Uptake routes of tumor-antigen MAGE-A3 by dendritic cells determine priming of naïve T-cell subtypes

Abstract

Induction of tumor-antigen-specific T cells in active cancer immunotherapy is generally difficult due to the very low anti-tumoral precursor cytotoxic T cells. By improving tumor-antigen uptake and presentation by dendritic cells (DCs), this problem can be overcome. Focusing on MAGE-A3 protein, frequently expressed in many types of tumors, we analyzed different DC-uptake routes after additional coating the recombinant MAGE-A3 protein with either a specific monoclonal antibody or an immune complex formulation. Opsonization of the protein with antibody resulted in increased DC-uptake compared to the uncoated rhMAGE-A3 protein. This was partly due to Fcγ receptor-dependent internalization. However, unspecific antigen internalization via macropinocytosis also played a role. When analyzing DC-uptake of MAGE-A3 antigen expressed in multiple myeloma cell line U266, pretreatment with proteasome inhibitor bortezomib resulted in increased apoptosis compared to γ-irradiation. Bortezomib-mediated immunogenic apoptosis, characterized by elevated surface expression of hsp90, triggered higher phagocytosis of U266 cells by DCs involving specific DC-derived receptors. We further investigated the impact of antigen delivery on T-cell priming. Induction of CD8(+) T-cell response was favored by stimulating naïve T cells with either antibody-opsonized MAGE-A3 protein or with the bortezomib-pretreated U266 cells, indicating that receptor-mediated uptake favors cross-presentation of antigens. In contrast, CD4(+) T cells were preferentially induced after stimulation with the uncoated protein or protein in the immune complex, both antigen formulations were preferentially internalized by DCs via macropinocytosis. In summary, receptor-mediated DC-uptake mechanisms favored the induction of CD8(+) T cells, relevant for clinical anti-tumor response.

Trastuzumab Increases HER2 Uptake and Cross-Presentation by Dendritic Cells

“…The balance between immune tolerance and priming in the setting of cross-presentation has been studied in the past with previous data suggesting that presentation by immature DCs results in a tolerogenic T-cell phenotype while presentation by mature DCs results in an antigen-specific response (40,41). It has also been shown that mature DCs, in the presence of antigen/antibody complexes, are better able to initiate a T-cell response when compared to mature DCs cultured with soluble antigen alone (34,42,43). This is consistent with our experimental findings in mature DCs and supports increased T-cell priming with trastuzumab treatment.…”

Epigenetic treatment of multiple myeloma mediates tumor intrinsic and extrinsic immunomodulatory effects

“…Upon treatment of U266 cells and primary MM samples with Bz, an increased in vitro immunogenicity has been linked to the induction of HSP90. 23,24 Carfilzomib and Bz have been shown to induce ecto-calreticulin in unpermeabilized MM.1S and U266 cells in vitro , an effect that was potentiated with the autophagy inhibitor chloroquine. 25 Concerning alkylating agents, to our knowledge, no reports on ICD hallmarks in MM have been published.…”

Association of WT1 IgG antibody against WT1 peptide with prolonged survival in glioblastoma multiforme patients vaccinated with WT1 peptide

“…Reportedly, opsonization of cancer antigen MAGE‐A3 with an antibody promoted its uptake by DCs. The induction of CD8 + T‐cell response rather than CD4 + T‐cell response was favored by naïve T cells stimulated with antibody‐opsonized MAGE‐A3 protein, indicating the existence of an uptake route‐dependent mechanism by which the subsequent immune responses were modulated . In addition, the efficacy of uptake could vary according to the subclass of opsonizing IgG antibody.…”