Internalization of CD239 highly expressed in breast cancer cells: a potential antigen for antibody-drug conjugates

Antibody-drug conjugates (ADCs) are attractive in cancer therapy because they can directly bind to cancer cells and provide anticancer activity. To kill cancer cells with ADCs, the target antigens are required not only to be highly and/or selectively expressed on cancer cells but also internalized by the cells. CD239, also known as the Lutheran blood group glycoprotein (Lu) or basal cell adhesion molecule (B-CAM), is a specific receptor for laminin α5, a major component of basement membranes. Here, we show that CD239 is strongly expressed in a subset of breast cancer cells and internalized into the cells. We also produced a human single-chain variable fragment (scFv) specific to CD239 fused with human IgG₁ Fc, called C7-Fc. The binding affinity of the C7-Fc antibody is similar to that of mouse monoclonal antibodies. Although the C7-Fc antibody alone does not influence cellular functions, when conjugated with a fragment of diphtheria toxin lacking the receptor-binding domain (fDT), it can selectively kill breast cancer cells. Interestingly, fDT-bound C7-Fc shows anticancer activity in CD239-highly positive SKBR3 cells, but not in weakly positive cells. Our results show that CD239 is a promising antigen for ADC-based breast cancer therapy.

Development of Potent Myostatin Inhibitory Peptides through Hydrophobic Residue-Directed Structural Modification

Myostatin, a negative regulator of skeletal muscle growth, is a promising target for treating muscle atrophic disorders. Recently, we discovered a minimal myostatin inhibitor 1 (WRQNTRYSRIEAIKIQILSKLRL-amide) derived from positions 21-43 of the mouse myostatin prodomain. We previously identified key residues (N-terminal Trp²¹, rodent-specific Tyr²⁷, and all aliphatic amino acids) required for effective inhibition through structure-activity relationship (SAR) studies based on 1 and characterized a 3-fold more potent inhibitor 2 bearing a 2-naphthyloxyacetyl group at position 21. Herein, we performed 1-based SAR studies focused on all aliphatic residues and Ala³², discovering that the incorporations of Trp and Ile at positions 32 and 38, respectively, enhanced the inhibitory activity. Combining these findings with 2, a novel peptide 3d displayed an IC₅₀ value of 0.32 μM, which is 11 times more potent than 1. The peptide 3d would have the potential to be a promising drug lead to develop better peptidomimetics.

Preparation of Angiopep-2 Peptide-Modified Bubble Liposomes for Delivery to the Brain

In the development of therapeutic approaches for central nervous system diseases, a significant obstacle is efficient drug delivery across the blood-brain barrier owing to its low permeability. Various nanocarriers have been developed for brain-targeted drug delivery by modification with specific ligands. We have previously developed polyethylene glycol-modified liposomes (Bubble liposomes [BLs]) that entrap ultrasound (US) contrast gas and can serve as both plasmid DNA or small interfering RNA carriers and US contrast agents. In this study, we attempted to prepare brain-targeting BLs modified with Angiopep-2 (Ang2) peptide (Ang2-BLs). Ang2 is expected to be a useful ligand for the efficient delivery of nanocarriers to the brain. We showed that Ang2-BLs interacted specifically with brain endothelial cells via low-density lipoprotein receptor-related protein-1. We also confirmed that Ang2-BLs could entrap US contrast gas and had US imaging ability as well as unmodified BLs. Furthermore, we demonstrated that Ang2-BLs accumulated in brain tissue after intravascular injection. These results suggested that Ang2-BLs may be a useful tool for brain-targeted delivery and US imaging via systemic administration.

Incorporating a TiOx shell in single-walled carbon nanotube/fullerodendron coaxial nanowires: increasing the photocatalytic evolution of H2 from water under irradiation with visible light

The SWCNT/fullerodendron/TiOx coaxial nanowire shows an enhanced photocatalytic activity (Φ = 0.47) for the evolution of hydrogen from water under irradiation with visible light (λ = 450 nm).

Gene delivery systems by the combination of lipid bubbles and ultrasound

Gene therapy is promising for the treatment of many diseases including cancers and genetic diseases. From the viewpoint of safety, ultrasound (US)-mediated gene delivery with nano/ microbubbles was recently developed as a novel non-viral vector system. US-mediated gene delivery using nano/microbubbles are able to produce transient changes in the permeability of the cell membrane after US-induced cavitation while reducing cellular damage and enables the tissue-specific or the site-specific intracellular delivery of gene both in vitro and in vivo. We have recently developed novel lipid nanobubbles (Lipid Bubbles). These nanobubbles can also be used to enhance the efficacy of the US-mediated genes (plasmid DNA, siRNA, and miRNA etc.) delivery. In this review, we describe US-mediated delivery systems combined with nano/microbubbles and discuss their feasibility as non-viral vector systems.

Ultrasound-mediated gene delivery systems by AG73-modified Bubble liposomes

Targeted gene delivery to neovascular vessels in tumors is considered a promising strategy for cancer therapy. We previously reported that "Bubble liposomes" (BLs), which are ultrasound (US) imaging gas-encapsulating liposomes, were suitable for US imaging and gene delivery. When BLs are exposed to US, the bubble is destroyed, creating a jet stream by cavitation, and resulting in the instantaneous ejection of extracellular plasmid DNA (pDNA) or other nucleic acids into the cytosol. We developed AG73 peptide-modified Bubble liposomes (AG73-BL) as a targeted US contrast agent, which was designed to attach to neovascular tumor vessels and to allow specific US detection of angiogenesis (Negishi et al., Biomaterials 2013, 34, 501-507). In this study, to evaluate the effectiveness of AG73-BL as a gene delivery tool for neovascular vessels, we examined the gene transfection efficiency of AG73-BL with US exposure in primary human endothelial cells (HUVEC). The transfection efficiency was significantly enhanced if the AG73-BL attached to the HUVEC was exposed to US compared to the BL-modified with no peptide or scrambled peptide. In addition, the cell viability was greater than 80% after transfection with AG73-BL. These results suggested that after the destruction of the AG73-BL with US exposure, a cavitation could be effectively induced by the US exposure against AG73-BL binding to the cell surface of the HUVEC, and the subsequent gene delivery into cells could be enhanced. Thus, AG73-BL may be useful for gene delivery as well as for US imaging of neovascular vessels.

Tumor growth suppression by the combination of nanobubbles and ultrasound

We previously developed novel liposomal nanobubbles (Bubble liposomes [BL]) that oscillate and collapse in an ultrasound field, generating heat and shock waves. We aimed to investigate the feasibility of cancer therapy using the combination of BL and ultrasound. In addition, we investigated the anti-tumor mechanism of this cancer therapy. Colon-26 cells were inoculated into the flank of BALB/c mice to induce tumors. After 8 days, BL or saline was intratumorally injected, followed by transdermal ultrasound exposure of tumor tissue (1 MHz, 0-4 W/cm2 , 2 min). The anti-tumor effects were evaluated by histology (necrosis) and tumor growth. In vivo cell depletion assays were performed to identify the immune cells responsible for anti-tumor effects. Tumor temperatures were significantly higher when treated with BL + ultrasound than ultrasound alone. Intratumoral BL caused extensive tissue necrosis at 3-4 W/cm2 of ultrasound exposure. In addition, BL + ultrasound significantly suppressed tumor growth at 2-4 W/cm2 . In vivo depletion of CD8+ T cells (not NK or CD4+ T cells) completely blocked the effect of BL + ultrasound on tumor growth. These data suggest that CD8+ T cells play a critical role in tumor growth suppression. Finally, we concluded that BL + ultrasound, which can prime the anti-tumor cellular immune system, may be an effective hyperthermia strategy for cancer treatment.

MicroRNA Imaging in Combination with Diagnostic Ultrasound and Bubble Liposomes for MicroRNA Delivery

MicroRNA (miRNA) is expected to play an important role in the diagnosis and therapy of various diseases. In miRNA therapy, the development of delivery tools to the target site is considered to be essential. By using a delivery tool possessing imaging ability, miRNA colocalized with the carrier could be visualized after administration. We prepared polyethylene glycol (PEG)-modified liposomes containing echo-contrast gas, "Bubble liposomes" (BLs), and confirmed that BLs containing cationic lipid were capable of loading miRNA. Furthermore, we also achieved the imaging and delivery of systemically injected miRNA to target site in combination with ultrasound exposure. MiRNA-loaded BLs could be a useful tool for imaging and therapy.

Potential effect of cationic liposomes on interactions with oral bacterial cells and biofilms

CONTEXT

Although oral infectious diseases have been attributed to bacteria, drug treatments remain ineffective because bacteria and their products exist as biofilms. Cationic liposomes have been suggested to electrostatically interact with the negative charge on the bacterial surface, thereby improving the effects of conventional drug therapies. However, the electrostatic interaction between oral bacteria and cationic liposomes has not yet been examined in detail.

OBJECTIVE

The aim of the present study was to examine the behavior of cationic liposomes and Streptococcus mutans in planktonic cells and biofilms.

MATERIALS AND METHODS

Liposomes with or without cationic lipid were prepared using a reverse-phase evaporation method. The zeta potentials of conventional liposomes (without cationic lipid) and cationic liposomes were -13 and 8 mV, respectively, and both had a mean particle size of approximately 180 nm. We first assessed the interaction between liposomes and planktonic bacterial cells with a flow cytometer. We then used a surface plasmon resonance method to examine the binding of liposomes to biofilms. We confirmed the binding behavior of liposomes with biofilms using confocal laser scanning microscopy.

RESULTS

The interactions between cationic liposomes and S. mutans cells and biofilms were stronger than those of conventional liposomes. Microscopic observations revealed that many cationic liposomes interacted with the bacterial mass and penetrated the deep layers of biofilms.

DISCUSSION AND CONCLUSION

In this study, we demonstrated that cationic liposomes had higher affinity not only to oral bacterial cells, but also biofilms than conventional liposomes. This electrostatic interaction may be useful as a potential drug delivery system to biofilms.

Identification of the minimum peptide from mouse myostatin prodomain for human myostatin inhibition

Myostatin, an endogenous negative regulator of skeletal muscle mass, is a therapeutic target for muscle atrophic disorders. Here, we identified minimum peptides 2 and 7 to effectively inhibit myostatin activity, which consist of 24 and 23 amino acids, respectively, derived from mouse myostatin prodomain. These peptides, which had the propensity to form α-helix structure, interacted to myostatin with KD values of 30-36 nM. Moreover, peptide 2 significantly increased muscle mass in Duchenne muscular dystrophy model mice.

Nonviral gene delivery systems by the combination of bubble liposomes and ultrasound

The combination of therapeutic ultrasound (US) and nano/microbubbles is an important system for establishing a novel and noninvasive gene delivery system. Genes are delivered more efficiently using this system compared with a conventional nonviral vector system such as the lipofection method, resulting in higher gene expression. This higher efficiency is due to the gene being delivered into the cytosol and bypassing the endocytosis pathway. Many in vivo studies have demonstrated US-mediated gene delivery with nano/microbubbles, and several gene therapy feasibility studies for various diseases have been reported. In addition, nano/microbubbles can deliver genes site specifically by the control of US exposure site. In the present review, we summarize the gene delivery systems by the combination of nano/microbubbles and US, describe their properties, and assess applications and challenges of US theranostics.

Combination of bubble liposomes and high-intensity focused ultrasound (HIFU) enhanced antitumor effect by tumor ablation

Ultrasound (US) is used in the clinical setting not only for diagnosis but also for therapy. As a therapeutic US technique, high-intensity focused ultrasound (HIFU) can be applied to treat cancer in a clinical setting. Microbubbles increased temperature and improved the low therapeutic efficiency under HIFU; however, microbubbles have room for improvement in size, stability, and targeting ability. To solve these issues, we reported that "Bubble liposomes" (BLs) containing the US imaging gas (perfluoropropane gas) liposomes were suitable for ultrasound imaging and gene delivery. In this study, we examined whether BLs and HIFU could enhance the ablation area of the tumor and the antitumor effect. First, we histologically analyzed the tumor after BLs and HIFU. The ablation area of the treatment of BLs and HIFU was broader than that of HIFU alone. Next, we monitored the temperature of the tumor, and examined the antitumor effect. The temperature increase with BLs and HIFU treatment was faster and higher than that with HIFU alone. Moreover, treatment with BLs and HIFU enhanced the antitumor effect, which was better than with HIFU alone. Thus, the combination of BLs and HIFU could be efficacious for cancer therapy.

Intracellular co-delivery of zinc ions and plasmid DNA for enhancing gene transfection activity

Zinc ions, methylated poly(1-vinylimidazole) (PVIm-Me) and plasmid DNA (pDNA) have formed ternary complexes for gene delivery. The resulting Zn-PVIm-Me-pDNA complexes have delivered both Zn(2+) ions and pDNA inside cells, leading to the nuclear translocation of the pDNA. By use of the pDNA containing a nuclear protein, NF-κB, binding sequence, the intracellular co-delivery of Zn(2+) ions and pDNA has enhanced gene expression. These results suggest that the intracellular Zn(2+) ions delivered by Zn-PVIm-Me-pDNA complexes activated the NF-κB, enhancing the nuclear translocation of the pDNA. In conclusion, it has been demonstrated that the Zn-PVIm-Me-pDNA complex is capable of enhancing the gene transfection activity by a synergic effect of the PVIm-Me and the co-delivered intracellular Zn(2+) ions.