SAHA may increase the expression of acetyl-histone 3 and 4 and thereby upregulate or down-regulate the mRNA expression of downstream genes, including Cyclin D1, p21, p27, c-myc and nanog. The histone acetylation may be positively linked to the tumorigenesis and differentiation of gastric cancer. The gene discussed is CDKN1B; the disease is gastric cancer.