The proteins of the present invention include central nervous system myelin associated proteins and metalloproteases associated with glioblastoma cells and other malignant tumors which can metastasize to the brain. The CNS myelin associated proteins inhibit neurite outgrowth in nerve cells and neuroblastoma cells, and can also inhibit fibroblast spreading. Such inhibitory proteins include a 35,000 dalton and a 250,000 dalton molecular weight protein. The CNS myelin associated inhibitory proteins may be used in the treatment of malignant tumors. Antibodies to the CNS myelin associated proteins can be used in the diagnosis and therapies of nerve damage. Monoclonal antibody IN-1 may be used to promote regeneration of nerve fibers over long distances in spinal cord lesions. The metalloproteases of the invention have value in diagnosis of malignancies and the treatment of nerve damage and degenerative disorders of the nervous system. Inhibitors of the metalloproteases in combination with the CNS myelin associated inhibitory proteins can be used in the treatment of malignant tumors. Methods of determining malignant potential of a cell by measuring metalloprotease activity are provided.