The levels of a trypsin-like neutral proteinase present on tumor cell surface (SNP) have been determined in P388, L1210, TLX5 leukemias, and in two lines of Lewis lung carcinoma having different metastatic potential. No correlation between metastatic potential and SNP levels of the tumor lines examined has been observed, and metastasis depression by antimetastatic and antineoplastic drugs was not accompanied by SNP inhibition. These data seem to support the view that metastatic potential is not necessarily related to tumor proteinase levels.
