Given that circ_0040039 promoted miR-874-3p (Figure 4H) but repressed ESR1 expression (Figures 4I,J), and miR-874-3p repressed ESR1 expression in NPCs (Figure 2D), it was speculated that circ_0040039 promoted NPC degeneration possibly via activating the miR-874-3p-ESR1 signaling pathway. This evidence concerns the gene ESR1 and nasopharyngeal carcinoma.