RESUMO
CD37 is a lineage-specific B-cell antigen that to date has been neglected as an attractive therapeutic target. To exploit this, novel CD37-specific small modular immunopharmaceuticals (CD37-SMIP) that include variable regions linked to modified human IgG(1) hinge, CH(2), and CH(3) domains were designed. The lead CD37-SMIP molecule induces potent apoptosis in the presence of a cross-linker, and antibody-dependent cellular cytotoxicity against B-cell leukemia/lymphoma cell lines and primary chronic lymphocytic leukemia (CLL) cells superior to therapeutic antibodies used in these diseases. The CD37-SMIP-dependent ADCC function in vitro was mediated by natural killer (NK) cells but not naive or activated monocytes. Significant in vivo therapeutic efficacy was demonstrated in a SCID mouse xenograft leukemia/lymphoma model. Depletion of NK cells in this mouse model resulted in diminished efficacy further supported the in vivo importance of NK cells in SMIP therapy. These findings provide strong justification for CD37 as a therapeutic target and introduce small modular immunopharmaceuticals as a novel class of targeted therapies for B-cell malignancies.
Assuntos
Antígenos CD/metabolismo , Antígenos de Neoplasias/metabolismo , Leucemia Linfocítica Crônica de Células B/metabolismo , Animais , Anticorpos Antineoplásicos/imunologia , Anticorpos Antineoplásicos/uso terapêutico , Citotoxicidade Celular Dependente de Anticorpos/imunologia , Antígenos CD/genética , Antígenos CD19/metabolismo , Antígenos de Neoplasias/genética , Apoptose , Caspases/metabolismo , Ativação Enzimática , Humanos , Células Matadoras Naturais/imunologia , Células Matadoras Naturais/metabolismo , Leucemia Linfocítica Crônica de Células B/tratamento farmacológico , Leucemia Linfocítica Crônica de Células B/imunologia , Leucemia Linfocítica Crônica de Células B/patologia , Camundongos , Camundongos SCID , Tetraspaninas , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Dendritic cells (DCs) are a phenotypically and functionally heterogenous population of leukocytes with distinct subsets serving a different set of specialized immune functions. Here we applied an in vitro whole cell panning approach using antibody phage display technology to identify cell-surface epitopes specifically expressed on human blood BDCA3(+) DCs. A single-chain antibody fragment (anti-1F12 scFv) was isolated that recognizes a conserved surface antigen expressed on both human BDCA3(+) DCs and mouse CD8alpha(+) DCs. We demonstrate that anti-1F12 scFv binds Nectin-like protein 2 (Necl2, Tslc1, SynCaM, SgIGSF, or Igsf4), an adhesion molecule involved in tumor suppression, synapse formation, and spermatogenesis. Thus, Necl2 defines a specialized subset of DCs in both mouse and human. We further show that Necl2 binds Class-I-restricted T-cell-associated molecule (CRTAM), a receptor primarily expressed on activated cytotoxic lymphocytes. When present on antigen presenting cells, Necl2 regulates IL-22 expression by activated CD8(+) T-cells. We propose that Necl2/CRTAM molecular pair could regulate a large panel of cell/cell interactions both within and outside of the immune system.
