Biochemical Assay: The FASN enzyme was isolated from SKBr3 cells. SKBr3 is a human breast cancer cell-line with high levels of FASN expression. It is estimated that FASN comprises about 25% of the cytosolic proteins in this cell line. SKBr3 cells were homogenized in a dounce homogenizer then centrifuged for 15 minutes at 4C. to remove particulate matter. The supernatant was then analyzed for protein content, diluted to the appropriate concentration, and used to measure FASN activity. The presence of FASN was confirmed by western blot analysis. A similar method for isolation of FASN from SKBr3 cells is described in Teresa, P. et al. (Clin. Cancer Res. 2009; 15(24), 7608-7615).FASN activity of the SKBr3 cell extract was determined by measuring either NADPH oxidation or the amount of thiol-containing coenzyme A (CoA) released during the fatty acid synthase reaction. The dye CPM (7-diethylamino-3-(4â-maleimidyl-phenyl)-4-methylcoumarin) contains a thiol reactive group that increases its fluorescence emission.
Biological Assay: Assay #1:Inhibition of FAS activity can be measured based on the detection of residual NADPH substrate after the FAS assay is quenched. This assay is run as a 10 uL endpoint assay in 384-well format, where the reaction contains 20 uM malonyl-CoA, 2 uM acetyl-CoA, 30 uM NADPH and 40 nM FAS in 50 mM sodium phosphate, pH 7.0. The assay is run by sequentially dispensing 5 ul of a malonyl-CoA solution, then enzyme solution (containing the acetyl-CoA, and NADPH) into a black, low volume assay plate (Greiner 784076) pre-dispensed with 100 nL compound solutions in DMSO. The reaction is incubated at ambient temperature for 60 minutes, then quenched with 5 uL of a developing solution composed of 90 uM resazurin, 0.3 IU/ml diaphorase in 50 mM sodium phosphate, pH 7.0. The developed reaction is read on a Molecular Devices Analyst or Acquest (or equivalent) plate reader using a 530 nm excitation wavelength filter, a 580 nm emission filter, and 561 nm dichroic filter.
Inhibition of purified recombinant FASN TE activity (unknown origin) using 4-MUH as substrate preincubated for 30 mins before substrate addition measured after 1 hr by fluorescence assay
Inhibition of FASN in human PANC1 cells assessed as inhibition of [14C]acetate incorporation preincubated for 4 hrs before [14C]acetate addition measured after 2 hrs by scintillation counting