Since it has been suggested that HDAC inhibitors induce increased expression of p21 in various tumor cells including ovarian cancer (Richon and O’Brien, 2002; Takai et al., 2004a; Garcia-Manero et al., 2006; Hrzenjak et al., 2006), we therefore examined whether p21 expression could be affected by 72 h of treatment with VPA and VE465, alone and in combination, in 2008/C13 cells. This evidence concerns the gene HDAC9 and ovarian cancer.