Granulocyte colony-stimulating receptor promotes beta1-integrin-mediated adhesion and invasion of bladder cancer cells.
OBJECTIVE
To determine whether granulocyte colony-stimulating factor receptor (G-CSFR) autocrine signaling promotes endothelial cell adhesion and invasion of bladder cancer cells through a beta1-integrin-mediated pathway. A significant fraction of invasive bladder carcinomas express both G-CSF and G-CSFR. Bladder carcinoma cell line 5637 constitutively secretes G-CSF but lacks G-CSFR expression. Thus, we studied the effects of G-CSFR expression on cell adhesion and invasion in this unique model system.


METHODS
Flow cytometry and adhesion assay were performed to detect expression of beta1-integrin in G-CSFR-expressing 5637 cells and adhesion of these cells to human umbilical vein endothelial cell, respectively. Furthermore, an invasion chamber assay was done with the 5637 cells. Next, we used the G-CSF-specific antibody, siRNA, and a truncated version of G-CSFR (GR19) to block G-CSFR autocrine loop in these cells. We also used a beta1-integrin-specific neutralizing antibody in the adhesion and invasion assays with the 5637 cells.


RESULTS
G-CSFR-mediated increased expression (approximately threefold) of beta1-integrin is significantly abrogated by G-CSF specific antibody or siRNA in 5637 cells. GR19 also completely blocked beta1-integrin expression. G-CSFR signaling increased adhesion (approximately 2.5-fold) of 5637 cells to human umbilical vein endothelial cells, which are potently blocked by beta1-integrin-specific antibody. G-CSF/G-CSFR autocrine signaling significantly increased the invasiveness of 5637 cells (approximately 10-fold), which was reduced by either attenuating G-CSF production (G-CSF-specific antibody and siRNA) or interfering with G-CSFR signaling (GR19). Furthermore, beta1-integrin-specific antibody completely blocked G-CSFR-mediated invasion of 5637 cells.


CONCLUSIONS
Autocrine G-CSF/G-CSFR signaling in bladder cancer can significantly contribute to cancer cell adhesion and invasion in a beta1-integrin-dependent manner.
Chakraborty
Arup
A
Section of Leukocyte Biology, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA. arupc@bcm.tmc.edu
White
Scott M
SM
Guha
Sushovan
S
D000268:Adhesiveness; D019898:Autocrine Communication; D045744:Cell Line, Tumor; D004730:Endothelium, Vascular / Q000473:pathology; D005434:Flow Cytometry; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism / Q000502:physiology*; D009361:Neoplasm Invasiveness; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000502:physiology*; D015398:Signal Transduction; D001749:Urinary Bladder Neoplasms / Q000473:pathology / Q000503:physiopathology*
D019012:Integrin beta1; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D016179:Granulocyte Colony-Stimulating Factor