The Contribution of Harold F. Dvorak to the Study of Tumor Angiogenesis and Stroma Generation Mechanisms

In 1983, Harold Dvorak and his colleagues were the first to show that tumor cells secreted vascular permeability factor (VPF) and that a blocking antibody to VPF could prevent the edema and fluid accumulation that is characteristic of human cancers. In 1986, Dvorak went on to demonstrate that VPF was secreted by a variety of human tumor cell lines and proposed that VPF was in part responsible for the abnormal vasculature seen in human tumors. As a result, he and other investigators demonstrated that VPF was capable of stimulating endothelial cell growth and angiogenesis. These fundamental discoveries led to additional research conducted by Napoleone Ferrara and his laboratory, confirming the cloning of VPF and renaming the protein vascular endothelial growth factor (VEGF). In 1986, Dvorak proposed that by secreting VPF, tumors induce angiogenesis by turning on the wound healing response. He noted that wounds, like tumors, secrete VPF, causing blood vessels to leak plasma fibrinogen, which stimulates blood vessel growth and provides a matrix on which they can spread. Unlike wounds, however, that turn off VPF production after healing, tumors did not turn off their VPF production and instead continued to make large amounts of VPF, allowing malignant cells to continue to induce new blood vessels and so to grow and spread. Thus, tumors behave like wounds that fail to heal. This work is again extremely significant for patients worldwide, as Dvorak's scientific research is leading his colleagues all over the world to examine how to treat a tumor through its blood supply.

The scientific contributions of M. Judah Folkman to cancer research

Dr Judah Folkman was frequently described as a highly compassionate physician who served his patients not only by performing surgery and offering them comfort and reassurance, but also by working tirelessly in the laboratory to find new approaches to the treatment of disease. His dedication to understanding the role of angiogenesis, the formation of new blood vessels, in human disease has given rise to new treatments for several diseases, including inflammatory diseases, vision-threatening diseases of the eye and, as will be emphasized in this Perspective, cancer.

[Neoplastic angiogenesis and age-related macular degeneration: historic aspects of the microcirculation of new vessels]

Angiogenesis is the process through which newly-formed vessels develop from pre-existing ones, following a series of sequential steps. The appearance of new vessels is essential in a number of physiological processes, but it is also associated with several pathological phenomena, such as arthritis, diabetic retinopathy and cancer. In the XIX century Rudolph Virchow ("Die Zellularpathologie", 1858) had already observed and described the rich vascularization which characterizes malignant tumors. This line of research was further developed by Goldman in the early XX century. With specific reference to the history of age-related macular degeneration, a disease model whose understanding is linked to the study of angiogenesis, in 1905 Oeller coined the definition "disciform macular degeneration", and twenty years later this expression was taken up by Kuhnt and Junius to describe disc-shaped lesions in the macula of elderly individuals. The historical evolution of the concept of angiogenesis, its characterizing evolutional steps and the most relevant scientific achievements in the field of macular degeneration up to the eighties of the XX century are here presented and discussed.

The crucial role of vascular permeability factor/vascular endothelial growth factor in angiogenesis: a historical review

Angiogenesis is a biological process by which new capillaries are formed and it occurs in many physiological and pathological conditions. It is controlled by the net balance between molecules that have positive and negative regulatory activity and this concept had led to the notion of the 'angiogenic switch', depending on an increased production of one or more of the positive regulators of angiogenesis. Numerous inducers of angiogenesis have been identified and this review offers a historical account of the relevant literature concerning the discovery of one of the best characterized angiogenic factors, namely vascular endothelial growth factor (VEGF)/vascular permeability factor. Moreover, different strategies, designed to stimulate and to inhibit VEGF production in the context of several potential therapeutical implications, are discussed.

The role of the vascular phase in solid tumor growth: a historical review

Angiogenesis is a biological process by which new capillaries are formed from pre-existing vessels. It occurs in both physiological conditions such as embryo development, cyclically in the female genital system and during wound repair, and pathological conditions, such as arthritis, diabetic retinopathy and tumors. In solid tumor growth, a specific critical turning point is the transition from the avascular to the vascular phase. Having developed an intrinsic vascular network, the neoplastic mass is able to grow indefinitely (unlike all the other forms, tumor angiogenesis is not limited in time) both in situ and at distant sites (metastasis) in so far as an intrinsic vascular network enables its cells to enter the vascular bed and colonize other organs. Tumor angiogenesis depends mainly on the release by neoplastic cells of growth factors specific for endothelial cells and able to stimulate growth of the host's blood vessels. This review describes its history as traced by the main contributions to the international medical literature and their contents. The specific new paradigm discussed here has been gaining general approval and considerable confirmation, thanks to its possible applications, as recently highlighted by the introduction of anti-angiogenic substances in adjuvant tumor management.