EXPRESSION OF ICAM-1 IN IMPLANTED PRIMARY AND METASTATIC SQUAMOUS-CELL CARCINOMAS IN RATS

FF6 tumor cells are dervied from a spontaneous rat squamous cell carci noma (SCC) which originally arose in the facial skin of a DA rat. In t his study, FF6 tumor cells were implanted into rat oral mucosa to esta blish an ex vivo metastatic model. We analyzed the expression of inter cellular cell adhesion molecule-1 (ICAM-1) in the implanted primary an d metastatic FF6 tumors by immunostaining with a monoclonal antibody ( mAb) against ICAM-1. The implanted primary FF6 cells showed strong exp ression of ICAM-1, whereas the tumor cells of metastatic lesions showe d weak or negative expression of ICAM-1. By immunostaining with mAb OX 6, a number of MHC class II-positive macro phages were detected in tum or mesenchyme and surrounding the metastatic foci. These results sugge sted that the local immune reaction in the lymph node influenced the e xpression of ICAM-1 on tumor cells, and that MHC class II-positive mac rophages may play a role in transplanted tumor growth and metastases.