As EZH1 is known to exert compensatory H3K27 methylation under EZH2 knockdown, we employed the use of an EZH2‐specific inhibitor and a nonspecific inhibitor to EZH2/1.33 EZH2/1 inhibition reduced nuclear NF‐κB expression, with the greatest reduction observed in ER+ breast cancer cells. This evidence concerns the gene NFKB1 and breast cancer.