PD-L1 and PD-L2 copy gain and further induction via JAK2/STAT signaling. (Left) The 9p24.1 amplicon in cHL includes PD-L1, PD-L2, and JAK2. (Right) JAK2 copy gain leads to increased JAK2 protein expression and enhanced JAK/STAT signaling, which further induces PD-1 ligand expression.