DETERMINING THE EFFECTS OF PRO‐ANGIOGENIC ELP‐VEGF THERAPY ON TUMOR GROWTH AND PROGRESSION

Abstract

The members of the Vascular Endothelial Growth Factor (VEGF) family are endogenous growth factors with a central role in angiogenesis and endothelial cell health. We recently showed the therapeutic potential of renal VEGF delivery using a fusion protein of VEGF bound to the carrier protein Elastin‐like Polypeptide (ELP‐VEGF) designed in our laboratory, to promote angiogenesis in chronic kidney diseases. Indeed, we showed that ELP‐VEGF therapy improves renal vascular density, decreased renal fibrosis, and improved glomerular filtration rate (GFR) in swine models of chronic renovascular disease and chronic kidney disease at therapeutic doses of 0.1 – 1.0 mg/kg.A potential limitation of the use of ELP‐VEGF as a therapeutic is the possibility of promoting uninhibited off‐target angiogenic growth which may be undesirable in certain disease processes such as cancer. In order to determine whether ELP‐VEGF therapy may be harmful for a patient with an undiagnosed tumor, the effects of a single administration of escalating doses (0.1 m/kg, 1 mg/kg, 10 mg/kg, 10 times the highest therapeutic dose) of ELP‐VEGF on tumor size and vascular density were determined in a mouse xenograft model of breast cancer.Human triple‐negative breast cancer cells (MDA‐MB‐231) that stably express a luciferase reporter were implanted into the mammary fat pad of athymic nude mice. Tumors were monitored thrice weekly for 7 weeks with external caliper measurements (blind) and bioluminescence imaging to assess tumor growth. Body weights of the mice were also recorded 3 times per week. At the end of the 7‐week period, mice were fully perfused with heparinized saline and microfil. Tumors were removed and scanned using micro‐computed tomography (u‐CT), and 3D reconstructions of the tumor vascular network were used to blindly quantify tumor vascular density.Caliper measurements and bioluminescence imaging showed no significant difference in tumor size or growth rate amongst the groups. There were also no significance differences in mouse body weights throughout the study or final weights of the tumors (0.1–10mg/kg 1.12±0.39 g, 1.233±0.46 g, 1.247±0.52 g, respectively; p=0.8695). However, analysis of the renal vasculature by u‐CT revealed a significant increase in total microvascular density after a single injection of ELP‐VEGF at 1mg/kg (78.88 ± 34.34 vessels/mm2; p = 0.0489 vs. controls) and 10mg/kg (97.17 ± 48.65 vessels/mm2; p = 0.0012 vs. controls). In conclusion, we determined that one‐time injection of ELP‐VEGF had no toxic effects on body weights and did not influence tumor growth rate, but it did significantly and dose‐dependently increase tumor vasculature density in a breast cancer xenograft model.Support or Funding InformationR01HL095638 and IPA34170267Figure 2. Analysis and results from ELP‐VEGF‐A administration to a rodent model of breast cancer. Results include body weight (a), tumor caliper measurements (b) tumor bioluminescence (c), final tumor mass(d).Figure 1Figure 3. Vasculature of each tumor was visualized using uCT scanner after microfi fixation. Blood vessels were divided and quantified by diameter between different ranges (a). Kidneys from these mice were also perfused with microfil, scanned through uCT scanner, and quantified by vessel diameter range (b).Figure 2