PF-06840003

HeLa cells were harvested from cell culture flasks using 0.25% trypsin/EDTA and neutralized with EMEM growth medium. Following resuspension in fresh growth media, cells were seeded at 20,000 cells per well in 200 μL growth media in a 96-well plate and allowed to adhere at 37 °C at 5% CO2 overnight. The following day, growth media was aspirated and replaced with 200 μL of reduced (2%) serum media containing 100 ng/mL recombinant human interferon gamma (rhIFNγ) and incubated at 37 °C with 5% CO2 for 48 h to induce IDO-1 expression. On day four, compounds were diluted to 10 mM in DMSO and 11-point three-fold dilutions were prepared. rhIFNγ-containing media was removed, and following dilution into EMEM, compounds were added to cells at 50 μM top concentration and allowed to incubate 16−24 h at 37 °C with 5% CO2. On day five of the assay, 100 μL of cell supernatant was transferred to a v-bottom 96-well plate. Thirty microliters of 30% trichloroacetic acid (TCA) was added to each well to precipitate proteins, and plates were centrifuged at 3000 rpm for 10 min. One hundred microliters was transferred to a fresh flat-bottom 96-well plate, and 100 μL/well of 2% 4-(dimethylamino)benzaldehyde (pDMAB) in acetic acid was added to derivatize N-formyl kynurenine to kynurenine for quantitative colorimetric readout. Assay plates were read at A492 on Envision plate reader.