HDAC9 and cancer: It was found that LC treatment mainly arrested cancer cell proliferation and only slightly induced cell death, which is possibly due to the following two reasons: on one hand, LC is not a strong HDAC inhibitor compared to classical inhibitors including TSA but LC and Buty exerted their inhibiting effects at a similar mM level; on the other hand, relative low level of LC could efficiently induced high expression of p21cip1 which has been reported to block HDAC inhibition-induced apoptosis [27], [28].