Cross‐linking of the CAMPATH‐1 antigen (CD52) mediates growth inhibition in human B‐ and T‐lymphoma cell lines, and subsequent emergence of CD52‐deficient cells

Abstract

SUMMARYThe CAMPATH-1H (CD52) antigen is a 21 000-28 000 MW glycopeptide antigen that is highly expressed on T and B lymphocytes and is coupled to the membrane by a glycosylphosphatidylinositol (GPI ) anchoring structure. The humanized CAMPATH-1H anti-CD52 antibody is extremely effective at mediating depletion of both normal and tumorigenic lymphocytes in vivo and has been used in clinical trials for lymphoid malignancy and rheumatoid arthritis. Cross-linking GPIanchored molecules, including CD52, on the surface of T lymphocytes in the presence of phorbol 12-myristate 13-acetate or anti-CD3, results in cellular activation. In the present study we have investigated the functional effects of cross-linking CD52 on T and B tumour cell lines. Crosslinking CD52 on either a B-cell line, Wien 133, which expresses high levels of endogenous CD52 or Jurkat T cells transfected and selected to express high levels of CD52 resulted in growth inhibition. This effect showed slower kinetics and occurred in a lower percentage of cells than growth inhibition stimulated via T-or B-cell receptors. Growth inhibition of the Wien 133 line was followed by the induction of apoptosis, which appeared independent of the Fas/Fas L pathway. Wien 133 cells surviving anti-CD52 treatment were selected and cloned and found to have down-regulated CD52 expression, with a characteristic biphasic pattern of 10% CD52-positive, 90% negative by fluorescence-activated cell sorter analysis. Interestingly, surface expression of other GPI-linked molecules, such as CD59 and CD55, was also down-regulated, but other transmembrane molecules such as surface IgM, CD19, CD20, HLA-DR were unaffected. The present study and previous work show that this is due to a defect in the synthesis of mature GPI precursors. Separation of CD52-positive and negative populations in vitro resulted in a rapid redistribution to the mixed population. Injection of CD52-negative cells into nude mice to form a subcutaneous tumour resulted in a substantial increase in expression of CD52. These results suggest that the defect in the Wien 133 cells is reversible, although the molecular mechanism is not clear. These observations have relevance to the clinical situation as a similar GPI-negative phenotype has been reported to occur in lymphocytes following CAMPATH-1H treatment in vivo.

International childhood Acute Lymphoblastic Leukemia workshop: Sausalito, CA, 30 November–1 December 2000

“…While lymphocytes are lysed by Campath-1H in the presence of complement, 82 the antibody can also induce human chronic lymphocytic leukemia cells to undergo apoptosis in vitro independent of complement mediated lysis. 83 This antibody has undergone extensive testing, and demonstrated significant activity in adult chronic lymphocytic leukemia, non-Hodgkin's lymphoma and ALL. [84][85][86][87][88] A murine form of Campath-1 has been used in pediatric bone marrow transplant for purposes of controlling GVH disease.…”

Therapeutic role of alemtuzumab (Campath-1H) in patients who have failed fludarabine: results of a large international study

“…13 Binding of alemtuzumab to CD52 on target cells may cause cell death by 3 different mechanisms: complement activation, 14 antibody-dependent cellular cytotoxicity, 15,16 and apoptosis. 17 Based on prior reports from small studies demonstrating that alemtuzumab was an effective salvage therapy for patients in whom fludarabine had failed, 18 this study was implemented to confirm these encouraging results in a larger cohort of patients with advanced B-CLL. These patients had all been treated previously with alkylating agents and had documented failure to fludarabine therapy.…”

Free circulating soluble CD52 as a tumor marker in chronic lymphocytic leukemia and its implication in therapy with anti‐CD52 antibodies

“…2,4 CD52 is expressed on the surface of T and B lymphocytes, monocytes/macrophages, eosinophils, and on some early hematopoietic cells. [5][6][7][8] It is also expressed in the male reproductive tract. 3,9 CD52 is necessary for spermatozoa to preserve normal motility.…”