CD274 and coinfection: Finally, EBV co-infection commonly seen in cHL can also upregulate PD-L1 on tumor cells via the EBV-encoded latent membrane protein (LMP)-1 that activates AP-1 (via cJUN/JUN-B components) or via JAK/STAT signaling pathways that activate the enhancer or promoter, respectively, of PD-L1 [21].