SP1 is a direct target of miR‐24 and involved in NPC cell radioresistance and growth. (A). Predicted miR‐24‐3p binding sequences in the 3′UTR of SP1. Quantification of (B). SP1 mRNA expression and (C). protein levels following transfection with miR‐24 mimic or miRNA mimic NC. (D). CNE‐1 and CNE‐2 cells were co‐transfected with a wt or mut SP1 3′UTR reporter gene and a miR‐24 mimic or a miRNA mimic NC. Wt and mut miR‐24 target sequences of the SP1 3′UTR are indicated. (E). Western blot analysis for SP1 48 h following transfection with SP1 siRNA or a negative control. (F). Clonogenic survival assays of CNE‐1 and CNE‐2 cells treated with SP1 siRNA or an NC followed by various doses of radiation. Surviving fractions were calculated as described. (G). Cell viability was determined following transfection with SP1 siRNA or an NC at days 1–5 in CNE‐1 and CNE‐2 cells. Values are presented as the mean ± standard deviation. *P < 0.05 versus miR‐NC. SP1, Specificity protein 1; miR, miRNA; NC, negative control; wt, wild‐type; mut, mutant; siRNA, small interfering RNA; UTR, untranslated region; hsa, Homo sapiens.