Clickable Shiga Toxin B Subunit for Drug Delivery in Cancer Therapy

Abstract

In recent years, receptor-mediated drug delivery has gained major attention in the treatment of cancer. The pathogenderived Shiga Toxin B subunit (STxB) can be used as a carrier that detects the tumor-associated glycosphingolipid globotriaosylceramide (Gb3) receptors. While drug conjugation via lysine or cysteine offers random drug attachment to carriers, click chemistry has the potential to improve the engineering of delivery systems as the site specificity can eliminate interference with the active binding site of tumor ligands. We present the production of recombinant STxB in its wild-type (STxB wt ) version or incorporating the noncanonical amino acid azido lysine (STxB AzK ). The STxB wt and STxB AzK were manufactured using a growthdecoupled Escherichia coli (E. coli)-based expression strain and analyzed via flow cytometry for Gb3 receptor recognition and specificity on two human colorectal adenocarcinoma cell lines�HT-29 and LS-174�characterized by high and low Gb3 abundance, respectively. Furthermore, STxB AzK was clicked to the antineoplastic agent monomethyl auristatin E (MMAE) and evaluated in cell-killing assays for its ability to deliver the drug to Gb3-expressing tumor cells. The STxB AzK −MMAE conjugate induced uptake and release of the MMAE drug in Gb3-positive tumor cells, reaching 94% of HT-29 cell elimination at 72 h posttreatment and low nanomolar doses while sparing LS-174 cells. STxB AzK is therefore presented as a well-functioning drug carrier, with a possible application in cancer therapy. This research demonstrates the feasibility of lectin carriers used in delivering drugs to tumor cells, with prospects for improved cancer therapy in terms of straightforward drug attachment and effective cancer cell elimination.

Identification of GB3 as a Novel Biomarker of Tumor-Derived Vasculature in Neuroblastoma Using a Stiffness-Based Model

“…The Shiga toxin is well-documented for its strong binding affinity to GB3 receptors [ 22 ]. By exploiting the natural affinity of the Shiga toxin for these receptors, researchers have developed toxin-based nanocarriers to target various cancer types [ 22 , 23 , 24 , 25 ] As a proof of concept, we decided to functionalize latex nanoparticles of 400 nm with the non-toxic subunit B (StxB) of the Shiga toxin for specific targeting of GB3-expressing cells. Notably, the confocal studies demonstrated a high degree of selectivity, with these nanoparticles exhibiting a strong affinity for GB3-positive cells while showing minimal interaction with GB3-negative cells ( Figure 6 ).…”

A Shiga Toxin B-Subunit-Based Lectibody Boosts T Cell Cytotoxicity towards Gb3-Positive Cancer Cells

“…Together, these aspects turn StxB into an engaging tool for addressing cancers that are characterized by the presence of Gb3 on their cell surfaces [45][46][47][48][49][50]. StxB has already been explored as a tool in cancer therapy, with promising results further encouraging its use in cancer treatment [49,50,[67][68][69][70]. We envisage tackling this issue by relying on the BiTE concept, replacing the TACA-targeting scFv with a monomeric StxB and fusing the lectin to the scFv of an αCD3 antibody.…”