YY1 and gastric cancer: Moreover, knockdown of p65, a subunit of NF-κB crucial for YY1 expression20, reduced the YY1 levels and prevented the gastric cancer cells from enhanced expression of YY1 and MMP-14, increased activity of MMP-14 promoter, and increased binding of YY1 to MMP-14 promoter induced by ectopic expression of YY1 (Fig. 2e,f,g).