LRMS [ES]+: = 396.0 (M + H)+. d. remain major hurdles in drug discovery. In the past decade, human sirtuins (homologues of yeast Silent Information Regulator Two or Sir-2) have emerged as targets for malignancy chemotherapy as well Rabbit Polyclonal to CST11 as for neurodegenerative and aging-related disorders such as Huntingtons disease, Alzheimers disease, and diabetes.2 Although strong evidence exists for sirtuins using a central role in these debilitating diseases, their validation as targets for therapeutic intervention using small molecule modulators has been controversial.3?5 The most publicized efforts at modulation of sirtuin activity have been with the plant polyphenol resveratrol.6 This purported sirtuin activator was shown to have highly beneficial effects in animal models of metabolic disorders (e.g., diabetes) and lifespan extension using experimental models that have since been largely shown to be flawed.7?9 EX-527, a potent and selective SIRT1 inhibitor (SIRT1: human sirtuin isoform 1), was found to be devoid of chemotherapeutic effect; however, cambinol, tenovin-1, tenovin-6, and salermide, nonselective SIRT1/SIRT2 inhibitors, were found to have significant antitumor activity.1,10?12 Combined use of a nonselective sirtuin inhibitor niacinamide (nicotinamide) and a pan-type I/II HDAC (i.e., zinc-dependent histone deacetylases) inhibitor vorinostat yielded encouraging results in a recent diffuse large B-cell lymphoma phase I clinical trial further validating sirtuins as antilymphoma drug targets.13 Additionally, SRT1720, a potent direct SIRT1 activator that was originally developed for its potential in lifespan extension or antiaging activity, was later found to be beneficial in a rat diabetes model employing a mechanism which may involve indirect activation of SIRT1.14 The recent functional characterization of other sirtuin isoforms such as SIRT3, SIRT5, SIRT6, and SIRT7 has further complicated the field as it is becoming increasingly clear that in addition to SIRT1 and 2, these isoforms may also play major functions in aging (SIRT3, SIRT6) as well as in cell-proliferation disorders (SIRT7).15 Additional controversies regarding artifacts of popular in vitro AST-1306 assays to identify novel small molecule modulators of sirtuin activity have also hampered the validation AST-1306 of these enzymes for pharmacological intervention.16 Previously, in an attempt to identify isoform selective sirtuin inhibitors, we carried out a phenotypic screen using an NCI chemical library that resulted in discovery of cambinol (5-[(2-hydroxy-1-naphthyl)methyl]-6-phenyl-2-thioxo-2,3-dihydro-4(1= 0.56, = AST-1306 0.0014) (Figure ?(Physique6),6), neither SIRT1 (= ?0.11) nor SIRT3 (= 0.21) (data not shown) inhibition correlates with Namalwa cytotoxicity. Three compounds, the SIRT1-selective 17, SIRT2-selective 24 and SIRT3-selective 8, were tested against an expanded panel of Burkitts lymphoma (Dakiki, Daudi, Mutu, Oku, Ramos and Namalwa), diffuse AST-1306 large B-cell lymphoma (SU-DHL4 and OCI-Ly8-LAM53), nontransformed EpsteinCBarr computer virus (EBV) immortalized B-cell lines (B1 and B2), and epithelial malignancy cell lines (HCT116-colon, MCF7-breast, NCI-H460-nonsmall cell lung malignancy and OVCAR3-ovarian) (Table 5). The SIRT2-selective inhibitor 24 exhibited potent cytotoxicity in both lymphoma and epithelial malignancy cell lines with IC50 ranging from 3 to 7 M relative to the nontransformed B-cell lines (IC50 22C28 M). Open in a separate window Physique 5 Induction of apoptosis in Namalwa cells treated with 24. FACS analysis of Namalwa cells treated with DMSO (left), 10 M (24) (center) and 25 M (24) (right) for 16 h. Cells were stained with annexin V-PE (and with particular activity against Burkitts lymphoma cell lines.1 In an effort to delineate the contribution of SIRT1 and SIRT2 inhibition in this antitumor activity, we sought.