A clonogenic survival assay showed that USP5 knockdown significantly decreased the colony formation ability of NPC cells in both 4Gy ionizing radiation (IR) and no irradiation groups, but the inhibitory effect of USP5 knockdown on colony formation ability was stronger in 4Gy IR group than in no irradiation group, and EphA2 overexpression recovered the colony formation ability of NPC cells with USP5 knockdown in both groups (Fig. 4A). Here, EPHA2 is linked to nasopharyngeal carcinoma.