Mistargeting of Normal Cells in Anti-CD30 Immunotherapy of Lymphoma Cells Is Blocked by Selective Metalloproteinase Inhibitor.

CD30 is a transmembrane receptor which is selectively overexpressed on Hodgkin lymphoma and large cell anaplastic lymphoma and therefore an interesting target for antibody-based immunotherapy. However, the receptor is cleaved by metalloproteinases and the ectodomain is released in the environment where it competes with the CD30-based immunotherapy. Moreover, therapeutic anti-CD30 antibodies stimulate this cleavage which results in a loss of target antigen and an enhanced release of the soluble ectodomain (sCD30). In order to improve immunotherapy, we analyzed the mechanism of the release and the function of resulting sCD30. By means of FACS analysis, we demonstrate that sCD30, like membrane-anchored CD30, binds to CD30 ligand (CD153)-expressing cells. Since monoclonal antibodies bind to both CD30 and sCD30, this results in unwanted targeting of these “non-target” cells via sCD30 bridging. To overcome the damage of normal cells in immunotherapy as a consequence of sCD30-binding, we analyzed the mechanism involved in the release of sCD30. Shedding of CD30 can be enhanced by PKC activation involving the disintegrin metalloproteinase ADAM17 but not free cytoplasmic calcium. In contrast, antibody-induced CD30 shedding is calcium-dependent and PKC-independent. Using the ADAM10 inhibitor GI254023X and a ADAM10-deficient cell line generated from embryonically lethal ADAM10⁻/⁻mouse we demonstrate that antibody-mediated shedding involves the related metalloproteinase ADAM10. In co-culture experiments, the antibody-induced transfer of sCD30 from the Hodgkin lymphoma cell line L540 to the CD30-negative but CD153-expressing mast cell line HMC-1 was inhibited by GI254023X.

These findings suggest that selective metalloproteinase inhibitors blocking antibody-induced shedding of target antigens could be of therapeutic value to increase the specificity and reduce side-effects of immunotherapy with monoclonal antibodies.