Reversal of CAMAL-mediated alterations of normal and leukemic in vitro myelopoiesis using inhibitors of proteolytic activity.

CAMAL (common antigen of myelogenous acute leukemia) is an antigenic preparation isolated in this laboratory from the bone marrow or peripheral blood leucocytes of persons with myeloid leukemias. Material from CAMAL preparations, which migrates in the range of 30 to 35 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE, P30-35 CAMAL), was shown to exert an inhibitory effect on in vitro colony formation by progenitor cells from normal healthy donors. The same preparations of P30-35 CAMAL, in contrast, exerted a stimulatory effect on in vitro colony formation by progenitor cells from patients with chronic myelogenous leukemia (CML). We now report that both the inhibitory effect on normal colony formation and the stimulatory effect on CML colony formation mediated by P30-35 CAMAL were blocked using phenyl methyl sulfonyl fluoride (PMSF), an inhibitor of the activity of serine proteases. Similarly, both the P30-35 CAMAL-mediated inhibitory effect on normal colony formation and the P30-35 CAMAL-mediated stimulatory effect on CML colony formation were blocked using the peptide ala-pro-phe-CMK, also an inhibitor of serine protease activity. These results suggest the involvement of proteolytic activity, either directly or indirectly, in the alterations of in vitro myelopoiesis exerted by P30-35 CAMAL.