The combined results of Figs. 4 and 6 thus suggest that G9a and EZH2 are critically involved in COX-2 promoter DNA methylation and that histone methylation and DNA methylation act interdependently to cause COX-2 epigenetic silencing in IPF cells; removal of one of these repressive epigenetic modifications leads to the removal of the other repressive epigenetic modifications and consequently the derepression of the COX-2 gene. This evidence concerns the gene PTGS2 and idiopathic pulmonary fibrosis.