EML4 and cancer: Expression of PD-L1 is induced via oncogenic signaling pathways, such as RAS/RAF/MEK/mitogen-activated protein kinase-ERK (20–23), phosphatidylinositol-3 kinase/phosphatase and tensin homolog/Akt/mammalian target of rapamycin (24–28), EGFR (8, 29–31), and EML4-ALK pathways (23, 32), in many cancer types.