RESUMO
The role of the B7 family molecules in the regulation of the immune response is well documented. A large body of experimental evidence indicates that costimulatory molecules such as B7-1, B7-2, B7-DC, B7-H1, B7-H2, B7-H3 and B7-H4 are critical for initiation, maintenance and down-regulation of the immune response. However the immunological function of butyrophilin (BTN)-like molecules, which are a part of the expanded B7 family, is not known. Here, we demonstrate that the extracellular portion of human BTNL8 can augment Ag-induced activation of T lymphocytes. BTNL8 has two alternatively spliced forms: B7-like and BTN-like. Both isoforms of BTNL8 were expressed concurrently in various human tissues. A putative BTNL8 receptor was detected only on resting T lymphocytes. Administration of BTNL8Ig fusion protein into mice promoted production of Ag-specific IgG during the primary, but not the secondary immune responses. BTNL8 may therefore play an essential role in priming of naïve T lymphocytes.
Assuntos
Antígenos/imunologia , Ativação Linfocitária/imunologia , Proteínas de Membrana/imunologia , Linfócitos T/imunologia , Processamento Alternativo , Sequência de Aminoácidos , Animais , Antígenos B7/genética , Antígenos B7/imunologia , Butirofilinas , Células CHO , Cricetinae , Cricetulus , Feminino , Células HEK293 , Humanos , Imunoglobulina G/genética , Imunoglobulina G/imunologia , Células Jurkat , Masculino , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/imunologia , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos BALB C , Dados de Sequência Molecular , Isoformas de Proteínas/genética , Isoformas de Proteínas/imunologia , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Linfócitos T/metabolismo , Transcriptoma/genética , Transcriptoma/imunologiaRESUMO
PURPOSE: Advanced melanoma is a highly drug-refractory neoplasm representing a significant unmet medical need. We sought to identify melanoma-associated cell surface molecules and to develop as well as preclinically test immunotherapeutic reagents designed to exploit such targets. EXPERIMENTAL DESIGN AND RESULTS: By transcript profiling, we identified glycoprotein NMB (GPNMB) as a gene that is expressed by most metastatic melanoma samples examined. GPNMB is predicted to be a transmembrane protein, thus making it a potential immunotherapeutic target in the treatment of this disease. A fully human monoclonal antibody, designated CR011, was generated to the extracellular domain of GPNMB and characterized for growth-inhibitory activity against melanoma. The CR011 monoclonal antibody showed surface staining of most melanoma cell lines by flow cytometry and reacted with a majority of metastatic melanoma specimens by immunohistochemistry. CR011 alone did not inhibit the growth of melanoma cells. However, when linked to the cytotoxic agent monomethylauristatin E (MMAE) to generate the CR011-vcMMAE antibody-drug conjugate, this reagent now potently and specifically inhibited the growth of GPNMB-positive melanoma cells in vitro. Ectopic overexpression and small interfering RNA transfection studies showed that GPNMB expression is both necessary and sufficient for sensitivity to low concentrations of CR011-vcMMAE. In a melanoma xenograft model, CR011-vcMMAE induced significant dose-proportional antitumor effects, including complete regressions, at doses as low as 1.25 mg/kg. CONCLUSION: These preclinical results support the continued evaluation of CR011-vcMMAE for the treatment of melanoma.