Histone acetyltransferase inhibitors block neuroblastoma cell growth in vivo.

J M Gajer,K Keller,H L Pahl,W Sippl,M Gothwal,F Colland,A Gründer,U Heinicke,S Fulda,M Jung,I Fichtner,S D Furdas

doi:10.1038/oncsis.2014.51

Abstract

We have previously described novel histone acetyltransferase (HAT) inhibitors that block neuroblastoma cell growth in vitro. Here we show that two selected pyridoisothiazolone HAT inhibitors, PU139 and PU141, induce cellular histone hypoacetylation and inhibit growth of several neoplastic cell lines originating from different tissues. Broader in vitro selectivity profiling shows that PU139 blocks the HATs Gcn5, p300/CBP-associated factor (PCAF), CREB (cAMP response element-binding) protein (CBP) and p300, whereas PU141 is selective toward CBP and p300. The pan-inhibitor PU139 triggers caspase-independent cell death in cell culture. Both inhibitors block growth of SK-N-SH neuroblastoma xenografts in mice and the PU139 was shown to synergize with doxorubicin in vivo. The latter also reduces histone lysine acetylation in vivo at concentrations that block neoplastic xenograft growth. This is one of the very few reports on hypoacetylating agents with in vivo anticancer activity.

Highlights

Reversible protein acetylation on lysine residues is one of the major posttranslational regulatory mechanisms of protein activity
Combining in performed using a histone H3 peptide as a substrate- and antibody-based assays with a time-resolved fluorescence readout, silico and in vitro screening conducted with the p300/CBP-associated factor (PCAF) catalytic commonly known as DELFIA
Growth was assessed using a sulforhodamine B cytotoxicity assay for the following solid tumor cell lines: A431, A549, A2780, HepG2, SW480, U-87 MG, HCT116 and again SK-N-SH and MCF7 to compare the relative potency in the different assay systems

Summary

Introduction

Reversible protein acetylation on lysine residues is one of the major posttranslational regulatory mechanisms of protein activity. Acetylation sites have been identified in many cellular proteins involved in differentiation and proliferation, signal transduction and metabolism, apoptosis and cytoskeleton dynamics.[1] histone lysine acetylation is one of the main epigenetic modifications that impact on gene expression and transcriptional activity.[2,3] The level of histone lysine acetylation is controlled by the antagonistic catalytic activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs).[4] In mammalian cells, the HAT family is comprised of three subfamilies: the GNAT5 (Gcn5related N-acetyltransferase), the p300/CBP6 (CREB (cAMP response element-binding) protein) and the MYST7 (Moz, Ybf[2], Sas[2], Tip). All subfamilies include transcription factors as well as steroid receptor co-activators[8] with catalytic activity.[9,10,11] Because they target both histone and non-histone substrates,[12] HATs have been more generally termed lysine acetyltransferases (KATs).[13]

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Conclusion