Prx1 knockout leads to a downregulation of ASK1. (A) mRNA expression level of ASK1 was elevated in mouse tongue premalignant lesions, as determined by RT-qPCR. (B) RT-qPCR determination of the relative expression of ASK1 mRNA in Prx1 knockout mice (a) control group, (b) 4NQO group and (c) 4NQO + H2O2 group. (C) Prx1 had no clear association with ASK1 in mouse tongue premalignant lesions in the (a) wild-type control group, (b) wild-type 4NQO group, (c) wild-type 4NQO + H2O2 group, (d) Prx1 knockout control group, (e) Prx1 knockout 4NQO group and (f) Prx1 knockout 4NQO + H2O2 group (magnification, ×200). (g) ASK1 MOD value. (D) Prx1 positively regulated the activation of phosphor-ASK1 in mouse tongue premalignant lesions in the (a) wild-type control group, (b) wild-type 4NQO group, (c) wild-type 4NQO + H2O2 group, (d) Prx1 knockout control group, (e) Prx1 knockout 4NQO group and (f) Prx1 knockout 4NQO + H2O2 group (magnification, ×200). (g) Phosphor-ASK1 MOD value. *0.01<P<0.05; **0.000<P<0.01. Prx1, peroxiredoxin 1; 4NQO, 4-nitroquinoline-1-oxide; ASK-1, apoptosis signal-regulating kinase 1; MOD, mean optical density; RT-qPCR, reverse transcription-quantitative polymerase chain reaction.