The G-protein-coupled formylpeptide receptor FPR confers a more invasive phenotype on human glioblastoma cells

Abstract

BACKGROUND: The G-protein-coupled formylpeptide receptor (FPR) that mediates chemotaxis of phagocytic leucocytes induced by bacterial and host-derived chemotactic peptides is selectively expressed by highly malignant human gliomas and contributes to tumour growth and angiogenesis. As invasion of surrounding normal tissues is one of the important features of tumour malignancy, we investigated the function of FPR in the invasive behaviour of human glioblastoma cells. METHODS: Cells (FPR þ and FPR À ) were isolated by single-cell cloning from a human glioblastoma cell line U-87MG. The FPR expression was assayed by flow cytometry and reverse transcription PCR. The function of FPR was investigated by chemotaxis and calcium flux induced by FPR agonist fMLF. Tumour cell motility was assayed by a wound-healing model in vitro. The growth and invasive phenotype were observed with subcutaneous implantation of tumour cells in nude mice. Over-expression of FPR in FPR À cells was performed by transfection of a plasmid vector-containing human FPR gene. RESULTS: One of the glioma clones F9 that expressed high level of FPR showed a more 'motile' phenotype in vitro as compared with a clone G3 without FPR expression. Although F9 and G3 clones both formed subcutaneous tumours in nude mice, only F9 tumours invaded surrounding mouse connective tissues. Over-expression of FPR in G3 clone (G3F) increased the cell motility in vitro and the capacity of the cells to form more rapidly growing and invasive tumours in nude mice. We further found that, in addition to supernatant of necrotic tumour cells, foetal calf serum and human serum used in culture media contained FPR agonist activity and increased the motility of FPR-expressing glioblastoma cells. CONCLUSION: The expression of FPR is responsible for increased motility of human glioblastoma cells and their formation of highly invasive tumours.

The Leukocyte Chemotactic Receptor FPR1 Is Functionally Expressed on Human Lens Epithelial Cells

“…The significance of our study is that to our knowledge it provides the first example of a non-hematopoietic setting for FPR1 expression linked directly to a biological phenotype in vivo, namely severe degeneration of lens structure in aging Fpr1 Ϫ/Ϫ mice. 4 Our characterization of the human FPR1 in human lens epithelial cells suggests that this property of Fpr1 may also be relevant to humans. How FPR1 functions to maintain the lens is not yet known.…”

“…work is consistent with a direct role in the lens for FPR1 in lens homeostasis, as evidenced by aging Fpr1 Ϫ/Ϫ mice, which develop severe cataracts. 4 At first glance the evidence for functional expression of the receptor in this cell line appears straightforward and consistent. 1) Full-length FPR1 mRNA was amplified and sequenced by PCR using specific primers and knocked down using specific siand shRNAs.…”

“…The biological significance of FPR1 expression on these cells is suggested by the phenotype of severe cataracts in aging Fpr1 Ϫ/Ϫ mice. 4 Thus FPR1 appears to have an important biological role in innate immunity through its expression on phagocytic leukocytes and in development through expression directly in the lens.…”

“…4 The mechanism may involve Fpr1 function directly on lens epithelial cells, as they express Fpr1 mRNA and are the only cell type in the lens. However, mouse lens epithelial cell lines are not available, and it is not feasible to obtain sufficient primary mouse lens cells for biochemical analysis.…”

Oligomer procyanidins (F2) isolated from grape seeds inhibits tumor angiogenesis and cell invasion by targeting HIF-1α in vitro

“…We also found that F2 could significantly inhibit the migration and invasion of fMLF (a FPR1 agonist)-induced U87 cells due to its partial agonist action on formyl peptide receptor 1 (FPR1) (10). FPR1 is a membrane receptor overexpressed in U87 cells, regulates the cell growth, survival, migration and invasion (11,12). Moreover, an in vivo study showed that repeated administration of F2 to mice had no adverse effects (13).…”