FOS and breast cancer: We identified three mRNAs, which were significantly upregulated in serum exosomes of patients with breast cancer with cerebral metastases (Supplemental Figure S1): HSPA5 (heat shock 70 kDa protein 5/binding immunoglobulin protein), FOS (Fos proto-oncogene/AP-1 transcription factor subunit), and LHB (luteinizing hormone subunit beta).