Stimulation of angiostatic platelet factor-4 variant (CXCL4L1/PF-4var) versus inhibition of angiogenic granulocyte chemotactic protein-2 (CXCL6/GCP-2) in normal and tumoral mesenchymal cells

Abstract

Chemokines affect inflammation and cancer through leukocyte attraction and angiogenesis. Here, we demonstrate that CXCL4L1/platelet factor-4 variant (PF-4var), a highly angiostatic chemokine, is poorly chemotactic for phagocytes and is inducible in monocytes by inflammatory mediators but remained undetectable in macrophages and neutrophils. In addition, CXCL4L1/PF-4var production by mesenchymal tumor cells was evidenced in vitro and in vivo by specific ELISA and immunohistochemistry. CXCL4L1/PF-4var, but not CXCL4/PF-4, was coinduced with the angiogenic chemokine CXCL6/granulocyte chemotactic protein-2 (GCP-2) by cytokines, e.g., IL-1beta and IL-17, in sarcoma cells, but not in diploid fibroblasts. Furthermore, the induction of CXCL6/GCP-2 in endothelial cells by IL-1beta was enhanced synergistically by TNF-alpha but inhibited by IFN-gamma, which synergized with IL-1beta to produce the angiostatic CXCL10/IFN-gamma-induced protein-10. These findings indicate that the equilibrium between angiostatic and angiogenic factors during inflammation and tumor progression is rather complex and differs depending on the chemokine, cell type, and stimulus. Selective intervention in the chemokine network may drastically disturb this delicate balance of angiogenesis and tissue repair. Application of angiostatic CXCL4L1/PF-4var without attraction of protumoral phagocytes may be beneficial in cancer therapy.

The COOH-Terminal Peptide of Platelet Factor-4 Variant (CXCL4L1/PF-4var47-70) Strongly Inhibits Angiogenesis and Suppresses B16 Melanoma Growth In vivo

“…2D), indicating a stronger angiostatic activity of CXCL4L1/PF-4var 47-70 compared with CXCL4/PF-4 . For comparison, inhibition of endothelial cell migration was obtained at 20 nmol/L CXCL4/PF-4 or 1 nmol/L CXCL4L1/PF-4var, confirming previously published data (18,19). This allowed us to conclude that CXCL4L1/PF-4var is equally angiostatic as the intact chemokine.…”

“…As a control, CXCL4/PF-4 and CXCL4L1/PF-4var were also tested in this assay. The results confirm that CXCL4L1/PF-4var inhibits endothelial cell migration at 1 nmol/L, being therefore a 20-fold more potent inhibitor than CXCL4/PF-4 (18,19). Next, it was found that both PF-4 peptides (from 5 nmol/L onwards) significantly inhibited FGF-2-induced HUVEC motility as observed by time-lapse microscopy ( Fig.…”

“…We have previously shown that both CXCL4/PF-4 and CXCL4L1/PF-4var are unable to stimulate phagocyte migration in vitro (18). CXCL4/ PF-4 and CXCL4L1/PF-4var were now tested for their potential to chemoattract activated T cells in the microchamber chemotaxis assay.…”

“…Inhibition of endothelial cell migration in vitro has previously been described in detail (18). Briefly, confluent monolayers of mitomycin C-treated HMVEC were wounded with a plastic pipette tip and repair was monitored microscopically after a 24-h treatment with natural human CXCL4/PF-4, recombinant human CXCL4L1/ PF-4var, synthetic CXCL4/PF-4 , or CXCL4L1/PF4var in culture medium [i.e., EBM-2 medium supplemented with the EGM-2MV Bullet kit containing FCS, ascorbic acid, hydrocortisone, fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), insulin-like growth factor I, and epidermal growth factor].…”

“…The variant of CXCL4/PF-4, encoded by a second nonallelic gene and differing in only three amino acids, is named CXCL4L1/PF-4var (15,16) and was isolated from thrombin-stimulated platelets (17). In a previous study, we showed that CXCL4L1/PF4var is also produced by osteosarcoma cells (18). CXCL4L1/PF-4var was found to be a more potent angiostatic and antitumoral chemokine than CXCL4/PF-4 in different in vitro assays and in vivo models (17,19).…”