Regulation of TARC by vorinostat. (A) Vorinostat inhibits TARC mRNA expression in HL cell lines. Cells were incubated with increasing concentrations of vorinostat for 24 hours before TARC mRNA levels were determined by RT-PCR as detailed in Methods section. Each value represents a mean of 3 independent experiments done in triplicate (± SEM). (B) Vorinostat decreased TARC secretion in L-428 and KM-H2. Cells were incubated with vorinostat 2 μM for 24 to 48 hours before TARC levels were determined in the supernatants by ELISA. Each value represents a mean of 3 independent experiments done in triplicate (± SEM). (C) Silencing STAT6 by siRNA decreases TARC secretion in the L-428 cells. Cells were transfected with STAT6 siRNA or control siRNA for 12 to 72 hours. At each time point, culture supernatants were collected and TARC levels were determined by ELISA. Each value represents a mean of 3 independent experiments done in triplicate (± SEM). (D) Vorinostat inhibits TARC secretion from DCs collected from 2 healthy donors and activated with TSLP (100 ng/mL). TARC levels were determined in DC supernatants after 24 hours in culture by ELISA. The right and left panels represent 2 independent experiments using DCs from 2 healthy donors.