Biochemical assays of HDAC activity are carried out by Nanosyn in a reaction volume of 10 μL in 384-well microplates. A standard enzymatic reaction contains 5 μL of 2× HDAC inhibitor (e.g., Entinostat), 4 μL of 2.5× enzyme, and 1 μL of 10× substrate in assay buffer (100 mM HEPES, pH 7.5, 25 mM KCl, 0.1% BSA, 0.01% Triton X-100, 1% DMSO). Final concentration of all HDACs in the enzymatic assays is between 0.5 and 5 nM. A final substrate concentration of 1 μM FAM-RHKK(Ac)-NH₂ or FAM-RHKK(trifluoroacetyl)-NH₂ is used in all assays and found to be below the determined K_m,app for each enzyme^[1].

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

SH-SY5Y cells are maintained under normal culture conditions in a humidified incubator at 37°C with 5% CO₂ and are split twice weekly. Cells are plated in black 384-well plates at 2500 cells/well in 20-μL volume of DMEM/F-12 culture media supplemented with 10% FBS and permitted to adhere overnight. The following day, HDAC inhibitors (e.g., Entinostat) are serially diluted in 100% DMSO, and this series is subsequently cross-diluted into culture media. 5 μL of compound (e.g., Entinostat) diluted in media is added to the appropriate well of the cell plate to afford the indicated final concentration of inhibitor (e.g., Entinostat) with a final 0.1% DMSO. Treated cells are incubated under normal tissue culture conditions for 6, 24, 48, 72, or 96 h prior to quantitation of cellular ATP levels as measured using CellTiter-Glo reagents. Similarly, after 6 h of incubation with HDAC inhibitors (e.g., Entinostat), media from separate cell plates are aspirated, and cells are washed once with media containing no inhibitors. 25 μL of media supplemented with 10% FBS and 0.1% DMSO (no inhibitors) is added back to the cells, and cellular ATP levels are determined using CellTiter-Glo after 24, 48, 72, or 96 h of incubation. Luminescence is measured at each time point using an Envision Instrument with a 0.1 s count time^[1].

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

Mice^[3]
A2780 cells (9×10⁶) are suspended in PBS and are injected subcutaneously into the flank of nude mouse. For the other tumor lines, KB-3-1, HCT-15, 4-1St, Calu-3, St-4, Capan-1, and HT-29, tumors are passaged several times before starting in vivo antitumor testing, and a tumor lump (2-3 mm in diameter) is transplanted subcutaneously into the flank of a nude mouse by using a trocar needle. Treatment (four or five mice in each experimental group) with the drugs is started after the tumors are confirmed to have grown in the body (tumor size, 20-100 mm³). Entinostat is administered orally once daily 5 days per week for 4 weeks. Tumor length and width are monitored twice weekly, and tumor volume is calculated.
Rats^[4]
Male Lewis rats (8-10 weeks, 170-200 g) are housed under a 12-h light/dark cycle with free access to food and water. For therapeutic treatment, EAN rats receive i.p. injection of MS-275 (3.5 mg/kg) daily from day 10 to day 14 (six rats/group). For injection, MS-275 is suspended in phosphate buffered saline (PBS) and the same volume (1 mL) of PBS is given to control rats.

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

• [1]. Lauffer BE, et al. Histone deacetylase (HDAC) inhibitor kinetic rate constants correlate with cellular histone acetylation but not transcription and cell viability. J Biol Chem. 2013 Sep 13;288(37):26926-43.  [Content Brief]

  [2]. Rosato RR, et al. The histone deacetylase inhibitor MS-275 promotes differentiation or apoptosis in human leukemia cells through a process regulated by generation of reactive oxygen species and induction of p21CIP1/WAF1 1. Cancer Res. 2003 Jul 1;63(13):36  [Content Brief]

  [3]. Saito A, et al. A synthetic inhibitor of histone deacetylase, MS-27-275, with marked in vivo antitumor activity against human tumors. Proc Natl Acad Sci U S A, 1999, 96(8), 4592-4597.  [Content Brief]

  [4]. Zhang ZY, et al. MS-275, an histone deacetylase inhibitor, reduces the inflammatory reaction in rat experimental autoimmune neuritis. Neurosci, 2010, 169, 370-377.  [Content Brief]