A Novel Model
for Visualization of Tumor Cell-induced Angiogenesis in vivo
LI Ling, XU Ping, HU Hong-Hui1,
LIU Wen-Wen, YI Miao-Yin, LI Chuan-Yuan2, HUANG Qian*
( Central Experimental Laboratory,1Department of
Pathology, The First People’s Hospital of Shanghai, Shanghai 200080,
China; 2Department of Radiation Oncology, Duke University
Medical Center, Durham, NC 27710, USA )
Abstract The bladder
transitional cell carcinoma cell line,
BTT739 from the T739 mouse,
was transfected with a plasmid that encoded an enhanced green fluorescence
protein (GFP) and the cells stably expressing GFP were selected and subcloned.
1×103―1×104 GFP-labeled BTT739 cells were injected under
the skin of ear ofT739 mice. On day 2―5 post injection, the most interesting manifestations
observed were the chemotaxis-like movement of the tumor cells toward the
pre-existing host vasculature,
host vessel dilation and tortuosity and increased extravasation. On day
10 or later, the sprout from
pre-existing host vasculature was observed. Once angiogenesis was triggered
on, the tumor cells grew more
rapidly and exhibited a specific growth pattern where tumor cells always
associated with or surrounded the vessels. The newly formed microvessels always
showed heavy extravasation. Immunohistochemistry staining revealed strong VEGF
and VEGFR2 (Flk-1) expression in tumor cells. Angiography using Rhodamin-labeled
dextran showed neovascularization with unprecedented clarity. However, the tumor mass, even bigger than 2 mm and being
neovascularized, shrunk and then
disappear in 3―5 days and left only delicated host vessels and recovered
extravasation. The evidence from this observation indicated that angiogenesis
induced by tumor cells after implantation into the host begins at very early
stage. The micrometastases foci could not form or survive without vigorous and
continuous angiogenesis. Furthermore,
there was active VEGF paracrine and autocrine expression in tumor and
high level VEGF secretion by tumor cells plays an important role in initiating
angiogenesis and supporting micrometastases.
Key words tumor;
angiogenesis; green
fluorescent protein; angiography
*Corresponding author:
Tel, 86-21-63240090-4601; e-mail, [email protected]