RESUMO
Elotuzumab is a monoclonal antibody in development for multiple myeloma (MM) that targets CS1, a cell surface glycoprotein expressed on MM cells. In preclinical models, elotuzumab exerts anti-MM efficacy via natural killer (NK)-cell-mediated antibody-dependent cellular cytotoxicity (ADCC). CS1 is also expressed at lower levels on NK cells where it acts as an activating receptor. We hypothesized that elotuzumab may have additional mechanisms of action via ligation of CS1 on NK cells that complement ADCC activity. Herein, we show that elotuzumab appears to induce activation of NK cells by binding to NK cell CS1 which promotes cytotoxicity against CS1(+) MM cells but not against autologous CS1(+) NK cells. Elotuzumab may also promote CS1-CS1 interactions between NK cells and CS1(+) target cells to enhance cytotoxicity in a manner independent of ADCC. NK cell activation appears dependent on differential expression of the signaling intermediary EAT-2 which is present in NK cells but absent in primary, human MM cells. Taken together, these data suggest elotuzumab may enhance NK cell function directly and confer anti-MM efficacy by means beyond ADCC alone.
Assuntos
Anticorpos Monoclonais Humanizados/farmacologia , Citotoxicidade Celular Dependente de Anticorpos/imunologia , Células Matadoras Naturais/imunologia , Mieloma Múltiplo/imunologia , Receptores Imunológicos/metabolismo , Western Blotting , Proliferação de Células , Citometria de Fluxo , Humanos , Imunoprecipitação , Interferon gama/metabolismo , Células Matadoras Naturais/efeitos dos fármacos , Células Matadoras Naturais/metabolismo , Ativação Linfocitária , Mieloma Múltiplo/tratamento farmacológico , Mieloma Múltiplo/metabolismo , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Receptores Imunológicos/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Família de Moléculas de Sinalização da Ativação Linfocitária , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Células Tumorais CultivadasRESUMO
Multiple myeloma (MM) patients who receive killer cell Ig-like receptor (KIR) ligand-mismatched, T cell-depleted, allogeneic transplantation may have a reduced risk of relapse compared with patients who receive KIR ligand-matched grafts, suggesting the importance of this signaling axis in the natural killer (NK) cell-versus-MM effect. Expanding on this concept, IPH2101 (1-7F9), an anti-inhibitory KIR mAb, enhances NK-cell function against autologous MM cells by blocking the engagement of inhibitory KIR with cognate ligands, promoting immune complex formation and NK-cell cytotoxicity specifically against MM cell targets but not normal cells. IPH2101 prevents negative regulatory signals by inhibitory KIR, whereas lenalidomide augments NK-cell function and also appears to up-regulate ligands for activating NK-cell receptors on MM cells. Lenalidomide and a murine anti-inhibitory NK-cell receptor Ab mediate in vivo rejection of a lenalidomide-resistant tumor. These mechanistic, preclinical data support the use of a combination of IPH2101 and lenalidomide in a phase 2 trial for MM.
