With promoter assay utilizing BRD4 promoter and shPRDM1-SNU-1, we can identify whether PRDM1 activates BRD4 promoter; with chromatin immunoprecipitation utilizing shPRDM1-SNU-1, we can identify whether PRDM1 binds to BRD4 promoter and whether this binding is lost after PRDM1 knockdown; and with RNA sequencing, we can identify how loss of PRDM1 in stomach cancer changes transcriptome, and with these clues, the source behind epigenetic regulation can be explored. Here, PRDM1 is linked to gastric cancer.