Functional annotation and enrichment analysis of 222 differentially expressed proteins with a greater than 1.5-fold change indicated that co-culturing with breast cancer cells leads to immunosuppression of PBMCs by modulating several specific tumor progression pathways (i.e., PPAR, IL-17, PI3K-Akt, positive regulation of protein kinase B signaling, and HIF-1 signaling pathway, positive regulation of NF-kB transcription factor activity). This evidence concerns the gene PPARA and breast cancer.