Another mechanistic study of PD-L1 expression in NPM-ALK fusion positive anaplastic large cell lymphoma found that PD-L1 expression was induced mainly through the MEK-ERK and STAT3 signaling pathways (Figure 4B), suggesting that the expression of PD-L1 in ALK fusion is regulated in different ways depending on tumor cell types or differences in ALK fusion partners (38, 39). This evidence concerns the gene CD274 and anaplastic large cell lymphoma.