Comparison of the necrotic effects of a flavonoid Tumor-VDA (ASA404) and a tubulin-binding Tumor-VDA (ZD6126). Panel A: hematoxylin and eosin stained section of a G3H prolactinoma 24 hours post-treatment with ASA404 (350 mg/kg) Grade 4, extensive necrosis (n=necrotic tissue, v=viable tissue) and Panel B: control – Grade 1, no necrosis.92 Panel C: stained section of a Calu-6 lung cancer xenograft (x 16 magnification) post-treatment with ZD6126 (200 mg/kg) and Panel D: corresponding vehicle-treated control (N=necrotic tissue, V=viable tissue). Panels E (x 100) and F (x 400): magnifications showing a thin viable rim of cells remaining, and contrasting the necrotic and viable cells (used with permission).52