BRD4770, a histone methyltransferase G9a inhibitor, induces cell senescence.

When used in conjunction with cotinine, BRD4770 increases the levels of LC3-II and the number of autophagosomes, thereby synergistically inducing cell death in the PANC-1 pancreatic cancer cell line. In these cells, BRD4770 induces senescence and inhibits both adhesion-dependent and -independent proliferation by suppressing G9a, which leads to a reduction in the cellular levels of di- and trimethylated H3K9.

Biochemical activity of G9a: Dissociation Enhanced Lanthanide Fluoro-ImmunoAssays (DELFIA) are performed in white, opaque 384-well plates coated with Neutravidin. Test compounds are diluted to 12 μg/mL in 50 mM Tris-HCl pH 8.5 containing 4% DMSO and 10 μL is dispensed into the wells. Blank and control wells received only compound buffer. GST-G9a at 10 μg/mL and SAM at 40 μM are diluted in 50 mM Tris HCl pH 8.5/10 mM DTT and added in a volume of 20 μL. Blank wells receives Tris/DTT buffer only. The reactions are initiated by the addition of 800 nM H3(1-20)-cysbiotin substrate in 50 mM Tris pH 8.5 in a volume of 10 μl, and incubated at room temperature for 60 minutes. The plates are washed 3 times with 100 μl of Wash Buffer (50 mM Tris pH 7.4, 150 mM NaCl, 0.05% Tween 20, 0.2% BSA). Next, 50 μl of Fluoroimmunoassay (FI) Buffer (50 mM Tris HCl pH 7.8, 150 mM NaCl, 0.05% Tween 40, 25 μM DTPA, 0.2% BSA, 0.05% BGG) containing 5ng α-2X-di-meth H3-K9 and 5ng goat anti-rabbit Eu chelate is added to all wells of the plate, and the plate is incubated for an additional hour at room temperature. The plates are washed 3 times with 100 μL of Wash Buffer, and 50 μL of Enhancement Solution is added to each well. Time resolved fluorescence is measured after 45 minutes on a Viewlux Microplate Imager imaging for 15 seconds with a 354 μs window, 400 μs delay, excitation at 360 nm, and emission at 618 nm.

PANC-1 cells are seeded and treated with BRD4770 in 6-well plates for 72 h. Cells are trypsinized and tested for soft agar colony formation using CytoSelect 96-Well Cell Transformation Assay, using the CyQuant GR dye to measure total cellular nucleic acid levels. Fluorescence is detected with an Analyst HT plate reader using a 485/520 nm filter set.(Only for Reference)