HPOB is an effective and specific HDAC6 inhibitor (IC50: 56 nM), >30-fold selectivity over other HDACs.

HDAC6:56 nM, HDAC8:2.8 μM, HDAC2:4.4 μM, HDAC10:3.0 μM, HDAC1:2.9 μM, HDAC3/NCOR2:1.7 μM

在负荷CWR22人前列腺癌异种移植物的小鼠体内,HPOB（300 mg/kg/day）与SAHA联用可抑制已生成肿瘤的生长,而单独使用时则无明显抑制作用.

在HFS细胞中,HPOB对依托泊苷,阿霉素,或SAHA诱导的转化细胞死亡具有增强作用。在转化细胞中,通过凋亡通路HPOB也会增强依托泊苷诱导的转化细胞死亡。在正常(HFS)和转化的(LNCaP,A549,和U87)细胞中,HPOB诱导α-微管蛋白,但不影响组蛋白,抑制细胞生长,但不影响细胞活性。

In Vitro Enzymatic Assay for Histone Deacetylases: In vitro activities of the 11 recombinant human zinc-dependent HDAC enzymes are detected by ?uorigenic release of 7-amino-4-methylcoumarin from substrate upon deacetylase enzymatic activity. A series of dilutions of the unique HDAC6 compound, tubacin, and SAHA are prepared with 10% DMSO in HDAC assay buffer, and 5 μL of the dilution was added to a 50-μL reaction so that the ?nal concentration of DMSO is 1% in all of the reactions. The enzymatic reactions are conducted in duplicate at 37 °C for 30 min in a 50-μL mixture containing HDAC assay buffer, 5 μg BSA, an HDAC substrate, an HDAC enzyme, and a test compound. After enzymatic reactions, 50 μL of 2× HDAC developer is added to each well, and the plate is incubated at room temperature for an additional 15 min. Fluorescence intensity is measured at an excitation of 360 nm and an emission of 460 nm using a Synergy microplate reader. Negative (no enzyme, no inhibitor, a drug with no HDAC inhibition activity) and positive controls (known HDAC inhibitor SAHA) are included in the assays. IC50 is determined at the drug concentration that results in 50% reduction of HDAC activity compared with the control.

Normal (HFS) and transformed (LNCaP, A549, and U87) cells are cultured with indicated doses of HPOB for 72 h. Five micromolars SAHA is a positive control.Graphs were constructed using Prism 5. (Only for Reference)