We found that by 48 h, 5-Aza-CdR, Jmjd3 and DZNep significantly up-regulated RUNX3 protein and mRNA which suggests that DNMT3b-mediated DNA methylation and H3K27me3 both participate in RUNX3 protein down-regulation during the late stages of hyperoxia-induced BPD. Here, RUNX3 is linked to bronchopulmonary dysplasia.