Anginex synergizes with radiation therapy to inhibit tumor growth by radiosensitizing endothelial cells

Abstract

We have demonstrated that the designed peptide anginex displays potent antiangiogenic activity. The aim of our study was to investigate the effect of anginex on established tumor vasculature as an adjuvant to radiation therapy of solid tumors. In the MA148 human ovarian carcinoma athymic mouse model, anginex (10 mg/kg) in combination with a suboptimal dose of radiation (5 Gy once weekly for 4 weeks) caused tumors to regress to an impalpable state. In the more aggressive SCK murine mammary carcinoma model, combination of anginex and a single radiation dose of 25 Gy synergistically increased the delay in tumor growth compared to the tumor growth delay caused by either treatment alone. Immunohistochemical analysis also demonstrated significantly enhanced effects of combined treatment on tumor microvessel density and tumor or endothelial cell proliferation and viability. In assessing physiologic effects of anginex, we observed a reduction in tumor perfusion and tumor oxygenation in SCK tumors after 5-7 daily treatments with anginex with no reduction in blood pressure. To test anginex as a radiosensitizer, additional studies using SCK tumors were performed. Three daily i.p. injections of anginex were able to enhance the effect of 2 radiation doses of 10 Gy, resulting in 50% complete responses, whereas the known antiangiogenic agent angiostatin did not enhance the radiation response of SCK tumors. Mechanistically, it appears that anginex functions as an endothelial cell-specific radiosensitizer because anginex showed no effect on in vitro radiosensitivity of SCK or MA148 tumor cells, whereas anginex significantly enhanced the in vitro radiosensitivity of 2 endothelial cell types. This work supports the idea that the combination of the antiangiogenic agent anginex and radiation may lead to improved clinical outcome in treating cancer patients. ' 2005 Wiley-Liss, Inc.

Ovarian tumor growth regression using a combination of vascular targeting agents anginex or topomimetic 0118 and the chemotherapeutic irofulven

“…Here, we observed greater than additive effects using a lower dose of irofulven (1.5 mg/kg) in combination with anginex or its topomimetic 0118 [30]. The augmentation from the combination of these agents was hypothesized since irofulven is predominantly cytotoxic to MA148 cells ( Figure 1A), whereas anginex is specific for activated EC and shows no effect on tumor cell lines, such as human ovarian MA148 [23], murine breast carcinoma SCK [26,27], and human squamous cell carcinoma SCCVII [45]. The proliferation inhibition of MA148 cells by irofulven (IC 50 of 50 nM), falls within the range of irofulven activity against other cancer cell types [46].…”

“…Combination of irofulven and anginex resulted in tumor growth inhibition of 91% compared to controls, and was deemed to be synergistic (synergy ratio [26,35] of 1.5; see Table 1 in the Supplemental Data Section). In addition, mice treated with this combination demonstrated 20% (2/10) complete responses and 30% (3/10) partial responses, with 10% (1/10) of animals with stable disease, an improved profile as compared to either single agent therapy at the doses tested (Table 1).…”

“…Human umbilical vein derived EC (HUVEC) and MA148, a human epithelial ovarian carcinoma cell line were kindly provided by Prof. Dr. Ramakrishnan (University of Minnesota) [35] and cultured as described earlier [26,27,30].…”

“…To determine whether or not and the degree to which the combination of irofulven and anginex or 0118 had synergistic effects on tumor growth inhibition, the following formula was applied [26,35]: {(tumor growth inhibition from irofulven) x (tumor growth inhibition from anginex or 0118)}/observed tumor growth inhibition from combination treatment. A ratio of >1 indicates a synergistic (greater than additive) effect.…”

“…By weakly binding to 'carrier protein' plasma fibronectin [25], anginex is transported through the cardiovascular system to the tumor where the peptide strongly binds gal-1 (K d = 90 nM) [9]. We have previously demonstrated that this peptide can synergistically enhance the effects of radiotherapy of several solid tumor types, presumably due to the anti-angiogenic and tumor vascular damaging effects induced by anginex treatment [26], as well as the induction of vascular normalization and reoxygenation of tumor tissue before radiation exposure [27].…”