The rationale for this combination stems from extensive preclinical data suggesting epigenetic modulation and post-translational modification of the ER by HDAC inhibitors enhances the anti-tumour effects of tamoxifen (Yang et al, 2001; Kawai et al, 2003; Alao et al, 2004; Jang et al, 2004; Saji et al, 2005; Kawai and Arinze, 2006; Sharma et al, 2006; Fiskus et al, 2007; Zhou et al, 2007; Bicaku et al, 2008). This evidence concerns the gene HDAC9 and neoplasm.