ABSTRACT
Different animal models and in vitro invasion assays have been developed to study the mechanisms involved in tumor cell invasion and metastasis. This chapter presents a review of the different model systems used to study the interactions between benign and malignant cells in vitro. Locally produced endocrine factors that are important for cell growth, migration, and differentiation in vivo may be present in small quantities in monolayer cultures. The chapter investigates how three-dimensional tumors invade and destroy syngeneic brain tissue, tumor spheroids were formed by reaggregating tumor cells initially grown as monolayer cultures, which using agar overlay tissue culture. Organotypic cultures are easily manipulated, and the three-dimensional arrangement of the tissues in vivo can be partly mimicked by the use of fragments or spheroids originating from normal and malignant tissues. A semiquantitative evaluation of invasion has proven valuable in assay systems where tumor spheroids have been confronted with chick heart fragments.
