Immunotoxins to the HER-2 oncogene product: functional and ultrastructural analysis of their cytotoxic activity.
Cancer Immunol Immunother
; 39(5): 318-24, 1994 Nov.
Article
em En
| MEDLINE
| ID: mdl-7987863
ABSTRACT
Two immunotoxins were prepared using monoclonal antibodies (mAb) directed towards two distinct epitopes of the gp185HER-2 extracellular domain, and the type I ribosome inactivating protein (RIP) plant toxin saporin 6. Cell protein synthesis inhibition assay reveals that the immunotoxins display a potent and specific cytotoxicity that is characterized by a slow rate, since the time required to inhibit incorporation of radiolabeled leucine completely ranges from 36 h to 60 h depending on the target cell line and the immunotoxin. Because this feature may hamper the immunotherapeutic use of these conjugates we analysed this further by studying the early phases of internalization of immunotoxins by immunoelectron microscopy. The results of this study have demonstrated that the distribution pattern of the immunotoxins and of the unconjugated mAb over the cell surface overlaps. Similarly the mAb and immunotoxins are internalized into the cell by two different pathways via clathrin-coated pits or via smaller uncoated pits and vesicles. A higher degree of internalization is achieved when the two immunotoxins are used in combination. Unlike the slow kinetics of cell intoxication the process of immunotoxin endocytosis is characterized by a rapid rate of internalization (above 40% at 5 min in the SK-BR-3 cell line). Although these findings provide no clue to explain the mechanisms of the slow rate of cytotoxicity of the two immunotoxins their rapid internalization indicates that these reagents can be exploited in immunotherapeutic approaches to gp185HER-2-expressing malignancies.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas de Plantas
/
Imunotoxinas
/
Receptor ErbB-2
/
Antineoplásicos Fitogênicos
/
N-Glicosil Hidrolases
Limite:
Animals
/
Female
/
Humans
Idioma:
En
Revista:
Cancer Immunol Immunother
Assunto da revista:
ALERGIA E IMUNOLOGIA
/
NEOPLASIAS
/
TERAPEUTICA
Ano de publicação:
1994
Tipo de documento:
Article
País de afiliação:
Itália