Antilymphoma effects of anti-HLA-DR and CD20 monoclonal antibodies (Lym-1 and Rituximab) on human lymphoma cells

Cancer Biother Radiopharm. 2004 Oct;19(5):545-61. doi: 10.1089/cbr.2004.19.545.


Aim: Anti-HLA-DR and anti-CD20 monoclonal antibodies (MAbs) have been effective for immunotherapy and radioimmunotherapy in non-Hodgkin's lymphoma (NHL). The aim of our study was to compare the antilymphoma effects of Lym-1 and rituximab in human lymphoma cell lines, using assays of viability, apoptosis, antibody-dependent cellular cytotoxicity (ADCC), and complement-dependent cytotoxicity (CDC), under conditions relevant to the clinic.

Methods: To characterize response relationships at varied concentrations of Lym-1 and rituximab, growth inhibition and cell death were assayed over 96 hours in four NHL cell lines derived from Burkitt's or large-cell lymphoma patients. Untreated cells and cells treated with an mLym-1 isotype-matched MAb were used as negative controls for direct assays. Western blot was used to detect apoptosis through the activation of caspase-3 and cleavage of poly (ADP-ribase) polymerase (PARP). The indirect cytotoxicity of Lym-1 and rituximab was assayed at varied concentrations, using ADCC activity in the presence of purified peripheral blood leukocytes and CDC activity in the presence of human donor serum.

Results: Lym-1 and rituximab showed significant direct and indirect antilymphoma effects. Lym-1 had a substantial, and statistically greater, effect than rituximab over longer intervals of time. In Raji and B35M cells, Lym-1 induced potent growth inhibition reflected by 90% and 94% reductions in viable cells, respectively, whereas rituximab induced 63% and 56% reductions. Concurrently, Lym-1 increased nonviable cells by 372% and 153% in these cells, respectively, whereas rituximab induced 139% and 43% increases. Lym-1-induced apoptosis was greater than that of rituximab in all cell lines tested. Lym-1, both the chimeric form and the mouse parent, mediate ADCC more effectively, in the presence of a total peripheral blood leukocyte (PBL) population, than does rituximab, although the results for CDC activity were mixed.

Conclusions: In conclusion, Lym-1 had more potent direct and indirect cytotoxic effects than rituximab in lymphoma cells under conditions achievable in patients. Because the HLA-DR target antigen of Lym-1 is enriched on most B-cell lymphomas, these results support its complementary use in patients as an alternative to CD20 for monoimmunotherapy and for combination immunotherapy with rituximab, because the HLA-DR and CD20 antigens are physically and functionally coupled on human B cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Monoclonal / therapeutic use*
  • Antibodies, Monoclonal, Murine-Derived
  • Antigens, CD20 / immunology*
  • Antineoplastic Agents / therapeutic use*
  • Apoptosis
  • Blotting, Western
  • Burkitt Lymphoma / drug therapy
  • Caspase 3
  • Caspases / metabolism
  • Cell Line, Tumor
  • Cell Proliferation
  • Cell Survival
  • Complement System Proteins
  • Dose-Response Relationship, Drug
  • Enzyme Activation
  • HLA-DR Antigens / immunology*
  • Humans
  • Immunotherapy / methods*
  • Leukocytes / cytology
  • Lymphoma / drug therapy*
  • Lymphoma, Large B-Cell, Diffuse / drug therapy
  • Poly(ADP-ribose) Polymerases / metabolism
  • Rituximab
  • Time Factors


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Murine-Derived
  • Antigens, CD20
  • Antineoplastic Agents
  • HLA-DR Antigens
  • Lym-1 monoclonal antibody
  • Rituximab
  • Complement System Proteins
  • Poly(ADP-ribose) Polymerases
  • CASP3 protein, human
  • Casp3 protein, mouse
  • Caspase 3
  • Caspases