Fig. 6: HNSCC-associated caspase-8 mutants exhibit differential capacities to mediate induction of IL-8, IL-6, and CXCL1.

HeLa-CASP8 KO cells engineered for DOX-inducible expression of WT caspase-8, MT caspase-8 proteins, or LacZ, were pre-treated with DOX, followed by treatment for an additional 6 h with DOX plus varying concentrations of TRAIL. RNA was then harvested and qPCR was performed for IL-8 (A), IL-6 (B), and CXCL1 (C) mRNA levels. Data were plotted as the fold induction relative to no TRAIL. Columns represent the means from triplicate wells; error bars represent the SEM. Black rectangles outline WT or MT caspase-8 proteins that mediated twofold or greater induction. Student’s t test was performed on samples exhibiting twofold or greater induction. Experiments were performed three times with similar results. D PE/CA-PJ49-CASP8 KO cells engineered for DOX-inducible expression of WT caspase-8 or MT caspase-8 (D303G) were pre-treated with DOX, followed by treatment for 6 h with DOX plus vehicle or DOX plus TRAIL (200 ng/mL). Cell supernatants were harvested and ELISA assays were used to determine levels of secreted IL-8 protein. Columns represent the means from three independent experiments; error bars represent the SEM. Student’s t test was performed to compare groups treated with or without TRAIL.