Abstract
Most triple negative breast cancers (TNBC) are characterized by elevated expression of mesothelin (MSLN), a cell surface antigen and one of the preferred targets for the therapy of solid tumors. Most continuous TNBC cell lines are MSLN-negative, which obstructs the development of MSLN-targeted therapy for TNBC. The aim of this study was to identify TNBC cell lines with MSLN hyperexpression and to obtain single-domain antibodies (nanobodies) capable of recognizing MSLN in TNBC cells. Mesothelin expression levels were measured in the panel of TNBC cell lines by real-time reverse-transcription PCR. PCR results were verified by measuring concentrations of the megakaryocyte potentiating factor (the secreted fragment of the mesothelin precursor) using sandwich ELISA. Immune phage-display VHH fragment libraries were prepared from mononuclear cells of Vicugna pacos using a modified library enrichment protocol. Two nanobody variants with high specificity for the target and Kd of about 140 and 95 nmol, respectively were obtained. Two MSLN+ and three MSLN– cell lines were identified in the TNBC cell lines panel. The nanobodies demonstrated the ability to recognize the target antigen in MSLN+ cells and had the low ability to bind to MSLN– cells. Thus, we found a convenient MSLN+ TNBC cell model for MSLN-targeted therapy testing. The new single-domain antibodies can be used as targeting components of chimeric antigen receptors.
Highlights
Most triple negative breast cancers (TNBC) are characterized by elevated expression of mesothelin (MSLN), a cell surface antigen and one of the preferred targets for the therapy of solid tumors
The first library was prepared from the total RNA isolated from mononuclear cells; the second library was prepared from the total RNA isolated from the cells that had undergone positive selection on magnetic beads coated with biotinylated mesothelin
48 clones were randomly chosen from each library and tested for response to mesothelin using ELISA; the clones characterized by the maximum level of signal intensity (Fig. 1C) were sequenced
Summary
Most triple negative breast cancers (TNBC) are characterized by elevated expression of mesothelin (MSLN), a cell surface antigen and one of the preferred targets for the therapy of solid tumors. Most continuous TNBC cell lines are MSLN-negative, which obstructs the development of MSLN-targeted therapy for TNBC. The aim of this study was to identify TNBC cell lines with MSLN hyperexpression and to obtain single-domain antibodies (nanobodies) capable of recognizing MSLN in TNBC cells. Mesothelin expression levels were measured in the panel of TNBC cell lines by real-time reverse-transcription PCR. The nanobodies demonstrated the ability to recognize the target antigen in MSLN+ cells and had the low ability to bind to MSLN– cells. Установлена удобная клеточная модель MSLN+ ТНРМЖ для тестирования MSLN-опосредованной терапии; новые однодоменные антитела могут быть использованы в качестве нацеливающих частей химерных антигенных рецепторов
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