Up-regulation of CXCR4 Expression in PC-3 Cells by Stromal- Derived Factor-1A (CXCL12) Increases Endothelial Adhesion and Transendothelial Migration: Role of MEK/ERK Signaling Pathway–Dependent NF-KB Activation

The chemokine stromal-derived factor-1A (SDF-1A/CXCL-12) and its receptor, CXCR4, play a crucial role in adhesion and transendothelium migration (TEM) of prostate cancer cells. We tested the hypothesis that enhanced expression of CXCR4 in prostate cancer cells is dependent upon SDF-1A-mediated activation of nuclear factor-KB (NF-KB). SDF-1A increased the CXCR4 mRNA and protein expression in PC-3 cells but not in LNCaP cells. Similarly, SDF-1A enhanced the NF-KBdependent transcriptional activity in PC-3 cells but not in LNCaP cells. SDF-1A increased PC-3 cell adhesion to the human umbilical vein endothelial cell monolayer and enhanced TEM, which was abrogated with anti-CXCR4 monoclonal antibody (mAb). Suppression of NF-KB activity in PC-3 cells by a mutant IKBA super-repressor adenoviral vector decreased the CXCR4 mRNA expression and inhibited adhesion and TEM. Transient overexpression of p65 subunit of NF-KB in PC-3 cells up-regulated CXCR4 receptor expression and increased the adhesion and TEM of these cells in response to SDF-1A gradient. Treatment of PC-3 cells with SDF-1A leads to nuclear translocation of NF-KB protein within 15 to 30 minutes, which correlated with IKBA phosphorylation. A p42/44 mitogen-activated protein kinase [MAPK, extracellular signal regulated kinase-1/2 (ERK-1/2)] biphasic activation pattern was observed in these cells at 15 minutes and 3 hours after SDF-1A treatment. Phosphorylation of IKB kinase A was observed within 30 minutes, which was blocked by PD98059 [MAPK kinase (MEK) inhibitor]. PD98059 cotreatment significantly inhibited SDF-1A-induced NF-KB reporter activity and CXCR4 receptor expression as shown by flow cytometry. These data suggest that SDF-1A-induced expression of CXCR4 in PC-3 cells is dependent on MEK/ERK signaling cascade and NF-KB activation. (Cancer Res 2005; 65(21): 9891-8)