CSF1 and nasopharyngeal carcinoma: A BARF1 protein encoded by the Bam H1-A fragment is a homolog of human colony-stimulating factor 1 (CSF1) receptor, and this secreted viral protein is believed to enhance NPC tumorigenicity through activation of the CSF-1 signaling axis, suppression of apoptosis by activation of BCL-2, and upregulation of expression of NF-κB, RelA, and cyclin D1 (35).