Figure 2. Ang2 is an attractant signal for TEMs in vitro and in vivo.

(A) THP-1 monocytic cells were exposed to IL-4, IL-13, and hypoxia and sorted as Tie2⁻ and Tie2^high+ (left panel). Their migratory properties towards Ang2 or vehicle (BSA) were measured using a modified Boyden chamber as depicted (right panel). (B) Data from experiment described in (A) are presented as relative mean ± SD number of migrating THP-1 cells per microscopic field (200x). ns, P > 0.05; **P < 0.01. (C) Quantification of gelatinolytic activity present in conditioned medium, containing Ang2 or vehicle, of sorted CD14⁺Tie2⁻ and CD14⁺Tie2^high+ cells. Data are presented as mean ± SD. au, arbitrary units. *P < 0.05; ***P < 0.001. (D) Brains of athymic mice bearing intracranial U87MG-derived tumors, treated with intratumoral delivery of an adenoviral vector expressing Ang2 (AdAng2) or a control vector (AdCMV), were analyzed for Iba1 (green) and Tie2 (red) expression. DAPI was used for nuclear staining (blue). White arrows indicate the presence of Iba1⁺Tie2⁺ cells. Scale bars = 20 μm. (E) Quantification of TEMs, defined as Iba1⁺Tie2⁺ cells, in surgical U87MG-derived xenografts treated intratumorally with AdCMV or AdAng2. Data are presented as mean ± SD. HPF, high-power field. **P < 0.01.