Article Figures & Data
Figures
- FIGURE 1.
SK-NEP-1 xenografts are initially inhibited but resume growth during prolonged administration of anti-VEGF antibody, “metronome” topotecan, or combined agents. Cultured human SK-NEP-1 Wilms' tumor cells (106) were implanted intrarenally in athymic mice (n = 60). Animals were divided into four cohorts receiving MAbs, “metronome” topotecan, combined agents, or control vehicle beginning 1 week after implantation. Mice were monitored biweekly with calipers and euthanized when tumors reached 1.5 cm in greatest dimension. Tumor growth was delayed but not abolished by MAbs or topotecan administration, emerging at ∼60 days after tumor implantation. Growth in combination-treated tumors was also detected although in a more delayed fashion.
- FIGURE 2.
Remodeling of endothelial and vascular MC compartments marks the tumors growing during antiangiogenic therapy. Xenografts, which grew during topotecan, MAbs, or MAbs + topotecan administration, displayed sparse but strikingly remodeled vasculature with irregular, large-caliber lumens and multiple layers of adhering vascular MC (most markedly in MAbs and MAbs + topotecan-treated tumors) in comparison with controls. Size bar = 200 μm.
- FIGURE 3.
Diameters of remodeled vessels increased significantly in the tumors growing during antiangiogenic therapy. Mean diameters, measured using fluorescent immunostaining for αSMA, increased significantly in treated xenografts versus controls: 68% in topotecan, 97% in MAbs, and 96% in MAbs + topotecan tumors. Columns, mean diameter (μm); bars, SEM.
- FIGURE 4.
Proliferation of vascular MC in vessels of tumors recurring during antiangiogenic treatment. Double-label immunostaining, indicated by yellow areas (arrows) where αSMA (green fluorescent signal) and the proliferation marker phosphohistone H3 (red fluorescent signal) coincide, demonstrates active proliferation in the MC of a vessel supplying a tumor that resumed growth during anti-VEGF blockade. Cross section of MAbs tumor (A) and longitudinal view of vessels in combination-treated tumor (B) demonstrating thick layer of vascular MC with frequent proliferating nuclei. In comparison, surviving vessels in tumors inhibited by VEGF antagonism at 6 weeks were quiescent (data not shown). Size bar = 50 μm.
- FIGURE 5.
Expression of VEGF at the periphery of viable tumor islands contrasts with central expression of VEGFR2. Control tumors express all proangiogenic cytokines at the growing, well-vascularized periphery. Tumors that recur during antiangiogenesis grow as viable clusters or islands around vessels. The peripheral expression of VEGF indicates that the centers of these islands are relatively normoxic; the localization of VEGFR2 indicates the presence of central vessels, which presumably provide perfusion to the viable area of tissue. Size bar = 400 μm.
- FIGURE 6.
Expression of PDGFB, PDGFRβ, and EFNB2 are expressed in remodeled vessels of tumor growing during antiangiogenesis. In contrast, expression of PDGFB and PDGFRβ appear at the periphery of control tumors. Controls express markers of both venous and arterial specification (EPHB4 and the gene for ephrinB2, EFNB2), whereas EFNB2 was detected in remodeled vessels of treated tumors. Size bar = 400 μm.
- FIGURE 7.
Vascular remodeling results from altered expression of angiogenic cytokines during chronic suppression of angiogenesis. A. In control tumors, expression of VEGF supports sprouting of new vessel branches, which perfuse growing areas of tumor. PDGFB and VEGF cooperate to recruit MC to endothelial vessels. EphrinB2 and EphB4 are diffusely expressed, consistent with widespread arterial and venous specification in control vessels. B. When angiogenesis is chronically blocked, PDGFB expression by surviving vessels increases, which enhances endothelial stability and recruitment of MC. Vessel diameter increases significantly. Tumors resume growth, forming viable layers circumferential to vessels. Vascular expression of EphrinB2 increases, whereas EphB4 expression is relatively less, suggesting that EphrinB2 plays a role in stabilization or remodeling of these vessels.
Volume 2, Issue 1
