A study on serum cancer-suppressive peptide

A peptide which was isolated from serum of cancer-bearing mice has an activity to kill cancer cells in vitro, but little effect on bone marrow cells. This peptide was named Serum Cancer-Suppressive Peptide (SCSP). SCSP can be crystallized and still has the activity to kill the cancer cells. It consists of more than ten kinds of amino acids with molecular weight about 2000-3000 daltons estimated by SDS-polyacrylamide gel electrophoresis. An antiserum was prepared from rabbits immunized with SCSP and the corresponding IgG could be obtained from the antiserum. The titers of SCSP in some cells of the normal and cancer-bearing mice were estimated by passive hemagglutination method. The results showed that the SCSP titer in spleen is much higher than those in muscle, liver and ascites tumor cells. The results suggest that SCSP is probably produced by spleen cells.