Validation of the FADD Kinase Reporter (FKR). (A) UMSCC1 FKR stable cells were transfected with siRNA targeting CK1α, FIST/HIPK3 or non-silencing siRNA (NSS). Bioluminescence was measured after 48 hours of transfection. Cell lysates were prepared and analyzed by western blotting using antibodies specific for FADD, phospho-FADD, CK1α, FIST/HIPK3 or actin as a loading control. (B, C) UMSCC1 FKR (WT and Mutant) stable cells were treated with 50 μM JNK inhibitor (SP600125) and 250 μM CKI-7 inhibitor. Bioluminescence activity was measured at the indicated time points. Cell lysates were prepared and analyzed by western blotting using the indicated antibodies. (D) UMSCC1 FKR stable cells were treated with 50 μM JNK inhibitor (SP600125). Bioluminescence activity was measured after 12 hours of treatment. Cells were lysed and cell lysates were precipitated with luciferase (Luc) antibody. The products were analyzed by p-Serine and Luc immunoblot analysis.