Angiosuppression

Angiogenesis and Cancer Control: From Concept to Therapeutic Trial

Background

There is extraordinary interest in developing angiosuppressive agents for cancer treatment. Several new agents appear promising for the treatment of a variety of human cancers. Current concepts and new agents in clinical trials are the focus of this article. In particular, the introduction of a new treatment for human brain tumors is presented in detail, using an antiangiogenic agent, penicillamine, and depletion of an obligatory cofactor of angiogenesis, copper.

Methods

The explosive increase in literature on antiangiogenesis is reviewed using computerized search, findings presented at the recent national cancer and angiogenesis meetings. A specific protocol, NABTT 97-04, “Penicillamine and Copper Reduction for Newly Diagnosed Glioblastoma,” is presented as an example of angiotherapeutic drug discovery.

Results

A number of promising molecular approaches are being introduced to suppress tumor angiogenesis. Major categories of angiogenesis antagonists include protease inhibitors, direct inhibitors of endothelial cell proliferation and migration, suppression of angiogenic growth factors, inhibition of endothelial-specific integrin/survival signaling, chelators of copper, and inhibitors with specific other mechanisms. The preliminary results of early trials offer a glimpse into how antiangiogenesis therapy will be integrated into future care of the patient with cancer.

Conclusions

Thirty-five antiangiogenesis therapies are currently being evaluated in clinical trials. As we learn more about the fundamental mechanisms of angiogenesis, eg, the role of copper in growth factor activation, effective methods of cancer control will be implemented.

Stimulation of angiogenesis by substance P and interleukin-1 in the rat and its inhibition by NK1 or interleukin-1 receptor antagonists

1. Daily administration of 1 nmol substance P or 3 pmol recombinant human interleukin-1 alpha (IL-1 alpha) caused intense neovascularization in a rat sponge model of angiogenesis. Lower doses of substance P (10 pmol) or IL-1 alpha (0.3 pmol) were ineffective when given alone. When combined at these low doses, substances P and IL-1 alpha interacted to produce an enhanced neovascular response. 2. By use of selective tachykinin NK1, NK2 and NK3 receptor agonists, ([Sar9,Met(O2)11]substance P, [beta-Ala8]neurokinin A(4-10), Succ-[Asp6,MePhe8]substance P(6-11) (senktide), respectively), it was established that the activation of NK1 receptors is most likely to mediate the angiogenic response to substance P in this model. 3. The angiogenic activity of substance P and IL-1 alpha (10 pmol and 0.3 pmol day-1, respectively) was abolished by co-administration of (i) the selective peptide NK1 receptor antagonist, L-668,169 (1 nmol day-1), (ii) the selective non-peptide NK1 receptor antagonists, RP 67580 and (+/-)-CP-96,345 (both at 1 nmol day-1) or (iii) the IL-1 receptor antagonist, IL-1ra, (50 micrograms day-1). In contrast, the selective NK2 receptor antagonist, L-659,874 (1 nmol day-1) was ineffective. 4. The angiogenic action of substance P and IL-1 alpha was resistant to modification by mepyramine (1 nmol day-1) and/or cimetidine (10 nmol day-1), indomethacin (7 nmol day-1) or the platelet-activating factor (PAF) antagonist, WEB-2086 (22 nmol day-1), indicating that histamine, prostaglandins and PAF are not likely to be involved in this neovascular response. 5. The inhibition of the substance P/IL-1 angiogenic response by selective NK1 receptor antagonists or by an IL-1 receptor antagonist demonstrates that angiosuppression can be achieved by blocking the activity of angiogenic factors at the receptor level.