Assay Method Information

Assay Name:  Cell-Based (HeLa) Assay for Measurement of IDO1 Inhibition
Description:  To measure IDO1 inhibition in tissue culture, HeLa cells were treated with a test compound in the presence of IFNγ, which induces IDO1 expression. Following incubation, cell supernatants were assayed for kynurenine levels, an indicator of IDO1 activity.H1-HeLa cells (ATCC #CRL-1958) were seeded in 384-well plates (Greiner #82051-282) at a volume of 50 μL/well in DMEM (Corning #15-018-CM) supplemented with 10% FBS (Corning #35-011-CV) and 1% P/S/G (Corning #30-009-CL) at a density of 1,250 cells/well and incubated overnight at 37° C., 5% CO2/100% humidity. The following day, the test compounds were added in DMSO (0.5% final) at various concentrations, and IDO1 was inducibly expressed by the addition of 50 uL/well of 50 ng/mL of INFγ (Peprotech #300-02) in cell plating media. As a positive control, 50 uL of the cell plating media without IFNγ was added to several wells. Following a 48 hour incubation, the plates were spun down at 1,200 RPM for 5 min at 10° C. 65 μL/well of the supernatant was then transferred to new 384-well plates (Thermo #262160) that contained 10 uL/well of 30% TCA (Sigma #TO699), and the plates were sealed and incubated at 60° C. for 30 min. The plates were then centrifuged for 15 min at 2,000 RPM at 10° C. 40 μL/well of the supernatant was transferred to new 384-well plates (Thermo #262160) and was reacted with 40 μL/well of 2% (w/v) p-dimethlyaminobenzaldehyde (Sigma #156417) in glacial acetic acid (Sigma #A6283). The reaction was incubated at room temperature for 10 min and absorbance at 480 nm was read using a PerkinElmer Envision plate reader.
Affinity data for this assay
 

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