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

Models that demonstrate histological invasion of extracellular matrix barri ers by tumor cell lines are useful for assessing new methods to treat or pr event tumor metastasis. An in vivo invasion model using acellular human der mal matrix has been described in a murine squamous cell carcinoma line. The present study examined the application of this tumor invasion model to ano ther epithelial cell line derived from a different species. A human follicu lar 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. Immunohistochemi cal staining of type TV collagen was used to identify the basement membrane and invasion was determined as penetration of the basement membrane by tum or 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 s uggests that the in vivo dermal matrix model of invasion is applicable to a broad range of epithelial carcinoma cell lines to study their capability t o penetrate basement membrane. A model such as this may be useful for study ing the local effects of genetic manipulations of implanted tumor cell popu lations, leading to the development of therapeutic agents that block invasi on.