Plasmid-based DLX4 overexpression and knockdown

The pIRES-EGFP2 plasmid encoding FLAG-tagged DLX4 has been previously described [25 (link)]. The DLX4 cDNA was subcloned into the pRetroQ-AcGFP retroviral vector (Clontech). Other plasmids were as follows: pGFP-V-RS plasmids containing non-targeting and DLX4 shRNAs (OriGene Technologies), pGIPZ plasmids containing NOS2 shRNAs (GE Healthcare), eGFP-STAT1 (provided by Alan Perantoni, National Cancer Institute, Frederick, MD; Addgene plasmid 12301) [48 (link)], pRc/CMV-Flag STAT1α Y701F [28 (link)] (provided by James Darnell, Rockefeller University, New York, NY; Addgene plasmid 8702). A firefly luciferase reporter construct driven by tandem GAS elements was purchased from SABiosciences.