In our study, we found that H3K36me2 was reduced both in the promoter and the transcribed regions of the COX-2 gene, indicating that H3K36me2 might play an important role in gene repression by mediating the transcriptional reactivation of COX-2 in human lung cancer cells (Figure 2D and 2E, Supplementary Figure S4A and S4B, and Supplementary Figure S6A and S6B). This evidence concerns the gene PTGS2 and lung cancer.