We discovered that (1) the Z142X specifically interacts with native LMP-2 protein on the cell membrane of EBV+ cell lines and specifically identifies the xenografts derived from EBV+ cells; (2) the Z142X binds to LMP-2 and kills the EBV LMP-2+ cells, but not the EBV- negative cells; (3) the Z142X inhibits tumor growth in mice bearing NPC tumor xenografts derived from EBV+ C666-1 and CNE-2Z cell lines, but not melanoma xenografts (EBV-negative melanoma A375 cell line). Here, PSMB9 is linked to melanoma.