Abstract
Bacterial outer membrane vesicles (OMVs) have recently drawn a great deal of attention due to their therapeutic efficiency and ability to target specific cells. In the present study, we sought to probe engineered OMVs as novel and promising carriers to target breast cancer cells. Following the fusion of the affiEGFR-GALA structure to the C-terminal of ClyA as an anchor protein, the ClyA-affiEGFR-GALA construct was successfully expressed on the surface of ∆msbB/∆pagP E. coli W3110-derived OMVs. Morphological features of the engineered and wild-type OMVs were identical. The engineered OMVs induced no endotoxicity, cytotoxicity, or immunogenicity, indicating the safety of their application. These OMVs could specifically bind to EGF receptors of MDA-MB-468 cells expressing high levels of EGFR and not to those with low levels of EGFR (HEK293T cells). Interestingly, despite a lower binding affinity of the engineered OMVs relative to the positive control Cetuximab, it was strong enough to identify these cells. Moreover, confocal microscopy revealed no uptake of the modified OMVs by the EGFR-overexpressing cells in the presence of EGFR competitors. These results suggest that OMVs might internalize into the cells with EGF receptors, as no OMVs entered the cells with any EGFR expression or those pretreated with EGF or Cetuximab. Regarding the EGFR-binding affinity of the engineered OMVs and their cellular uptake, they are presented here as a potential carrier for cell-specific drug delivery to treat a wide variety of cancer cells. Interestingly, the engineered OMVs are capable of reaching the cytoplasm while escaping the endosome due to the incorporation of a fusogenic GALA peptide in the construct.
Highlights
Outer membrane vesicles (OMVs) are a kind of proteoliposomes that exist by nature with a diameter of 20–250 nm and are shed by Gram-negative bacteria through budding of the outer membrane (Bitto and Kaparakis-Liaskos, 2017)
To verify whether the fusion protein was present on the surface of OMVs, the intact W3110 cells and OMVs were subjected to anti-affibody antibody treatment and analyzed by flow cytometry
Since triple-negative breast cancer is known to overexpress Epidermal growth factor receptors (EGFRs) and the Epidermal growth factor (EGF) receptor is a well-established cancer therapy target (Seshacharyulu et al, 2012), using E. coli OMVs and the ClyA displaying system, we introduced a platform with a capability of targeting triple-negative breast cancer, which can be further employed for cancers overexpressing EGF receptors
Summary
Outer membrane vesicles (OMVs) are a kind of proteoliposomes that exist by nature with a diameter of 20–250 nm and are shed by Gram-negative bacteria through budding of the outer membrane (Bitto and Kaparakis-Liaskos, 2017). It is worth noting that effective cancer chemotherapy usually requires a high-dose administration of drugs as these chemo drugs are prone to rapid clearance and poor circulating half-life (Iyer et al, 2013). This can result in severe and long-lasting side effects (Miller et al, 2016). In this sense, OMVs, as the naturally occurring nanoparticle delivery scaffolds, could be expected to serve as a promising drug delivery vehicle in cancer therapy
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