Identification of Novel Isoform-Selective Inhibitors within Class I Histone Deacetylases

Abstract

Histone deacetylases (HDACs) represent an expanding family of protein modifying-enzymes that play important roles in cell proliferation, chromosome remodeling, and gene transcription. We have previously shown that recombinant human HDAC8 can be expressed in bacteria and retain its catalytic activity. To further explore the catalytic activity of HDACs, we expressed two additional human class I HDACs, HDAC1 and HDAC3, in baculovirus. Recombinant HDAC1 and HDAC3 fusion proteins remained soluble and catalytically active and were purified to near homogeneity. Interestingly, trichostatin (TSA) was found to be a potent inhibitor for all three HDACs (IC 50 value of ϳ0.1-0.3 M), whereas another HDAC inhibitor MS-27-275 (N-(2-aminophenyl)-4-[N-(pyridin-3-methyloxycarbonyl)-aminomethyl]benzamide) preferentially inhibited HDAC1 (IC 50 value of ϳ0.3 M) versus HDAC3 (IC 50 value of ϳ8 M) and had no inhibitory activity toward HDAC8 (IC 50 value Ͼ100 M). MS-27-275 as well as TSA increased histone H4 acetylation, induced apoptosis in the human colon cancer cell line SW620, and activated the simian virus 40 early promoter. HDAC1 protein was more abundantly expressed in SW620 cells compared with that of HDAC3 and HDAC8. Using purified recombinant HDAC proteins, we identified several novel HDAC inhibitors that preferentially inhibit HDAC1 or HDAC8. These inhibitors displayed distinct properties in inducing histone acetylation and reporter gene expression. These results suggest selective HDAC inhibitors could be identified using recombinantly expressed HDACs and that HDAC1 may be a promising therapeutic target for designing HDAC inhibitors for proliferative diseases such as cancer.

R306465 is a novel potent inhibitor of class I histone deacetylases with broad-spectrum antitumoral activity against solid and haematological malignancies

“…R306465 differs from other hydroxamate-based inhibitors currently in clinical development in that it has preferential activity towards class I HDACs compared to HDAC6. So far, for the HDAC inhibitors in clinical development, HDAC1 selectivity has been reported only for non-hydroxamic acid-based HDAC inhibitors, such as the benzamide MS-275 (Blagosklonny et al, 2002;Hu et al, 2003;Glaser et al, 2004). In our hands, however, MS-275 did not inhibit the activity of HDAC1 complexes precipitated from tumour cells and induced cellular H3 acetylation only at very high concentrations.…”

“…In our hands, however, MS-275 did not inhibit the activity of HDAC1 complexes precipitated from tumour cells and induced cellular H3 acetylation only at very high concentrations. HDAC1 inhibition by MS-275 in vitro has usually been demonstrated using recombinant HDAC1 enzymes (Hu et al, 2003). Assessing HDAC inhibitor selectivity in vitro must be approached with caution since active enzymes consist of a multiprotein complex containing other HDACs and cofactors.…”

Reduced expression of class II histone deacetylase genes is associated with poor prognosis in lung cancer patients

“…22 Moreover, patients with BRG1/BRM-negative lung carcinomas, independent of stage, have significantly poorer prognosis. Because HP1␣ interacts with BRG1 23 in addition to class II HDACs, class II HDACs, HP1␣ and 25 ) have demonstrated inhibitory activity, specifically against class I HDACs. These HDAC inhibitors with class I specificity might be desirable as they exhibit anticancer effects.…”

Histone deacetylase inhibitors: molecular mechanisms of action

“…Certain HDACi may selectively inhibit different HDACs. For example, MS-275 preferentially inhibits HDAC1 with IC 50 , at 0.3 mM, compared to HDAC3 with an IC 50 of about 8 mM, and has little or no inhibitory effect against HDAC6 and HDAC8 (Hu et al, 2003). Two novel synthetic compounds, SK7041 and SK7068, preferentially target HDAC1 and 2 and exhibit growth inhibitory effects in human cancer cell lines and tumor xenograft models (Kim et al, 2003a).…”