A nude mice model of human rhabdomyosarcoma lung metastases for evaluating the role of polysialic acids in the metastatic process.

PSA is an oncodevelopmental antigen usually expressed in human tumors with high metastatic potential. Here we set up a metastatic model in nude mice by using TE671 cells, which strongly express PSA-NCAM. We observed the formation of lung metastases when TE671 cells were injected intravenously, intramuscularly, and intraperitoneally, but not subcutaneously. Intraperitoneal injections also induced peritoneal carcinosis, ascites, and liver metastases. To evaluate the putative role of PSA in the metastatic process we used a specific cleavage of PSA on NCAM by endoneuraminidase-N on intraperitoneal primary tumors. Mice with primary intramuscular tumors were taken as control. Repeated injections of endoneuraminidase-N led to a decrease in PSA expression in primary intraperitoneal nodules and ascites but not in intramuscular primary tumors. Endoneuraminidase-N also increased the delay in ascitic formation and decreased the number of lung or liver metastases in the case of intraperitoneal tumors but not in the case of intramuscular tumors. When metastases occurred in endoneuraminidase-N injected animals, they strongly expressed PSA-NCAM. Therefore, we established a relationship between PSA expression on the surface of primary tumor cells and the metastatic process.