Overproduction of biologically active TNF-α by FA-C cells. (A) TNF-α accumulation in the supernatant of normal cells (HSC93), and FA-C (HSC536) and its derived cell lines, HSC536Neo and HSC536Corr. HSC536 cells were transfected with an empty vector (HSC536Neo) or with a vector bearing the wild-type FANCC cDNA (HSC536Corr). Cells were collected by centrifugation, washed, and resuspended in fresh medium (3 × 10⁵ cells/mL/well in 3 mL medium in 6-well tissue culture plates). Supernatants were collected 24 hours and 48 hours after subculturing. The level of TNF-α in supernatants was determined by ELISA. Data presented are the mean (± SD) of at least 5 independent experiments. *P < .01. (B) Luciferase activity in 293T/NF-κB-Luc cells cultured in conditioned medium from lymphoblasts. 293T/NF-κB-Luc cells were plated (10⁶ cells/well in 6-well tissue culture plates) 48 hours before treatment with supernatant collected from 48-hours-old lymphoblasts cultures. One volume of supernatant, equivalent to 10⁶ lymphoblasts, was added per well of 293T/NF-κB-Luc cells. Cells were harvested 24 hours after treatment for luciferase measurement. Luciferase activity of 293T/NF-κB-Luc cells cultured in supernatant from HSC536Corr cells was considered equal to 1 in each experiment. Data presented are the mean (± SD) of at least 3 independent experiments done in triplicate. *P < .05.