Copolymer micelles function as pH-responsive nanocarriers to enhance the cytotoxicity of a HER2 aptamer in HER2-positive breast cancer cells

Abstract

Efficient delivery of nucleic acids into target cells is crucial for nucleic acid-based therapies. Various nucleic acid delivery systems have been developed, each with its own advantages and limitations. We previously developed a nanoparticle-based delivery system for small chemical drugs using pH-responsive PEG 8 -PDPA 100 -PEG 8 polymer micelles as carriers. In this study, we extend the application of these pH-responsive micelle-like nanoparticles (MNPs) to deliver oligonucleotides. We demonstrate that the MNPs efficiently encapsulate and deliver oligonucleotides of different lengths (20–100 nt) into cells. The cargo oligonucleotides are rapidly released at pH 5.0. We prepared MNPs carrying a Texas red-fluorescently labeled anti-human epidermal growth factor receptor 2 (HER2) aptamer (HApt). Compared to free HApt, the HApt-MNPs resulted in significantly better cellular uptake, reduced cell viability, and increased apoptosis in SKBR3 breast cancer cells, which overexpress HER2. Moreover, HApt-MNPs were significantly less cytotoxic to MCF7 breast cancer cells, which express low levels of HER2. After cellular uptake, HApt-MNPs mainly accumulated in lysosomes; inhibition of lysosomal activity using bafilomycin A1 and LysoTracker Red staining confirmed that lysosomal activity and low pH were required for HApt-MNP accumulation and release. Furthermore, HER2 protein expression declined significantly following treatment with HApt-MNPs in SKBR3 cells, indicating that HApt-induced translocation of HER2 to lysosomes exerted a potent cytotoxic effect by altering signaling downstream of HER2. In conclusion, this pH-responsive and lysosome-targeting nanoparticle system can efficiently deliver oligonucleotides to specific target cells and has significant potential for nucleic acid-based cancer therapies.

<p>A dual-functional HER2 aptamer-conjugated, pH-activated mesoporous silica nanocarrier-based drug delivery system provides in vitro synergistic cytotoxicity in HER2-positive breast cancer cells</p>

“…To investigate the role of HApt on targeted cellular uptake and endocytosis of MSN-BM/CD-HApt@DOX, we used SKBR3 breast cancer cells as a cellular model of HER2 overexpression and MCF7 cells as a model of low HER2 expression; the two cell lines were verified and used in our previous work. 43 Endocytosis of MSN-BM/CD-HApt@DOX was evaluated using confocal laser scanning microscopy (CLSM) and flow cytometry.…”

“…We previously demonstrated the aptamer HApt, which possesses both targeting and therapeutic capabilities, 42 specifically crosslinks with HER2 protein on the cell surface, which induces translocation of HER2 from the plasma membrane to cytoplasmic vesicles (mainly lysosomes) and subsequent digestion by proteases. 43 HAptmediated targeting and downregulation of HER2 could inhibit cell proliferation and lead to cell death. 43 Therefore, HApt could potentially function as both a targeting ligand and biotherapeutic agent for smart drug delivery systems to improve the efficacy of chemotherapy for HER2-positive tumors.…”

“…43 HAptmediated targeting and downregulation of HER2 could inhibit cell proliferation and lead to cell death. 43 Therefore, HApt could potentially function as both a targeting ligand and biotherapeutic agent for smart drug delivery systems to improve the efficacy of chemotherapy for HER2-positive tumors. HER2 is expressed at higher levels (≈100-fold more) on the plasma membranes of various tumors, 42 including human ovarian, breast, lung and gastric cancer cells, than the corresponding normal cells.…”

pH-Control in Aptamer-Based Diagnostics, Therapeutics, and Analytical Applications

“…In addition to their role in drug delivery, some aptamers show therapeutic properties themselves [ 23 ]. Shen et al in 2018 published an artificial micelle system designed to carry a therapeutic aptamer [ 23 ].…”

“…In addition to their role in drug delivery, some aptamers show therapeutic properties themselves [ 23 ]. Shen et al in 2018 published an artificial micelle system designed to carry a therapeutic aptamer [ 23 ]. The polymer used as a coating reduces interactions with plasma proteins, while the core polymer is hydrophobic at neutral pH, but at pH 6.0 becomes hydrophilic and causes the micelle to swell and disaggregate [ 23 ].…”