Determination of the class and isoform selectivity of small-molecule histone deacetylase inhibitors.
The human HDAC (histone deacetylase) family, a well-validated anticancer target, plays a key role in the control of gene expression through regulation of transcription. While HDACs can be subdivided into three main classes, the class I, class II and class III HDACs (sirtuins), it is presently unclear whether inhibiting multiple HDACs using pan-HDAC inhibitors, or targeting specific isoforms that show aberrant levels in tumours, will prove more effective as an anticancer strategy in the clinic. To address the above issues, we have tested a number of clinically relevant HDACis (HDAC inhibitors) against a panel of rhHDAC (recombinant human HDAC) isoforms. Eight rhHDACs were expressed using a baculoviral system, and a Fluor de Lystrade mark (Biomol International) HDAC assay was optimized for each purified isoform. The potency and selectivity of ten HDACs on class I isoforms (rhHDAC1, rhHDAC2, rhHDAC3 and rhHDAC8) and class II HDAC isoforms (rhHDAC4, rhHDAC6, rhHDAC7 and rhHDAC9) was determined. MS-275 was HDAC1-selective, MGCD0103 was HDAC1- and HDAC2-selective, apicidin was HDAC2- and HDAC3-selective and valproic acid was a specific inhibitor of class I HDACs. The hydroxamic acid-derived compounds (trichostatin A, NVP-LAQ824, panobinostat, ITF2357, vorinostat and belinostat) were potent pan-HDAC inhibitors. The growth-inhibitory effect of the HDACis on HeLa cells showed that both pan-HDAC and class-I-specific inhibitors inhibited cell growth. The results also showed that both pan-HDAC and class-I-specific inhibitor treatment resulted in increased acetylation of histones, but only pan-HDAC inhibitor treatment resulted in increased tubulin acetylation, which is in agreement with their activity towards the HDAC6 isoform.
Khan
Nagma
N
Topotarget UK Ltd, 87a Milton Park, Abingdon, Oxon, OX14 4RY, UK. nagmabkhan@yahoo.co.uk
Jeffers
Michael
M
Kumar
Sampath
S
Hackett
Craig
C
Boldog
Ferenc
F
Khramtsov
Nicholai
N
Qian
Xiaozhong
X
Mills
Evan
E
Berghs
Stanny C
SC
Carey
Nessa
N
Finn
Paul W
PW
Collins
Laura S
LS
Tumber
Anthony
A
Ritchie
James W
JW
Jensen
Peter Buhl
PB
Lichenstein
Henri S
HS
Sehested
Maxwell
M
D000107:Acetylation; D049109:Cell Proliferation; D003001:Cloning, Molecular; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D006367:HeLa Cells; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000145:classification / Q000378:metabolism; D006801:Humans; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D020033:Protein Isoforms; D011994:Recombinant Proteins; D006655:Histone Deacetylases