STAT3-mediated induction of ICOS gene expression. (A) Binding of STAT3 to the ICOS gene promoter in vitro detected by electromobility shift assay in the 2 depicted ALK⁺ TCL cell lines. (B) Binding of STAT3 to the endogenous ICOS gene promoter in vivo detected by chromatin immunoprecipitation. (C) Impact of siRNA-mediated depletion of STAT3 on ICOS gene promoter activity detected by the luciferase gene reporter assay. (D) Kinetics of STAT3 siRNA-mediated inhibition of ICOS mRNA expression detected by a genome-scale DNA oligonucleotide array. The results are depicted as fold increase in miR-21 mRNA expression in the STAT3 siRNA-treated compared with the control, non-sense siRNA (NS siRNA)–treated cells. (E) STAT3 siRNA depletion-induced decrease in ICOS mRNA expression detected by quantitative RT-PCR.