Romidepsin, the lone cyclic peptide HDAC inhibitor, has been shown at nanomolar levels in glioblastoma cell lines to cause inhibition of cell proliferation and induction of apoptosis (through the increased expression of the cell cycle inhibitor p21Waf1/Cip1 and the pro-apoptotic protein Bad and the decreased expression of the anti-apoptotic proteins Bcl-xL and Bcl-2)[73]. This evidence concerns the gene HDAC9 and glioblastoma.