We previously reported the existence of a
growth inhibitory factor for
mitogen-stimulated lymphocytes and murine tumor cell lines, MM46 and L-929, in inflammatory polymorphonuclear leukocytes. In this study, by using mouse MM46 mammary
carcinoma as target, we purified the inhibitor from lysate of rat inflammatory peritoneal exudate cells by
ammonium sulfate precipitation, gel filtration, isoelectrofocusing, and
anion exchange chromatography. Although the in vitro inhibitory activity for MM46 growth was partitioned into three peaks in the final step, it was found that these inhibitory samples all consist of 8- and 13-kDa
peptides. Analysis of amino acid sequences revealed that the partial sequences of the 8- and 13-kDa
peptides completely agree with the smaller and larger components of rat
calprotectin, which are predicted from
cDNA, respectively, suggesting the cell
growth inhibitory factor is
calprotectin. In addition to MM46, the partially purified
calprotectin inhibited the growth of a rat, three mice, and a human tumor cell line in similar dose-response relationships in vitro. Moreover, it exerted a cytolytic effect against all examined
tumor cells. It was confirmed that the purified
calprotectin induces growth inhibition and the lysis of MM46 cells and that the minimum effective concentration is between 50 and 100 micrograms/ml. The factor also inhibited the growth of bone marrow cells and macrophages. These results suggest that
calprotectin is a negative regulatory factor for the growth and/or survival states of normal and
tumor cells.