Invasion of human follicular thyroid carcinoma cells in an in vivo invasion model.

Models that demonstrate histological invasion of extracellular matrix barriers by tumor cell lines are useful for assessing new methods to treat or prevent tumor metastasis. An in vivo invasion model using acellular human dermal matrix has been described in a murine squamous cell carcinoma line. The present study examined the application of this tumor invasion model to another epithelial cell line derived from a different species. A human follicular thyroid carcinoma cell line, known to be invasive by other assays, was grown on the dermal-epidermal basement membrane surface of human acellular dermal matrix in culture and then grafted in athymic mice. Immunohistochemical staining of type IV collagen was used to identify the basement membrane and invasion was determined as penetration of the basement membrane by tumor cells. Identification of the human tumor cells in the in vivo grafts was done by in situ hybridization with species specific probes. FTC-133 tumor cells did not invade the matrix after 4 weeks of growth in in vitro culture, but there was extensive loss of the basement membrane and infiltration of the tumor cells into the dermis after 2 weeks growth in vivo. This study suggests that the in vivo dermal matrix model of invasion is applicable to a broad range of epithelial carcinoma cell lines to study their capability to penetrate basement membrane. A model such as this may be useful for studying the local effects of genetic manipulations of implanted tumor cell populations, leading to the development of therapeutic agents that block invasion.