Formylpeptide receptor FPR and the rapid growth of malignant human gliomas.
BACKGROUND
The formylpeptide receptor (FPR) is a G-protein-coupled receptor (GPCR) that mediates chemotaxis of phagocytic leukocytes induced by bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLF). We previously showed that selected human glioma cell lines also express functional FPR. We therefore investigated the relationship between FPR expression and the biologic behavior of glioma cells.


METHODS
Expression and function of FPR in the human glioblastoma cell line U-87 were examined by reverse transcription-polymerase chain reaction (RT-PCR) and chemotaxis assays, respectively. FPR protein expression was detected in specimens from 33 human primary gliomas by immunohistochemistry. FPR short interfering (si) RNA was used to block FPR expression in U-87 cells. Cell proliferation was assessed by measuring DNA synthesis. Xenograft tumor formation and growth were measured in nude mice. Endogenous FPR agonist activity released by necrotic tumor cells was assessed by measuring FPR activation in an FPR-transfected basophil leukemia cell line and live U-87 cells. Vascular endothelial growth factor (VEGF) mRNA was assessed by RT-PCR, and VEGF protein was assessed by enzyme-linked immunosorbent assay. All statistical tests were two-sided.


RESULTS
FPR was selectively expressed by the highly malignant human glioblastoma cell line U-87 and most primary grade IV glioblastomas multiforme and grade III anaplastic astrocytomas. U-87 cells responded to the FPR agonist fMLF by chemotaxis (i.e., increased motility), increased cell proliferation, and increased production of VEGF protein. FPR siRNA substantially reduced the tumorigenicity of U-87 cells in nude mice (38 days after implantation, mean tumor volume from wild-type U-87 cells = 842 mm3, 95% confidence interval [CI] = 721 to 963 mm3; and from FPR-siRNA transfected U-87 cells = 225 mm3, 95% CI = 194 to 256 mm3; P = .001). Necrotic glioblastoma cells released a factor(s) that activated FPR in live U-87 cells.


CONCLUSIONS
FPR is expressed by highly malignant human glioma cells and appears to mediate motility, growth, and angiogenesis of human glioblastoma by interacting with host-derived agonists. Thus, FPR may represent a molecular target for the development of novel antiglioma therapeutics.
Zhou
Ye
Y
Laboratory of Molecular Immunoregulation, CCR, NCI-Frederick, Building 560, Room 31-40, Frederick, MD 21702-1201, USA.
Bian
Xiuwu
X
Le
Yingying
Y
Gong
Wanghua
W
Hu
Jinyue
J
Zhang
Xia
X
Wang
Lihua
L
Iribarren
Pablo
P
Salcedo
Rosalba
R
Howard
O M Zack
OM
Farrar
William
W
Wang
Ji Ming
JM
D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002633:Chemotaxis; D024202:Electrophoretic Mobility Shift Assay; D004797:Enzyme-Linked Immunosorbent Assay; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D034741:RNA, Small Interfering; D044042:Receptors, Formyl Peptide / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014183:Transplantation, Heterologous; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis
D034741:RNA, Small Interfering; D044042:Receptors, Formyl Peptide; D042461:Vascular Endothelial Growth Factor A