Induction of VEGFR-3 expression during tumor-induced angiogenesis.

Immunostaining for VEGFR-3 (A) and PECAM-1 (B) in adjacent sections of C6 subcutaneous tumors (day 7) in nude mice (×200). Intratumoral VEGFR-3⁺ (A, arrows) containing blood cells are also positive for PECAM-1 expression (B, arrows). Note that hemorrhages are not conspicuous at this stage. (C) Immunostaining for VEGFR-3 in a section of C6 tumors with surrounding tissues (×100). Note the presence of VEGFR-3⁺ (black arrows) and VEGFR-3⁻(white arrows) vessels, both containing hematopoietic cells. Arrowheads indicate VEGFR-3⁺ vessels that do not contain hematopoietic cells. Asterisk indicates the edge of a tumor.