Critical Reviews in Oral Biology & Medicine, Vol 10, 153-164, Copyright © 1999 by International & American Associations for Dental Research
Angiogenesis in the development of head and neck cancer and its inhibition by chemopreventive agents
M. W. Lingen
Department of Pathology and the Cardinal Bernardin Cancer Center, Loyola University Medical Center, Maywood, Illinois 60153, USA.
Squamous cell carcinoma is an aggressive malignancy that often develops as
multiple independent lesions throughout the mucosa of the upper
aerodigestive tract. Therefore, the comprehensive treatment of this disease
must not only address the initial primary neoplasm, but also prevent the
progression of the premalignant lesions lurking throughout the rest of the
mucosal surfaces. The need to treat these lesions has resulted in a search
for chemopreventive agents that can halt or even reverse their malignant
progression. The biologic and molecular mechanisms by which most
chemopreventive agents act have remained unclear and controversial. Recent
work from several laboratories has demonstrated that some drugs may act in
part by inhibiting the ability of tumors to induce blood vessel growth.
Angiogenesis, the growth of new blood vessels from pre-existing ones, is
absolutely required for solid neoplasms to grow beyond 2-3 mm in diameter.
Therefore, chemopreventive agents that act to inhibit angiogenesis may
provide a very powerful modality by which one may limit the growth of both
pre-malignant lesions and small nests of tumor cells. This review will
outline the basic changes that occur in tumor cells that result in the
switch from an anti-angiogenic to an angiogenic phenotype. In addition, it
will discuss the mechanisms by which some chemopreventive agents, presently
under clinical investigation, inhibit tumor angiogenesis. Finally, this
paper will present a rationale for the use of multiple anti-angiogenic
agents as a means of developing new chemopreventive protocols that result
in reduced patient toxicity while maintaining similar clinical efficacies.