Tenovin-D3, a Novel Small-Molecule Inhibitor of Sirtuin SirT2, Increases p21 (CDKN1A) Expression in a p53-Independent Manner

Abstract

While small-molecule inhibitors of class I/II histone deacetylases (HDAC) have been approved for cancer treatment, inhibitors of the sirtuins (a family of class III HDACs) still require further validation and optimization to enter clinical trials. Recent studies show that tenovin-6, a small-molecule inhibitor of sirtuins SirT1 and SirT2, reduces tumor growth in vivo and eliminates leukemic stem cells in a murine model for chronic myelogenous leukemia. Here, we describe a tenovin analogue, tenovin-D3, that preferentially inhibits sirtuin SirT2 and induces predicted phenotypes for SirT2 inhibition. Unlike tenovin-6 and in agreement with its weak effect on SirT1 (a p53 deacetylase), tenovin-D3 fails to increase p53 levels or transcription factor activity. However, tenovin-D3 promotes expression of the cell-cycle regulator and p53 target p21 WAF1/CIP1 (CDKN1A) in a p53-independent manner. Structure-activity relationship studies strongly support that the ability of tenovin-D3 to inhibit SirT2 contributes to this p53-independent induction of p21. The ability of tenovin-D3 to increase p21 mRNA and protein levels is shared with class I/II HDAC inhibitors currently used in the clinic and therefore suggests that SirT2 inhibition and class I/II HDAC inhibitors have similar effects on cell-cycle progression. Mol Cancer Ther; 12(4); 352-60. Ó2013 AACR.

Modulation of p53 C-Terminal Acetylation by mdm2, p14ARF, and Cytoplasmic SirT2

“…3C). Tenovin-D3 is a novel tenovin analogue that shows selectivity for SirT2 (31). As expected for a SirT2 inhibitor, tenovin-D3 increases the levels of acetylated-K40 a-tubulin (31).…”

“…Etoposide, nutlin-3 (racemic), EX527, and MG132 were purchased from Sigma. Tenovins (tnv1, tnv6, and tnvD3) were synthesized as described previously (30,31) …”

“…As expected for a SirT2 inhibitor, tenovin-D3 increases the levels of acetylated-K40 a-tubulin (31). However, unlike tenovin-6, tenovin-D3 has reduced activity against SirT1 and is very poor at increasing p53 levels (31). Here, we examined whether tenovin-D3 could increase the levels of p53 and p53AcK382 in the C s fraction.…”

Sirtuin Inhibitors as Anticancer Agents

“…SIRT2 inhibition has been shown to increase the levels of tumor suppressor genes, such as p53 and p21 [4,47]. Increased p53 level is achieved through deacetylation of p53, but the mechanism for increased p21 level is not clear.…”

SIRT2 is required for efficient reprogramming of mouse embryonic fibroblasts toward pluripotency

“…We observed that p16 Ink4a , p15 Ink4b , and p19 Arf , three genes encoded by the INK4/ARK locus, and their respective downstream effectors, Rb and p21, were upregulated in SIRT2-KO-MEFs. Although p53, a mediator of p19 Arf and p21, showed slightly higher expression levels in WT cells than in KO cells, a previous study using the specific SIRT2 inhibitor tenovin-D3 revealed that SIRT2 inhibition may directly upregulate p21, irrespective of p53 50 . Another study revealed that SIRT2 inhibition by resveratrol treatment or SIRT2 knockdown using siRNA for SIRT2 in human fibroblasts induced INK4/ARF locus gene expression through DNA damage 51 .…”