Combretastatin A-4 (CA4) is a
natural product isolated from Combretum caffrum that inhibits
tubulin polymerization by binding to the
colchicine-binding site. A corresponding water soluble
pro-drug (referred to as CA4P), has undergone extensive clinical trials and has been evaluated in pre-clinical studies using multiple modalities. We previously reported a novel assay based on dynamic bioluminescent imaging to assess
tumor vascular disruption and now present its application to assessing multiple
tumors simultaneously. The current study evaluated the vascular-disrupting activity of CA4P on subcutaneous 9L rat
brain tumor xenografts in mice using dynamic bioluminescence imaging. A single dose of CA4P (120 mg/kg, intraperitoneally) induced rapid, temporary
tumor vascular shutdown revealed by a rapid and reproducible decrease of light emission from
luciferase-expressing 9L
tumors following administration of
luciferin as a substrate. A time-dependent reduction of
tumor perfusion after CA4P treatment was confirmed by immunohistological assessment of the perfusion marker
Hoechst 33342 and the
tumor vasculature marker CD31. The vasculature showed distinct recovery within 24 h post
therapy. Multiple
tumors behaved similarly, although a size dependent vascular inhibition was observed. In conclusion, CA4P caused rapid, temporary
tumor vascular shutdown and led to reduction of
tumor perfusion in rat
brain tumor xenografts and the multiple
tumor approach should lead to more efficient studies requiring fewer animals and greater consistency.