Abstract
Lectins have been increasingly utilized as carriers for targeted drug delivery based on their specific binding to glycans located on mammalian cells. This study employed two lectins, B subunit of bacterial Shiga holotoxin (Stx1B) and fungal Clitocybe nebularis lectin (CNL), for surface display on the lactic acid bacterium Lactococcus lactis. The specific adhesion of these engineered, lectin-displaying L. lactis to cancer cells was evaluated. The expression and surface display of both lectins on L. lactis were demonstrated by western blotting and flow cytometry, respectively. MTS assays revealed that recombinant Stx1B had no effect on Caco-2 cell viability at concentrations of ≤25 µg/mL, whereas CNL was non-toxic even at relatively high concentrations of ≤250 µg/mL. Stx1B bound to Caco-2, HT-29 and HeLa cells after 1 h of incubation. CNL bound to Caco-2 cells and recognized several glycoproteins in HT-29 and Caco-2 cell homogenates of which a 70 kDa protein predominated. Confocal microscopy revealed adhesion of Stx1B-displaying L. lactis to HeLa, Caco-2, and, to a lesser extent, HT-29 cells; CNL-displaying L. lactis showed a relatively similar level of adherence to HT-29 and Caco-2 cells. Thus, lectin-displaying L. lactis might serve as a carrier in targeted drug delivery when coupled to a therapeutic moiety.
Highlights
Accepted: 20 January 2021Altered glycosylation patterns and overexpression of specific carbohydrate epitopes are hallmarks of many cancers [1]
The colorectal cancer cell lines HT-29 and Caco-2 were tested for the expression of the Gb3 receptor, while HeLa cells were included as a control, as they are known to express Gb3 and bind Stx1B
The engineered, lectin-functionalized, bacteria would be suitable for delivery of therapeutic proteins to the gastrointestinal tract via oral route for the treatment of colorectal cancer, thanks to the ability of L. lactis to survive harsh conditions in gastrointestinal tract, as well as the stability of lectins in gastro-intestinal fluids and their resistance to degradation by digestive processes [54]. This is the first report on lectin-displaying bacteria engineered for glycan-targeting cancer therapy
Summary
Accepted: 20 January 2021Altered glycosylation patterns and overexpression of specific carbohydrate epitopes are hallmarks of many cancers [1]. Changes in the oligosaccharide structures of tumorassociated glycoproteins or glycolipids include increased N-glycan branching, a higher Oglycan density, and the generation of truncated versions or modification of terminal glycan molecules through sialylation and fucosylation [2]. These alterations can be exploited for targeted therapy, which is one of the goals of precision medicine. Human endogenous lectins are involved, through their specific interactions with complex carbohydrates, in numerous physiological and pathological processes, such as intracellular trafficking, recognition processes, cell homing, endocytosis, phagocytosis, and inflammation [5]
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