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Figure 4. Research hierarchy from basic research-driven target identification and validation to clinical exploitation. The arrow denotes the relative knowledge gradient of the discipline. Much has been learnt about the basic mechanisms of angiogenesis within the last 20 years and solid proof-of-principle and proof-of-concept experiments have been performed in laboratory animals to demonstrate that anti-angiogenic intervention can not just halt tumour progression but actually induce active tumour regression. More than 50 compounds with anti-angiogenic activity are presently in various phases of clinical development. Yet, the inclusion and exclusion criteria of these clinical trials are largely not angiogenesis-based. Likewise, monitoring techniques to trace the efficacy of an anti-angiogenic intervention are urgently required. The necessary intermediate step, a better knowledge of the functional properties of the vasculature in human tumours, is emerging as the rate-limiting step in translating basic angiogenesis knowledge rationally into the clinic. Work aimed at better analysing the human tumour vasculature will also lead to the development of useful techniques for individualized functional angiodiagnostic procedures.
