal paths with SKBR3 breast cancer cells, and the protein levels of p-STAT1, p-STAT3, p-STAT5, p-AKT and p-ERK were detected after treatment with MLN8237. Here, STAT3 is linked to breast cancer.