Collagen IV and CXC chemokine-derived antiangiogenic peptides suppress glioma xenograft growth

Abstract

Peptides are receiving increasing attention as therapeutic agents due to their high binding specificity and versatility to be modified as targeting or carrier molecules. Particularly, peptides with antiangiogenic activity are of high interest because of their applicability to a wide range of cancers. In this study, we investigate the biological activity of two novel antiangiogenic peptides in preclinical glioma models. One peptide SP2000 is derived from collagen IV and the other peptide SP3019 belongs to the CXC family. We have previously characterized the capacity of SP2000 and SP3019 to inhibit multiple biological endpoints linked to angiogenesis in human endothelial cells in several assays. Here, we report additional studies using endothelial cells and focus on the activity of these peptides against human glioma cell growth, migration and adhesion in vitro, and growth as tumor xenografts in vivo. We found that SP2000 completely inhibits migration of the glioma cells at 50 µmol/l and SP3019 produced 50% inhibition at 100 µmol/l. Their relative antiadhesion activities were similar, with SP2000 and SP3019 generating 50% adhesion inhibition at 4.9 ± 0.82 and 21.3 ± 5.92 µmol/l, respectively. In-vivo glioma growth inhibition was 63% for SP2000 and 76% for SP3019 after 2 weeks of administration at daily doses of 10 and 20 mg/kg, respectively. The direct activity of these peptides against glioma cells in conjunction with their antiangiogenic activities warrants their further development as either stand-alone agents or in combination with standard cytotoxic or emerging targeted therapies in malignant brain tumors.

Figure 1. Proliferation activity

The activity of the peptides on U87 glioma cell proliferation. The cells were incubated in the presence of peptides and the % of live cells was calculated in comparison to cells incubated with media containing the solubility vehicle. Error bars depict STD

Figure 2

Migration activity. The inhibitory activity of the peptides on the migration of the glioma cells U87. Panel (A) illustrates the positive control (untreated cells); panels (B) through (D) depict the inhibition activity of the SP2000 at several concentrations, Panel (E) illustrates a typical background measurement (image of the well with the stopper removed immediately preceding the imaging) and panels (F) through (H) demonstrate the inhibitory activity of SP3019 peptide. Panel (I) illustrates the quantification of the images. The negative values are due to the subtraction of the background values which can vary significantly between the wells depending on the alignment of the stopper in the well. Error bars depict STD. * indicates statistical significance (p < 0.05) from the control.

Figure 3

Inhibition of adhesion. Panel (A) illustrates the inhibition activity on the adhesion of HUVEC and panel (B) demonstrates the activity of both peptides at inhibiting the adhesion of U87 glioma cells. Error bars depict STD.

Figure 4

Tube formation inhibition. Panel (A) illustrates the positive control, HUVEC cell on Matrigel in complete media without any peptide treatment; panel (B) the inhibition of tube formation with SP3019; and panel (C) with SP2000.

Figure 5

In vivo tumor xenograft inhibition. Tumor volume of subcutaneous glioma xenograft measured every third day. Squares depict the control group which received i.p. injection of the solubility vehicle (PBS), solid circle represents the tumor growth of the group treated with daily i.p. injections of SP2000 and the open circles of tumors treated with SP3019. Error bars depict STD.