A bispecific, crosslinking lectibody activates cytotoxic T cells and induces cancer cell death

Abstract

AbstractBackground Aberrant glycosylation patterns play a crucial role in the development of cancer cells as they promote tumor growth and aggressiveness. Lectins recognize carbohydrate antigens attached to proteins and lipids on cell surfaces and represent potential tools for application in cancer diagnostics and therapy. Among the emerging therapeutic strategies, immunotherapy has become a promising treatment modality for various hematological and solid malignancies. Here we present an approach to redirect the immune system into fighting cancer by means of a “lectibody”, a bispecific construct that is composed of a lectin linked to an antibody fragment. This lectibody is inspired by bispecific T cell engager (BiTEs) antibodies that recruit cytotoxic T lymphocytes while simultaneously binding to tumor-associated antigens (TAAs) on cancer cells. The tumor-related glycosphingolipid globotriaosylceramide (Gb3) represents the target of this proof-of-concept study. It is recognized with high selectivity by the B-subunit of the pathogen-derived Shiga toxin, presenting an opportunity for clinical development. Methods The lectibody was realized by conjugating an anti-CD3 single-chain antibody fragment to the B-subunit of Shiga toxin to target Gb3+cancer cells. The reactive non-canonical amino acid azidolysine (AzK) was inserted at predefined single positions in both proteins. The azido groups were functionalized by bioorthogonal conjugation with individual linkers that facilitated selective couplingviaan alternative bioorthogonal click chemistry reaction.In vitrocell-based assays were conducted to evaluate the antitumoral activity of the lectibody. Cytotoxic T lymphocytes (CTLs) isolated from healthy donors and Burkitt´s lymphoma-derived cells were screened in flow cytometry and cytotoxicity assays for their activation and lysis, respectively. Results This proof-of-concept study demonstrates that the lectibody activates T cells for their cytotoxic signaling, redirecting CTLs´ cytotoxicity in a highly selective manner and resulting in nearly complete tumor cell lysis – up to 93% – of Gb3+tumor cellsin vitro. Conclusions This research highlights the potential of lectins for targeting of certain tumors, with an opportunity for new cancer treatments. In a combinatorial strategy, lectin-based platforms of this type offer the possibility to target glycan epitopes on tumor cells and boost the efficacy of current therapies, providing an additional strategy for tumor eradication and improving patient outcomes.