In vitro activity: LAQ824 activates the expression of the gene encoding the p21 cell cycle inhibitor by activating the p21 promoter with 50% of the maximal promoter activation (AC50) of 0.30 μM. LAQ824 inhibits the cell growth of both H1299, a non-small cell lung carcinoma line, and HCT116, a colon cancer cell line with IC50 of 0.15 μM and 0.01 μM, respectively, and the antiproliferative effect of LAQ824 is selective toward the tumor cell lines while inducing only growth arrest in normal fibroblasts. Furthermore, LAQ824 induces a dose-dependent increase of p21 protein in A549 cells and an increase in the hypophosphorylated state of the Rb tumor suppressor. A recent study shows that LAQ824 induces chromatin changes at the level of the IL-10 gene promoter that lead to enhanced recruitment of the transcriptional repressors HDAC11 and PU.1 and inhibits IL-10 production in BALB/c murine macrophages.

Kinase Assay: HDAC enzymes are partially purified from H1299 cell lysate by ion exchange chromatography using the Q Sepharose Fast Flow column. Enzyme complexes are collected from 500 mg of total cell lysate by immunoprecipitation with cdk2 polyclonal antibody or cdk1/cdc2 monoclonal antibody. Immunoprecipitates are resuspended in kinase buffer (50 mM Hepes, pH 8, 10 mM MgCl2, 2.5 mM EDTA, 1 mM dithiothreitol, 20 mM ATP, 10 mM β-glycerophosphate, 0.1 mM NaVO4, 1 mM sodium fluoride, 50 mM ATP, 10 μCi of [γ-32P]ATP) along with 1 μg of pRb recombinant protein substrate (cdk2) or 10 mL of H1 histone mixture containing 20 μg of substrate (cdc2). Phosphorylated Rb and H1 histone are resolved by electrophoresis and quantitated using a PhosphorImager.

Cell Assay: Cell proliferation is measured using an adaptation of published procedures (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfonyl)-2H-tetrazolium assay). The cells are seeded in 12-well dishes and cultured in RPMI 1640 containing 10% FBS. The cells are cultured in the presence of various concentrations of TSA (up to 1,000 ng/mL). To examine the growth inhibition by TSA, viable cell numbers are determined by trypan blue dye exclusion, counted in a Nesbauer-type hemocytometer for 0 hour, 24 hours, and 48 hours. The same amount of ethanol is added to the RPMI 1640 medium as the control experiment. All experiments are performed in duplicate and repeated 3 times The average background value (treatment with medium alone) is subtracted from each experimental well; triplicate values are averaged for each compound dilution. The following formulas are used to calculate the percentage of growth: If XT0, %Growth=(X-T0)/(GC-T0)*100. where T0 is the average value of T0 – background, GC is the average value of untreated cells (in triplicate) – background, and X is the average value of compound-treated cells (in triplicate)-background. The “% Growth” is plotted against compound concentration and used to calculate the IC50 using the linear regression techniques between data points to predict the concentration of compounds at 50% inhibition.

Cancer Res. 2004 Jan 15;64(2):689-95; J Immunol. 2011 Apr 1;186(7):3986-96.