CD274 and breast cancer: Together, the observations presented in this part of the study provided the first evidence to the indispensable roles of S283 in mediating PD-L1 signaling and induction of pro-metastatic effects in breast cancer cells; they also illustrated the increased binding efficiency of WT-PD-L1 to AMPK, over the binding efficiency of mutated PD-L1, that carries a serine to alanine alteration.