PDPK1 and breast cancer: Differentially expressed genes (DEGs) were identified via bioinformatics analysis, and we formulated predictive models and exosome scores (ES) for patients with breast cancer based on the expression of four genes, phosphoinositide-dependent protein kinase 1 (PDPK1), WD Repeat and SOCS Box Containing 2 (WSB2), pirin (PIR), and Methylenetetrahydrofolate Dehydrogenase 2 (MTHFD2).