Production of heparanase by normal and neoplastic murine B‐lymphocytes

The production of heparanase, an endoglycosidase capable of degrading heparan sulfate from the subendothelial extracellular matrix (ECM), was investigated in various murine B‐lymphoid tumors representing distinct maturation stages of the B‐cell lineage. We found that heparanase is produced and released by 3 out of 4 pre‐B lymphomas and by 4 B lymphomas examined. In contrast, 5 plasmacytomas and resting normal B lymphocytes, expressed little, if any, heparanase activity. Treatment with LPS resulted in high expression of the enzyme by normal B‐lymphocytes, but there was no effect on the constitutive production of heparanase by myeloma or B‐lymphoma cells. Our results indicate that heparanase is produced by B cells during discrete stages of their maturation. We suggest that heparanase may play a role in B‐cell migration by enabling pre‐B and B lymphocytes to leave the bone‐marrow compartment and recirculate among peripheral lymphoid organs.