CDKN1A and gastric cancer: Since BRD4 is a key regulator of RNAPII-dependent gene expression5, the dramatically enhanced cellular levels of p21 in JQ1-treated or Brd4 knockdown MKN28 cells raised the possibility that BRD4 might regulate the transcription of p21. Since BRD4 is overexpressed in gastric cancer tissues (Fig. 1b)26, we then examined the mRNA levels of Brd4 and p21 (also called CDKN1A) in gastric cancer samples using the RNAseq datasets from TCGA (http://cancergenome.nih.gov/).