| Abstract: |
Background: Anaplastic thyroid cancer (ATC) is one of the most aggressive and highly lethal human cancers. Median survival after diagnosis is 4-6 months despite available radiotherapy and chemotherapy. Additional treatments are needed for ATC. Vascular endothelial growth factor (VEGF) is a potent angiogenic stimulus, which is expressed by ATC. Previously, anti-VEGF antibody was used to block VEGF-dependent angiogenesis in ATC xenografts. This treatment induced partial (56%) but not complete tumor regression. Aplidin (APLD) is a marine derived antitumor agent currently in phase II clinical studies. Multiple activities of this compound have been described which likely contribute to its antiproliferative effect. Notably, APLD has been shown to have antiangiogenic properties which include: inhibition of VEGF secretion, reduction in the synthesis of the VEGF receptor (FLT-1), and blockade of matrix metalloproteinase production by endothelial cells. We hypothesized that Aplidin, with its broad spectrum of action and antiangiogenic properties, would be a potentially effective drug against ATC. Methods: Thirty BALB/c nu/nu mice were injected with ATC cells (ARO-81, 1×106) and allowed to implant for 3 weeks. Animals were randomized to receive daily intraperitoneal injections of vehicle, low dose (0.5 mg/kg/day), or high dose (1.0 mg/kg/day) APLD. After 3 days, the animals were killed and the tumors were removed, weighed, and divided for RNA and protein analyses. Results: APLD significantly reduced ATC xenograft growth (low dose, 20% reduction, P=0.01; high dose, 40% reduction, P<0.001). This was associated with increased levels of apoptosis related proteins polyadenosylribose polymerase 85 (PARP-85, 75% increase, P=0.024) and caspase 8 (greater than fivefold increase, P=0.03). APLD treatment was further associated with lost or reduced expression of several genes that support angiogenesis to include: VEGF, hypoxia inducible factor 1(HIF-1), transforming growth factor-beta (TGFβ), TGFβ receptor 2 (TGFβR2), melanoma growth stimulating factor 1 (GRO1), cadherin, and vasostatin. Conclusions: This data supports the hypothesis that APLD may be an effective adjunctive therapy against ATC. The demonstrated molecular impact against angiogenic related genes specifically supports future strategies combining APLD with VEGF interacting agents. © Springer-Verlag 2005. |
| Keywords: |
vasculotropin; controlled study; unclassified drug; cancer growth; drug efficacy; nonhuman; antineoplastic agents; drug megadose; protein analysis; mouse; animals; mice; animal tissue; low drug dose; transforming growth factor beta; animal experiment; animal model; antineoplastic activity; tumor xenograft; drug effect; dose-response relationship, drug; xenograft model antitumor assays; angiogenesis; neovascularization, pathologic; cancer model; mice, inbred balb c; rna; gene expression regulation; cancer inhibition; blotting, western; gene expression regulation, neoplastic; drug mechanism; carcinoma; caspase 8; thyroid cancer; thyroid carcinoma; thyroid neoplasms; randomization; angiogenesis inhibitors; tumor vascularization; cadherin; hypoxia inducible factor 1alpha; nicotinamide adenine dinucleotide adenosine diphosphate ribosyltransferase; antiangiogenic activity; neovascularization (pathology); depsipeptides; anaplastic carcinoma; angiogenic factor; weight; rna analysis; transforming growth factor beta receptor 2; aplidin; dehydrodidemnin b; melanoma growth stimulatory activity factor; vasostatin
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