Introduction: Neuropilin-1 (NRP-1) is expressed on tumor cells and tumor-infiltrating immune cells. Since NRP-1 promotes tumor growth, we investigated single domain antibodies (sdAbs) targeting NRP-1 to block tumor progression in vivo.
Materials & methods: Lentiviral particles encoding sdAb M2, HS45 (NRP-1) and BCII10 (control) were produced and used to engineer MC38 tumor cell lines. The cell lines’ were evaluated for growth (Incucyte real time analysis), NRP-1 expression (flow cytometry) and ability to produce sdAbs (Western blot) in vitro. The tumor cells were subcutaneously transplanted into C57BL/6 mice and the growth was monitored. Tumors were analyzed for gene expression and immune infiltration by qRT-PCR and flow cytometry, respectively. Macrophages were isolated by flow cytometry and analyzed for gene expression. Anti-CD8 antibodies were intraperitoneally injected in order to deplete CD8+ T cells and determine the role of cytotoxic T cells in tumor progression.
Results: We generated MC38 cell lines that produce sdAb BCII10 (control), M2 or HS45 (NRP-1). These show similar growth, NRP-1 and sdAb expression in vitro. In vivo, the tumor volume was significantly lower on week 3 when MC38 cells produced sdAbs targeting NRP-1. While the immune infiltrate in NRP-1 sdAb producing tumors of 1000 mm3 was not altered, tumors of 500 mm3 showed to be less infiltrated by type 2 and more infiltrated by type 1 tumor associated macrophages (TAMs) and granulocytes. Moreover, gene expression analysis of presorted TAMs showed that CD206 and Arginase-1 expression is significantly decreased in TAMs derived from HS45 producing tumors. Depletion of CD8+ T cells abrogates the life extending effects of sdAb HS45 indicating that HS45 delays tumor growth in a CD8 dependent manner.
Discussion and conclusions: Targeting NRP-1 using sdAb M2 or HS45 hampers MC38 tumor progression. Both sdAbs alter the myeloid cell composition in the tumor differently. The data suggests that prolonged survival could be achieved in a CD8 dependent way in animals bearing HS45 but not M2 producing tumors. Therefore, these promising data warrant further investigation of this approach and the exact underlying cellular and molecular mechanisms contributing to delayed tumor development in M2 and HS45.
Originele taal-2English
StatusPublished - 1 feb 2019
EvenementBelgian Association for Cancer Research: Annual meeting 2019 - University of Antwerp, Antwerp, Belgium
Duur: 1 feb 2019 → …


ConferenceBelgian Association for Cancer Research: Annual meeting 2019
Periode1/02/19 → …


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