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Anti-vascular approaches to solid tumour therapy: evaluation of vinblastine and flavone acetic acid
S A Hill1, L E Sampson, D J Chaplin
1Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Middlesex, UK.
Abstract:
Several agents have now been identified which exert their anti-tumour effects in large part via the tumour vasculature; these include TNF alpha and flavone acetic acid (FAA). More recently, Vincristine and Vinblastine have also been shown to cause a prolonged and selective decrease in tumour perfusion. Vinblastine, unlike, FAA, causes no increase in plasma TNF alpha levels in mice bearing the CaNT tumour, suggesting 2 distinct mechanisms of anti-vascular activity for these structurally diverse agents. Since FAA and Vinblastine also show quite different normal tissue toxicities, which are separately dose-limiting, we have examined the strategy of combining these 2 agents. When Vinblastine preceded FAA by 24 hr or less, tumour growth delay was significantly enhanced without a concomitant increase in toxicity. The level of enhancement was not significantly reduced by a 5-fold decrease in Vinblastine dose, though any reduction in the dose of FAA caused a rapid reduction in treatment effectiveness. Investigation of the functional vasculature of treated tumours suggested that increased anti-vascular effects may contribute to the enhanced growth inhibition of the combined treatment. Our results demonstrate the potential benefit of combining 2 different classes of anti-vascular agent, using Vinblastine and FAA (or 5,6-MeXAA) as prototype drugs.
Insights
Combining Vinblastine and flavone acetic acid (FAA) enhances anti-tumour effects by targeting tumour vasculature. This combination significantly delays tumour growth without increasing toxicity, showing potential for novel cancer therapies.
Area of Science:
- Oncology
- Pharmacology
- Cancer Biology
Background:
- Tumour vasculature is a key target for anti-cancer agents.
- Agents like TNF alpha, flavone acetic acid (FAA), Vincristine, and Vinblastine affect tumour perfusion.
- Distinct mechanisms of anti-vascular activity exist for different agents.
Purpose of the Study:
- To investigate the combined efficacy of Vinblastine and FAA, two anti-vascular agents with different toxicity profiles.
- To determine if combining these agents enhances anti-tumour effects without increasing toxicity.
Main Methods:
- Administering Vinblastine before FAA at varying time intervals (≤24 hours).
- Assessing tumour growth delay and normal tissue toxicity.
- Investigating the functional tumour vasculature post-treatment.
Main Results:
- Combining Vinblastine and FAA significantly enhanced tumour growth delay when Vinblastine preceded FAA.
- The enhancement was maintained even with a reduced Vinblastine dose, but sensitive to FAA dose reduction.
- No significant increase in toxicity was observed with the combined treatment.
- Increased anti-vascular effects in tumours were suggested as a contributing factor.
Conclusions:
- Combining Vinblastine and FAA represents a promising strategy for enhancing anti-cancer therapy.
- This approach leverages distinct anti-vascular mechanisms to improve treatment outcomes.
- Vinblastine and FAA (or 5,6-MeXAA) serve as effective prototype drugs for this combined anti-vascular strategy.