GLI2 Transcription Factor Mediates Cytokine Cross-talk in the Tumor Microenvironment

Abstract

Tumor cells interact with their surrounding microenvironment to survive and persist within the host. Cytokines play a key role in regulating this crosstalk between malignant cells and surrounding cells in the microenvironment. Although this phenomenon is clearly established, the molecular mechanisms mediating this cellular event remain elusive. Here, using as a model bone marrow stromal cells, we describe a novel signaling mechanism initiated by CCL5 in these cells leading to up-regulation of immunoglobulin secretion by malignant B cells. CCL5 increases IL-6 expression and secretion in bone marrow stromal cells. IL-6 in turn induces Ig secretion by malignant B cells. Analysis of the mechanism reveals that CCL5 signaling induces GLI2 through a PI3K-AKT-IB␣-p65 pathway and requires GLI2 transcriptional activity to modulate IL-6 expression and Ig secretion in vitro and in vivo. Together, these results identify a novel signaling pathway mediating the stromal-cancer cell interactions, leading to increased Ig production by malignant cells.

Activation of the Transcription Factor GLI1 by WNT Signaling Underlies the Role of SULFATASE 2 as a Regulator of Tissue Regeneration

“…Control siRNA (sc-37007) and siRNA targeting ␤-CATENIN (sc-44253) were from Santa Cruz Biotechnology. Constructs expressing NT sequences or shRNA targeting GLI1 were previously described (20). TOPFLASH (TCF binding site TK-luciferase reporter) plasmids were obtained from Dr. Wanguo Liu as previously described (11,21).…”

“…The GLI-luciferase reporter was kindly provided by Dr. Chi-chung Hui (University of Toronto, Toronto, Ontario, Canada), and the sleeping beauty and parental transposon vectors were provided by Dr. Karl Clark (Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN). The GLI1-containing transposon construct was cloned into the pKT2C-mC vector using standard recombinant DNA methodology (20). For the chromatin immunoprecipitation (ChIP) assay, the EZ-Magna ChIP G kit (17-409, Millipore, Billerica, MA) was used.…”

“…The medium was changed daily. Four hours after the isolation of hepatocytes, the medium was changed, and cells were either transfected with control siRNA, siRNA targeting ␤-CATENIN or vectors expressing either non-targeting (NT) shRNA or shRNA targeting GLI1 (11,20). Transfection of isolated mouse hepatocytes was performed using Fugene 6 transfection reagent (Roche Diagnostics GmbH, Mannheim, Germany) following the manufacturer's protocol.…”

“…WT MEFs were a gift from Dr. John Hawse (Mayo Clinic, Rochester, MN) and were cultured in DMEM supplemented with 10% FBS. AML12 and HepG2 cell lines were obtained from American Type Culture Collection (ATCC) (Manassas, VA) and cultured as previously described (11,20).…”

Nuclear Factor of Activated T Cells-dependent Down-regulation of the Transcription Factor Glioma-associated Protein 1 (GLI1) Underlies the Growth Inhibitory Properties of Arachidonic Acid

“…Expression and shRNA Constructs, siRNAs, and Transfection-Expression vectors for NFATc1 and the shRNA constructs were described previously in Elsawa et al (33) and Köenig et al (34). GLI1 expression construct and siRNA targeting GLI1 were described previously (35).…”